Building A Responsive 250rwkw+ Rb25

[aDrew_C]

Not really building, as I want to keep internals stock where possible, this is on the cheap to an extent. Yes I've searched, I've seen the options, but can't get enough comparison between them cause of deleted dynographs and other reasons.

But, I've been researching turbo's for quite a bit, and was convinced on a highflow of some kind, but am now changing my mind.

I want 2335 type response, with the ability to break 250rwkw. Initially I'd be more than happy with 230rwkw or around there, maybe less seeing dyno wont be in shootout. My current mods are: microtech ltx-12, 3" turboback exhaust, 300x600x75 fmic and custom 2.5" (?) piping, pod, splitfire coils. I will be buying 550cc injectors and a HD clutch when I buy the turbo.

So what do I want:

- I'd prefer something that's easy to bolt on, tune, and drive away. Either as a bolt on replacement or in kit form.

- boost to start building around 2500rpm at most

- 1bar before 3500rpm

- 250rwkw+ potential

I'm really leaning towards a HKS GT-RS, but keep getting mixed feedback. I really want to know, without cams, when one actually starts spooling on an RB25 with mods similar to mine, and when it will reach ~1bar. What power can the 0.64 housing reach? Is it worth considering the 0.8x housing for what I want?

Another thing is wastegates, for the price of a HKS kit, i'm not far off buying a gt3071, cheap manifold, and external gate. Will I find an internal gate frustrating at the power I'm after? Can someone also confirm the responsiveness of a gt3071?

Ok the last of 21 questions. Cams, are a good set of 256-260 degree cams worth it, my mechanic advised against it, but the benefits are just too tempting. Do cams of this size cause a notable drop in low end response, or is it that small and the midrange-top end gains way to big to even worry about it. Also, are just straight matched intake and exhaust cams the best for response, or would 256 on intake and 260 on exhaust or vice versa be worth it?

Well hope I can get at least some help here, I have found most bits of this info from searching, but I can't relate it all to what I want out of my 25, so I hope someone can make it a bit clearer for me

[nsanity]

I'm chasing the similar power gains, and have no desire to f**k with internals.

The shopping list.

Full Catback Exhaust + Dump pipe

Hi-Flow Cat

FMIC

K&N Airfilter or Pod, with Cold Air Induction snorkel

Fuel Pump (think Bosch 040 or 044)

Coil Pack

PowerFC (or similar)

Boost Controller (Electronic is easier)

Z32 AFM

Cams (Tomei for example)

Injectors (shoot for 80% duty with your target output, that way something can fail and you wont blow your engine)

HiFlow RB25 Turbo

Thats roughly the order too.

All that, plus a tune by someone who knows whats up, you're looking at 250-280rwkw, every bit as responsive as the original turbo, and very very quick. (n.b this is for an RB25, RB20 you'd probably need to massage a little more)

Edited February 19, 2007 by nsanity

[aDrew_C]

Looked into the highflows quite a bit, a lot of mixed results, and in the end I'm just not 100% on them. Still considering it though, I have two rb25 tubos, the one I'm not using is a 34 neo turbo with an OP6 rear housing. I have a walbro pump, not the best but yeah, hopefully just injectors, clutch and turbo and that will do it.

Starting to like the idea of a 3071 now, they give results on par with a hks 2835, right? Same response in 0.64 form? A 2835 is less hassle for sure, but will an internal gate be something I regret keeping for over 250rwkw?

[aDrew_C]

Can someone point me in the direction of some dynos of 3071's and 3076's with psi graphed? I can't seem to find anyone on here whos posted one that's still showing, or has the info I need. Both 0.64 and 0.86 exhaust housings. This is getting a bit frustrating :\

I know a 3071 with 0.63 turbine housing A/R will give me the results I want, but without much future potential.. I'm really after a proper comparison between the 0.64 and 0.86 version, and the 3076, which I'd really only prefer in its 0.86 form, due to the larger compressor, but I'm still to be convinced!

3071 0.5 Comp A/R, 0.64 Turbine A/R

3071 0.5 Comp A/R, 0.86 Turbine A/R

3076/37 0.6 Comp A/R (shrouded), 0.64 Turbine A/R

3076/37 0.6 Comp A/R (shrouded), 0.86 Turbine A/R

There are the four I'm lacking decent comparisons between. Someone please help shed some light on how these turbo's actually perform on an RB25, with response vs. top end being the major factor.

Cheers.

[paulr33]

if you want 250rwkw gcg hiflow

dont bother with the gt30xx variants, you dont need the extra compressor flow, youll just get more lag. the smaller the a/r rear the better, given you want 2500rpm wind up forgoet the 0.86 rear options, dont bother.

[YSR020]

Hey mate - I did similar reaserch sometime back for my old R33 and had similar goals to yourself, as most R33 owners do. I spent more time using the SAU search function than I'd admit to, spoke to many workshops and turbo builders and also a heap of time on the net, and here's my two cents based on what you've said above;

- An internal wastegate will support 250-260kW with relative ease

- Cams are worthwhile for your requirements, especially at the price you can get them now...Poncams baby!

- You cannot go past an HKS turbocharger (My vote is GTRS - been proven to make 300kW, altho inefficiant at this power level I'd imagine, it shows what it's capable of). Ultimately HKS spend millions of yen developing that product specifically for RB25 (in this example) and in my opinion absolutely blow away the R&D level of any other turbocharger made to suit your specific application...ie Highflow, 3071R etc...

- This will be useful to you; http://www.skylinesaustralia.com/forums/in...st&id=25136

Best of luck!

Chris

[aDrew_C]

Thanks for that.

I was sold on a highflow before, mainly cause of the stock-like response and easy replacement. But for the price of a gcg, I'd rather fork out the extra $400-500 for a HKS GT-RS kit.

The only problem I have with the GT-RS is actual results. Chris, that graph you linked to is exactly why it looks like the perfect turbo for me, decent response, insane midrange, and good top end. I just need to see some dynos that back this up! I can't find any that also have the boost graphed!

Well I'm on the right track at least.

Cheers

[YSR020]

I know it doesn't show boost, but GTRS = 150kW+ @ 3500rpm...which would have to be nearing 1 bar surely...! Even so...1 bar or not that's big power at such low rpm for a 2500cc engine...in my books anyway...

Another point to consider is that you're running a somewhat unusual Microtech which would be a performance advantage over the common PFC due to being able to do away with AFMs etc...

Once again my 2c...PM me your results if you don't mind mate...curious as!

[NYTSKY]

At present ill be fitting a highflowed RB25 turbo with a VG30 rear housing(ball bearing).

With the mods i have i reckon ill pull a 260-280rwkw when its all done.That might be the way to go for your setup.