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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Headers and exhaust camshaft modding.
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Wed, 15 October 2003 12:31
 
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good to hear you are actually interested in modding the engine rather than just bolt ons and gold dipped wheels 
4-1 extractors are primarily best at high rpm, like above 6000rpm. below that, you will still benefit from their free flowing nature, but you would be best making up a 4-2-1 tuned length set. should be pretty easy for a FWD motor, and may or may not make a difference. making the primaries and secondaries around 1.5 feet long would be a good start and will tune for maybe 4500-5000rpm?? the collector (the last pipe) shoudl be about twice as long as the first sections (ie 3 feet, if the others are 1.5 feet each) before the cat, although this will prolly make the cat less effective (less heat in it).
as for exhaust cam timing, retarding will increase overlap, and may help draw more new charge thru the intake valve (scavenging effect) ... but the cost of getting adjustable timing gears made up might be bad.. you could always drill new dowel positions on the sprocket to offset it, cheap if you have a machining buddy...
then you can muck around with it and see how it affects things..
imho, the best way to learn is have a go, and don't be afraid to start with an 'unpopular' motor 
have fun,
Cya, Stewart
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