Maximum Response Setup For Rb25

[colourclassic]

So I've decided to go ahead and put together a setup which offers similar response to a stock T28-turbo RB25, while maximising mid-range power and response. I think this is ideal for a mostly street-driven car, where high rpm power is not really that practical.

The overall goal is around 230rwkw on less than 18psi, with full boost at or before 2800rpm and 100rwkw at 3,000rpm. Turbo must be internally gated and bolt-on.

The proposed setup is as follows:

RB25DET 100,xxxkms, timing belt replaced

HyperGear Factory-Spec highflow/rebuild

JJR Dump -> 100cpsi cat -> Apexi N1

S15 Injectors

R33 GT-R fuel pump

PowerFC and Z32 AFM

Scotty's Intake Pipe

JJR return flow intercooler

BCPR7ES

This is the dyno graph of the turbo in question:

*Note that this tune was limited by the injectors according to HyperGear, with the turbo able to flow a max of ~230rwkw.

*Stock R33 turbo is light blue plot.

Before going ahead with the purchase of the turbo (I have all the other stuff from previous builds), I'd like some feedback:

•Are there any other turbo options which would offer similar response but higher maximum power? I wouldn't mind having 250rwkw, just not at the expense of increased lag.

•Would 20-40rwkw gains over stock be a noticeable and worthwhile increase?

•Would it be worthwhile running e85 on this setup, and what would be needed?

Cheers!

Edited February 3, 2015 by colourclassic

[AngryRB]

Definitely run E85 and ditch those injectors and pump for Xspurts and 400Lp/h walbro, then bolt a either a GT2871 0.8rear or a GT3071 or a hypergear equivalent.

Going cheap on dump pipes and all the bolt on's will lead to disappointments, and headaches.

[Badgaz]

yep...that'll work...here are my results with my factory high flow.

z32

powerfc

850cc injectors

chinese split dump

high flow factory turbo

gtr fuel pump

chinese blitz return flow FMIC copy.

full 3" exhaust from dump pipe back 1 x resonator 1 x straight through muffler

[Badgaz]

Definitely run E85 and ditch those injectors and pump for Xspurts and 400Lp/h walbro, then bolt a either a GT2871 0.8rear or a GT3071 or a hypergear equivalent.

Going cheap on dump pipes and all the bolt on's will lead to disappointments, and headaches.

i went cheap for purely interests sake and a bit of research and just changing the factory dump to a chinese split dump made a dyno proven 5kw gain.....not everything that is cheap is useless.

[colourclassic]

yep...that'll work...here are my results with my factory high flow.

z32

powerfc

850cc injectors

chinese split dump

high flow factory turbo

gtr fuel pump

chinese blitz return flow FMIC copy.

full 3" exhaust from dump pipe back 1 x resonator 1 x straight through muffler

Who did the highflow and was this result on pulp? What is the real-world driving impression like over the stock turbo/stock boost? Cheers!

Edited February 3, 2015 by colourclassic

[Badgaz]

Yes the result is on 98 octane PULP. the real word driving is pretty good actually, i've since changed to a hypergear atr43ss2 which i find better suits my driving style....the high flow turbo makes positive boost pressure really early which can sometimes be annoying on slight inclines etc when you lift off a little as the bov has a hard time staying shut.

we had to take a fair bit of timing out as the rear housing is quite small and induced knock when the timing was too high.

my high flow was built by a friend who worked here in NZ for deisel services ltd rebuilding turbos...he's since moved to Australia. Hypergear i would highly recommend.

[Dose Pipe Sutututu]

If you don't mind running E85, that would be a good option as you can run a bucket load more timing giving you all that early torque & mid range you want.

[DoseVader]

+1 for Hypergear just got my turbo yesterday in the mail so I am yet to install, but Hypergears highflows have been proven time and time again to make 250rwkw easily with the right mods on pump 98.

Edited February 4, 2015 by DoseVader

[Dose Pipe Sutututu]

+1 for Hypergear just got my turbo yesterday in the mail so I am yet to install, but Hypergears highflows have been proven time and time again to make 250rwkw easily with the right mods on pump 98.

and awesome pre/post sales support at any weird hour of the day

[KiwiRS4T]

Sounds good but get a brand new fuel pump and preferably new injectors as well.

[RBrennan25]

and awesome pre/post sales support at any weird hour of the day

1000 times this. Really bends over backwards to keep his customers happy, he's a great bloke

[Ryno]

My car has greater than 260 rwkw and has 100 rwkw by 3000rpm.

This is on regular 98 octane, and I'm confident I could push the turbo harder to achieve closer to 300 rwkw - but it is really not needed as my car is a daily driver and I don't ever seem to use the high boost setting as it is.

My setup is a HKS GT-RS turbo mounted on a MX Performance exhaust manifold. The key to the response and power is this manifold. It has 1" runners and smashes the exhaust wheel to produce positive boost at 1200 rpm and 5 pound by 2000 rpm. You have to run an external gate though, as with the internal gate it will struggle to avoid over boosting. I ended up welding the internal flapper shut and used a Turbosmart external gate.

My car has more power everywhere in the rev range when compared to the stock turbo and is unreal to drive on the street.

I have a build thread in the Projects section if you want more info and pictures.

[AngryRB]

Yeah I think most manifold's are built for massive horsepower and not the responsive streeter, when I went a 6boost manifold over stock, the runners were longer and diameter larger than stock, and pretty sure it was the cause of lost response over stock manifold.

Edited February 4, 2015 by AngryRB

[owen1r]

Yeah I think most manifold's are built for massive horsepower and not the responsive streeter, when I went a 6boost manifold over stock, the runners were longer and diameter larger than stock, and pretty sure it was the cause of lost response over stock manifold.

That's certainly surprising, is that including the swap to external gate?

Currently deciding if I should bother with 6boob and gate for 280kw

[Ryno]

That's certainly surprising, is that including the swap to external gate?

Currently deciding if I should bother with 6boob and gate for 280kw

Go the Mx Performance manifold, it will shit all over a 6 Boost manifold in that power range. Mine has transformed the car, it's one of the best upgrades I've done.

[Ryno]

Yeah I think most manifold's are built for massive horsepower and not the responsive streeter, when I went a 6boost manifold over stock, the runners were longer and diameter larger than stock, and pretty sure it was the cause of lost response over stock manifold.

You're absolutely right, by keeping the runner diameter smaller you are maximizing the gas speed at all times. This in turn will bring the boost on much earlier.

A mate has a R32 setup up for drift which uses a MX Performance (small diameter runner) twin scroll and gate manifold. His RB26 produces around 400 rwkw with good response for drifting. So even at that power range the smaller runners are producing the goods.

[colourclassic]

Larger manifold/runners would reduce exhaust velocity/pressure. Good for high hp, not so much for response.

I'm now starting to consider the HyperGear 21U highflow as an option. I had the OP6 highflow previously and it was lacking slightly in response. Maybe the 21U will be a sweet middle ground.

[AngryRB]

Well I cant prove it was the manifold, but the setup was identical and tune was identical for both, external gate same, simply swapped stock manifold GTX3076 with gate off housing to a 6boost TS with GT3076 with TS rear and it lost response , about 500rpm, that was a single gate though so maybe that effected things.

Edited February 4, 2015 by AngryRB

[owen1r]

Well I cant prove it was the manifold, but the setup was identical and tune was identical for both, external gate same, simply swapped stock manifold GTX3076 with gate off housing to a 6boost TS with GT3076 with TS rear and it lost response , about 500rpm, that was a single gate though so maybe that effected things.

That is indeed significant but I agree that it is hard to make that call. Did you pick up anymore power from the switch? When are you seeing full boost?

[AngryRB]

never got a power run, it broke a ring landing from me playing with the boost controller, wasn't lacking power just felt lazy, full boost 4400rpm and more progressive,

just some food for thought ,

Edited February 4, 2015 by AngryRB