Best Size Exhaust

[newboost]

I am currently using a 3.5 inch exhaust from the cat back on my r33 s2, it hangs down to low with clearance of only 75mm, Is this exhaust to big for the rb25det. What size would be better suited to the car and what type of performance and sound levels are being acheived.

Mod so far are

FMIC, Microtech lt12, Turbosmart Eboost 2, Split fire coils.

Any help with this would be very helpfull.

[bumble_bee]

is it just a custom job exhaust?

or is it actually a brand design exhaust?

maybe check the rubber linkage that hold the exhaust in-place..

happen'd to my old car..one fell-out and i was movin all-around..lol

but didnt drop low at all from wat i can remba....

also mayb take a photo???

[Cubes]

3.5" is fine.. Apart from them being louder than a similiar setup 3" they are a good thing when pushing over 250+rwkw

[R33Matt]

Hey Newboost,

The 3.5inch cat back exhaust your using isnt to big for the stock Rb25 turbo. Although if its riding to low and your looking for a change, a 3inch system from the turbo back would be the best option. Would give you a good performance gain and would also sound nice. If you dont mind it riding low and just looking for performance than the 3.5inch cat back will be fine. You will just need to get a 3inch Dump/Front pipe and a 3inch Hi-Flow cat.

[R31Nismoid]

3" is all you really need, 3.5" is overkill

[newboost]

I do have a 3 " dump pipe and hi flow cat, It is a brand system not a custom job. (Xforce exhaust system) Has anyone got 3 " system from Liverpool Exhuast in sydney. The sales guy told me that if i was to use his setup i shold get an extra 15 to 25 rwkw or he just trying for the extra sale.

[Pattygtst]

If only you were in WA i would swap my 3 inch x force for the 3.5, its fairly new too.

That liverpool dude is full of it

Out of interest off topic how do you like your eboost 2 i too have one. I have read great things about them but when i took it to xspeed they were "oh you got one of those and chuckled"

Edited June 19, 2008 by Pattygtst

[newboost]

on the subject of the eboost2 i have also got mixed answers when it comes to getting it tuned correctly. I have not yet found any one that seems to know how to set it up correctly. everyone who has has had a go has managed to set up only half and i am still looking for a good tuner in the Melbourne area. I have gone to Pro Maz for tuning and found to have some problems in the way they setup the overboost settings and it is not holding peak boost levels.

[Pattygtst]

well just ring around and ask if they are familar with the eboost 2, maybe even talk to turbosmart apparently they are very helpful

Xspeed apparently got a guy from turbosmart flown over to there workshop to show them how to do it. They also said that they tested it compared to the blitz profec spec2 and that apparently held boost better. I dont know but mine holds very well,

They say it all comes down to how good the solenoid is. HKS apparently have the best one.

But if you check out alot of car mags there wild about the eboost 2

I guess it just comes down to the tuner

[raZ1911]

3.5 inch is only good when your running a lot of power like 300 kw isnt it?

[GeeTR]

But if you check out alot of car mags there wild about the eboost 2

All local car mags go wild with said local manufacture. TS must have a form of mafia that roughs up unwary editors.

Just sayin... *cough*

[blk94r33]

3.5 inch is only good when your running a lot of power like 300 kw isnt it?

Is this true? Is there a direct relationship between power output and exhaust size, in turbo applications?

Car's getting a high-flow cat and back including piping tomorrow, excluding the rear muffler which is already 3", should I go to 3" for the piping, or keep it 2.5", keeping in mind it's still using a stock dump and front pipes.

Car is a 25DE+T with R34 turbo, doubt i'll be running 9psi any time soon, and given that a standard GTST exhaust can flow that, should a custom 2.5" one do it also?

What is the standard piping size of a GTST front-pipe? As I can't measure right now...

[ARTZ]

get a 3 inch for sure bud..

standard nissan cats are pretty good youd be better to invest 200$ in one of these

http://justjap.com/store/product.php?productid=17317

they make a shitload of difference to the feel of the car, you wont regret

[blk94r33]

Cheers for the reply.

I was keen on 2.5" to keep noise down, but with a *very* long term power goal of around ~220rwkw, didn't know which way to go. Given i'm still running the N/A cat, centre pipe and centre muffler I think even 2.5" would be an improvement.

What size is the standard dumo/front pipes on a 33 GTST? (what's currently on the car) As I don't see much point going bigger?

[KiwiRS4T]

To the OP - if you have 3.5in on now keep it - yes 3in would do for now but no point in changing it just secure it a bit better if its hanging down. You may be glad of it later if your power ambitions grow like most people's do!

[R31Nismoid]

You can get a 3" exhaust legal with two large as possible mufflers and a CAT.

So there is no issue there if it is built right.

Some off-shelf jap exhausts that are quiet - are not a "true" 3" either. They have restrictors inside them to get them quiet. Some brands have made under 90dB either way, but you can certainly do it without the restriction.

[TiTAN]

You can get a 3" exhaust legal with two large as possible mufflers and a CAT.

So there is no issue there if it is built right.

Some off-shelf jap exhausts that are quiet - are not a "true" 3" either. They have restrictors inside them to get them quiet. Some brands have made under 90dB either way, but you can certainly do it without the restriction.

dont even need two large mufflers to make 3" legal. mines got a hot dog muffler and a large oval muffler and its legal (as tested by the RTA).

[R31Nismoid]

What dB @ what RPM?

I always talk in Vic laws - 90dB @ 4700rpm for a RB25 (from around 40cm away)

[TiTAN]

What dB @ what RPM?

I always talk in Vic laws - 90dB @ 4700rpm for a RB25 (from around 40cm away)

tad over 3500rpm 89dB @ a little over 3500rpm and 50cm (45 degrees from exhaust tip). if i was to take it to 4700 im not sure if it would pass but its only a 16x11x6 muffler and you can fit an 18x12x8 in the back comfortably.

[R31Nismoid]

Ye our rules in Vic still seem to be the worst lol.

I WISH our RB25 test was 3500rpm.

Our RB26 test is @ 5100rpm *sigh*