Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Loc: FLORIDA USA
09-15-08 06:29 AM - Post#1522643
In response to mouse55
SHORT answer, unless your running a very low restriction exhaust or no exhaust past the collectors theres unlikely to be a significant differance between true tunned headers and most commercially available street headers as the restriction tends to kill off the benefits, yes with open exhaust theres gains to be had, with a tunned header, but unless the compression,displacement, cam timing and intake design match, those gains the correctly designed header can produce are hard to see.
IN most cases when your running an exhaust system behind the header collectors the restrictiion to flow kills off some of the benefits, ANY significant BACK PRESSURE HURTS the effective scavaging, the header scavaging was supposed to provide. HEADERS are supposed to be designed to increase cylinder scavaging ,thus increasing the next cylinders volumetric fill efficiency, that boosts torque due to a larger percentage of the fuel/air mix being available to burn and produce cylinder pressure,thus producing power, but unless the cam timing and intake design are roughtly matched to that same rpm band they can,t effectively scavage the cylinders.
theres plenty of fluid dynamics math and research out there to show that the distances the exhaust travels between exhaust pulses and the diam. and length are easily calculated, and past that length the second previous pulse has little effect compared to the current and previous pulse energy and reflective wave
and lets not forget the cam timing displacement and intake port all effect the cylinder scavaging the headers can effectively provide also.
theres not much sence in paying a great deal more for a true tunned exhaust header unless your willing to match the other components to the combos intended rpm band and the cars gearing keeps you in that rpm band!
| IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!|
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
Edited by grumpyvette on 09-15-08 06:46 AM. Reason for edit: No reason given.