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Would I Gain Anything With Exhaust Cutout On -5S ?

cobrAA

By cobrAA,
in Engines & Forced Induction

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cobrAA Mentor

cobrAA

Posted
Posted

My tuner here in canada managed to tune a rb28 with gt860-5 with stock cam I believe and it made 640whp on a dynapack.

I can say I have all the supportive bolt-on mods you could get + haltech ecu + aquamist kit. running 3 inch exhaust.

Do you think/ have anyone made the test on a dyno I would be gaining something ''worth the hassle'' of an exhaust cutout on my RS*R front pipe ?

If we're talking 10whp, with no extra torque or more responsive engine, I think we can say its not worth to hack a RS*R pipe + the cost of labour and cutout. However, if I can make the engine more responsive, add 15 lbs of torque .. then it could be interesting.

Your though ?

GTScotT Grand Master

GTScotT

Posted
Posted

Can you elaborate on what you mean by cut out?

640whp is mega. I believe Piggaz is the only one in Aus running just shy of that with -5s on an RB28.

General rule of thumb is that if you drop your exhaust before the cat and gain lots of power you have a restriction in your exhaust. Otherwise you should realistically be looking at 10-20whp tops.. And a 3" system should support close to the asking price.

Piggaz Grand Master

Piggaz

Posted
Posted

3 inch?

Throw that in the bin and put something decent on there.

How much boost and what fuel are you running to achieve those figures?

I'm running a twin 3 inch system on my car.

As a comparison, GT RS's at 2 bar made 414 rwkw using a kakimoto full mega N1 (rubbish catback which was 80mm into a 90mm into some peanut rear muffler which at best would have been 2.75 inch inside). Going back to -5's, from pods to stock airbox and the much bigger exhaust netted 426 rwkw at 23 psi, cam gears and the rear of the setup remained unchanged. Same car, same tuner, same fuel, same dyno. At that power level there is much to be gained.

XKLABA Grand Master

XKLABA

Posted
Posted

Dynapack is a hub dyno where Paulie is on a chassis dyno so I think Paul is still ahead, just

3" exhaust IMO is to small for that power range and I'm sure you would pick up a fair bit with a 3.5", but as already mentioned drop the cat and run again and see if there is a restriction in the rest of the exhaust

cobrAA Mentor

cobrAA

Posted
  • Author
Posted

heres the cutout I'm looking for and will be installed before the cat :



I wanted to drop the catback and see by myself.. but the tuner said he's not a fan of messing up with the car while the car is on the dyno.. so if I have to pay 300$ just to see if theres a gain, I might as well pay 300$ to buy the cutout and have it installed lol.
cobrAA Mentor

cobrAA

Posted
  • Author
Posted (edited)

3 inch?

Throw that in the bin and put something decent on there.

How much boost and what fuel are you running to achieve those figures?

I'm running a twin 3 inch system on my car.

As a comparison, GT RS's at 2 bar made 414 rwkw using a kakimoto full mega N1 (rubbish catback which was 80mm into a 90mm into some peanut rear muffler which at best would have been 2.75 inch inside). Going back to -5's, from pods to stock airbox and the much bigger exhaust netted 426 rwkw at 23 psi, cam gears and the rear of the setup remained unchanged. Same car, same tuner, same fuel, same dyno. At that power level there is much to be gained.

right now tuned for 23psi with 94 octane (us fuel) I'm running r34 dump ( 58mm) to a RS*R 70x2 to 1x80mm all the way to the end (no cat). Already bought myself a set of 70mm dump pipe, would just need to install a cutout right after the merge to unleash more flow. ( I have no choice to run max. 3 inch exhaust if I dont want more cop attention than my skyline already draw lol)

Edited by cobrAA
XKLABA Grand Master

XKLABA

Posted
Posted

That cut out is dodgy as hell and if you put that in your front pipe here it would be an instant $10,000 EPA fine

Not to mention it would drop back pressure from your engine leaning your motor out, do it properly and up grade the exhaust with the dump pipes you already have then a matching front pipe with a 3.5" outlet and the 3.5" cat back

3.5" exhausts can be made very quite with good quality mufflers, I had a custom twin 3" into single 4" made for my car and it is quieter then the 80mm jap spec that can off it

cobrAA Mentor

cobrAA

Posted
  • Author
Posted

Why can you not run a bigger exhaust? Is it the noise or just the size of the pipe that attracts attention? Going to 3.5in from 3in will allow roughly 35% more flow.

Both! but even if your car is quiet.. a big pipe will still draw useless attention.

That cut out is dodgy as hell and if you put that in your front pipe here it would be an instant $10,000 EPA fine

Not to mention it would drop back pressure from your engine leaning your motor out, do it properly and up grade the exhaust with the dump pipes you already have then a matching front pipe with a 3.5" outlet and the 3.5" cat back

3.5" exhausts can be made very quite with good quality mufflers, I had a custom twin 3" into single 4" made for my car and it is quieter then the 80mm jap spec that can off it

Well, i tried and couldn't find any quiet resonator in 3.5 inch. So I decided to go the cutout route, but since you mentionned that 10k fine, I can see now why in Aus, guys dont put cutout. we don't have this fine over here.

Ben C34 Grand Master

Ben C34

Posted
Posted

it all depends on the turbo and what its capable of...wont get much if you have a 3 inch turbo outlet flange and go 4 inch in exhaust. Gotta increase flow from the source then work your way down.

Sort of.

cobrAA Mentor

cobrAA

Posted
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Posted (edited)

It will surely sound very angry, but I would only activate it on a drag strip or on a highway if I meet with a modded supra hahaha. I'm just scared that I will gain little with this mods. Like, how many have been able to break the 600whp marks on a dynapack with a pair of -5s ( on a rb26) ? Not to mention when I did 576whp, I still had stock intercooler, no water-meth and nistune maf ecu.

Edited by cobrAA

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