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I supported Toymods
Location:
melbourne
Registered:
June 2002
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Re: Exhaust Question
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Sat, 05 April 2003 00:20
 
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the thing that has been stressed with this subject before (the only thong i kindof believe anyway) is its not really "back pressure" you are after, but having exhaust pipe that is too big a diameter will mean the exhaust gas will cool down before it leaves the pipe, which leads to power loss as the engine has to "force" the exhaust out, rather than it "rushing out by itself" (remember, exhaust valves are always smaller than intake, fot this purpose, in a 20 valve 4age there are two exhaust valves, 3 intake etc)
Now, to try and answer the actual question,
as for damaging the valves, id say the way you would damage exhaust valves is by overheating them, i would gues that the exhaust config doesn't have too much too much to do with it, but if anything i would say that having too much "back pressure" would be bad, as the echaust gas would hanga around for too long, and heat up the valves for longer. if anything, a low back pressure system would be better.
but as a (dodgy) rule
1.6 litre engine 2 inch
2.o litre engine 2.125 inch (thats 2 and a 1/4)
3.0 litre 2.5 inch (strting to guess now)
what is much more important to the exhaust valve damage is a/f ratio and spark timing, maybeye exhaust cam timing too, but i think this wouldn't matter too much.
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