I want your advice - Exhausts

[paramour]

Hello,
This has probably been asked before but I want to know the pro's & cons of exhaust upgrades as follows.

2001 Evo 6.5 TME,
What is best Exhaust upgrade eg 2.5" 3", 3.5" or what ever size,

What are the benefits or drawbacks of Cat back V's Turbo back. (Considering when I bought it it had no cat). Standard one on for now.

Any suggestions on makes and expected prices.

Cheers

 

[3zercrowd]

I would go for a full turbo back exhaust for the best results!

Get a hi flow cat put in as well and you will be sweet :wink:

You will feel a bigger difference with a turbo back then a cat back!

My 2 cents :wink:

 

[GSRSOL]

I would go for a full turbo back exhaust for the best results!

Get a hi flow cat put in as well and you will be sweet :wink:

You will feel a bigger difference with a turbo back then a cat back!

My 2 cents :wink:

yeop i agree.

get a full 3" system from turbo back inc. hi-flow cat.

there should be heaps of a/m stuff available

 

[Rockabilly]

Get a single biscuit hp cat or turn your hollowed cat over to have the heat
shield at the bottom so it can't realy be tapped to hear it being hollow !
A good resinator after the cat will kill the db a fair bit. Hp rear muffler.
Can't go wrong with a good twin dump at the turbo.
I personaly have 76mm & 70mm after the back seat to have backpressure

 

[CLuTZ]

Cat back exhausts are just for sound. You need it off the turbo. Imagine your trying to blow a pea through a straw. It wont fit. If you blew it through a piece of garden hose, it would come out the other end easy. Now say you were trying to blow the pea through a straw with a piece of garden hose on the end, you'd still have trouble getting it thought the straw, but no worries with the other end. Same thing goes for exhausts. If you want more than a couple of HP from modifying your exhaust, get it done off the turbo.

A 3" is ideal, you will notice a large increase in top end power with it!

I know of a buddyclub 3" catback exhaust for sale, pm me if you want more details. All you need then is a front pipe and dump, and your away laughing.

Or there's this:

http://4gtuner.com/forums/viewtopic.php?t=1735&highlight=exhaust

dre

 

[Lee]

I personaly have 76mm & 70mm after the back seat to have backpressure

Why would you want backpressure :?: :?: :?
Is your car N/A or something?

Basicly if your car is turbo (Or forced induction of another type) the bigger the better!!! The only reason why most people go for the 3" is that it's a more common size with bends (Mandrel of course), & it might get a bit pricey with a good muffler & it will be a big more in niose, but get the biggest you can fit & Afford. :wink:

 

[GSRSOL]

I personaly have 76mm & 70mm after the back seat to have backpressure

Why would you want backpressure :?: :?: :?
Is your car N/A or something?

Basicly if your car is turbo (Or forced induction of another type) the bigger the better!!!

not really..... Smaller turbos actually peform better with some backpressure. It improves responsiveness. With my GSR and the stock TD04, the car was heaps more reponsive when i had my "EPA legal" exhaust on which you can see here: (thanks holden :lol: )

 

[Lee]

I personaly have 76mm & 70mm after the back seat to have backpressure

Why would you want backpressure :?: :?: :?
Is your car N/A or something?

Basicly if your car is turbo (Or forced induction of another type) the bigger the better!!!

not really..... Smaller turbos actually peform better with some backpressure. It improves responsiveness.

How can a more chocked up exhaust improve responsiveness (ie: Lag/spoolup) on a spinning turbine wheel?
Doesnt make sence mate. :?
Care to explain?

 

[bazeng]

its true...

backpressure is much better for down low torque...

when i had my tdo5/6 23g, i used an exhaust valve...
with the valve closed, torque was much stronger down low, but ran out of puff

with it open, there was alot less torque down low, but topend was much better...

i guess its to do with the pre boost revs.. eg, before boost...
better torque off boost...

 

[GSRSOL]

"When contemplating a modified exhaust system there are those who want the biggest diameter pipe that can be had. Their idea must be that fatter pipes are more effective at venting than narrower pipes. This sounds reasonable but it is not quite correct. Sure wider pipes have greater volume and higher flow capacity, but that is just half of the story. Capacity is one consideration but gas velocity is the other factor.

An experienced exhaust designer knows that the best exhaust is one that balances flow capacity with velocity. A given volume/time of gasses will travel faster through a 2" pipe than the same volume of gas passing through a 3" pipe. So when taken to its extremes we can see that a too narrow pipe will create backpressure (restrictions to positive flow) problems and a too wide pipe will cause a very slow flow with no backpressure.

The optimum is where the fastest velocity is achieved with the least constriction possible."

I did say small turbos. And this does apply.......

big turbos however, yes ---> bigger exhaust the better.

 

[Rockabilly]

Lee it takes resistance/backpressure to make the motor feel load so it
then fights to overcome the backpressure. I'm only talking 76mm down to
70mm = nothing as far as stoping my mid & top end performance.
My dump that I made is very streamline for flow & even in that I wanted
the turbo to keep the dump full of air through the bend. I made it tapered
from 60 to 65 to 76 through the bend. I cut the side of the bend & pulled
the back inwards to reduce the dia & to make the back curved instead of
the flow hitting a 60 degree back wall. Having a bit of backpressure is like
having a bit of added compression. Which gives the motor a reason to
work earlier to overcome the resistance. eg: You don't make a tube exh
mani with 45 - 50mm tube unless you have 550 - 600hp on tap.
For under 400hp you only need 32 - 38mm dia tube to give backpressure.
A 7 degree rise in dia over 4x the pipe dia in length is the formular used
for making bike expansion chambers. My trade is sheet metal btw & if you
look at any industrial air/con ducting, you will see it is reduced in size to
maintain equal pressure over the whole run of the ducting.
I hope this makes some sense to you Lee. Cheers !

 

[Lee]

Cool, thanks for that, as they say: you lean something new everyday.

Kinda makes sence now i think about it. (im mostly thinking of big turbo's & huge hp)

 

[paramour]

Thanks fella's, there is no end to the wealth of knowledge on this forum.

Jules

 

[Jason Broadhurst]

How much HP are you aiming for?

What you need to ask yourself is; are you willing to sacarafice 2-3kw for a much MUCH quieter exhaust which will sound nicer and be more plesent to drive.

if yes, get a 2.5" system
if no, get a 2.75" system

both need a middle resonator and a large ofset muffler at the end, or they will sound crap. you will need a highflow cat aswell.

mandrell ofcourse, or dont waste your money.

you also need to realise that for a sub 300hp motor, 2.5 is already overkill and there is no power gains to be had from any larger piping.

 

[Lee]

What sort/size do you have on the Charade?

 

[Jason Broadhurst]

2.5" with a very big muffler, a resonator and a high flow cat and a 2" dump.

my muffler isn't straight through either.