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MG Midget and Sprite Technical - Butterflies not fully open
| Whilst having great 'fun' with the carbs recently I saw that the butterflies weren't able to be fully opened by the control cable and newly acquired and fitted 'Throttle link and lever - AEA597'.
Have I wired it right? See photo below - . black arrow - to throttle stop foot that rests against heat shield . blue arrow - upper hole, trunnion pin (altho' the pin fitted neither hole but that's a different matter) . purple arrow - lower hole, return spring. This is how I thought I'd remembered they were and seemed logical - though my memory and logic sometimes (often) fail me. Previously I had a homemade lever fitted which worked but was fitted backwards so like a fool I decided to change it some day, I've no idea if that caused the same issue as I never looked. I've checked the cable both ends for unnecessary slack and there isn't any. The new throttle link and lever I've fitted as per book, well as much as I could see in illustrations. If I've wired it right any other thoughts? Thanks in advance (and hope).  |
| Nigel Atkins |
| Sounds right to me. If you disconnect the cable and operate the lever by hand, do the butterflies open fully? |
| Jeremy MkIII |
| Hi Jeremy, they flop open very easily when off the car. |
| Nigel Atkins |
| Why are they not opening fully? Is the pedal hitting the floor before full opening is achieved? Is the hole for the trunnion pin reaching its apex before full opening is achieved? Is the hole for the trunnion pin not the correct distance from the rotation axis? |
| Dave O'Neill 2 |
| Perhaps the heatshield is bent, or not fitted properly? |
| GuyW |
| Hi Nigel think it's a question of a process of elimination. If they open when disconnected from the cable then possibly the cable needs adjustment or as Dave and Guy have pointed out, there may be something obstructing its movement. |
| Jeremy MkIII |
| pic of the installation may help? |
| David Smith |
| DaveO, yes, not sure but don't think so, no idea purchased part. Guy, heat shield isn't bent, might be micro indented or worn from forcing SU supplied part round as I was too lazy to take the carbs apart yet again. Jeremy, yes, but what, I need a fresh pair of eyes and mind on it as mine are worn and my attitude to it is poor. DavidS, I've took a few quick photos but can't get a good angle or shot but can try again given more direction (other than taking the !//*?! carbs apart again).   |
| Nigel Atkins |
| Not sure the throttle link should touch the heatshield as yours but as that's from memory, it's likely to be completely wrong. Will check in the morning and see what the set up on mine looks like. |
| Jeremy MkIII |
| When you say the throttles aren't opening fully, how is that showing up? |
| GuyW |
| Jeremy,
have look in the good book. The foot rests against the shield as a throttle stop, the linkage lever fingers are set to not be touching on the openings of the cams of the carbs so that the throttle is fully at rest. Putting a 0.015" feeler gauge behind the foot so separating it from the hearshield and lightly setting the fingers just lightly touching the bottom of the cam opening gives the 0.8mm clearance on them when you remove the gauge - well that's how I remembered it. For the first three out of four times of doing this it worked spot on but after that I lost the knack and I just set the lever fingers by eye and they seemed correct when I was able to measure them with metric bent wire feeler set, until I dropped into the gravel (or the plastic burnt away as I'd dropped it on the exhaust and metal part blown to the weeds). |
| Nigel Atkins |
| Guy, cam arms don't go fully to the stops (top of carb bodies) - and when the dampers were off I saw the butterflies weren't fully open. Formerly trying to get the SU supplied part to fit alerted me to the possibility. |
| Nigel Atkins |
| Have you not consulted the 'Good Book' recently ? Pages 48 and 49 Verse's 10- 23 ! R. |
| richard b |
| which pedal arrangement do you have? I've just got a bit more travel on mine (organ pedal arrangement with the pedal bit taken off) by bending the pedal arm a bit - make sure it's not getting stuck on the carpet or anything. |
| Rob Armstrong |
| Rich, I read that section repeatedly until my vision went blurry and the pages so doggy-eared that they're now like tissue - and it's verses 1-23. ;) |
| Nigel Atkins |
| Cross posted Nigel, see you are really reading it not just preaching it ! Only the later verse's cover air balance in my version. Don't have such problems with my HIF6! but will if I ever get back to Devon to sort out the 'B'. |
| richard b |
| Hi Rob,
not sure I'm brave enough to remove pedal bit (link?, pedal itself?) or bending the bar bit but I have tried for as much movement as possible and even took a nick out of the rubber overmat, the 'carpet' is the cheapest set known to man and is so thin I think they'd be the same as removing the paint from footwell. Got me thinking though if the anti-drum pad might be there, if so I could cut a section out, too dark and cold now to look. Thanks all, keep the ideas coming please as I'm sure it'll be some obvious stupid mistake I've missed (I've only used modern made replacement parts so that's always a concern). |
| Nigel Atkins |
| Rich, I read it - but not saying I always fully understand it! Despite the over numerous times I've had to refill the coolant system I still check that section in the good book as I suddenly always doubt myself, but by following the instructions in the good book only and doing nothing extra I've never had any problems with airlocks and hotspots (other than when I left the blue roll in the stat housing but that's not in the book). |
| Nigel Atkins |
| easiest way to check is to wedge the pedal down as far as possible then see if there's any spare slack in the operation at the carb end. |
| Rob Armstrong |
| I've had a glamorous assistant several times floor the pedal whilst I look (and am) clueless under the bonnet. |
| Nigel Atkins |
| Couple more photos.
In the first I take the arms arrowed as being the throttle stops of WOT that stop against the carb bodies to prevent going passed/over WOT. You can even see a blue mark (circled) on the heatshield where I was working out, with the heat shield was out of the car, the ends of linkages, the off-centre of the cable and the trunnion fixing side of throttle lever (for previous offset SU throttle lever). Close up the filters appear to be holding some debris, I'll give them a clean and reoil.   |
| Nigel Atkins |
| First off Nigel, I have read the handbook and can't find anywhere that you should have half a farm growing on your airfilters , that's disgusting behavior and won't be tolerated at any price , not even a good glass of stout from you is enough to excuse such behavior
Now that you've fixed that,- cheers How far off the WOT position are the stops with the pedal right down--for me i prefer them not quite touching, reason being if you have them touching at full throttle it strains the cable and it's fittings- Don't know how many race cars i've seen with broken throttle cables ,and it's always because of them being adjusted up too far and pinging the end off the cable Better off concentrating on getting the initial opening setup correct The last little bit of throttle does nothing really The shaft is much thicker than the butterfly , the butterfly is like under an 1/8 so the butterfly can be back a fair bit and you'll still have full throttle limited by the thickness of the shaft itself As long as it's nearly there it's good |
| William Revit |
| Nigel
I am with Willy on this - your throttle cable might be a bit too tight - I'd be loosening it by about 1/8" to a 1/4" inch (do not measure that - just so not cable strained at rest). Can you take a picture showing your connection of the cable to the throttle quadrant (triangular thingy) at the carbs. Also what bits have you replaced - seems lots of shiny stuff visible (any of them new but rubbish, whereas some dirty but serviceable stuff is on your bench and hopefully not in the bin?). What about putting some of the old stuff back on, retracing your steps? What problem(s) were you trying to fix? I am not sure the good book shows K&N filters. Maybe this is the problem as a return to standard filters would mean you would have changed the paper elements at the correct service interval! Someone on here is always wisley advising getting the car running and serviced correctly according to BMC/BLMC/BL requirements and specifications in the Driver's Handbook before modifying!! Cheers Mike PS 1500 (non organ) pedal is an easy replacement. Available secondhand. Just need to make sure you cover up the two unused holes in the floor so the Wilton does not get waterlogged. |
| M Wood |
| My quadrant only has one hole (its in the same place as you have the spring) The spring is attached to the cable clamp with a washer which has a hole in it. I would respectfully suggest that where you have fitted your cable results in the cable reaching the top of its travel before the butterflies fully open. |
| Bob Beaumont |
| You might be right Bob, it looks a bit like it's up too high and will go over centre on full throttle A pic at full throttle would tell the story on that It might just be the angle the pic has been taken from The other little issue I've struck in the past is the pedal rest adjustment, I've seen a few of these that have had the adjuster bolt screwed right in as though it's a bolt holding something, but with it right in all it does is reduce the overall amount of available pedal travel---? |
| William Revit |
| Willy,
I was surprised to see that debris when I put the photo up, for excuses we're at a windy hilltop and one of my neighbour's is remodelling his property and he and tradesmen mates are extremely untidy workers, for about 18 months the front 'garden' has the look of a fly-tipped area, there's an open bag of cement left to blow in the wind. Last attempt to set carbs and he's power cutting breeze blocks so I had to work around his work as he'd "only half-a-dozen cuts to make", he made dozens over the best part of the day. I think the photo made it look worse but I have vacuum and brush cleaned the filter and will wash and reoil them tomorrow. The throttle stops are about roughly, at a guess, with poor eyes and poor brain, 1/4" above bodies, I can't remember how much the butterflies were off but it'd be commensurate. Previously with the cable I've tried more slack and tighter carb end, now I've taken the slack off the pedal end otherwise surely I loose pedal and cable travel(?). I'll see if I can get a photo tomorrow of full throttle but it does require the assistance of my (rightly so) reluctant glamorous assistant. |
| Nigel Atkins |
| Mike,
the car came with those K&Ns and I have actually cleaned them beyond their service requirements, I have the instructions, sales leaflet but sadly not the original box and packaging. The photo I put up of the throttle lever linkage was from Moss and looked rough to me so mine's from MGOC and smoother but still the holes were too small for the trunnion (which I already had from elsewhere). See reply to Willy for cable. I've had the car 13 years and it has (at some periods of time) run very well and this is actually a retro refit to standard parts, originally attempted by using the original manufacturer, but it's not the same people and times. Changing the pedal would be a modification, I couldn't hold with such! |
| Nigel Atkins |
| Bob, AFAIK the throttle lever linkage AEA597 is the one for my car and has two holes but your idea was the one I had as a fall back position because the trunnion I bought came with a swinging link bar. I couldn't remember seeing any like this on Spridgets but it had a copper washer (I mean, a copper washer!) and I didn't have any copper washers that size so I had to have that trunion kit. |
| Nigel Atkins |
| It might not seem like it but I am open to ideas and have already tried some, if I did them correctly is another matter. I often try the opposite of what I think is right as I often mix up opposites or just forget which way/direction I should go or have just gone, even if I right it down I forget if I've do so with that movement, or was it the last.
For the cable surely if the throttle lever is at rest on the heat shield (and there is a little slack in the cable that end) and the rod of the lever is fixed so the fitting of the rod into the carb also gives a fixed point to its rotation - then provided the throttle lever is the correct shape and size it should arc correctly and there's no value in having the cable pull beyond a certain point. I must admit I didn't fully strictly follow the book as I left the idle screws set at previous settings as I thought that wouldn't restrict the WOT but hasten it on cable pull. |
| Nigel Atkins |
| And that pedal rest adjustment bolt, next to the cable fitting on the firewall, a pic of that as well while you're going |
| William Revit |
| Nigel I don't think I have seen a quadrant with 2 holes in it. Either way my quadrant has the hole for the cable clamp at the bottom rather than the middle where yours is. It came with the carbs when I purchased the 1275 engine many moons ago. Interestingly I ordered a replacement (For another project) from Burlen and it was supplied with only one hole at the bottom. Good luck wih finding the solution! |
| Bob Beaumont |
| >>I don't think I have seen a quadrant with 2 holes in it<< I have. Three times now and always on 1500s. Including my car which caused a good deal of headscratching when I was trying to figure out the cause of the sticky throttle,although it turned out to be irrelevant to the problem. I still have no freaking idea why the two holes. |
| Greybeard |
| Ah Ha Therein could lie the issue.Thanks Greybeard. I was referring to A series engines. |
| Bob Beaumont |
| The Burlen reconditioned/rebuilt ones that I have use a quadrant with two holes, like that one in Nigel's photo. So too does the original carb set from the Austin Sprite, though I think the upper hole for the cable is further down almost alongside the hole for the spring. |
| GuyW |
| Just checked my original set of carb's for a '72 RWA and it has 2 holes and is set up with cable trunnion in middle and return spring in bottom hole. Theese are original as it came out of the factory AFAIK. |
| richard b |
| Guy
I think you're thinking the same as me That centre hole looks too high (In the assembled pic anyway-could be the angle of the pic. still though) If it is too high it will get around to a point where it won't rotate any further because of the angle of the cable, Hopefully Nigels forthcoming pic at full throttle might put some light on that I'm still interested to see if the pedal stop bolt has been screwed right down by mistake as well A pic of it and/or from down in the footwell of the top end of the throttle pedal where the cable attaches would answer that |
| William Revit |
| Photos to follow, just waiting for availability of my glamorous assistant. |
| Nigel Atkins |
| As soon as I put the photos on the computer I realised I'd forgot to take a face-on shot but if needed I could, I'd have to remove breather hoses to see anything, just ask. Second photo is for Willy, note threads showing on setscrew (and dust from neighbour, fibre dirt is probably a vintage collection of mine). Guy, note clutch spring, same for brake. :)   |
| Nigel Atkins |
| don't understand why Nigel's new quadrant thingy has two holes. Why do repro manufacturers insist on mucking around with OE spec? It worked OK with one hole for 50 years! Here's a shot from underneath of a pair from a '72 RWA that had been off the road since '89 so almost certainly the original carb setup. One hole and fairly near the bottom.  |
| David Smith |
| The assumption is that one hole is for the spring, and one a cable attachment point. But maybe that is not the correct assumption to make. My '71 car quadrant has 2 holes but they are closer together than on Nigel's. What if these aftermarket manufacturers are making a "universal" quadrant and you are expected to select the one hole to suit your applicaton, fastening the cable and the spring attachement together as in the original and ignoring the other hole. |
| GuyW |
| see my earlier comment regarding two holes and that a new quadreant from Burlen had only one hole. David's comment echo's mine |
| Bob Beaumont |
| That's kind of what I was getting at, Bob. Clearly one hole was sufficient, and original on at least some (if not most) cars. I was concocting an explanation of why some quadrants have two holes, but that they were then being wrongly assembled, rather than the holes being seen as alternatives suitable for different model applications. |
| GuyW |
| The ironic part is both holes were too small for the trunion so I had to drill the top one (and file it as I didn't have the correct size drill bit) and I did consider drilling (and filing) both just in case - but didn't. Photo of trunnion type that I can't recall ever seeing on a Spridget but I got it at the time anyway, good job I did, now where did I put the parts I didn't use(?). ETA: I've only ever noticed them with two holes but I've never really took much notice before.  |
| Nigel Atkins |
| Nigel That cable clamp is the one I use. The return spring goes into the elongated washer with the hole in it. Ironic that it doesn't fit the quadrant you purchased without adjustment!! |
| Bob Beaumont |
| Bob, when I first saw that trunnion set I thought it might be for another marque but ANG list it as a MGA kit. The SU supplied (choke style) trunnion didn't fit either hole of the throttle lever too, both trunnion pins seemed to be same diameter. |
| Nigel Atkins |
| I'm not blaming David, thanks for the photo, but in it the lever piece is a different shape compared with the original photo I put up, but if you cut off the bottom portion, with the lower hole, across it would look the same(?) as the one in David's photo, making the (upper) hole positions the same(?). I was wondering if I went to the fixing at the lower hole on the one I have whether then I'd run out of cable travel - unfortunately I think there's only one way to find out. |
| Nigel Atkins |
| I don't see why you would run out of cable travel. If anything, having more cable between that point and the outer cable ferrule on the heat shield, means more cable travel. What might then limit it is pedal travel (adjustable) , or more likely the stops on the carburettors. |
| GuyW |
| Thanks Guy that's what I really meant, but the change in cable 'slack' pedal end might be it (as Willy pointed out earlier). |
| Nigel Atkins |
| Nigel
Looks like it's not getting much more than 2/3 throttle to me, comparing it with your earlier pics I'd be going to the bottom hole, fitting your lost trunion for the spring fitting, adjust the cable up for the new spot and then check to see if you're getting full throttle If you still can't get full throttle you can let that pedal adjuster back a turn or two, adjust the cable, and try again--You probably won't need to do this but there's a few turns adjustment left there if you need to The only other thing I can see is that compared to Dave's lever, your lever appears to be closer to the heatshield which would mean it's longer and give different/slower leverage---might just be the angle of the pic. the only way to check that is to measure the distance from the shaft to the trunion and compare- If it's wrong you could drill a new hole just above and inboard of the bottom hole---- If you're going to pull it all apart again it might be worth checking against another car first |
| William Revit |
| Dunno if it helps but when I was fooling around with mine I had the vertical link in both holes, one after the other. I had a cable tie on the crosslink between the carbs and saw the same deflection in each position when the Attractive Assistant floored the pedal.
Of course the lower hole gives a greater radius to the operating arc so must make it a quicker action but I honestly didn't notice any difference driving the car. I'm going to stick my neck out and speculate that the drilled quadrant is a generic part- one size fits all across a range of carb setups- and that which one was originally installed was probably random. Whichever came out of the box first. QA? What's QA,then? |
| Greybeard |
| Grey A smaller radius will give you quicker (but heavier) action, and more rotation for the same pedal travel. |
| Dave O'Neill 2 |
| Willy,
I'll start with the good, I've cleaned and re-oiled the K&N filters. The spray head on the bottle of K&N cleaner was bunged up and wouldn't clean off and operate, all other unused spray heads had gone to recycling and all others in use were a different size and thread to the K&N bottle. So I emptied the contents of another bottle into a jug for temporary storage whilst I cleaned out the bottle, dried and refilled with the K&N cleaner. Three cycles of using the cleaner used it all up so I was able to again wash and dry that bottle and refill it with its previous contents from the jug used, wash and dry jug. After allowing more than enough drying time this morning I re-oiled the filters, this time careful not to over do it. I think it must be the angle of the photo as I'm sure it's more than 2/3rds, more like 4/5ths. I had come to the same 'joyous' conclusion that you had to try lower hole with link piece for spring and that possibly a third middle hole maybe required, until Grey's post. |
| Nigel Atkins |
| I know least of all me but I do find it strange that it isn't a matter of simply fitting the part as standard and adjusting cable as required.
The carbs, heatshield and linkages are as standard and I thought the throttle link and lever was the standard item, I think the length of the quadrant and location of the link rod was the same on the previous homemade one that was previously fitted but that got binned (I've already got too much car stuff cluttering the place up). Perhap the one I got is a different size to the Moss one illustrated. I was hoping it'd be a case of a stupid and obvious mistake I'd made, perhaps it's a stupid but not obvious mistake I've made. The car is easily drivable without worrying about this and will get to higher revs than I ever use (unless I pull off too quick in T9 first which has he needle bouncing back) but I'd like this to be as sorted as much as it can before final carbs settings are made that will be never looked at or touched again. |
| Nigel Atkins |
| Grey, 'that one size fits all' is what I was saying earlier. Buy one, and use whichever hole best suits your application.
I also think that the radius is the same for the two holes. The photo is deceptive but the curved outer edge of the quadrant is an arc, centred on the shaft. And the two holes are the same distance in from that arc, just at different heights. Choosing one hole for the cable connection as against the other won't give a faster or slower action, but will give a different 'stroke' length to the cable pull. Subject, that is, to the available pedal movement and the limit of the carb lever stops. |
| GuyW |
I’ve just found this in a box of carb bits. It probably hasn’t been fitted to a car for at least 25 years, so likely original.
 |
| Dave O'Neill 2 |
| The originals look a different shape, the throttle stop foot on those appear deeper but not as tall - but the radius to holes on all three levers could be the same(?). I'm wondering if me having the idle screws set before attaching the cable is my error and problem(?). I might first try completely backing off the idle screws and refitting the cable to throttle lever, as it means not having to take the carbs off yet again, I'm wearing the threads out.   |
| Nigel Atkins |
| It would be interesting to compare Dave's (which looks very much like mine) and Nigels. Perhaps Dave could be persuaded to sketch out his ? (mine packed away in the top loft)- punch a hole in a bit of card and draw round + dim up would be my method. Nigel could then confirm if different as its pretty impossible from pics. R. |
| richard b |
| Time to get serious Nigel
The rest on Dave's appears to have a greater step back to the radiused part which 'could' mean his pivot point for the trunion is shorter to the centre of the shaft than yours giving quicker action-- Adjusting your cable with the idle screws backed out will make it worse --when you adjust the idles back up you will then have extra slack in the cable reducing available travel You could try adjusting the pedal stop and then readjusting the cable but it looks like there's only a few threads there and i suspect you need more than that SO If you feel like taking some measurements we'll work out what's happening With the assistance of your Happy Helper--- With a measuring tape or ruler or whatever, get her to give it around 1/2 throttle to get the trunion up where you can get a good measurement and measure from the centre of the trunion to the centre of the shaft SU levers come in increments of 1/16" so as acurate as you can here to within the nearest 1/16 Now with the throttle released poke your measuring tape down parallel to the cable from up near the top of the heat shield where the cable mounts with the 0 on your tape lined up with the centre of the trunion--then get your throttle lady to give it full throttle and measure off how far the trunion moved up the tape(cable travel)-- Then while it's in this position, manually open the throttle further to full throttle position to see how much more measured travel is needed to get to full throttle Now with the throttle released and the measuring tape in position again line the 0 up with the centre of the bottom hole, pull the throttle round manually to full throttle and measure off the travel of that hole at full throttle As Richard without a capitol r says, it's a bit hard from pics so we'll do the measuring thing It might mean drilling a new hole but from these measurements we can work out where If you want The difference might just be the position of the bottom hole is enough, with the hole down lower it's more down round the corner and because of the changed angle of pull on the cable the arc moves more outwards initially instead of the top holes upwards so there 'should,could' be a gain in quicker initial rotation from the bottom hole If you have to pull it out again to open up the bottom hole it may as well be measured up and see if that's enough or if it needs a new hole IF we ask Dave real nice,, he might measure from the centre of his trunion to the centre of the shaft as well , Thanks willy Nigel, if this throttle link thingy is a new addition, why did you relace it, were you getting full throttle previously, do you still have the old one for show & tell and measuring etc if needed |
| William Revit |
| This is no doubt correct, but crazily complex for someone who repeatedly says his eyesight and measuring skills are poor!
I would, without dismantling anything else, remove the split pin from the cable toggle and relocate it into the lower hole. Readjust the cable length to suit. Hook the spring over the stub or through the eye of the split pin. See what now happens. If necessary now Loosen the throttle lever clamps and adjust tickover on each carb and then retighten the clamps. Try it out, flooring the throttle pedal and looking to see how near to horizontal the butterfly now goes. The other thing that will effect this is the thickness of the phenolic insulating spacers used. Are they all the same? I rather think I have seen different thickness ones but they may have been for a different car. Fatter ones will make more degrees of rotation of that quadrant available. |
| GuyW |
| All good Guy, but Nigel has to pull the quadrant out and redrill the hole to fit his trunion as it's too big for the hole The measuring is to check if it's going to work in the bottom hole or if it needs another hole in a yet to be determined spot I think his insulators are correct as the stop sits squarely to the heatshield at rest willy |
| William Revit |
| There are different thicknesses of phenolic spacers, but they aren't readily interchangeable, without also changing the studs. If you try to fit a thicker one, you won't have enough stud available to put a nut on. Similarly, if you fit a thinner spacer, the studs will be too long and foul on the dashpots. Off to work now, but I'll measure the quadrant later. |
| Dave O'Neill 2 |
| Now, a few thoughts:
The photo in Nigel's first message isn't his quadrant, just a downloaded example similar to his. It may not be identical. S.U definitely made these as both single hole and two hole versions. I am still not convinced that there is actually a problem. How far off the horizontal is the butterfly disc with the pedal full to the floor? Slightly angled is not going to be a problem for a road car driven with verve. It might even add to the fuel atomisation caused in the turbulent air flow. Unless the head, valves and cams are heavily modified the air volume that the carbs will flow on full throttle is rarely, if ever going to be a limiting factor in normal driving. Unless of course there really is something stopping the butterflies from opening at a much lower angle. I don't know what the rotation should be but as the start angle isnt 90degs to the throat axis, I suspect a rotation of around 65 - 70 degs would be it. |
| GuyW |
| Willy,
Guy is right I'm afraid, with my wonky eye(s) there's no way I could make accurate measurements in situ, I'm lucky to see 16ths when measuring on a desktop - but I have another idea for seeing how far the butterflies don't open with the use of my favourite tool on the car, Blutac (or whitetac), all with be revealed after I have the assistance again of my glamorous assistant. Willy I done something on the roundtoit list by mistake, it's a bit like Withnail & I's "We're gone on holiday by mistake" - are you the throttle lever... - http://www.youtube.com/watch?v=JD2P9Px3enI I've not kept the old lever, I did for a while, but not now, it was home made and fitted backwards. I've no idea if it opened the butterflies fully as I never looked. I'm glad you said about the idle screws as my original thought was as yours but then I thought if goes on to the linkage that's the lever too, I got confused then a nosebleed and thought just try it. Guy, AFAIK those black blocks are correct and fit correctly. As for getting the split pin out in situ, take a look at the photo, once I decide a fitting is stopping there, it's stopping there, plus as you'll find there's not a lot of room to operate as it's a very congested area with hoses, clips, cables, springs, fixings, rods, levers, and that's with the air filters fully removed (and I've yet to fit the last two hose clips). Easiest is to fully slacken off the four 3/8" thin nuts, though with the bottom two you don't get much spanner swing, and angling the carb bodies on the manifold studs if you're lucky you can just get enough slack to remove the linkages, otherwise it's at least dashpots off. |
| Nigel Atkins |
|
<<As for getting the split pin out in situ,>> I suggested that as an easy option, certainly easier than the accurate measuring Willy had advised. Your photo shows an easy direct view of the split pin which can be reached with a pair of long nosed pliers. Unhooking the spring and rotating the quadrant upwards will give even easier access to it so nothing else would need disturbing. I admit, the comment about the phenolic spacers was a bit of an aside - thicker ones would give more rotation of the quadrant but as Dave says, that would introduce different problems so its not really a solution. I still question whether you have a real fault at all in the first place. |
| GuyW |
| OK Nigel
Give this a try then-- Grab hold of the outer throttle cable where it goes into the fitting on the top of the heat shield and pull it up and see if you can get full throttle at the carbs If you can then see if you can measure how far you have to lift the cable to do that Make sure the outer cable goes back in it's hole when you release it next Then, get Lovely to give it full throttle, then while it's there, grab hold of the outer throttle cable at the heatshield fitting again and see how far up extra you have to pull it to get full throttle Guy Nigel still has to pull it all apart for any changes as his bottom hole is a smaller diameter than the pin on his trunion , it has to come out to be drilled out anyway and i'm just trying to work out if it needs another seperate hole drilled while it's out The measurements aren't rocket science but if the eyes don't agree I guess that's different I was judging the quadrant and insulators etc from Nigels pics on- Posted 24 September 2020 at 19:20:25 BST The first pic shows the trunion in a position that looks too high for the rest position, it should be level with or just below the height of the throttle shaft at roughly half throttle--not at idle as it appears in the pic Could still be the angle the pic was taken from but i don't think so The second pic shows the stop resting against the heat shield at a near perfect angle indicating that the insulator blocks are the correct thickness I'm hanging out for the bluetac experiment |
| William Revit |
| <<The first pic shows the trunion in a position that looks too high for the rest position, it should be level with or just below the height of the throttle shaft at roughly half throttle--not at idle as it appears>> Exactly, which is why I think the toggle (trunion?) should be in the lower hole. I must admit, I hadn't realised there was a problem with the size of the quadrant holes v. the toggle pin. |
| GuyW |
| Guy I think it should be in the lower hole as well but it'd be a real pissoff for Nigel if he goes to all the trouble of pulling it apart to open the hole up and it doesn't fix it Measuring is the way to go, the old measure twice,cut once |
| William Revit |
| Quite right Willy. I would measure it too. But I was pandering to Nigel's regular comments that he struggles with eyesight and measurements. But from his response, altering that cable position with the carbs in situ would be an even greater challenge. |
| GuyW |
| OK, I’ve measured it and it’s as near as damn it exactly 1”, centre to centre. |
| Dave O'Neill 2 |
| Thanks Dave, I'll measure the one on my car if I have to take it off. |
| Nigel Atkins |
| Guy, I think you'd find getting that split pin off in situ to be more awkward than you'd expect, unless you have some special surgical offset pliers or you're not too fussed how much you scratch my heat shield. I'd need a 7/16" spanner, long thin screwdriver blade and narrow-nose pliers. Getting the split pin in when in situ is a right fiddle, guess how I know, I'd be asking "Are you the split-pin?". |
| Nigel Atkins |
| Right, so, I suggested my glamorous assistant might be better than me to take the measurements and got the look that told me this wasn't going to happen.
I pulled the cable by hand and measured from the top of the trunnion nut to top of heat shield 74mm, using the pedal was 64mm (60 and 70 plus 4mm before the markings start on the ruler) this is the limit of accuracy with this tester. I've taken a photo to replicate how things are using the pedal, but I think I might have caught the edge of the box and very slightly and opened the butterfly just a bit. The gap from the throttle cam stop to the carb body was more than I was expecting but *looked* about the same to what I saw on the car (this is the limit of accuracy with this tester).  |
| Nigel Atkins |
| Nigel
Thanks, from that it's 10mm short in travel which is a fair bit Could you measure from that same spot on the top of the trunion nut to the same spot on the heat shield as it sits with it in the rest/idle position please to give us a base measurement to compare with Dave has helpfully measured his lever at 1" centres and I've asked the question to Moss how long these new ones are so we'll have to wait for them to get back with that--unless you can talk some random passer by to measure it---centre of the trunion pin to the centre of the shaft- I take it that it reached full throttle by pulling the cable up by hand--- we'll get there willy |
| William Revit |
| Hi Willy,
best I can tell 90mm (flat of the nut moves with lift and is at a point when cable is at rest). Allowing for the fact that the measuring tape is balancing on the trunnion/split pin paraphernalia and the top of the lever rod it's about 27mm so might be around the 25.4mm Dave found. No, full throttle is not reached by pulling the cable up by hand, well the throttle cams stops don't touch the carb bodies, in fact as far as I can tell it *appears to me* as the cams reach about the same level whether pulling by hand or flooring pedal. The black phenolic insulating blocks looks to be the usually available 23mm - though SU's is 21mm, listed in metric not imperial. I'm beginning to see now why the homemade one was perhaps fitted the other way round. I remember now one of the reasons I wanted to change it, the way it was before at early pedal pressing going over bumps the pull back on the pedal could give a little kangerooing! Thanks for your great interest and help and contacting Moss but mine wasn't from Moss because the original photo I posted is from Moss and I thought the part hown looked a little rough/unfinished so I got mine from MGOC and as you can see it has a flatter finish and perhaps a slightly different shape to the Moss photo. For all I know Moss might supply exactly the same part as MGOC but it's not the one in the photo if so. |
| Nigel Atkins |
| and just to humour me and keep you off the streets If you grab hold of the outer cable just above the heatshield and lift it up--roughly how far do you reckon it lifts before the throttle butterfly shafts start to move off the idle screws |
| William Revit |
| The bonnet's up and down like ... a fiddler's elbow. Just the slack in the cable and/or gap between the linkage lever fingers and carb throttle forks - about a few millimetres - it's had a precision operative working on it yer know! |
| Nigel Atkins |
| Ok---just checking, should have known better
-- you pull on the cable up out of the heatshield as far as you can but it still doesn't give full throttle--bit strange If you do that, and get as much throttle as possible can you then, while still holding up on the cable get hold of the quadrant and move it to full throttle, -what happens to the outer cable when you do this, does it move up at all I'm thinking that with it in the top hole the trunion might be getting as high in it's arc as it can get and going over centre and will need the trunion moving to the bottom hole but it's travel still seems short Think i'll draw up a giant quadrant and check this all out If you could do that full throttle thing ,that would be good |
| William Revit |
| Here's one I did earlier... (not to scale, I hasten to add).  |
| Dave O'Neill 2 |
| Just looking at that pic, I guess you would have drawn it up from something (not to scale noted) But just comparing it to Nigel's, his top hole looks a lot higher There's something not right about this getting close to midnight here i'm off to the cot willy |
| William Revit |
| My carbs and linkages are original on my '66 Sprite. A number of years ago, I was having the same trouble and I never worked out quite why. But I suspect it was after I changed the heat shield for a new one. I seem to think the original heat shield had a different shape to accomodate the throttle lever in some way.
I take the view that originality isn't as important as function. So my solution was alter the shape of the throttle lever( grind it ) to clear the heat shield. This is the result. Shown at full throttle by pulling the inner cable through the heat shield, by gripping the outer cable. Both butterflies wide open, and throttle stops in contact. Only two holes. If pulling on the outer cable results in only partially open throttles, then the angle of the throttle lever, AEA597, is wrong when at rest. It needs to be set lower, because otherwise if it is set too high at rest, then when you try to pull the thottles open, you attempt to pull the trunnion (throttle pin) past vertical. This was mentioned a number of posts back. What may stop you setting the throttle lever low enough, is the the stop on the throttle lever. Mine was hitting my heat shield so I ground it off.  |
| anamnesis |
| Thanks Willy I'll look sometime tomorrow if/when it's not bucketing down with rain.
Looking at the throttle lever I have the foot on it is less pronounced and arc to it more forward to the heat shield leaving less gap as it passes the heat shield but as it misses the heat shield so it's doing that part of the job at least. I've not got an original lever to compare against and the previous homemade one seemed to be modelled on the Moss one and the one I have and only tiny fractions out with the one I have now considering it was homemade. But this homemade one was fitted backwards perhaps I'm finding out why now. It was only today I saw SU have the insulating blocks a different colour and as 21mm and not 23mm. As I've always previously seen them as black I assume (always dangerous) that they're 23mm too and the 2mm makes very little actual difference, or not enough to be noticed, or to be concerned with. Today I was going to remove the return spring and try the spare SU sourced trunnion in the lower hole to confirm it didn't fit and I'm not going more crazy, but I had others things to do. More irony, and perhaps further proof that the homemade one was a copy from a more modern replacement part, is that the trunnion only fitted one hole on that homemade one and turning it the other way would have meant drilling the hole to enlarge it and I didn't have a drill bit of the correct size so would also have had to file the hole - exactly as I had to do with the one now fitted!  |
| Nigel Atkins |
| Hi stranger (and they don't come much stranger ...) thanks for your photo and info.
My heat shield looks standard for later models, I doubt it's an original, unless it was well refurbed, but it was on the car when I got it. Normally I'm an absolute stickler for originality but I'm prepared to let it go this once for the sake of my sanity but of course I do need to know exactly what modification is required for full function, Grinding for me is a hacksaw and file. I'd be interesting to see the angle the top of the quadrant is at on original parts to see how much lower the foot sits against the heat shield. I don't mind losing the stop foot as there wasn't one in operation until recently. I've just had a lightbulb moment I'm surprised no one suggested it before - shame on you all for being slower than me! :) |
| Nigel Atkins |
| Using that photo of yours, visualise the quadrant rotating upwards, pivoting clockwise around the connecting shaft. The highest it could go would be when the cable connecting pin comes around to fall on a straight line drawn between the connecting shaft axis and the outer cable housing bracket at top left.
(The connecting shaft axis is just visible, screened by the black fuel pipe) The difference in length from the outer cable bracket to the cable pin at the start as in the photo, and the bracket to this visualised position on that line gives the max amount of lift and therefore rotation, available on that setup. Now if you were to shift the cable pin to the lower hole, you get a longer length for the start position, but the quadrant can rotate through more degrees before the newly positioned cable pin arrives on that straight line between the connecting shaft axis and the upper cable bracket. You get more rotation of the shaft and greater opening of the butterflies. |
| GuyW |
| Yes, I did see this might be the case (if I'm thinking right) but didn't know if I would have enough pedal (mechanism) travel to make up for difference between the two holes and get to WOT? IF I've got it right, bit like photo? Cheers.  |
| Nigel Atkins |
| Basically, the butterfly - and quadrant - needs to rotate almost 90º to achieve WOT. If the throttle cable (blue line) reaches the yellow line before WOT has been achieved, it cannot go any further. Having the trunnion in the lower hole means more rotation can take place before the limit is reached, but it is still governed by the amount of pedal travel. If the pedal runs out of travel before WOT is achieved, you would need to shorten the distance between the shaft and the trunnion hole.  |
| Dave O'Neill 2 |
| It might be an optical illusion, but your heatshield looks a bit bent. If the cable mount is pushed towards the engine, it will limit the amount of rotation.  |
| Dave O'Neill 2 |
| Heat shield seemed flat when it was off the car - or do you mean the (90 degree) bent part that the cable ferrule sits in? The cable has always been tight across the fresh air trunking but there's a little slack or I could try tucking it under the fresh air trunking, neither is ideal, or do I need longer outer sleeving? I thought it was the length of the inner cable that mattered, as long long as the outer cable wasn't overtight. |
| Nigel Atkins |
| It might be the angle of the photo, but it looks bent at the top, where I've put the red arrow. If the position of the cable was moved in the direction of the yellow arrow, the quadrant could rotate further, assuming there's enough pedal travel.  |
| Dave O'Neill 2 |
| I 'think' we're all thinking the same here now that it's going too far over centre and that it needs to be in the bottom hole----but
My concern is that if Nigel goes to all the trouble of getting his quadrant out to open the hole up to swap it over and it still doesn't get full throttle ,Nigel won't be a happy chappy I've got measurements back from Moss and MGOC which was interesting one in inches one metric The plan is to draw it all up and see what works or not so that Nigel can drill a new hole if needed while the trunion is out to get it sorted willy |
| William Revit |
| Reference Dave O'Neill's comments. This is a picture of the heat shield in a very early 1980s catalogue. Notice the shape of the cable mount. I seem to recall mine was like this before I put a new heat shield on. This would allow the cable to pull the trunnion further towards the spindle at full lift; - PERHAPS. Cut off the foot and set the quadrant lower at rest.  |
| anamnesis |
Interesting. Yes, I can see it now, but perhaps not as pronounced as the illustration would suggest.
 |
| Dave O'Neill 2 |
| Actually, looking at that picture, I can't tell definitely if the cable mount is set back or forward. But it could be set back, which would aggravate the problem. Just bending it forward without reinforcement might not last. Set the quadrant as low as possible at rest. The foot limits this, as it sits against the heat shield. That's why I ground my foot off. No limp induced as a result.🙃 Update: Ah that original heat shield shows it set back. Interesting indeed. |
| anamnesis |
| The outer cable attachment point is supposed to be set back so that the pull is in the plane of the shield. If it is moved forward, then repeated flooring of the throttle will gradually bend the shield forward, putting a curve in it and a springy feel to the throttle.
Although the maximum rotation of the quadrant is achieved when the cable attachment pin (Willy calls it a trunion, I think) rises to intersect a straight line between the outer cable bracket and the quadrant spindle, in practice the effectiveness of the cable pull is reducing to a minimum as it rises around the arc up towards that point. The best 'feel' will be when the pull of the inner cable at the pin is tangential, or nearly so, to the arc of the quadrant. This should coincide with low to medium revs so the butterflies at this point will be partially open but probably not WOT. The at rest position of the quadrant (butterflies closed) is set by design by that stub on the quadrant. It could be filed, but that is the original design. The cable pin can be moved down on the quadrant simply by using the lower hole and this will bring the WOT position down the arc that the quadrant moves through. It seems to me the simplest (and reversible) solution. I am also not convinced that a standard spec road engine would benefit from butterflies that open to be fully flat in the carb throat. it may be ideal but few degrees off that isn't going to be a limiting factor on a standard engine. The rotation needed is quite a bit less than 90 degrees because when closed, the discs are a fair bit off from 90 degrees across the carb throat. They close probably at 10 to 15 degrees, so a rotation of around 80 degrees, possibly a bit less is needed to achieve WOT. |
| GuyW |
| Although I altered mine to achieve wot, in practice, who needs wot on the public roads? I guess I felt I did a few moons ago, but not these days. Perhaps in standard spec, the butterflies never actually fully open anyway. |
| anamnesis |
| To answer Dave and an-am(I) query the shield, as best I can tell as I didn't have a suitable sized straight edge that I could fit there, isn't bent or twisted other than by design.
The shield at that point is bent formed and shaped to provide strength there. I think the radiused edges there and the angle of the photo exaggerated the effect of bending. These photos give a little more info to this but it's difficult to get a good overall shot with the shield fitted in the car. I did think about getting a 135 degree ferrule for the cable but have never got around to it and thought it might tap the rocker cover anyway.   |
| Nigel Atkins |
| Standard setup. Spring in bottom hole. Foot rests against the heatshield with a minimal gap. This is the limiting factor. Hence I ground my foot off. But perhaps it was never intended that the butterflies open fully, because as described by Guy, it isn't neccessary for full power, or any that makes an appreciable difference?  |
| anamnesis |
| But wait; -- what does Vizard say? He makes much of the butterfly and the obstruction it and the shaft/screws cause. See pages 111, 112, and 113. This suggests that having the butterflies open as much as possible, is actually worth it.   |
| anamnesis |
| As I was able to get on to the car early this morning I got on with Willy request and the answer was no but I did it slightly differently.
I thought before it'd sound silly and irrelevant if I mentioned the three new springs seemed very strong for what is required even allowing for stretch with age and use but as they make hold the cable up by the outer sheath and measuring a bit of a hassle for a weakling like me without mechanic's forearms I thought I'd see what happens if I removed them in sequence. With all three springs removed and a blue brick (from the neighbour's front 'garden') wedge behind the brake pedal and with an ordinary brick bracing against the I had the pedal fully depressed (well as much as I could tell) and see photo below for result. Green arrow to cam stop against carb body meaning butterfly is fully open. (Red oval is another mark where I was trying to work out best fitting for SU supplied throttle lever but that's a wholeeee other story, best left). I also note I should had filed the edges of the snipped split pin. Replacing the throttle return spring lifted the cam stop a little, and refitting the two carb return springs without the throttle return spring lifted the cam stops to about the position mentioned in previous posts and previous photo. Having refitted the throttle return spring, closed the bonnet, gone indoors, took my coat off I then remember I hadn't tested to see if the (SU supplied) throttle cable trunnion fitted the lower hole, at the risk of dropping it in the engine bay/chassis/peebles - it didn't.  |
| Nigel Atkins |
I hate to say it as I think I know the source but that isn't a very accurate illustration, as a precision operative I think whoever drew that was having a go at another department or having a laugh. Only now that the drawing is blown up so that I can see it more do I see why it's never looked right to me. |
| Nigel Atkins |
| Ah ha. As Clouseau might say, "the case is solve-ed then? ? https://getyarn.io/yarn-clip/f1977ae0-6b72-42f4-911d-9de81ed60cdf |
| anamnesis |
I think I'd be tempted to drill a new hole ;o)
 |
| Dave O'Neill 2 |
| Anam, that drawing has mislead you, the foot rests against the heat shield without gap, the feeler gauge is withdrawn and the gap should then be between the throttle lever linkage fingers and carb cam forks if you done it right, see the text in the book. Not often I can give you instruction, usually the other way round - but I'm now a precision operative (well that's what I tell Willy). I take nothing from Vizard as he's never worked on my car! :) |
| Nigel Atkins |
| Yep, understood that once the feeler blade is removed, the foot sits against the heat shield, thus preventing the quadrant being set at a lower level. I found that prevented me getting wide open butterlies, and hence I ground off the foot to set the quadrant lower, and thence obtain wide open butterflies.
However in your case, your latest pictures suggest that you are in fact getting wide open butterflies, as shown by the throttle stops. Which is why I thought the case is solve-ed. And perhaps if I had investigated further, I need not have sacrificed my foot. ;-). The question is now, why the springs are able to pull them closed a little, because as long as the pedal is held firmly down -- (the cable should be taut --), the action of the levers between the forks, should keep the butterflies open. |
| anamnesis |
| Nigel
First off thankyou for taking the trouble to get the measurements I was asking for It was all to determine how much travel you were getting and what's available, I was into drawing it up thinking doing this is going over the top a bit, but then you posted that last pick with the springs off and it answered the question so it's in the bin. Congrats on your measuring though, I asked Moss and MGOC for the specs of the quadrent and got 27.5mm for both holes from Moss and 26.75 top and 27.5 bot. from MGOC, so your 27mm is right in there Now that you have answered the question of what happens to the cable at full throttle held on manually (nothing) and you have put the picture up at full throttle with the springs off, it's obvious what's causing the trouble If you look at your springs off pic. -with the trunion in the hole that it's in (top), the arc of that hole as the throttle is pulled right on is getting up around the arc too far and the trunnion travel is topped out causing the cable to pull in a straight line to the throttle shaft ,all it's doing is trying to pull the whole shaft straight up, there's probably still more travel left in the cable/pedal but it can't do anything with the trunion up around the corner like that "The trunnion needs to go in the bottom hole and all will be well" Dave's mentioned drilling a new hole and that's what I've been thinking as well, but now I think there is probably more travel left in the pedal so it won't be necessary, -There is also a little bit left in that pedal adjuster if needed but i think if you go to the bottom hole it will be ok as is You'd think they wouldn't be selling these quadrents if they didn't work so shouldn't need extra holes really--The quadrent itself looks good, the angle of the stop fits the heatshield spoton and the arc clears ok --it's good For me i'd get it out and open that bottom hole up to fit your trunion in there, refit it and adjust that cable up and i expect you will get full throttle The throttle butterfly moves through 77 degrees from zero to hero and needs 28mm throttle cable travel on that 27mm lever length to get it You've measured 26mm back earlier and there's probably more there that can't do anything because the trunion is topped out in it's arc--I think she(or he) will be good in the bottom hole willy The pic of the feeler gauge under the edge of the quadrent in that sketch also shows a fault, not the position of the feeler but the position of the trunion at what is supposed to be the idle position--it's way too high, above the shaft when it should be way below- |
| William Revit |
| This picture posted by Nigel, sugests he doesn't have a problem with the quadrant. The throttles can't be opened any more than this. Green arrow. If the springs when re-fitted are pulling the throttle closed a little, then the cable isn't taut. Or possibly the brick used for wot, wasn't heavy enough to resist the pull of the springs, but a lead foot would be.  |
| anamnesis |
| When I said the centre to centre distance was near enough 1", it was actually 0.989" or 25.12mm, so not 27mm. |
| Dave O'Neill 2 |
| All good Dave, it's all within a couple of mm so not an issue really, if it was 5mm or so different i'd be thinking drill it, but it'll be ok in the bottom hole
an---, have a look at the pic again, it's in the full throttle position there but there's no way the cable can pull it into that position with the trunion up around the corner like that-it's only gone there because there's no resistance with the springs off "Roughly speaking" the line through the throttle shaft and the trunion should run at a rightangle to the cableat around half throttle--so with (round figures)80 degrees of throttle movement all up the line through the lever to the cable would idealy be 40 deg down at rest and 40 up at WOT NOT up there parallel to the cable at WOT where it has lost all it's leverage/action |
| William Revit |
| I don't see what the issue with drawing D6 is, unless that the feeler blade appears to get in front of the throttle cable? But the instruction is clear enough - its just a method of getting the butterfly lever pins correctly positioned between their forks when the throttles are closed.
I know Vizard makes a big deal about the butterfly even down to feather edging the disc (yep, done that) but he is talking about modified engines looking for that extra tenth if a hp. Not Nigel's car. But I am now lost about why putting the springs back on in turn is now preventing spindle from turning to meet the cam stops (green arrow). Are you suggesting the springs won't extend any more, or simply that your brick (AKA foot) isn't heavy enough. If the latter, then I suppose there has never been a problem with the carb set up all along. I also think that those stops are an extreme position added to prevent the brass butterfly discs from going too far round and beginning to close the throat again. If the lever bit doesn't firmly contact the stop ledge it doesn't make that much difference, it just needs to be close. From the way S.U s were designed, if that was important they would have had adjusting screws fitted there as well! |
| GuyW |
| What really gets me is how clean these carbs and all the nuts etc are! You would think this car is never driven. They are as clean as my new ex Burlen workshops set that I have in my Frogeye. |
| GuyW |
| anam,
despite the sheer joy I was in squeezing myself into the driver's foot well I can't guarantee the double wedged heavy 'blue' (damp course) brick had the cable at full stretch. I even removed the rubber overmat despite previously giving it a cut out to allow for the pedal link after Rob's (?) post. My glamorous assistant was previously putting the pedal-to-the-metal, whether with a sufficiently heavy foot I can't be sure but it wasn't the occasion to suggest changing roles despite her being better for the more intricate observation than I. Despite the cable looking taught, in the photos, to some I had allowed a little slack both ends but only just enough - operating with precision. I expect Mr Vizard will be on the phone to me now this is known. |
| Nigel Atkins |
| Dave was measuring an original item, mine is modern made. Would the 2mm deeper insulating blocks relate to the difference in the modern made ones, or just errors in copies, or did the dimensions change over time. Bear in mind the MGOC and Moss modern made items have different measurements to each other too. But Dave, what battery was in your Vernier? :) |
| Nigel Atkins |
| Under pedal to metal conditions, the cable will be taut in proportion to the spring strengthen won't it? That's why I mentioned it, and questioned why the throttles should back off a little only because the springs are refitted.
Yep, I see the point about the trunnion pulling in a straight line to the spindle. But Nigel's picture clearly shows that the lever between the throttle forks, has been able to pull the butterflies all the way open. If just adding the springs results in the throttles closing a little, then they are themselves exerting pressure on the levers via the forks, and either taking up slack in the cable, or stretching it, or lifting the brick, or lead foot. How much EXACTLY? As I say, I am not now convinced there is a problem, or for that matter, that I needed to cut my foot off. I should have checked more perhaps; but no matter because it works. As for vizard, my 1275 with a standard cam and head, at 20 thou overbore, definitely benefited from better airflow via stubstacks, so I think it's reasonable to also accept that fully open butterflies make a difference, albeit not much, and probably not noticeably much. |
| anamnesis |
| Guy,
when you've been messing with those carbs as much as I have seeing D6 blown up to that size the anomalies jump out at you (one). I've never been worried about if I can't get absolute complete WOT and no idea if I ever had on the car, but the butterflies didn't open as near to it as I'd expect even if they never do. Only my thought, I'd expect they should go WOT but not necessarily give much if any gain. At an appropriate time I will try to persuade my wife to look at the throttle stops whilst I press the pedal with my previously proven heavy foot - but she already thinks it's 'sad' that she can identify car parts and identify faults from the noises they make on the car and all much better than me (though that's not saying much - unless it's twin HS2s). Some of the parts are new SU Burlen, and sadly yes they're remained far too clean from far to little driving recently. But please note the fly on the rear insulating block, he hitched a ride a while but hasn't been removed by cleaning anything. Must remember to include a photo of the clean, red (and black) air filters for Willy. |
| Nigel Atkins |
| An example of chaos theory perhaps? A pair of butterflies beat their wings in Northampton, and the result is 114 posts as of now. 🤣 |
| anamnesis |
| ETA: they only beat shut or there'd be 230 posts!
I weight tested the old return springs and some 'Jaguar' springs given to me but can't remember the figures now. I decided to replace all three again as one was so brittle I snapped the hook head part off when I tried to straighten it from being a bit twisted. I decided to buy the best looking ones from other than the previous supplier and when I fitted them I *thought* they *seemed/felt* stronger but didn't test them and now I've built so much muscle from fitting them I hardly notice. |
| Nigel Atkins |
| I will try my foot to the pedal just to confirm things. - BUT - Is it the consensus that I should drill and file out the lower holer so that the cable trunnion(s) I have fits into it precision fit cable and linkages and see if butterflies open enough not to have sleepless nights over WOT? |
| Nigel Atkins |
| 230 posts? 😆. I think before drilling, you should ensure a have lead foot hard on the pedal, and then press back on one or both throttle levers, and measure the resultant gap under the throttle stops. |
| anamnesis |
| Clean Machine Are you sure you haven't been buying new carbs Nigel? These don't seem to be the same as the one you photo'd earlier sitting on a cardboard box. Not you, the carbs. |
| GuyW |
| Guy, that is just an old carb I use when giving tutorials. :) At some point I needed a lid screw for some reason so I asked a mate with a stack of old MG parts and he gave me a spare set of carbs to take my pick from, I keep forgetting I've not thrown them out - he uses Webbers on his MGs. |
| Nigel Atkins |
| Ah good. Explains away that puzzle! Naturally you will realise that I am very much in favour that you should maintain a large stockpile of used, duplicate and sometimes completely knackered OEM parts. |
| GuyW |
| I do, they're all on the car! |
| Nigel Atkins |
| I said "Darling get your coat on I'm taking you out."
"Now stand at the wing so the drizzle doesn't blow into the engine" and she did, too used to too many roadside breakdowns over the decades" We started with her at engine end and me pressing the pedal (out of the drizzle) but the cable wouldn't move when she lifted it and she hadn't the strength (or more likely technique) to push the cams round. As she said she pushed the pedal hard down last time we swapped roles. I couldn't pull the cable up any further, so that was confirmed. I could push the cams to their stops though. Thank you all for all the help already. I think I will try removing the lever and linkages again and drill and file the second hole. I think technically (as if I know about maths and engineering) Dave's idea of a third hole slightly inboard between the other two might be more Vizard et al but I don't fancy a third hole so close to the other two in what might be poor quality material, and I could always add it later if required. Once I've done that I can get the mixture a bit nearer, then try adjusting the timing so I can play with the mixture again. Then on to the engine and/or suspension, I'm not going to have time for driving but at least I'll discover just how many tools boxes I have, and extent of borrowed tools. But where did I put that trunnion spring link and creased washer(?). |
| Nigel Atkins |
| Its not actually visible in any of your photos, but I hope you are not clamping the throttle cable between its nut and the quadrant face? It needs to rotate freely so the wire must be gripped between the washer and the nut. And the pin must also rotate easily in its hole in the quadrant so don't pack it over tightly with washers even if it looks neater that way.
Also, looking at your earlier photos taken from the front one can see that with the cable pin in the top hole, by the time it moves around to its limit, i.e. when it lies on an imaginary line between the outer cable bracket and the quadrant pivot shaft, then the straight edge of the quadrant will be standing vertical. This is exactly the condition in your later photo when the springs were removed, indicating that although the photo angle doesnt make it clear, the cable pin is on that line and at its absolute limit of rotation.The cable pull as it nears that extreme is furthest from tangential, so it will take a disproportionate effort to pull the quadrant round fully to that position. Fastened to the lower hole will give a more direct angle for the cable pull as it nears the WOT position. |
| GuyW |
| Well I think you should join me. Cut yer foot off. 🤣🤣 |
| anamnesis |
| Before you commit to taking it apart and enlarging that hole, test it first. Just feed the end of the cable through the lower hole, and clamp it in place on the other side of the hole, with a small electrical connector block. If that does the job, great. If not, you haven't wasted so much effort. |
| anamnesis |
| Guy,
thanks, the nut goes against a coper washer no less, then the cable against the hex section on the pin which very inconveniently is narrower than the previous one more difficult to get a spanner on to stop the spin spinning when tightening the nut or try to fit a split pin in situ to never come off requirements. I've actually got less on the trunnion pin than it came with and I have a selection of different thickness washers I can utilise, all gaps are to fingernail clippings (not mine though). I was confirming the testing as requested on the cable and throttle lever, even when at the car its difficult to tell angles with other sloping angles around and having to stand at a certain point to be able to lift the cable and not sustain further injuries. I am just the wrong height to bend my back comfortably to fit between the wings, rad grille and underside of bonnet, when I get backache it can aggravate other ailments, injuries and other elements of crumbling old age. Sitting in the driving seat whilst driving the car is the most comfortable and least stressful to my physical and mental health. |
| Nigel Atkins |
| anam, good idea (not the one about cutting a foot off) subject to fiddling and farting about factor as it's a congested area, but why didn't you come up with this a lot sooner, you need more mental exercise. |
| Nigel Atkins |
| I wasn't suggesting that you check those quadrant angles on the car again. I was saying what the photos you have already taken and posted confirm.
Good to hear you have attached the cable correctly. I thought you would have! I like Can-am's suggestion for a temporary fixing of the cable into the lower hole. I suspect you would also find that the small nipple type of cable clamp that S.U use for the choke cable would be small enough to use in your undersized quadrant hole. I presume you may have one with that spare carb of yours. Something more to look forward to tomorrow 😄 |
| GuyW |
| Guy,
I knew what you meant even if it didn't seem that way and you're best to check and confirm anything I've done as I do make lots of stupid mistake and don't really know what I'm doing anyway, I'm just cheap and normally readily to hand. I have a brand new SU supplied trunnion pin, it's just a hollowed out pin with a thread run down it and a hole cross drilled through for the cable, a small, quite loose threaded, screw goes down the pin the hold the cable. It's the same one as they use on the choke cable. On this brand new SU supplied trunnion pin I had to debur both sides of the drilled cable hole. I didn't like the idea of this holding the accelerator cable, imagine if it broke as I was overtaking a brace of Bs! The SU supplied trunnion pin is the same diameter as the trunnion on the car now and the trunnion I removed from the previous throttle lever but it won't fit the lower hole as I've checked three times now, I don't trust myself, with good cause, and I forget but I also try to check what I've already doubled checked - but more often than not forget to check at all. I only got two mismatched carbs, unfortunately no linkage or other controls, but then I only asked for one lid screw. And I realised after posting I spelt Weber with two bs, I know someone with that spelling of name. |
| Nigel Atkins |
| Have you got it in the bottom hole yet----
to answer Guy and Peter ,the quadrent is good,it fits the heatshield perfectly and rotates clearly round to full throttle The issue , THE only issue is the trunion is mounted too high and needs to go in the bottom hole to get good action , With it in the bottom hole the initial opening of the throttle will be slightly faster so will feel 'sharper' when driving and full throttle 'will' happen The driving feel will be much better than where it is now All this stuff about springs is nothing what's happening with the trunion in the top hole is that the trunion is going over centre or close to it and getting to the stage of being a straight pull , while the springs on the other hand are on the rotating quadrant and are trying and being successfull at pulling the quadrant back aroud The fulcrum is being pulled sideways back while the cable is trying to go up----won't work, it's like trying to open your door upwards while the hinges go sideways Nigel Just get it in the bottom hole, it'll be fine No need to go drilling another hole, it's only a mm or so and you've got more than that in pedal adjustment if really needed but i don't think it'll come to that congrats to Dave also for his dead acurate measuring but to be honest and with all due respect , his lever also is an unknown ,did it come from a midget etc. it was in a box of bits I can't wait till you get it done and drive it, I expect you'll notice the difference from being a bit on the sluggish side to being how it should be |
| William Revit |
| Mental exercise? I'm already mentally exercised, cuckoo's nest style. 😉.
Great idea, I didn't think about the choke cable clamp. I'd be very surprised if when I had this problem, I didn't try using the bottom hole myself, before cutting off my foot. Thats why I suggest a trial run. Actually I cut off way more than I needed too. I think just a couple of mm off the foot would probably be enough to drop the quadrant below where it sits now, to achieve wot at full pedal press. And that retains the bottom hole for the spring, which I find is easier to fit in the bottom hole. Maybe that's why I did it that way. It was a long time ago. But in whatever way you skin this cat, as long as you have room to swing it afterwards, it won't get your tongue or eat anymore canaries; -- or butterfies. 😊 |
| anamnesis |
| Willy,
unfortunately I can't do much until the weekend, when heavy rain is forecast. The problem as I see it is replacement parts, you kindly found out for me that the specs of the quadrant as Moss at 27.5mm for both holes and the MGOC one I have as 26.75 top and 27.5 bottom. Do I guess that the one I have with the bottom hole more inboard is better in this application - but the bottom hole was originally for the return spring not the trunnion, and the two holes are too small for the trunnions I had. Do the 23 instead of 21mm deep insulation blocks make a difference, is it them or the throttle lever or a combination of both. Replacing simple parts like these should just be undo, replace, do up, not all this farting and fiddling about to get the job done properly. I now understand why it was previously the way it was. The springs were just an aside. But all is not lost the air filters got cleaned - just think of the first power run after all this is finished. I must correct Guy I don't dealing in tenths of hp but tens! :) |
| Nigel Atkins |
| anam,
in effect my previous homemade throttle lever was footless as it faced the other way and for a long time it didn't even have a return spring on it until DavidS mentioned it. For now I'm with the lower hole, if I can find the other trunnion parts, stored safely somewhere but I forget where, one of the fasteners boxes I hope. One thing I meant to check but have forgotten to do so far is that the throttle return spring sits at a reasonable tension on the trunion swinging link bar, I'm sure it will but I was sure I'd got plenty of engine oil until I went looking for it to find I'd used it the year before. |
| Nigel Atkins |
| Nigel
Mate, you're overthinking it all, to me it's obvious what the issue is and with the trunion fitted to the bottom hole it's going to be all good The thickness of your spacers are fine Your quadrent doesn't need anything cutting off it to wreck it,why buy a new quadrent and chop it up, it's good as is, it butts up to the heatshield perfectly as is and gets full throttle without binding on anything and clears the heatshield fine The closest thing i can think of to explain what's happening is that if you stand at the front of your car door and open it your arm (pretend throttle cable)will pull round nicely and open the door right open Now if you stand back towards the back wheel and try and open the door your arm (pretend throttle cable ) is pulling the wrong way against the swing of the door and you can't get it open far This is exactly what's happening with your t/cable in the top hole, the cable's pulling up but the trunion is trying to go accross when it's up near the top---Lowering the starting point into the bottom hole will also lower the finishing(WOT) position and prevent it getting to this over the top of the arc position It will fix it That centre spring--as long as it has even the tiniest bit of tension it will be fine--all it has to do is help return, you don't need it to be stetched/tensioned right out |
| William Revit |
| Hi Willy, no I've got it, you might have missed a post, or part of, the very few posts I've put here. I'm not going to get another throttle lever and I don't want to remove or alter the one I've got but I will to get the trunnion and spring fitted to the lower hole. I'm sure the throttle return spring will fit and it could do with less tension, the carb springs only seem OTT for what's required. And I fully expect that to work, if not I know my options.
I've already pissed about with an SU supplied lever that wouldn't work as it should but that's another story which I've not bothered with here as who's going to believe a sacred cow like SU Burlen sells products that are less than perfect, but they will believe the usual suppliers sell products that are wrong which my lever might or might not be, I don't know for sure. I know parts can be piss-poorly made, I might have said so before, but I still think they should be made properly, I know, I know, but I wouldn't expect to buy a pair of trousers with one leg shorter than the other and then have to walk around with a limp to get the hems level. If I done that I'd end up going round in circles, I've got throttle levers to give me that type of exercise. :) TBH I don't expect to notice any difference on the road but I want to have things best they can before a rolling road set up. With that I might even go for ego figures, I'll take my own graph along and get it plotted into the program and print out, I've decided on orange and purples for the lines, one high and flat other flying like an arrow off a turret. I know I'm alone here in thinking that other than safety there's nothing that serious or of any real importance, with cars. They're just (not so well formed) lumps of metal to me, how they feel to me when I drive them is all that matters. If I had a brain in the time I've had this Midget I could have had a fleet of MX-5s, no hassles, and lots more money in the bank or wasted on ale and Driver's Handbooks. :) |
| Nigel Atkins |
| A fleet of MX5's--is that a shudder i felt going through me- My son has a MX5, which doesn't get much road use, It's parked up broken at the moment and has been for a couple of years now waiting for parts to fixit. Magic car when it's going but fragile |
| William Revit |
| Willy, my fleet would have been kept more or less standard. A chap that lives on the road we walk to the shops on literally had a fleet of them parked on his drive under individual covers, but he owns a car repairs garage and you know how many spare cars they collect, or race, and their nice homes despite the tax office knowing they've not two-happ'nys to rub together. :) Or two helicopters for sme 'poor' farmers. :) |
| Nigel Atkins |
| I hadn't realised I've wrecked my quadrant by cutting a bit off it. And yet, it all functions PERFECTLY, including at wot, fully open butterflies. Guess it can't be that much of a wreck then. 😉. Plenty of ways to skin a cat, and get the same satisfactory result. |
| anamnesis |
| Willy "congrats to Dave also for his dead acurate measuring but to be honest and with all due respect , his lever also is an unknown ,did it come from a Midget " Yes, it did come from a Midget. "Your quadrent doesn't need anything cutting off it to wreck it,why buy a new quadrent and chop it up, it's good as is" We've already established that the holes are the wrong size, why would we assume they're in the right place? |
| Dave O'Neill 2 |
My apologies if I've offended you Dave, that was definitely not my intention |
| William Revit |
Well it's done, I can't tell you the fun and joy it was, only the 'fun and 'joy'. For any ordinary and sane readers out there I can list the 'joys' but as the usual lot will see it as whinging I won't now.  |
| Nigel Atkins |
| For Jeremy, not just slack but slop I let in, I took a little out pedal end but still plenty of slack between them. Don't ask about the angle of trunnion pin or I will tell you, at length, you have been warned.  |
| Nigel Atkins |
| For Willy, foot against shield, and cleaned filters. Don't ask about the throttle return spring or I will tell you, at length, you have been warned. BTW, I wondered what that mark was almost in line with the cable, then I realised what is was, don't ask or I will tell, at length, you have been warned.   |
| Nigel Atkins |
| Yay,that looks better,well done that man, been on the road with it yet-
NOW, tell the details of what's happened in this exciting little episode--- My guess is you might have fitted the little spring plate in with the cable under the nut and it all jammed up on the heatshield and you had an oh poo moment and had to pull it all apart again or struggle with that nice splitpin to fit it back to the other side Congrats on your final result and nice clean filters willy Just out of interest ,if you compare that single pic in your 2nd last post with the sketch back a few posts -Posted 30 September 2020 at 11:48:11 BST of the feeler gauge behind the stop on the quadrant you can see where your trunion is now in the correct position but in that sketch it's way up above the shaft ---like yours was Hope wifey has a relaxing week |
| William Revit |
| That's better Nigel. Well done.
Clearly the two - hole quadrant is an emissions testing cheat device, predating the VW/AUDIE attempts at this by some 45 years. Upper hole only gives partial throttle opening for the test cycles and lower hole for selection after purchase! It will be interesting to hear what you think of the throttle response. It should feel sharper possibly almost to the point of a jerkiness at low speeds or in traffic. Who knows, you may decide to revert to the original arrangement now that you have concluded this little experiment in the name of science. BTW, the new carbs on my Frogeye are the same. i.e. 2 hole quadrant, cable in top hole, pulling quadrant over to highest point and then giving only around 80% butterfly opening. |
| GuyW |
| I'm still convinced the quadrant isn't made correctly as I had to drill both holes out plus other issues.
There may be other variations with other parts from original like those black insulation block spacers but I don't know. Using the link tag on the bottom hole meant the spring attachment point was, at a sheer guess, only 7/8mm lower but that was enough to take the tension out of the throttle return spring which meant shortening it (after experimenting with another spring and the fun of trying to get it installed). I put the link tag on the other side of the trunion to the cable attachment with the quadrant between them which causes the trunnion to be pulled down lopsided by the return spring. I thought I'd picked up and used an oversized drill bit but on checking the holes I made are a fraction smaller than SU use. I may have to try to do as Guy suggested earlier and remove the trunion in situ and place the link tag on the same side as the cable so at least the tension on the trunnion through the quadrant hole is more even when the cable is in use (plus as is looks too much of a bodge after all this). I left the split pin a lot more open this time round. So I do hope it doesn't then jam against the heatsheild! I've not even pushed the pedal let alone drove the car, but my wife said the accelerator feels a lot better than it did before, more positive. She was very contented as two days of shopping and two times of me driving back from the micropub, as soon as I saw her cider being poured I knew I'd be sipping my ale slowly. With the previous quadrant being fitted backwards, in effect same ae anam's, I think I would have got WOT but I never looked or checked. The reason I put this new quadrant on was to prevent the initial pull-off or very low speed jerkiness so I hope it's still not there or all has been a waste of time. I was hoping I'd be driving today but that's now uncertain but I will report back my finds as soon as I can. |
| Nigel Atkins |
| It would be interesting to see if people using the standard set-up, with twin SUs and the trunnion in the top hole, are actually achieving fully open butterflies. |
| Dave O'Neill 2 |
| Cat skinned well then. 😀.
Quadrant effectively upside down in my case? Yep pretty much; except that it would have to have been rotated even further back, to stop the foot hitting the shield at wide open throttle. So I opted for a foot grind, kept the trunnion in the top hole, and the spring pulling evenly in the bottom hole. Yep agreed about the standard setup. As I said earlier, perhaps in standard spec, the butterflies never actually fully open anyway because they don't need to, in order to get as near as damn it full power on the road. But many of us love refinements, aka fiddling.🤣. Albeit that some refinements are distinct and obvious improvements over factory original. 😉. |
| anamnesis |
| Now that the butterfies can be fully open I am interested if the piston can reach the top of the suction chamber so the airflow can be at max. At my standard HS it is not. Flip  |
| Flip Brühl |
| It is a very long time since I read Vizard, but didn't he say something about modifying the bottom of the piston to smooth the airflow? |
| Jonathan Severn |
| Flip If you screw the damper out of the top of the dashpot, will it go right up then, might have the wrong dampers |
| William Revit |
| Dave’O: yesterday at 19:03 - I’m using the standard set up with the two hole quadrant and with the trunion in the top hole; spring in the lower. I’ve been to the garage to see if I can achieve WOT. Initially no - until I cut away the rubber floor mat so I could bury the organ pedal in the carpet. Then I got to WOT. |
| Philip Sellen |
| Funny you should put that Flip as I was thinking that too. IIRC when testing before I didn't think the piston on mine looked as if went up far enough on my HS but I'd forgotten this with all the farting about with the quadrant. I'll check next time the air filter is off, but not until then(!). Willy, on mine the dampers *should* be correct as I got them from SU Burlen but they're not as well made as those they replaced. Unusually for me I've kept the previous ones so could do a comparison test. |
| Nigel Atkins |
| The "long" damper is a common problem*. I solved it by modifying the suction chambers AND made one of the damper assembly's shorter.
Flip *Peter B wrote: Hi Willy, on some of the larger SUs they were fitted with shortened dashpots to prevent full lift to keep power down. Seen mainly on V8 Rover engines in military vehicles to stop the 'lads' (and lasses) thrashing the bejaizus out of the engines. I haven't noticed this on the smaller sus but knowing Flip is such an animal with the throttle and always being chased by the law, maybe it is a good thing :) |
| Flip Brühl |
| Guy,
you'd have been proud of me, I released the throttle trunnion just by removing the (more open) split pin, and moved the link tag to cable side of the quadrant. It only took me about 10-15 minutes plus about another 30 minutes fiddling and farting around with relieving the tag hole to trunnion, sorting right washers and (they'll have to do) split pin(s), losing split pin whilst cutting it, refitting spring the right way round and getting the head piece fully back inside the coils, and getting the over length split pin bent and cut, and bent and cut again. (Not counting looking for the tool I was using minutes or seconds ago.) The only tools I needed were long-nose pliers, small and medium screwdrivers, magnet, wire-cutters, small pliers, 1/4" drive ratchet handle and short extension bar, 8mm and 1/2" sockets, small round file. Done but with next to no satisfaction. |
| Nigel Atkins |
| Conclusion -
- the action of the 'engine controls' feel positive on the pedal, no noticeable difference at WOT than a little before it (but my timing and carbs are only at very basic running settings and I only had a very brief opportunity of WOT). I kept the rubber overmat out of the footwell to ensure fuller pedal movement, unfortunately as I put I could only try WOT for 4 or 5 seconds because of circumstances of roads, congestion, rain showers. I didn't go on any really rough roads at low speed but at pulling off from standing or accelerating at very low speeds there didn't seem to be any jerkiness. The pedal feel was positive through the range. No doubt I'm tempting fate by putting this but all seemed alright. |
| Nigel Atkins |
| << no noticeable difference at WOT>> As I said very early on in this long thread, I think it unlikely that a standard engine, without heavy modification, can make use of that last bit of throttle opening to WOT. But it's been an interesting saga. Nigel I thought you wre going to raise an issue about me keeping quiet throughout, that my Frogeye carb set have the same quadrant, set up in the same way as yours. I was just waiting to learn from the outcome of your experimentations! |
| GuyW |
| I can't possibly comment on the various parts on custom cars (or modified as they seem to prefer now). :)
Do bear in mind my timing and carbs I've now got set at a very base level (the carbs were probably better set before I went to testing near the red of the rev counter where I never normally never bother to go) and that my car is modestly modified and might benefit from a slight bit more opening of the butterflies than was available in the top hole even if WOT was a waste. BTW I deal in tens not tenths of hp. ;) We can't be certain your quadrant is the same as the one I've got, if it matches the dimensions Willy got then it might (or might not) be. I wasn't that worried about WOT but the quadrant set up didn't seem right to me I couldn't remember having such issues in my previous Spridget. Perhaps it is spot on and I just needed to be more forceful with getting the trunnions through the holes as they were and accept how far it opened the throttle. I was honestly hoping I'd made a stupid obvious mistake rather than another part giving me problems. From my last post I delete about the other broken part I only discovered today, but as we're moving on, a new modern made part that was a warranty replacement for the new modern made part that broke more thoroughly. I know you will be using as many original parts as you can but I pity anyone restoring these cars now as with very, very few exceptions you can't fully rely on the manufacturers or suppliers. |
| Nigel Atkins |
| Flip
I thought you had sorted that out They are supposed to go much higher than that I can remember talking to you and Peter B about it and him mentioning the bigger SUs being limited I think it was the Rover2000 that had 2" carbs with restricted pistons Anyway- Did you have HS2 orHS4, I seem to remember you had the 4s I think but can't remember,But I think that there is an issue with non matching parts between internally vented dashpots and externally with either damper plungers or difference in length of the piston or dashpot cover and if you get the wrong combo you get what you've got there Here's a pic of a 4 fully up, it would hang in the bore by 1/2-1 mm max. at a guess And a pic of the piston guide at full lift showing it at roughly level with the top of the housing and the cutout in the damper piston to accept it I've got a feeling the difference is in how long thepiston guide hangs down in the housing but havn't got another to measure, this one has the internally vented plunger housing Happy to take some measurements if you need them if you're on HS4   |
| William Revit |
plunger
 |
| William Revit |
| Here are a pair of HS2s from a 1300GT (ADO16), from under my bench. The pistons don't go all the way up.   |
| Dave O'Neill 2 |
| You have a big bench, Dave. Is it just the 1300GT or do you have other cars under there? |
| GuyW |
| Being a precision operative in this subject may I proffer - the area of piston not retracted and the area the bridge takes up in the aperture are roughly about somewot equal to the area of the edge of the butterfly, its spindle and training screws, so giving full venturi flow of mixture. |
| Nigel Atkins |
| Guy,
bad/good/different news for you. I was able to go on a better drive today with a couple of opportunities to test the difference of WOT to an approximation (guess with pedal not fully down) of where the butterflies were open with use of upper quadrant hole. I was able to have the pedal to the metal (well, world's cheapest, thinest carpet) for a second or two to find position then lift off a little to close the butterflies a little, then hold in this bit-off position to get the effects of this position. After a sufficient time at that setting I floored the pedal and held it there for a comparison. I was able to do this twice at different speeds and gears, there was now a noticeable difference in noise and needle movement with WOT giving benefit to momentum if not fuel conservation. I might be able to confirm this later with independent professional testing equipment, but for the moment you'll have to accept or not the anecdotal evidence without independant collaboration of this rough testing. Depending on weather tomorrow I might be out with the verbal handbrake but be able to get temporary mute if driving conditions are suitable and repeat the testing - it reminds me what fun the car can be (observing responsible driving obviously). |
| Nigel Atkins |
| Intetesting. Perhaps your verbal handbrake will alter in pitch/volume to accurately indicate the degree of change in a more quantifiable manner. |
| GuyW |
| In the past there has been variation in pitch and/or volume and alarm level settings. CiderNav setting seems override and dial-down other settings especially navigational response. I drive my better half to drink in many respects. Exhaust noise seems more of a trigger than acceleration or speed, luckily the exhaust seems clogged up and/or more muted by settings at the moment. I could drive the Honda a lot faster and quicker before alarm than the TVRs. |
| Nigel Atkins |
| I feel you have a newly revived interest in the go side of Midgeting. It is your duty to securely strap said audible warning device into the vehicle, venture out onto the road, and set the volume and pitch to the highest possible level then proceed to a corner at this accurately set velocity to attempt to cancel out the warning by overriding with tyre noise. It may only be a momentary relief but the pleasure derived from this action will be immensely rewarding for yourself but at the risk of a permanent percussion induced audio infection. from this point on the possibility of a clogged up exhaust sound will no longer be an issue , any audible warnings won't be evident and so could be looked at as a value enhancing exercise |
| William Revit |
This thread was discussed between 24/09/2020 and 08/10/2020
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