Zorst? 3" Vs 4"

[yogibear]

i have a rb26 in a r32 gtr witht he following mods

cp forged pistons

to4z with screamer

3" zorst

700cc injetors

PFC

z32 afm's

few other bits and paces

But what i wanna know if i go to a 4" zorst will i make abit more power and / or bring boost on abit quicker?

thanks

[R31Nismoid]

most likely. 3" is not enough for 400rwkw+

[BMYHOE]

It would make more peak power but dont see the response improving much....

[Rolls]

It would make more peak power but dont see the response improving much....

it isn't going to make it worse though

[yogibear]

but no real benefits?

[R31Nismoid]

read my post.

you need 4" for 400-440 (t04z) range.

3" will be hurting that setup.

[VB-]

in my experience, 3" starts to choke ~350rwkw, obviously depending on the exhaust design itself obviously, but as a general rule...

edit - ^ what he said

Edited November 9, 2010 by VB-

[XRATED]

but no real benefits?

Take some pressure readings along your exhaust before each component. If you have more than a few psi of presssure anywhere then you have power robbing restriction.

If you have restriction... remove it.

Personally I would go bigger pipe size for that turbo, unless it's a straight pipe with no mufflers.

Cheers

Justin

[Nee-san]

most likely. 3" is not enough

That's what she said

LOL

But yes, go as big as you can.

[phat_man]

it isn't going to make it worse though

This is what I think, Although after some discussion with some really experienced builders, they think this is not the case.

It is thought that having to big of an exhaust does effect torque. Personally if i was chasing every hp possible i would do what 'XRATED' said, just like inlet lengths need to be tuned so does the exhaust. although turbo cars are no where near as fussy as other cars (after the manifold) it would still make a couple of hp difference.

Edited November 10, 2010 by phat_man

[Rolls]

It isn't like an NA car where tuned extractors and smaller pipes to maximise velocity help, on a turbo car the exhaust is under such a high pressure due to the collector you want it as free as possible, I really wouldn't doubt if a straight pipe helped power over the entire graph.

[bubba]

With turbos, you just want to get the gasses out of there as fast as possible, any back pressure post-turbine will slow the turbine down.

With long exhausts on a street car, stepping the size of the exhaust down helps maintain velocity. For example, a 4" dump in to a 3.5" front then 3" catback would probably work quite well (or maybe 2x 2.5" so you still get the volume but you increase the velocity).

[SimonR32]

read my post.

you need 4" for 400-440 (t04z) range.

3" will be hurting that setup.

Not true at all, at top end when you are making that kind of power a whole lot of exhaust is bypassing the exhaust via the wastegate...

3" on 26 with T04z regularly make between 430-470rwkw

[Brezza]

It really depends on your power level.

I'm running a 3in exhaust from cat back. and putting out 350rwkw

i've got a 3in decat, 3.5in muffler and a aftermarket front pipe.

its a pretty straight design with minimal bends. it does the job!

i think if i were heading for closer to the 400rwkw mark i would be looking into a 4in exhaust or at least a 3.5in

i also think that some people get confussed thinking that a bigger exhaust will allow faster spool up, but that's only true if the current exhaust is a restriction at that rpm and load point, which i would higly doubt that a 3in is a restriction at 4,000rpm. it'd be a restriction up higher and when 25psi or more boost starts pumping through the motor.

it might make your decision easier to listen to what a car with a 3in sounds like vs a 4in exhaust, i like my 3in because its quiet enough to not attract too much attention and if flows well enough for my needs.

[Harey]

Garrett engineers on their website clearly state that the less restriction after the turbo the better. Sure this needs to be weighed up with physical limitations and noise levels etc. But a greater flowing exhaust can only improve response and top end power. Obviously, whether its even noticeable depends on your power levels but at 400rwkw I think it would be very noticeable.

Just because some cars manage to get 400rwkw through a 3" exhaust doesnt mean they couldnt be a heap better with a larger exhaust.

Min 3.5" IMO

[Harey]

i also think that some people get confussed thinking that a bigger exhaust will allow faster spool up, but that's only true if the current exhaust is a restriction at that rpm and load point, which i would higly doubt that a 3in is a restriction at 4,000rpm. it'd be a restriction up higher and when 25psi or more boost starts pumping through the motor.

Very interesting point, makes sense.

[NYTSKY]

I made a 15rwkw gain changing from a 3" to a 3.5". That was the mid 300rwkw mark.

Now having a custom 4" being made for mid 400rwkw.

[N1GTR]

Speaking of custom.....looky what's arrived for mine

4" ID

[NYTSKY]

I see your 4" muffler and raise you two 888 Motorsport 4" mufflers

Arrived today too. The race is on Steveo

[Rolls]

Speaking of custom.....looky what's arrived for mine

4" ID

is it actually possible for a 4" straight through muffler to really do any muffling at all? Even if the oval was 1 meter wide on its own it would still do bugger all surely?