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MG MGF Technical - Black soot residue on exhaust

Hi, Ive started noticing a black residue on bottom side on my exhaust i know its supposed to get sooty but its a little odd as it hasnt done this before. Anyone care to explain and reassure me?


I cant explain or reassure you but I washed my F last night (1998 VVC Abingdon) and I noticed that it had soot over the exhaust and under the tailpipes on the rear valance!!
Kevin s

Mine always gets this to some extent. Probably nothing to worry about unless you see blue smoke or you are using excessive amounts of oil...
Rob Bell

Not a sign it's running rich?
Bob Millar

Could be. Although my car's been on RR more often than most, it appears bad luck has always been in the way of getting a good lambda trace at the same time :o(
If my original FPR is overfuelling, I'd be surprised - but maybe there are gains to be had...
Rob Bell

I have black soot on one exhaust but the other is very clean, also noticed the clean one has a valve of some sort, can anyone tell me what this is for, its an mgtf Sunstorm that I now have,this valve was not on my last car which was an R reg F
Gordon (Lincs)

It's a noise control valve Gordon, designed so as the car can have a fruity sounding exhaust system, yet pass drive-by noise regulations.

You can easily disable the valve by disconnecting the loom plug:

We didn't see any power gains by doing this at Emerald, but the car certainly sounded better! :o)
Rob Bell

Thanks Rob ... is the valve operated by the engine revs or by some other means ? if its the revs when does it open ?


PS. not posted for ages as have been playing with my other big boys toys, rc planes and helicopters.
Gordon (Lincs)

I don't know if you are aware of this Rob, apparently the valve automaticaly stays open after a certain milage. That explains why some TF owner report there butterfly is open although they have not disconnected the pipe. If that's the case, the valve ain't there for noise regulation but for backpressure (running in the cat??)

Gordon, the ECU controls opening and closing of the valve: it uses engine vacuum as the actuating force...

Thierry, I have heard this about the valve. I wasn't sure whether this was something built into the software or whether, in fact, it was the valve just sticking open?

Interestingly, the default position of the valve is 'open' (the valve will open once the ignition is switched off for example) - so when the valve sticks due to corrosion/dirt, it will do so in the open position. You see? MG engineers have our wishes at heart! :o)
Rob Bell

This thread was discussed between 27/07/2004 and 29/07/2004

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