Quote:
Originally Posted by bryan213
You don't want any backpressure in an exhaust system.!!!!!!!!!!!! haha lie!!! u need back pressure unless ur wanting to buy a new motor dont even touch ur resnatior
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Quote:
Originally Posted by AlbinoMonkeyRat
my personal experience: you need at least a little back pressure (not a lot though) for NA/SC, and more for Turbo (just to get spooled)
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Sorry, you don't want any backpressure at all in your exhaust system. Backpressure = a restriction somewhere. Think about it.....backpressure is exhaust trying to push back to where it came from. That is bad. You want the exhaust to get out of the engine and out of the exhaust pipes as quick as possible.
On a naturally aspirated engine you want to choose the right pipe size to maintain fast exhaust velocity to help with scavenging. With a header and the right sized exhaust, the velocity helps pull the exhaust out of the cylinder, and during valve overlap, actually helps pull the intake air into the cylinder. You also want to get rid of the retrictions with free flowing, straight through mufflers.
On a supercharged or turbo engine, the air is being forced in, and there isn't much of the scavenging effect that there is on the NA engine. With boost, there's also a bigger volume of exhaust gas to get out of the engine, so you can go with larger piping than NA.
If you have backpressure on a turbo engine, the pressure pushes back on the turbine wheel. That slows down spool, it doesn't help it. The turbo is the restriction, and you want to get all the restriction off the turbo, so the larger the piping the better. The lower the backpressure in the exhaust system, the faster the turbo can spool, and the more power it can make.
Quote:
Originally Posted by bryan213
u have a 4 cylinder point less!
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Your whole post was pretty well thought out and informative. And I agree, 4 cylinders are pointless, and can't possibly be very powerful...
/sarcasm
This deserves another