There is a myth that engines need back pressure to funtion properly. Actually as explained in the following links, there is a confusion regarding exhaust velocity and back pressure. Basically, high exhaust velocity is a good thing, while back pressure is not so good. Read and enjoy.

http://auto.howstuffworks.com/question172.h
http://www.uucmotorwerks.com/html_pr...torquemyth.htm
http://www.warnertechnology.com/Cars/backpressure.shtml

 

In some ways, clear as mud. ;-) Seriously, it could use a little better explanation, IMHO.

 

i disagree. backpressure isnt what it seems. backpressure should be velocity. no back pressure at all to me is worse then a tiny bit to much. you want enough flow for scavenging. in other words back pressure should state that enough resistance should be left in an exhaust system to create the correct velocity in order to create a vacuum in the cylinder when exhaust pulses hit. since they are pulses per cylinder they have to hit the exhaust stream in a manner in to which they go thru the exhaust with the correct travel speed to create a type of suction for the next.

http://my.prostreetonline.com/forums...php?t-1639.htm
http://www.thumpertalk.com/forum/sho...d.php?t=659727
http://www.nsxprime.com/FAQ/Miscella...austtheory.htm

 

I made an awesome long *** post on this site one time about this so called back pressure myth but I can't seem to dig it up. I think it was deleted =(

 

What it all boils down to is... anything shorter than long tube headers is no good. Long tube headers in themselves create the neccessary scavenging to reach peak output. A factory manifold with absolutely no cats or mufflers (with a full length system out the rear) has enough restriction to slow an engine down to less than peak. If backpressure was needed, dragstrips would be selling restriction devices like hotcakes.