Quote:
Originally Posted by Vettezuki
That's it. I can't take it anymore. Everyone state your case if you think engine back pressure IS or IS NOT good (i.e., desirable). Qualify your assertion with details, context, quantification, etc. Links to actual studies and engineering docs would be nice. There seem to be roughly two schools on this:
A: It's all crap. You don't ever want engine back pressure. Headers exist to create a scavenging effect, not back pressure. You want as little as possible to keep the "air pump" (a.k.a., engine) flowing as efficiently as possible.
B: Some back pressure is necessary. Not sure why, something to due with cylinder pressures, and therefore torque/power. The most typical case sited is small import engines that LOSE power when big exhaust systems are put on them.
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A) that is it--no back pressure more power. End of story.
B) over scavenging can effect power--but no back pressure makes more power than any amount of back pressure.
