300rwkw With 3"?

[drgnball34]

Would a 3" turbo back exhaust be enough to handle 300rwkw from a Rb25DET? Or 3.5"?

[R31Nismoid]

It will.

But ideally 3.5"

[Craved]

yeah it does

but if you are getting a new exhaust, go for 3.5" atleast

wish i knew that 7 months ago

[drgnball34]

I have a exsisting xforce turbo back set up. The dump and front pipe in one is 3 inch. Since im getting a high mount set up, I need new ones fabricated in 3.5inch. Any idea as to how much this will cost? Also the cat is three inch so should i get a larger size too? Im thinking of just hollowing it out instead

[Craved]

well if your only running 3" after the cat .. i would run 3" before the cat too ...

im running 3" from turbo back, running stainless custom with an xforce muffler..

cost me $1100 including the new cat..

============

remember hollowing out the cat with induce flames on the overrun etc, and will potentially melt stuff, as well as be very illegal ... big fines and EPA tests etc.

up to you on that bit. i say dont do it

[drgnball34]

fair enough....yeah the exhaust system is 3.5" after cat...So it woud be a good idea to get a bigger cat to match aswell?

[Craved]

yes get a 3.5" or 4" metalcat or similar.

[Gav]

400+ rwkw through my HKS 80mm (3-and-a-bit inches) exhaust. I can't see a problem for 300kw on 3" system.

[r33_racer]

I had no cat on my rb20det sil-80, i fabbed up a piece of pipe same length at cat with two flanges and put that inbetween, had some mad flames. I kept the full proper unbutchered cat in garage, then when i sold the car i put it back on. I had it intended if i got sent over the pits at qld tpt, before i went i would put cat back on. Cops couldnt see, cause car was too low anyway. That was back in my young silly days hehe.

I hear the metalcats/magic cats are supposed to flow really really well.

[Abo Bob]

Mik has about 370rwkw with a 3" system. I know mine is only 255 but it's certainly no restriction at that level.

[R31Nismoid]

Have the guys using full 3" exhausts dropped them from the dump and seen if there is a power increase at all?

So that they can definately say there is no gain?

[mr_rbman]

Have the guys using full 3" exhausts dropped them from the dump and seen if there is a power increase at all?

So that they can definately say there is no gain?

hope u got ear muffs when she's on the dyno, that would be bloody loud when she starts to boost!

[Daz]

3" should easily be good for 300 rwks, ideally yeah 3.5 but that will also mean extra noise.

[The Dan]

As a general rule, a 3" exhaust is good for 600 engine hp. That equals around 380rwkw.

As for running larger dump pipes. There is absolutely no need in running anything more than a 1/4 inch larger diameter than the turbine wheel anyway. Any of the 600hp turbos out there should have a fairly large turbine wheel and a 3" usually goes straight up. 3.5 inch is just stupid unless you are chasing 400rwkw or more.

[R31Nismoid]

As a general rule, a 3" exhaust is good for 600 engine hp. That equals around 380rwkw.

What rule?

I've seen cars aroun d the 330rwkw mark change to a 3.5 or 4" and pickup another 20rwkw and lots of midrange.

380rwkw & 3" is sus

[benm]

Forget about 3 or 3.5 and worry more about the cat + mufflers.

I have a DoLuck 3" cat-back exhaust which has flowed 328awkw without any problems but was so loud and droned so much you could hear me from 2km away.

For a noise reduction quickfix I got a local muffler place to bolt on a quieter muffler. Whilst my exhaust is now quieter it is sooo restrictive that my boost level is all over the place and the engine just doesnt want to rev above about 5000rpm, at a guess i'd say i've lost an easy 50rwkw (I can hear the massive back pressure just on idle).

The DoLuck canon is basically a massive straight through pipe with baffling around the outside (which does... nothing). The quiet muffler has all sorts of baffling channels around the inside channeling the gases all over the place to help reduce noise, but created a massive restriction.

Edited June 4, 2006 by benm

[The Dan]

What rule?

My rule.

And that would be the same rule they use to design turbos and rate them accordingly.

A 3 inch exhaust is enough to sufficiently remove gases from an engine producing 600hp....this is roughly of course but is a good general indication of the system you will require.

In most cases the swap to a 3.5inch would see a gain only in the CAT upsize as this is the largest restriction. Unless the people who made the 20rwkw gain aren't running a cat. It would be silly to say 'oh I've got 380rwkw so I should be good for a 3 inch system' Just because your injectors flow at 550cc or 700cc, doesn't mean you run them at 100% because they can flow that. Anything around the 350rwkw mark and you would automatically upgrade to a larger size.

[MR331307]

Have the guys using full 3" exhausts dropped them from the dump and seen if there is a power increase at all?

So that they can definately say there is no gain?

I can say yes i have tried this and i didnt gain any HP at the wheels but did gain 30 lbs of torque

I run a Single 3" exhuast with a punched cat on my skyline and its fine. Making 400 kws or so with NOS

Exhausts vary on Engine Size,Cams,Turbo Size & amount of boost.