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MG MGF Technical - Pinking Noise ?????

Gents , I have a problem with what I can only describe as a pinking noise. If any of you can remember back to owning a car and adjusting the timing slightly by rotating the distributor cap.........when slightly out, the engine would "pink" under load.....im getting this very same sound only under load and only from about 2300-2700 RPM.... any ideas ???
D Jamieson

You should never get "pinking" (we call it pinging in Oz) with ECU controlled spark timing.
The only thing I can suggest is that you are using fuel with the octane rating too low for the factory set timing.
As a test, just add a dose of that octane booster that is available in auto stores.
Even if the fuel you use is supposed to be the correct octane there are many reasons why it might not be.
Contaminated supply from the seller, dishonest seller adding cheaper products to his fuel. They have been known to do that in this country, adding untaxed toluene or ethanol to their fuel.

Mick

Mick
M F Anderson

Thanks MF... I may try another fuel. The UK readers may be able to tell me if adding some 4 star fuel or maybe using the new shell optimax may cure it.

Im now wondering if my ECU is going wonky :-(
D Jamieson

It is very unlikely to be an ECU problem.
The crankshaft and camshaft sensors cannot vary their position and the software program can't just simply get its calculations wrong.
If the ECU fails it is a electonic failure and all types of symptoms occur, but the software will not only get its spark timing calculations wrong.
I do a lot of software work on programable ECU's for competition engines.
For anyone interested there is a demonstration program of the programable ECU software that I use. It is at:

http://www.motec.com.au

Just go to the software section, download the small Demo file, and install.
Have a look at both the engine tuning and data interpretation parts of the program.

Mick
M F Anderson

I forgot to mention.
DO NOT allow the pinking (pinging) to continue for even a short time. Add octane booster NOW!
If you wait for your next fuelling it will most likely be too late.
Pinking is destructive to engines, it will break the top rings and cause small pieces to break away from the top edge of the piston.
The top rings shatter into small pieces.

Mick
M F Anderson

Thanks for the input MF. BUT...the pinging has been occurring since i got the car......6 months ago :-(..... as it is only for a second or two when accelerating harder than normal I let it go.

Im wondering if I have done internal damage although I cant see any other warning signs other than the noise.

I will experimant with some additives or different octane fuel as of today.


I have a tracknight planned in 3 weeks...... Should I refrain or take the gamble ??? To be honest the car has had some punishment as Im not a Sunday driver so I do have faith in the robustness of the engine. Its a 1995 MPI with 55K miles and full dealer history.
D Jamieson

I would not enter competition with it pinging. I think that you have been lucky.
Pinging at one RPM range for a couple of seconds is probably why the engine has survived.
If higher octane, or an octane booster, cures the pinging I would, on an acceptable risk basis, assume no damage has yet occurred.
A compression test would indicate the condition of the top rings (carried out dry, do not add any oil to the cylinders for the test).

Mick
M F Anderson

DJ

I know you are a regular BBS contributor and that you (a)use the car abit like the rest of us.

I cannot get a similar noise in my VVC although I probably wouldn't have too much load on the engine at those sort of revs.

I also have a bike and am used to using revs a bit and tend to do so in the F as well.

I once tried Optimax in the bike and really couldn't detect any difference although I suspect it is very different in a laboratory. Bikes tend to be higher compression ratio, higher reving and higher specific output than most cars (I'm a master of generalisation) and I would expect more fuel related problems but not in reality.

Granny, eggs, sucking etc etc but are the plugs clean and correctly gapped? are the leads clean with no obvious arcing?

You've obviously been around the block a bit if you remember adjusting ignition timing - is it pinking as we think we remeber it or is it a short duration vibration or "sizzle"?

I'm going for a blast later today so shall have a good listen and report back.
JohnP

John P..... Havent been around the block too long im only 34 but I cut my teeth so to speak owning a few 2.0S Capris in my youth with the Ford Pinto Engine.

I have to put my hand up to this and say that I have missed maybe an obvious point you raised....PLUGS !!.....why didnt I think of putting a new set in to try ? DOH.....guess what Im doing tomorrow :-)
D Jamieson

DJ,

Are you talking misfiring or pinging?
Two different things.
Misfiring, yes try new plugs.
Pinging is something altogether different.
It is when the spark occurs too early and the combustion pressure builds up excessively before TDC and the piston tries to go back down the bore in reverse. This is not allowed by the rotating engine mass and you get excessive combustion chamber pressures.
The second type of pinging is when the octane rating is too low for the compression ratio and the firing explosion is unstable, instead of a controlled burn type of explosion.
The pinging caused by spark plugs is when there is a sharp edge on the plug, usually at the exposed end of the thread.
If this edge retains a red hot glow as the fuel/air mixture is compressed it can cause premature ignition. To hot a heat range of plug can also have a glowing hot tip and do the same.
Firstly, determine if you have a misfire or pinging.

Mick
M F Anderson

Guys.....quick update.....ran the car almost dry yesterday and filled the tank today with the Shell Optimax. The pinking ( pinging ) vanished instantly and completely :-)

Thoughts on going back to regular unleaded or continue with the optimax ??
D Jamieson


Optimax: Subjective.

In theory we can't make the most out of it as the MEMS doesn't compensate for the differening octane rating. But, I felt a slight difference and noticed slightly better fuel economy. Both of these could be down to other factors.

If you have the money, it'll certainly will do no harm.

I bung it in once every few tanks when I'm feeling flush. ;-)

Have you tried "posh" branded petrol as opposed to supermarket petrol?

P.
Paul Nothard

Hi Paul , I usually fill the tank once a week so I may try and alternate between normal and optimax week about.

"Posh" fuel ?? if things go the way they look like going in the Gulf.........ANY fuel will be posh fuel if the price hikes feared come into play :-(
D Jamieson

My Australian delivered MGF has a label inside the filler area the states "High Octane Unleaded fuel Only" I have only run my MGF on Optimax and have no pinging problems, but My 230E (Which is supposed to run on normal unleaded) had a bad case of pinging some months ago. I immediately topped up the tank with optimax and have been using it ever since with no more problems. Fuel companies here have been adding more and more Ethanol to the petrol mix which also affects fuel performance and the ONLY way to be sure is to use Optimax (Which Shell advertise as ethanol free) I am not sure about UK fuel but to me your problem definitely sounds fuel related.
Phil Stafford

DJ,

As per my comments earlier in the thread.
If the higher octane fuel fixed the pinging, DO NOT USE ANYTHING ELSE BUT HIGH OCTANE.
Pinging, if continued for some time, will shatter the top rings and cause fragments to come away from the top edge of the piston.
It also overloads the conrods and bearings, as the piston tries to go backwards down the bore as the rotating engine mass forces it forwards. A very messy result in all!
I don't see that you have any choice.

Mick
(Member, but using my work computer!)
M F Anderson

Mick , I can see you have a very technical background in engines and tuning. Out of curiosity..... what would cause the ignition , ECU etc to start requiring Higher Octane to work %100 ?. I always thought the ECU software was set in stone or could it be as Phil Stafford suggests that the Fuel companies are altering the mix and as my car is 1995 with 1995 programmed ECU the tolerance for mixture is now out of tolerance.

Im glad the fault is cured but wonder why its happened to begin with. Also its more expensive to fill up now :-(
D Jamieson

DJ,

Without the full history of your car diagnosis can be difficult. You say that you got the car six months ago and it has pinged since you got it. What then makes you think anything has changed, as you say it has in your last message? The previous owner may also have had pinging, or he may have used high octane fuel.
In analysing the problem you have to look at those things that cannot cause pinging and those things that can.
The timing is set by the crank position sensor and the ECU software.
The sensor position cannot change. The program an only be changed by someone with the Rover equipment and a library of Rover software.
Was the car sold new in the UK and been there ever since? This determines if the software loaded was for local fuel types.
Companies can load different versions, for countries with different fuel (I don't know if Rover does this, but other companies do it).
Does your Owners Handbook specify a UK fuel type? Is there a label for fuel type in the fuel filler area, as is compulsory in Australia?
If you could give me some background the discussion could reach some conclusions.

Mick


M F Anderson

I'm still curious.

Could this behaviour be indicative of another problem?
Is it in fact pinking?
I'm guessing here I admit, but as far as I know all MGFs are setup to use a decent range of petrol - which excplicity includes allowing the use of even the cheapest supermarket petrol.

Only when you start playing with ignition maps via Superchips and the like should you need to be extra careful about the octane rating.

P.
Paul Nothard

will do some detective work in regards to Micks questions later today.
D Jamieson

Hmmm.

Interesting one. I'd avoid 4 star as I suspect it'd damage the cat. Where do you buy your fuel normally? I've started going to shell, just 'cos I find it better than supermarket stuff (though it's probably the same!). Also try 'mixing' the optimax with standard fuel (i.e. fill up again when half-empty with standard stuff).

You might not need to run solely on optimax. Odd though as the 'F' should be capable of running on any standard unleaded fuel.

Leigh
Leigh

Hi Leigh...... Ive tried standard unleaded from everyone. Ive never stuck to a particular brand nor individual petrol station so I cant blame a brand nor a garages dirty tanks. I will experiment with the 50-50 option and see how that goes .....although Gerry Hiorns told me he gets the same problem every now and then and cures it with optimax and it goes away for a while allowing normal unleaded use then it rears its ugly head again.
D Jamieson

Could be worth a tin of injector cleaner next time the tank is nearly empty: the optimax could be doing (part of) the same job?

Neil.
Neil

This thread was discussed between 14/03/2003 and 17/03/2003

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