As southy said, you are wrong is some cases. Most NA engines, while being too restricted and having too much backpressure from the factory need to keep some backpressure to maintain down low torque.
If you lose all your backpressure on an NA car, chances are your peak power will increase, but you will lose a large portion of your down low torque that gets you there.
Once you get to forced induction, the games changes.

In theory with forced induction it doesnt really matter because its all coming out the turbo and you would want next to no backpressure. BUT this is in 6 cylinder workshop. NOT V8 workshop and not forced induction. That is why i havnt talked about it because i hardly know about the 8's and hairdryers.

its funny when these people are wrong...

quick question, cause i dont think its been clearly answered, but would an i6 with extractors and a straight through redback exhaust be over the sound limit?
if so, whats the best redback system to go with?
im pritty sure lukey straight throughs would be over the limit yeah??

thanks.

Its actually 2.25"

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Last edited by blackjack_original on Sat Jun 07, 2014 12:18 am, edited 1 time in total.

So someone who knows nothing about exhausts is claiming to be an expert!?!? Why bother trying to write a doco on something you know nothing about?

As for back pressure, you definately need it.
Southy was right, Luke and blackjack are wrong, you need a balance.
The exhaust was shagged on my EF, the muffler was that f**k it was almost straight through, it had absolutely no power below 3000 rpm, at 100 k to overtake i had to drop to 3rd gear to get the revs up, once i threw on a new 2.5 inch the power it gained was incredible, from go to red line it had balls.
No back pressure = loss of power from low to mid range, too much of course will also cause loss of power, you need to find a balance for your application.

If i had the time to make this up as a sticky i would, but until someone who actually knows like stockstandard or another experienced guy then i'm not going to take notice.

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Last edited by blackjack_original on Sat Jun 07, 2014 12:18 am, edited 1 time in total.

I was just tring to make something to stop those annoying posts from newbies asking what exhaust. Maybe someone els eshould try doing something like this. Blackjack...South....who ever....

I'm thinking of getting a 3inch magnaflow cat and getting it stepped down to the 2.5 inch pipes. Am I going to lose too much back pressure with this?