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MG Midget and Sprite Technical - Lead additive in unleaded engine?

Hi,

I don't know if my car is converted to unleaded. The previous owner said it was but i've no documentation to prove it. If I use a lead additive as a precaution, what will the effect be if the engine is actually converted to unleaded?
W Headon

An expensive drain on your wallet.

No other effects have been recorded.


To be brutal, there is a very slender chance of any damage at all if the engine has run a few thousand miles on "leaded" fuel.

Leaded fuel is said to coat valve seats to protect them from valve recession even if only used for a short time.

There will assuredly be further opinions along to turn this into a debate :)

Bill 1

Lead is not realy needed
It might only slightly improve valve seat life but not in a relevant way.
This is because the cast iron is rather hard to begin with.
In alloy heads you can not live without hardend valve seats but that is because the material is a lot softer.

So don't use aditives as you most likely will need the money to put in other parts of the car
Onno Könemann

Standard cast iron seats are not up to the job of handling leadfree fuel. Flame/induction hardened seats are better but not really up to the job either. The problem is the valve and seat microweld together and over a period of time the valves recess in the head a little like the spark errosion process. As Bill says, an engine which has run on leaded fuel for a goodly length of time has a barrier to this microwelding.

The exhaust inserts fitted to go leadfree are not hardened as such, they are of the correct materials not to weld with the ex valve.

Best practice to be honest is just use the car and either set tappets regularly to prevent premature ex valve burning or just drive until the compression drops too much, remove the head and recon to leadfree.

Peter


P Burgess

Thanks for the replies.

So in a nutshell, if it turns out that the engine is in fact converted to unleaded, the additive will not be harmful, just cost a few quid extra!
However it might over time help slightly to improve valve seat life.
W Headon

To be honest I would not bother with the additive, enjoy the car and convert the head at a later date if it 'lets you know' it needs doing.

Peter
P Burgess

well this thread will have saved me a bit of money with the land rover! As I've almost reached the end of my current stock of Redex additive that was mis-priced in a garage - 3 for 27p! I bought it ALL, about 12 bottles!
Rob Armstrong

... and if you stay away from WOT and high rpm, the life of the valves/seats will be extended...

A
Anthony Cutler

>>... and if you stay away from WOT and high rpm, the life of the valves/seats will be extended...<<
true but every now and again you have to do just that or there's no point driving a Spridget

unless you do a lot of track driving or drive like a nutter all the time on the road then don't think about just enjoy yourself this issue has been rumbling on for about 20 years, most of the Spridgets are more likely to have rusted away than had head work done

treat yourself and your car to Tesco Momentum, Shell V-Power and BP ulitimate every now and again that will encourage you to give the car a good cleaning blow out every now again as well as the fuel helping things

N Atkins

Nigel
Several dutch ane german consumer testing agencys have concluded that all the v-power exeliums etc are rubbish.

Economy improvements where around the 1% mark and the cleaning action could not be proven!

So keep your money in your pocket and buy normal high octane fuel.
Onno Könemann

Tests over here seem to reckon 8 out of 10 cats prefer whiskas and Tesco Momentum....many of our race drivers use it to good effect(Tesco not Whiskas!). The Shell stuff wasnt at all happy in race cars the year before last!

Peter
P Burgess

Onno you could well be right but they normally do the tests with modern cars that have modern electronic engine management not the run-it-as-cheap-as-possble classic car owners

over here I'm not sure I know of any normal high octane other than the leading brands if I'm missing any I'll gladly give them a go

I think W Headon is better off putting in the ocassional couple of tank fulls of Tesco 99, if only for placebo effect, than continuing to pay for regular use of additives

and giving the car a good blow out now and again is probably more beneficial than harmfull and what better time to do this than to justifuy the extra expense of the high octane fuels

I was trying to encourage the habits of actually spending on the car, which the OP is clearly prepared to do as far as petrol for the car at least, and to drive the car and have fun with it

personally my car is set up for 95 octane (usual petrol here) as that's all I can normally get were I like to tour and push the car a bit harder than normal but I do 'feel' better putting 99 octane in for faster runs such as when giving rides for charity or running with faster and more powerfull cars when club touring or PH runs or with my mates in their new Porsches, though obviously I have to just let them go on the straights

I can't do a test on petrols as when I know I've paid for 99 octane I usually just end up driving quicker and I use a fuel system cleaner once a year out of habit, I accept it might be a false believe to do that but that's the trouble with believes they are very difficult for others to question and usually go against one's normal logical thinking

I think Peter best summed it up by don't bother with additives just drive the car - I was offering a half way house solution for those that like belt and braces solutions

As always plenty of different ideas
N Atkins

My mate has a Subaru Impreza which he has spent loads of money on bigger turbo and intercooler, exhaust system, special mapping etc. etc. and he says it is mapped to run on Shell Vpower and it goes like stink but doesn't run very well on anything else. So I tried it in my Sprite and to be honest I didn't notice any difference at all. So that seems to endorse what Nigel says about modern management systems. I do however, use Valvoline Valvemaster with octane booster. Am I wasting my money?(15 quid a bottle)

Bernie.
b higginson

Bernie there have been tests that say octane boosters do not

Scoobys (as far as I know) are warranted for use with V-Power a member of the clubs that works for a track day car hire company told me that the manufacturer insists on V-Power use (but they don't, sshh)

probably more of a marketing arrangement between Subrau and Shell

my BGT used to run better on Shell what'sit'sname before Optimax but that was provably more down to the increased octane
N Atkins

The only additive I use is a heavy right foot, in everyday general useage.

And a tankfull of 98/99 when I am going on a track day.

I doubt if my Metro head has been taken from a later (unleaded) car but I simply haven't noticed any tappet clearance effects on the very odd occasions that I check the settings.


Bugger wasting money on slurpy additives.
Bill 1

"Bernie there have been tests that say octane boosters do not"

That's not strictly true.

Generally speaking the ones you find in places like Halfrauds are a marketing ploy - they may claim to boost Octane by 'X Points', but the points system they use are actually TENTHS of a point.

In other words they are next to bloody useless.

The only octane boosters I know of (short of mixing up your own with Toluene) are those made by Millers.

We (legally) use Millers CVL (Compound Valve Lubricant) in the racer on top of Tescos 99 or V power and it boosts the Octane to 103.

It does rather make the spark plugs go a natty shade of orange though!


The reason we use it is as a 'belts 'n' braces' factor on a race engine that is running 11.75 : 1 Static CR - it's not necessary on a 'Stock' motor.
Deborah Evans

Here in Holland we have the expensive A brand premium fuels some are 95 other 97 other 98 octane.
And White brand ron 95/98

The additives are rubish they do not give results high enough to justify the price.
This has been tested in modern ecu cars and older carborated cars.

The only thing that does make a difference is the octane number.
Even in the subaru of Bernie's friend a fuel of the same octane rating as the one it has been set up on will make it run just as well.

I just run white brand ron98 as 95 makes my midget a bit pinkey
In our GT we mostly run ron95 and only use 98 when the engine is being pushed more (mountains on holiday trips etc)
Onno Könemann

I just run white brand ron98 as 95 makes my midget a bit pinkey
In our GT we mostly run ron95

That's A-series engines for ya ........ ;)!
rachmacb

I think we broadly have a concencus of opinion

and over here supermarkets appear to be the only places to get 97-99 octane at lower prices, unless I'm wrong

with a tank and filler neck that seems to hold about less than 6 gallons I tend to fill up where I can on route rather than looking or even taking any notice of price - unless I'm with my wife who sensibly has full information on prices but will insist on refilling as soon as possibly once the gauge goes much below half (and a spare gallon in the boot) - just because a few times in the past I've run the tank dry
N Atkins

FYI

http://www.youtube.com/watch?v=gQghB4asSnI

Cheers,
Malcolm
M Le Chevalier

Wow if only I'd remembered that I'd have filled up with Shell V-Power (one more octane than Optimax IRRC) and shredded Peter's rollers and got an ego power figure on my graph - let alone the extra psi in the tyres :)
N Atkins

Rach that is a 11.5:1 CR for ya ;)
Onno Könemann

We ran a car up on 114 Octane Race fuel last Thursday....just noticed (Monday)our auxilliary silencer has a lovely grey coating....lead oxide or what!!!


BTW Aldon Octane Booster works well and does what it says on the can (bottle).

Peter
P Burgess

Going off at a slight tangent, in response to Deborah's post . . . what is a 'static' compression ratio? Being the ratio of areas of (cyl+combustion chamber) to (comb. chamber), I thought all compression ratios are inherently a 'static' figure? Cheers . . .
Andy Hock

Static compression ratio aka geometric compression ratio is what you get from the arithemetic, and is the figure normally quoted.

But it's not the same as reality... consider;

- when you squeeze the gas in the cylinder rapidly, it heats up and so the effective compression at TDC is higher than the static figure

- as the engine turns faster at WOT, there's not sufficient gas flow in the inlet/head/exhuast to fill the cylinder so effective compression is lower(hence drop of torque with increasing revs above a threshold)

- as you run on low throttles, you're restricting the gas entering the engine (to control the torque), and so are lowering the effective compression (and efficiency; diesels are different in this respect as they are not throttled)

Gases... they only do what they want to do.

A
Anthony Cutler

Anthony is quite correct.

You then have to factor in the Valve Time Area, ie how long the valves are open.

For eg. On a racing Climax motor I am using a cam with 320 degrees duration. That is to say the valves are open for 320/360 ie 8/9 of each revolution of the crank. In order to get this to work (and produce grunt) the Static CR has to be up around 12.5 : 1 !
Deborah Evans

Anthony and Deborah - thanks for your replies, I understand what you're saying.

But I'm a fully paid-up, card carrying 'pedant' (I have to spell that carefully!). I still feel that any meaningful expression of the term 'compression ratio' is, as you correctly describe, 'geometric CR'.

I contest that a 'dynamic CR' is close-to impossible to define (and hence meaningless) because of the near-infinite variables involved in its calculation: density and temperature of atmospheric air, moisture content of the air, velocity/acceleration of gases (air/moisture/petrol vapour) at any given instance, density of petrol vapour, valve timings/overlap/ velocity of valves, velocity/acceleration of piston at any given position in its bore, engine speed, etc etc. All of the above will result in an infinite number of 'dynamic compression ratios' depending at which split moment the 'dynamic cr' could be measured.

Yes, all of the above (including the 'static CR' figure) go towards calculating engine efficiency, torque, power at any given speed, but a 'dynamic CR' seems meaningless to me.

Now having exposed my ignorance, I will now run away very fast . . . .
Andy Hock

Dynamic CR may be difficult to work out and ascribe a number to precisely, but that doesn't mean it don't exist! The effect is very real.

Best example is the ease of cranking a high static CR engine with a race cam profile. Major difference when compared with the same engine with a street cam, which will often see the starter struggle. The difference shows up in the ignition advance rate as well.
Paul Walbran

Andy, static CR is nothing else as P1xV1 = P2xV2, letting T out of the equation. It actually says little about the dynamic CR which depends, as said, on valve opening and overlap and percentage of cylinder filling.

And on the cleaning forces of expensive fuels: I almost only fill up with BP excelium, due to availabilty of high octane. And my pistons are NOT very clean...
The oil consumption of my engine is quite low, 1l for 10.000 km, including dripping ;)
Alex G Matla

Old car-mags (The Motor, The Autocar etc) in the 1960s and earlier used to quote BMEP numbers... (brake mean effective pressure) which gives some idea of the dynamic breathing/compressing capability of an engine. It gave a figure that could be interpreted broadly as a 'goodness' factor re the engine's ability to make torque, that was independent of capacity, so great for comparison between engines.

Makes you want to read the old tests again... or watch a John Bolster youtube vid...

BTW: 320 deg crank open for 320/720? (Since one cycle = 720 deg?)

A

Anthony Cutler

I think you need to keep in mind we have to have a starting point which is not abstract. We all know the effective CR varies as an engine runs and also with the different cams/port velocities etc etc.Using a static CR allows one to forumulate an engine build. No good having 13:1 with a standard cam for road use and no good running a race engine at 7:1 (unless forced induction), it is merely a starting point we can all work from and have a 'feeling' for.

Millers CVL ....Competition Valve Lubricant.....called Competition to get around rules for non addition of octane boosters for race purposes whilst allowing additives for leadfree fuel, I think people use it more as a booster than a lead replacement.

Aldon Automotive Octane Booster works very well as does TetraBoost.

The 114 Octane stuff we used the other week cost £90 for 25 litres!!!!!!

Peter
P Burgess

This thread was discussed between 02/07/2011 and 06/07/2011

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