Cat Back Exhausts

[gargantua]

Hey guys,

Pretty soon I am going to be getting a 3" X FORCE Stainless Steel Cat Back Exhaust.

I have been told that putting a cat back on my car will make my acceleration sluggish because I have a stock turbo.

Is this true? If so how sluggish will it be?

Also is X FORCE a good brand for exhausts?

I am getting this exhaust for around 100 bucks and i have seen them advertised for about 800.

So what do you guys think.

thanks.

[moonus]

theyre good enuf. you put on an exhuast to allow for better outflow, thus power. so if u mean more power will make it sluggish then i see youve bin taking good advice.

[RBwhatever]

You haven't been talking to someone that drives a naturally aspirated car have you?

I once said to someone i was going to change my exhaust and he goes "no can't put an exhaust that big on your car, you've only got a little motor and you'll lose your backpressure". Obviously he doesn't know much about turbos.

Whoever said that to you is uneducated in turbo performance.

If you want power, do your dump pipe and cat too.

[Howie]

SAU mythbusters to the rescue

[scathing]

I once said to someone i was going to change my exhaust and he goes "no can't put an exhaust that big on your car, you've only got a little motor and you'll lose your backpressure". Obviously he doesn't know much about turbos.

He doesn't know much about anything.

You don't ever want backpressure in your exhaust, whether your car is FI or NA.

[scathing]

Also is X FORCE a good brand for exhausts?

XForce make reasonable quality copies of Japanese aftermarket exhausts. They're not the last word in build quality, but they generally flow pretty well and fit just as well as Jap ones (since they're a pretty accurate copy).

My mate had a Trust exhaust that he ripped open on a speed hump. He bought an X-Force rear pipe section when the exhaust shop found it was a direct fit (from the flanges to the mounting hooks, to the shape of the bends). No noticable drop in power, either.

[GeeTR]

He doesn't know much about anything.

You don't ever want backpressure in your exhaust, whether your car is FI or NA.

... i think you'll find NA motors, require and manage back pressure to attain some level of reversion pulse tuning... with exactors.

What bout NA rota's, 2 strokes and expansion chambers...

M

[Godzilla32]

I aggree you do need some backpressure on a NA engine.

[RBwhatever]

Yeah NA engines need back pressure. They don't stick 2 1/2 inch systems on V8's for nothing.

[gargantua]

Sweet thanks for the info guys. I just gotta look around some more.

Oh yeah 1 more thing whats the difference between a cat back and a turbo back?

[RBwhatever]

The catalytic converter is roughly just under the passenger seat. Poke your head under the car and have a look.

Cat back - Exhaust system from the cat too and including the rear muffler (doesn't include the cat).

Turbo Back - Exhaust system from the turbo to and including the rear muffler. Consists of Dump/front Pipe, HiFlow Cat, cat back.

[gargantua]

Ok im confused now. What do you reckon I should get I have the stock exhaust at the moment. I want the car to be loud but not too loud where its illegal. Also which one gives you more performance.

[Munkyb0y]

get a turbo back exhaust. you could always add the dump pipe and cat later (that's the stuff that's not included in a cat back system).

3 inch, with a decent cannon, and maybe a resonator half way, wont be tooo loud, but will sound grumpy and mean.

[gargantua]

sweeeet thanks munkyboy. How much do you reckon it will cost to to the whole shabang?

[Link]

I got quoted:

$895 for a full 3 inch turbo back system inc hi flow cat

$400 for a 3 inch cat back system

Go for the turbo back system - saves the hassle of trying to replace the stock dump pipe and cat later on.

Tell the exhaust place how loud (or quiet) you want it and they should be able to do it for you

[gargantua]

cool thanks fat33.

[Munkyb0y]

here you go. listen to my exhaust here 3 inch turbo back. it's a bit louder since the highflow cat went on, but will fix that with a resonator soon enough.

http://www.skylinesaustralia.com/forums/in...st&id=65540

Edited November 24, 2006 by Munkyb0y

[Howie]

That sounds awesome Munkyboy. How is it on the highway? Is it really drony?

[Munkyb0y]

That sounds awesome Munkyboy. How is it on the highway? Is it really drony?

thanks. i like it

that vid was before i put the highflow cat on. no drone at all. perfect.

but since i put the highflow, there's a bit of drone in the cabin.

so i'm gonna put a resonator on, since there's none on my system besides the cannon.

most systems have a muffler/resonator between the cat and cannon.

[mokompri]

... i think you'll find NA motors, require and manage back pressure to attain some level of reversion pulse tuning... with exactors.

What bout NA rota's, 2 strokes and expansion chambers...

M

i agree with scathing on this one.

its not about backpressure, backpressure by definition is a restriction and causes a loss of power. pulse tuning is a timing thing, you dont aim for backpressure, but it might be an unfortunate result of having extractors with the best scavenging affect, that will give more power overall. after the extractors the less backpressure the better.

2 strokes do need it, but who cares about 2 stroke

edit: with 2 strokes, i think its important to remember that its a secondary effect of backpressure which gives more power, not a primary effect. the secondary effect being that the backpressure stops the air/fuel charge from blowing straight through the chamber. if the charge didnt blow through from a lack of backpressure, and we took away the backpressure, power would increase. (ala 4 stroke)

Edited November 24, 2006 by mokompri