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Message: <blockquote data-quote="turbology" data-source="post: 313358" data-attributes="member: 10223">True, but there is more.My last post mentioned the 2 Vs, Velocity and Volume.With right velocity and volume, at a certain resonance(pulse), a good exhaust/header will create a suction effect to "vacuum" the exhaust air out from combusion chamber.This help to create more Hp by having less dirty/used air trap in combustion chamber (by suck it out), and have clearner/vacuum combusiton chamber on the next intake stroke.This is also part of the reason why performance cam have longer intake & exhaust interval.Having equal length exhaust manifold also help. Also 6-2-1 exhast manifold instead of 6-1 design. (6-2-1 help in the pulse effect)Again, the 2 Vs. Big exhaust have good volume but not enough velocity. Not enough speed to exhale the exhaust gas.Splitting the pipe interfere the pulsation of the exhaust. You are loosing the Vs quickerAnd if I recall, lots of racing dont' use quad exhaust, or double (unless is a V-engine). Maybe the reason is here.For turbo application, the easier, quicker to expand the hot air (hot turbine side), the faster and sooner it will spool. (eliminate pumping loss) I never come across anyone who complaint their exhaust is too big for thier turbo-ed car <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile    :)" loading="lazy" data-shortname=":)" />Maybe you loose some driveability at low rpm. Corky Bell said the same in his book.Cheers.</blockquote>

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