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MG MGF Technical - Hek! what have I done?

Help ??? what have I done to my Trophy 160.
A real MGF day today, hood down giving it some whelly, showing a BMW rag top (hood up !!!!???)and a golf GTI driver a clean backend along a dual carriageway. Went to change into 5th at 120 ish and hit 3rd!!!! Declutched asap but saw 8k on the rev counter.
Now engine is very lumpy on tick over and low rpm but seems ok at higher revs?? Bent or dropped valve?
Any Ideas?? be gentle please.
Dave

spookly
me done this in mg miget {very high speck for da time}
years ago.

it Pharked the clutch big time. only a guess but it could be

1 knackered

2lost a lump ov lining

3not alinging

all answers alchol related @ present

P Sayer

Sure its just alchol, would mind some sensible feed back.
Dave

Sorry - can't be gentle as I for one hope you've done enough engine (and ego) damage to restrict your driving on public roads to responsible behaviour and safer speeds.

Mike
Mike Wilman

Hmmm, are there any odd sounds coming from the top end to suggest damage there as you suspect? Is it possible the timing belt has jumped a few teeth?

And Mike, sorry, but I can't be gentle either.
You are making assumptions about Dave's incident without being fully aware of all the facts. 120mph might be illegal (on public roads in the UK) but it isn't necessarily "unsafe" nor "irresponsible" depending on circumstances and the individual involved.
For your information I have exceeded 140mph on a public dual carriageway.
There, put that in your self-righteous pipe, then when you've voiced how negligent I am I'll enlighten you as to how and why it came about.
Bob

Sorry Bob but I support Mike. If he was on a dual carriageway the speed limit is 60 and he admits to racing other cars at twice this speed. This is dangerous and wildly irresponsible, particularly when he has not learnt to change gear yet!

Cheers

Patrick
Patrick Beet

> If he was on a dual carriageway the speed limit is 60 and he

Surely national speed limit on a dual carrageway for a car is 70?

Leigh
Leigh

Hi everybody!

Don't be angry, men!

Dave was in a German highway when he failed to change to 5th, so don't worry about his speed...

LOL.

:)
Spinder00

Mike, Patrick, and anyone else that's gonna chip in...
Give the guy a break. He asked for advice on engines. Not a lecture. He even asked us to be gentle!
Feel free to have your views (as I'm sure you will), but probably best to keep them to another non technical forum.

Dave, if it's lumpy on tickover then it ain't gonna be good at higher revs!! The high revs will most probably just mask the sound and possible damage being done.
I'd advise to get it checked asap and to probably not drive the car if at all possible.
My best guess would be a jumped timing belt. Hope it's that simple!

All the best!
Paul.
Paul Nothard

Dave,

Dave livingstone had this very same problem on his VVC the last time we went to North Weald. I'll drop Dave a line. I think it turned out to be a sensor.

Tim
tim woolcott

Hi Tim - thanks for the prod.

Dave, Bedford,

Whether this is your problem or not is still in question, but lumpy at low revs and driving fine at higher revs is, as Tim said, exactly what happened to my VVC after some high rev activity on North Weald airfield.

The problem turned out to be the VVC control mechanism. I was desperate to get my car repaired quickly as I had a track day to attend and so it went into the local MGR dealer - the result was a hefty bill for over £200 quoting "replace VVC Spool Valve and two Solenoids".

I later learnt, from my trusted specialists (Tech-Speed Motorsport) that sometimes this can occur through dirt in the mechanism and cleaning the existing unit can fix it, rather than a full replacement. I also later learnt from Dave Andrews (K-series Guru) that he had a number of spare VVC control mechanisms lying around at second hand prices since one of the performance modifications he offers involves dumping the VVC.

HTH,

Dave
Dave

very interesting ....
My '97 VVC was delivered - brand new, unregistered - with some 50miles on the clock; with significant gearbox faults and the same VVC fault as described by Dave Andrews.
Looks like someone thrashed my car before I got it (I thought so at the time, and would've rejected the car if I hadn't waited so long for it)
Thanks MG
Steve

>> Went to change into 5th at 120 ish and hit 3rd!!!! Declutched asap but saw 8k on the rev counter.<<

Ouch! :oO

Good news is that your car still runs - so that would appear to rule out anything too catastrophic having occured as a result of over-revving the engine.

I suspect that this is a fairly common thing to occur to race engines, with the wrong cog being selected in "the heat of battle"

Might be a sensor - might be something else. 8k rpm is not too excessive for a K-series (at least not for such a short duration), but 8k might not have been the highest rpm the engine achieved during this incident.

I think some sage advice is required. I'd suggest you drop Tech-speed motorsport a line - they're likely to be very experienced with this sort of problem, running and maintaining as they do, the MGF Cup racers.

Do let us know how you get on...
Rob Bell

If it reached 8k rpm, then a sensor wasn't working! It should have rev-limited at 7200 and I don't think it would have reached 8000 before the limiter took effect.

Neil
Neil

Neil, it is possible to over-rev the engine even with a rev-limiter: if you select 3rd instead of 5th and drop the clutch, you are going to mechanically over-run the engine completely independently of ignition... :o(

And going from 6k rpm in 4th to 3rd gear... you're going to see a good deal more than 8k rpm. :o( :o(
Rob Bell

ITWneilM is that the rev limiter works by removing the spark, and the spark is the signal used by the rev counter, so you should not see 8k, but if you beat the system then I spose you could (did). Anyone had a look at the speed vs rpm graphs to work out the RPM for 3rd at 120?
Will Munns

"ITWneilM" and your point is...?
JohnP - Herts

Ok Will - I didn't get where I am today by being quick witted but I think What You Meant was ....
JohnP - Herts

>>Anyone had a look at the speed vs rpm graphs to work out the RPM for 3rd at 120? <<

About 9,500 rpm Will...
Rob Bell

9.5k, not the end of the earth, my money would be on a slipped belt or the MEMS has chosen to act scared.
Will Munns

Thought the rev-limiter was fuel based, not ignition based? If so, then the engine over-speed will be registered on the tacho.

Tim.
Tim Jenner

>Thought the rev-limiter was fuel based, not ignition based?

Not usually, it is 'safer' to blow fuel thru with no spark than to risk pre-ignition due to a weak mixture.
Will Munns

>>is that the rev limiter works by removing the spark, and the spark is the signal used by the rev counter, so you should not see 8k<<
I thought the rev limiter works by switching off the fuel injectors (else you get unburnt fuel into a hot cat).
The revcounter is driven by MEMs which takes its signal from the flywheel/crank sensor ?

I would think the engine can take higher rev limits when its not producing power (i.e. when the rev limiter hits) ? although the valve gear is still cause for concern.

On a big bike, a downshift (instead of an upshift) won't overrev the engine - the back wheel will slip; a dramatic demonstration of engine braking vs engine breaking !
Steve

http://www.mgfcar.de/schedules/sb9.jpg
indicates they are seperate lines from the MEMS, but they share the same colouring (indicating they are common internally)
Will Munns

>>a dramatic demonstration of engine braking vs engine breaking !<<

Nice turn of phrase there Steve :o) And I suspect this is what will have happened to Dave's car; engine braking will have prevented the engine speed actually reaching 9.5k rpm. Probably still well in excess of 8k though.

If valve gear problems (bent valve), a compression test will tell you if there is a problem.

However, I imagine that the VVC mechanism may itself be a weak point... could mean damage to the VVC gears. A rebuild may be necessary - hence the suggestion to seek expert opinion (I wonder if Dave Andrews is reading this thread?)
Rob Bell

>>However, I imagine that the VVC mechanism may itself be a weak point... could mean damage to the VVC gears<<
Good point - 7200RPM is a low rev limit for an engine using variable valve timing - Rover could have used solid tappets and maybe got more. Certainly all tuners dump the variable valve bits...

Will - for sure there's some commonality between spark pulses and rev counter display
Steve

Can believe no-one has asked Bob for his explanation!

Okay Bob...here goes: "You irresponsible bugger, you! What the hell were u doing that speed on the public highways of our beloved green and pleasant land?"

(That self-righteous enough?)
Mark B

I was in Germany (wearing the passenger seat of a Porsche at the time) where their attitude to speed makes us look positively Miss Daisy-like in our approach to driving!
Bob

Thanks fore the feed back - car now in the dealer and I'm waiting for the bill!!
As for the self righteous comments, I do 50k miles a year on business have done for 15 years, have a nearly clean licence, No dings and able to make a well informed judgement to other peoples safetly as well as my own!! So get a life, MGF's are great fun and designed to be driven.
Enjoy - there's too much other crap about.
Dave

>>I do 50k miles a year on business have done for 15 years, have a nearly clean licence, No dings and able to make a well informed judgement to other peoples safetly as well as my own<<

Your point being that entitles you to drive outside the law at 120 mph, race, and endanger others who don't posess your apparent sixth sense for reading other drivers minds? That should stand up well in court. Er sorry no. Like the earlier contributor I too hope you have a huge bill which keeps you off the road for as long as possible.

mark
mark webster

Just for the record and to answer Leigh the limit is 70 on a dual carriageway/ M'way... unless you are driving a 'transit' (GVW >3500kg) or larger when it's 60 and 50 on other roads not subject to a lower limit..

Lots of White Van Men get caught out with that one.

ER
Ewan Ramage

Mark
>Your point being that entitles you to drive outside the law at 120 mph, race, and endanger others who don't posess your apparent sixth sense for reading other drivers minds? That should stand up well in court. Er sorry no. Like the earlier contributor I too hope you have a huge bill which keeps you off the road for as long as possible<

As I said I enjoy my car - I dont and wont put any body a risk - never have, Clear road - my risk my judgment. Do you own an MG or just wishing, if you do, just how much do you enjoy your car or is that not allowed in Leeds. I'm not suggesting that you should try to enjoy because with this atitude you will surly be a danger.
Dave

Dave, give in on this one and just drop it. :-)
You'll never change people like Mark's views on this. :-(
Paul Nothard

Paul.
I agree.
We should all enjoy our cars within our capabilities and not be a danger to others.
Dave

Hi

We all have our views on speeding.. Anyone who says they have 'never' exceeded the speed limit is most probably lying!

Problem is the law seems to take the easy route and go for speeding and not dangerous and wreckless driving...

I put it to you which of these are you most likely to loose your licence for:

1) virtually empty motorway, daylight, dry conditions doing 110mph

2) Busy motorway rush hour traffic white van man doing 85mph 10ft from the car infront.

Has everyone got a mental block when it comes to braking distances? When you do leave a sensible gap some prat either pulls out and fills it or the plonker behind you is trying to get fresh with your exhaust pipe.

Speeding is not dangerous in the right circumstances but crazy reckless driving is in all situations.. Wish the police would concentrate more on the latter..

I am sick of all the twats out there tailgating... Maybe they should reset all those poxy cameras to take pictures of the idiots driving too close at speed...

Safe driving all

Stu




Stu

"I am sick of all the twats out there tailgating... Maybe they should reset all those poxy cameras to take pictures of the idiots driving too close at speed..."

Stu,couldn't agree more - and I am a "White Van Man" !!


Jonty
John Tait

I can relate to Dave's experience, as unfortunately I went a couple of times through a similar problem. The gear change being so bad on the TF I ended up at high speed in 3rd instead of 5th whilst changing up from 4th.
The rev limiter kicked in straight away (an always very unpleasant shake). I did not see the needle going over 7000 rpm though....Since then, I have covered quite a lot of miles. It all seems fine but I do recall on some occasions (only a few), when reving up the engine, having the impression that the engine would not go over say 6,000. Then a couple of secs later it was all fine.

I can't help somehow but worry.
What should I ask my dealer to look into (just to be on the safe side, and should I not want to be telling him that I've hit the rev limiter several times by accident)? Whhat would you recommend?

Cheers,
Stephane

You should not have a problem with hitting the rev limiter in normal reving up through the gears, it's ment to protect your engine. My problem was the forced over reving of the engine because of the lower raitio in 3rd x high the road speed. If you have a rev hessitance it could be more related to Dave of Amersham's example above. There should be no problem in going back to your dealer, dont bother trying to explain or argue about the gear shift ( i'm going to get a Quick shift) just plead ignorance and describe the hessitance.
Good Luck.
Dave

Mark B...get a life mate !!....if you have nothing better to do other than act as Miss Daisy then go polish the leather patches on the elbows of your anorak. Each to their own.


regarding the cooments hoping Dave has a huge bill.....lets hope your car that probably never goes above 30mph doesnt need repair as im sure there are a lot of folk on here praying that YOU have an equally large outlay.


To make a comment like that just blew any respect your posting may have had right out the window.
D Jamieson

Speeding ... You Youngsters today don't know you're born ..:O)

I have exceeded 100 mph on UK roads on many, many occasions. All quite legally. This was prior to 1966 when the temporary experimental 70 mph was introduced for, IIRC, a six month period. Here we are some 37 years later and what are the benefits of that experiment now? Precious little.

Back then, if you did 70 mph on any road it was very unlikely that you'd have 40+ tons of "just in time" over-loaded articulated truck or white van man a metre or two from your rear end as frequently happens today. That is very dangerous, far moreso than merely exceeding the speed limit in most circumstances. In 44 years of regular driving, perhaps on only two occasions have I been in any danger as a result of someone speeding. Lost count of the times when I was in danger from other examples of bad driving such as tailgating, tailgating and tailgating. This is by far and away the most under penalised dangerous driving activity of all on our modern roads. Combine tailgating with simultaneous mobile phone use and you have the perfect recipe for disaster, often on a masive scale. It is so frequent with so many "professional" drivers now chasing money on our roads, trying to make near impossible appointment dealines you name it, is it any wonder there are sooo many motorway pile-ups. I've witnessed two of these from a distance. Both were due to tailgating by drivers who are not half as clever as they think they are.

Said it many times and it's worth repeating. We've become a nation who excel at getting it wrong ...... when it comes to penalising speeders in preference to tailgaters and other bad driving practices which we all now see every day on our roads, we've got it wrong in spades!

Worrying thing is, I see no evidence of any change in the thinking by those who do have some say in these matters.

Back to the original reason for this thread .... possible over-revving of an mgtf engine. Sure thing - to get 3rd from 6,000 rpm in 4th is a recipe for severe over-revving leading to possible engine damage irrespective of any rev-limiter or other restraint. The cars momentum is driving the engine remember and not the fuel.

Bent valve(s), slipped belt, or worse ... There are many possibilities. Plenty of sound advice already but you've made a good start. However, get AT LEAST TWO professional opinions from those who know these cars before deciding on any course of action..... and do it soon. Driving it meantime could make things worse.

Good luck.

JMcF

John McFeely

Lets get back to the point of the mechanical diagnosis and refrain from acting as the Speeding Judiciary .
D Jamieson

Dave,
Is there something I am missing? Going from 4th to 3rd instead of 5th at 100mph is not normal reving up but really forced over reving, isn't it? Which is why I am getting worried...but if you say that the rev limiter kicking in is good enough to keep the engien unharmed then great!
Stéphane




Stephane

Probably jumped on the timing belt without bending valves ,hopefully.
Mike
mike


The engine "rev limiter" cannot protect from, as John points out, the car's momentum from pushing the engine way over the rev limit.

So, if you ever drop down a gear when at peak revs of the higher gear... then you're a bit stuffed really! You get all sorts of "breaking" as opposed to "braking" (thanks Steve!).

The consensus seems to be don't drive the car if at all possible, maybe you've been lucky and there's nothing wrong at all, maybe a slipped timing belt... or finally bent valves.

Either way let us know how you get on.

P.

ps. John McF: nice post! Couldn't agree more. :-)
Paul Nothard

This thread was discussed between 31/05/2003 and 06/06/2003

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