Exhaust Diameter For High Powered RB26

[Shaun]

GDay,

Im in the process of putting an RB26 in my R32 gtst. Its a full rebuild engine with all the forged stuff and a single 700hp garrett high mount turbo. The guy who has done the engine work, and who will be modifying the exhaust, has recommended a new 3.5inch exhaust. I currently have a stainless 3inch turbo back system which cost around $2000. I dont want to upgrade if its unneccessary.

My question is:

Will a 3inch exhaust be sufficient for around 350rwkw maximum?

If not, is four inch better?

I have been told (and read) that anything greater that 3inch is overkill. Is this correct for my application?

Any advice from people with first hand knowledge in this area would be appreciated.

Shaun.

[CEF11E]

Try the one you have ATM it shouldnt be throttling/choking the engine. my freinds car just dyno'd 394rwkw with a 3" exhaust its a rb30det with a big single KKK turbo.

Then he took off the cat and put a straight thru pipe and dynoed 412rwkw!

you cat might hold you back but the exhaust will prob be fine for your application

[WetGTR]

My GTR R33 has been dynoed at 412awkw and I have a 3" exhaust system.

The thing is when I removed the external wastegate pipe to be plumped out to atmosphere I picked up another 5kw.

This is using a straight through pipe as my cat which was also at 3" but I am now ungrading to 3.5" system as there is more power there.

There are no gains above this and the outlet on the turbo would be no greater then 3.5" so there is no point in going any larger.

Your exhaust system is as big as the smallest point in the system.

I don't want to to this as well as I am so very happy with the way my car sounds and don't want to lose it but the extra power is just sitting there doing nothing....

[Shaun]

Thanks for the advice. I just dont want to spend more money! I might just keep the 3inch system for now and get a larger one when money (girlfriend) permits.

Shaun.

[Russco]

My GTR R33 has been dynoed at 412awkw and I have a 3" exhaust system.

Wow, what mods have you done to get this?

[WetGTR]

The following modifications are as follows:

RB26 ENGINE

HKS 88MM FORGED PISTONS

HKS CON RODS

HKS STEP 2 280 CAMSHAFTS

HKS CAM GEARS

HKS 1.6MM HEADGASKET

JUN OIL PUMP

PERFORMANCE METALCRAFT 8L RACING SUMP

PORTED HEAD

NISMO BEARINGS

NISMO CAMBELT

AUTRONIC SMC AND LOOM

1000CC INJECTORS

BLITZ FUEL RAIL

MALPASSI FUEL REG

SPLITFIRE COIL PACKS

GARRET BALL BEARING TURBO(NEW T04Z) - RACEPACE CUSTOM

RACEPACE CUSTOM EXHAUST MANIFOLD

TRUST EXTERNAL WASTEGATE

NISMO G-MAX TWIN PLATE CLUTCH

HKS GT SPEC DRAG INTERCOOLER

CUSTOM FUEL SWIRL POT - TWIN OUTLETS FED BY GTR FUEL PUMP

2 X BOSCH 044 EXTERNAL FUEL PUMPS

HKS OIL COOLER KIT

TRUST EXHAUST 3"

ARC ALLOY RADIATOR

ARC OIL CATCH TANK

HKS EVC4

HKS COLD AIR INTAKE

TUNED BY BEN @ RACEPACE MELBOURNE

CURRENTLY MAKING 417KW@THE WHEELS AT 1.3 BAR

WAS MAKING OVER 500KW WITH PREVIOUSLY FITTED HKS T51R

[Russco]

WetGTR, impressive list - what are the 280 cams like on the street?

Shaun, I went from 3" to 3.5" on mine - picked up about 60rwhp but having said that my 3" system was not a quality system like Trust, CES etc.

[WetGTR]

Cams make the engine lumpy like a V8 but it's idle is awesome.

I don't find any faults with street driving at all, has good power off boost and loooovvvves to rev and pull's hard all the way to redline @9500rpm.

Like to see if I pik up more power with a 3.5" exhaust, I think there is some left in it..... well just have to see

[MSRB26]

I would not hesitate to recommend larger than 3 inch for a RB26 pushing anything over about 300kw atw. Once you go bigger you quickly realise how much it was being strangled. It's easy power

[Cubes]

Generally a 3.5" is required up over 300rwkw to be 'optimal'.

I want to keep the noise down so I will be going a 3.5" dump in to a 3.5" cat, then a 3.5" pipe in to a intermediate muffler that splits the 3.5" in to 2 x 2.5" pipes, 2.5" pipes to the rear of the car where there is another large muffler, 2x 2.5" tips out of the muffler.

It will flow really well, not drone and sound quite nice.

Its very similiar to the XR6 APS exhaust system.

[WetGTR]

Generally a 3.5" is required up over 300rwkw to be 'optimal'.

I want to keep the noise down so I will be going a 3.5" dump in to a 3.5" cat, then a 3.5" pipe in to a intermediate muffler that splits the 3.5" in to 2 x 2.5" pipes, 2.5" pipes to the rear of the car where there is another large muffler, 2x 2.5" tips out of the muffler.

It will flow really well, not drone and sound quite nice.

Its very similiar to the XR6 APS exhaust system.

Hey cubes, this is a clever way of reducing the noise and still keeping the noise levels down....I like it

Q. How would a HKS Super Dragger Exhaust sound (3.5" straight through) on a built RB26?

This is what I was thinking of doing when I replace my 3" system to a 3.5" system.

Weird thing is I have a 3.5" system to the cat then 3" system to the rear :microwave

[Cubes]

i'm not sure how the Super Dragger would sound.. Obviously loud.

My goal was to make the exhaust look fairly standard out the rear and sound as quiet as possible with no drone inside the cabin. The large intermediate muffler was the only way to go with 2 x 2.5" pipes.

Apparently a single 3.5" does flow better than 2 x 2.5" pipes but it is much louder.

[Shaun]

Ive just sold my 3 inch exhaust in favour of going to 3.5. Can anyone recommend a japanese brand exhaust that has the following features?:

• Stainless steel

• Sits nice and close to the body. Ive heard that some jap exhausts hang down too low.

• Isnt offensively loud so that it attracts cops.

Also, if anyone has info relating to where i can get such an exhaust, can you let me know?

Any feedback would be appreciated.

Thanks,

Shaun.

0414972596

[MSRB26]

I would highly reccomend a Trust TR (they are 3.75 inch i think) they fit the bill for your requirements except for the stainless steel part which is really nothing major. The silencer system they have is very effective and they make room for large power increases.

Advan Perfromance in Silverwater stock them - 9647 1326

[Shaun]

Yeah, i rang them today. They retail for about $1700 for cat back. Does anyone think this is expensive considering theyre mild steel?

[MSRB26]

I think you would be hard pressed to find another exhaust of that size around much cheaper than that. Also remember the TR comes with a cat replecement pipe (for racing use only) which alot of others don't.

[Cubes]

There's better value systems out on the market. $1700 for a cat back mild steel. lol

Why not run a twin 2.5" or even better 3" with a rear and intermediate canon muffler?

[Gts-t]

IMO a japanese car needs a new japanese exaust.

Believe it or not but japanesemotorsport have much better prices on the trust exausts. I think mine was around 1200 delivered(2years ago), took me minutes to install, not much louder than stock at idle, great note, no drone, etc, etc.

Do not commit the sin of the australian made catback system., it will look and sound like shite, not to mention being the japanese ones are typically designed on CAD software.

Support local front/dump pipes instead!!!111@2

For look, sound, performance you cant go past a japanese system, stuff the price :wassup:

[Shaun]

Support local front/dump pipes instead!!

Ha Ha, Funny sh1t! Thats exactly what im doing. Ill give JMS a ring, but if im gonna pay the dollars i think i want stainless. I might look into Apexi.

[Guest two.06l]

Support local front/dump pipes instead!!

Ha Ha, Funny sh1t! Thats exactly what im doing. Ill give JMS a ring, but if im gonna pay the dollars i think i want stainless. I might look into Apexi.

Give Peter a ring at Advan, they get some great TRUST front pipe copies made up...you would be hard pressed to tell the difference!

P.S. why do you want stainless?