The Myth about "BackPressure"

[Wymun]

Read this post from the US-based Nissan Forums, and thought it was well said and put. Backpressure is a bad thing and I'd thought it be good to be more accurate in future representation.... :

 

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Anyways, I noticed something that really was getting on my nerves something fierce that people kept saying. "The GA motor needs backpressure to run right."

 

B*LLSH*T!

 

Whew. Sorry. I had to get that out of my system. On any car, with ANY size engine, BACKPRESSURE IS BAD. Re-read that kids. BACKPRESSURE IS BAD.

 

The fact that the GA loses power with piping bigger than 2" has ABSOLUTELY NOTHING WHATSOEVER TO DO WITH BACKPRESSURE. It has to do with EXHAUST VELOCITY!!!

 

When your exhaust is traveling through your piping, it is spinning around the outer diameter of the pipe. If the pipe is too small, it can't get out fast enough, and it causes backpressure, which, if you've been reading, is a BAD THING. If the piping is too big, the gasses can't swirl out fast enough, causing, you guessed it, BACKPRESSURE. If the piping is just right, the gasses swirl right out and in fact help suck out the exhaust gasses that are exiting from the engine.

 

Let's recap. BACKPRESSURE IS BAD. Properly tuned exhaust systems let the exhaust gasses flow right out, creating NO BACKPRESSURE.