Quote:
Originally Posted by wickedS14
 And your wondering why it takes long to get up to rev. 3inch on a 24e, thats overkill. You sir need all the back pressure you can get. |
Correction.. It's called pulse scavaging. Back pressure is for emissions only and has nothing to do with increasing performance. The least amount of back pressure the faster the car will accelerate. The larger the pipe diameter being to big the more the pulse scavging becomes disrupted. Pulse scavaging is what draws in a positive vacuum to allow flow to increase at a faster velocity though pipe. During valve overlap in high rev this helps increase the intake velocity as well.
Basically there is a lower velocity travelling through the exhaust which is disrupting intake velocity in the higher RPM range.
In refrence o KA's using a 3" exhaust pipe. It would be more for KA24de's rather than KA24e's. KA24e's have one less exhaust valve per cylinder and the CFM rating on the SOHC head is about a 1/5th less in flow to the DOHC head. Timing on the KA24e is slow too, you negate power losses with a large pipe and that kind of timing, with CFM rate.