back pressure
92zcamaroperson
10-23-2005, 11:36 AM
Dont engines need some sort of back pressure to run properly? Ive heard that if you run header dumps you can burn a valve. Now ive seen people driving around with their exhaust dumping right out of long tubes with no issues. Id like to get a cutout and ive been told that they usually go as close to the headers as possible. So is the burning a valve thing just a myth that ive heard or what?
philly rs
10-23-2005, 03:36 PM
i never heard of that, but like i said i never "heard of that", and i plan on running dumps on mines and that has never come up
kahjdh
10-23-2005, 04:34 PM
With a v8 i wouldnt worry about it. 4's and 6's usally run better with some back pressure.
92zcamaroperson
10-23-2005, 05:53 PM
cool thanks
Savage Messiah
10-23-2005, 06:56 PM
NO car runs better with backpressure
what the goal is is high exhaust velocity, and pipes being too big or too short can have a negative impact on the e.v.
people who refer to this property as backpressure dont have much idea what theyre saying
what the goal is is high exhaust velocity, and pipes being too big or too short can have a negative impact on the e.v.
people who refer to this property as backpressure dont have much idea what theyre saying
scoobytuff
10-25-2005, 12:45 PM
It's not the backpressure that you need, but the exhaust scavenging effect. Too big a pipe and you lose this causing high exhaust gas temperatures and exhaust that does'nt move out as fast as it should. Bigger is not always better. No engine needs backpressure but with none you actaully lose power due to the lack of exhaust pulsations that help pull the exhaust away from the engine. Hope this helps.
flatlander757
10-25-2005, 02:17 PM
I think this is a fitting analogy...
Take a bottle of soda, open it up, and hold it vertically upsidedown, drinking it and guzzling as fast as you can, don't break the seal, and constantly chug it down.
Now do the same thing, but just let it pour out onto the floor. It will go CLUG CLUG CLUG and take forever to get it all out.
You may not be able to physically drink it faster, but you get the idea i guess...
If backpressure were the main priority, then we would be running around without any headers on at all, open valves. Now that WILL burn the valves. Headers collect all of the exhaust pulses and smoothly combine them into one, creating a smooth flow leaving behind them a sort of vacuum which in turn helps to suck the exhaust from the next stroke out of the cylinder head. This is the idea of scavenging as mentioned by scoobytuff.
Take a bottle of soda, open it up, and hold it vertically upsidedown, drinking it and guzzling as fast as you can, don't break the seal, and constantly chug it down.
Now do the same thing, but just let it pour out onto the floor. It will go CLUG CLUG CLUG and take forever to get it all out.
You may not be able to physically drink it faster, but you get the idea i guess...
If backpressure were the main priority, then we would be running around without any headers on at all, open valves. Now that WILL burn the valves. Headers collect all of the exhaust pulses and smoothly combine them into one, creating a smooth flow leaving behind them a sort of vacuum which in turn helps to suck the exhaust from the next stroke out of the cylinder head. This is the idea of scavenging as mentioned by scoobytuff.
Automotive Network, Inc., Copyright ©2026