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Last edited by blackjack_original on Fri Jun 06, 2014 9:46 pm, edited 1 time in total.

this is where stiddy quotes his 400m time to prove a point, but the point isnt proven as he never tried a 2.5" exhaust to see the results.

This is an incredibly over assumed and continuously stated myth... NO an engine does not require back pressure to run, and yes any back pressure WILL hurt power somewhere in the range... What is far less understood but is far more important is the way sound waves travel down the pipe... While this involves flow and pressure in many and varied ways, it has more to do with muffler choice, tuned length, volume of the pipe/system etc. for example an open chamber muffler appears like the end of a tailpipe to anything before it, thus ending the tuned length and causing a transmitted and reflected wave up and down the tuned part of the system, which at some RPM will hurt power, and at others will help due to scavenging... hence the design of extractors. you will often find that after the tuned length you can use any size pipe (as long as it doesn't restrict the flow) and power will be within 2-3hp ie open to smallest size that will still flow enough exhuast to not cause further backpressure should all be very close on the dyno... The maths required to work out exactly what will suit an engine both in terms of intake design and exhaust design is absolutely heinous, and I'de be very surprised if any "off the shelf" exhaust has had any thought put into it more than trial and error, this is what has caused the myth to build over the years as a 3" system probably doesn't outflow a 2.5" with a standard engine, hence muffler choice, extractor choice, actual tuned length etc would have had more of a bearing. However as we see more and more people moving to JMM/ITS/Alted/Forced Induction, with higher revs and higher flow perhaps the 2.5" won't flow enough and will hurt power, hence people will fit 3" and start saying 3" is the shiz and then everyone will fit a 3" regardless. </rant>

Having said all of that, you will find that the 3" systems beginning (length of extractor, 3" pipe, 3" cat) will become your tuned length, and the larger volume of the 3" pipe over the 2.5" pipe will make the 'tuned rpm' higher. Hence a little lost down low and a little gained up high. perhaps we can FINALLY put this myth to rest, and move on, that way we can all go about 'designing' our exhausts rather than just fitting said pipe size.

you should start slappin people now, this wont end well.

a 3" might be a good system to have to PEAK power like at redline, but even then not sure.

BUT, there would be so little gas velocity down low, you'dd have the power of a 1.6 baleno down low.

p.s. as to "backpressure is a rumor" all i can say is LOL

Congratulations.. You have just proved the theory that there is no limit to human stupidity. your ineffective imitation of good posting style only serves to illuminate your lack of substance, good taste, and decency.
now dullard, do yourself and everyone else a favor: disconnect your computer from the Internet.
Go suck on a frozen pineapple, a**hole.

saying "Go suck on a frozen pineapple, a**hole." to respected and well known members of the forums will not get you or your argument very far at all.

as a wise man once said "Woooosaaaaahh"

I know who he is, and know that he is 'well known' but respected? LMAO..

I explained myself in a previous post.. to do with Effalcon well, thats just off-topic.

Well, years ago, Hot Rod magazine did a dyno test of various exhaust
set-ups using only one vehicle and discovered that some back pressure is
actually beneficial. This may vary from engine to engine but I've heard
many people say that total elimination of back pressure actually hurt
engine performance.
Don't jump down my throat just posting what i know it is a forum after all not a way to attack others opinions

ED-MONTY was after off the shelf cat back 3" system for Turbo use you fools, looks like you guys are getting side track with bigger is better debate s**t.

There is no right or wrong way, each setup is different & respond differently to what your aiming for.

the 3" exhausts seem to work alright. so im failing to see a problem here.

back on topic guys ,if you want to have a s**t fight dont post it in my thread.i dont want to know about back pressure or any other crap ,if you have a 3" off the shelf system please post

cheers jb.

i know u can get them. south geelong exorst had one but i forget what brand. quoted me $450 cat-back with one muffler and one hotdog. pretty good i rekon

i'm %95 sure you'll have to modify the 3inch V8 one.