Very informative post right here...

A varex can't be a waste of money if it's going to save you hundreds and hundreds of dollars in epa and civic compliance fines...

At the end of the day, a muffler is a muffler. Obviously full on tricked out custom whatever are an exception, but they're still just another bit of pipe.

But not all mufflers have a remote control butterfly valve..

Ahhh no.

f**k we are really on a roll with good posts today.

Yeah if you use two of them on a V8 it'll be fine for that power.

Funny thing is I've seen 180hp 4cyl engine step up from a 2inch to a 2.5inch system and pick up power from 3000 rpm through to 7500rpm.
Both systems were mandrel bent and both had lukey mufflers of the same design.

The only way to know is to measure for back pressure across the operating rpm of the engine.

I just put a hotdog on my 3inch system last week, because without the cat it wasnt bearable for a street car.
Also had the headers fiddled with. Picked up another 11rwkw.

i run a twin 2.5 on my n/a hehe

DAMN! - based on all the "experts" you should be lucky to make 100Kw

hahaha is making 245rwkw at the moment.. more tuning next wk..

Whose this aimed at? Have been purposely biting my tongue over your earlier post comparing an oversized exhaust to venting directly to the atmosphere...

No that wasn't specifically aimed at you - I just have a general issue with the concept that larger than a certain size is arbitrarily "oversized" - I've had similar experiences to tickford_6 (respect) where certain things that should be true don't actually end up that way - things that should work don't and others that have no business being any good at all work out terrific Suffice it to say I prefer to be open minded than not

Also I never compared "oversized" system with venting direct to atmosphere as such (altho the notion that bigger is going to be closer to that than than smaller IS implicit, but it's of course not that simple - it's about what ACTUALLY happens at the ports) - I was illustrating my THEORY of "subflow" by pointing out that flow into a chamber is different to flow thru a pipe (column flow) - an example being ambient atmospere as the ultimate chamber

Trav 4.0 has already proved the gain of the 3" system, there is no "its too big issue" now..

Ahh yess 3" isn't to big if you have the right supporting mods.. 3" On standard engine or with just a cai would be over the top.. But if your running cams or more compression well then its no problem

There always will be a too big issue, just like there will always be a too small issue putting a 2.5" system on a worked engine designed to make peak power in the upper RPM.

Most people struggle with getting good results from their modifications because they look at each individual part. As an extreme view: y, you might get an increase in top end power on a stock engine with a 3" system, but overall your car will probably be slower than someone running a 2.5" as it will under perform in a greater proportion of the rpm range where the rest of the engine (heads,cam, intake manifold, maybe headers) was designed to work. The person with the stock engine running 2.5" system has a much more efficient design overall as it will match the flow of a stock engine throughout a greater proportion.

It is like putting a custom intake manifold (which essentially shares same theory as exhaust headers) on a stock engine. You put something with short runners designed with all reflection points around 5000rpm on a stock engine and you will notice an increase in top end (at expense of bottom end). But if you put it on a worked engine with matched heads/cam/exhaust which are most efficient at this point you will notice a much greater increase in top end from the fitting of this individual part.

This is why 90% of people on here shouldn't be fitting a 3" system as even though it will benefit their top end they will end up decreasing overall performance of their car.

Last edited by skidder on Tue Oct 04, 2011 12:59 pm, edited 1 time in total.

I don't think I have referred to any system being arbitarily oversized? Everything is in relativity; no point putting a 3" system on a stock car where it isn't going to make power in the upper rpm anyway.

I was referring to the above comment where it seemed like you were comparing flow in a column (as you pointed out) with flow into a chamber.

Willing to be proven wrong, but I don't think you will get an N/A i6 to flow enough to give a noticeable gain with a 3.5" over a 3". If you did would be a pig to drive on the street.

I was referring to my car about the 3" not being to big