I race with a 91 CRX motor. Right now I have a 20"long 1.5"dia straight pipe coming from the manifold exiting on the passenger side.

How important is back-pressure to these motors? The operating range that I am in 100% of the time is from 4000-7500 rpm at WOT.

I've sometimes heard of people seeing power gains from running a muffler vs. straight pipe. What do you all think? Thanks.

side note. Regulations state that all cars must at least have a 20" long exhaust pipe, no larger than 1.5"dia, existing behind the drivers position.

 

your motor is a giant air pump. do pumps work well when there is restriction on the dump pipe?

 

From my understanding, a bit of restriction is great for stock motors and all non force induction hondas. once you go forced induction, you want straight pipes

 

^^Exactly what he said

 

to mu understanding back pressure will help with a little lower end power

 

All motor cars lose bottom end power with straight pipe but gain a lil top end power, as to force induction cars run best without it

 

On Naturally Aspirated engines, you DO WANT some backpressure, otherwise you can lose low end torque.

On Turbo engines, you want almost zero backpressure to help spool the turbine sooner to avoid boost-lag as much as possible.

 

Wow, so much misinformation in this thread.

You never want back pressure. Ever. It does not improve low end torque, and such is just yet another fallacy from the 60s still being passed around as fact.

What the engine does want is to keep the exhaust velocity from slowing down too much. Large exhaust pipes reduce back pressure, but they also reduce the velocity of the flow, which is what hurts power production.

Keep the speed up and the pressure down for optimal operation. However, these can become conflicting goals depending on how large of an rpm range typical operation of the engine is.

It isn't easily doable, but ideal would be a zero back pressure, variable diameter exhaust system.

It's 2012 people. Lets pass around the actual facts, not old skool hot rod "wives' tales".