What Turbo(s) For Race R33 Gts-t With Steel Rb26 Engine?

[Chris Wilson]

I am wondering if the turbo experts here could offer their advice please? I have nearly finished my RB26 engine and the spec is as follows. What I need to decide now is the turbo(s) to use. I am after total manifold reliability in long distance circuit race usage, so tubular manifolds are not an option as I can't afford something with slip joints, in Inconel, and anything other will, to me, be suspect. I have 2 brand new HKS low mount cast iron manifolds for single turbos, and I have stock RB26 manifolds. I am not totally sure what material spec these HKS things are, so they may well crack, but I do have a spare and maybe access to a good used one as well. So I need advice what set up to run. I am looking for about 580 to 620 flywheel horsepower, with as little lag as possible, on UK pump fuel (98 RON), ad maybe more on race fuel for a bit of fun, with a second map. Engine spec below. Thanks.

New N1 block, new head ported and cleaned up casting. Steel crank, steel rods at stock stroke and 86.5 mm bore. Tomei cooling channel forged pistons, CR 8.5 to 1. A pair of Tomei 280 degree cams with 10.8 mm lift, SARD 700 cc injectors in modified stock rail, stock throttle bodies bored out to 50 mm with bigger throttle plates, Tomei oil pump, wet sump, external head drain assistance. ECU is a Motec M800, running closed loop with wideband. Fuel pump is Bosch 044 fed from a swirl pot.

Chassis is race spec RWD R33 GTS-t run as a 2 WD set up on slicks. Gearbox is uprated T5 dog box.

Thanks.

[Chris Wilson]

Just want to stress it's the cam duration that's worrying me, I think if I choose a turbo(s) with fairly small turbine size the back pressure versus the long duration may cause flow reversal. I went with 280 degrees so I could build something a bit stouter when I get bored with 600 FWHP, or decide to put it in a 4WD car. Thanks

[Chris Wilson]

I know the forum has been a bit slow and jittery so I am bumping this in hope of some replies, thanks guys!

[Dale FZ1]

What sort of race duration do you call long distance?

Have you checked out the fabricated manifolds done by Full-Race? High quality items, and sale of the HKS units you have would probably cover the purchase of one. Send them a message and find out. Alternatively speak with 6boost and get something direct from Australia - he has an excellent reputation. Either way you'd be getting away from cast iron if you have concerns about the HKS gear being able to survive circuit race use. They (HKS) might crack, but I doubt they'd fail.

Turbo-wise you'd best consider using an external gate setup. For the required power IMO it would be hard to beat a single GT3582, probably in 0.82A/R for a balance between lower rpm response and high rpm breathing capacity. I have nothing against twins, and there is plenty of experience on this board with the various GT2560 combos, but I think the single would lose nothing in terms of response and be easier to access for general maintenance/inspection work.

What is the targeted useable rpm range BTW?

[discopotato03]

Hi Chris , if it were me I'd use a pulse divided exhaust manifold like either your HKS cast RB26 manifolds or (IMO) the Rolls Royce - one of Geoff raicers (FullRace Motorsports in US) brilliant fabricated stainless steel ones . I know most will baulk a fabbed stainless ones but Geoffs ones are without peer . Don't take my word for it , search Full Races site and bash Geoff out some E mails .

Every performance turbo site I've seen in the US swears by FR's turbo manifolds , they may swear at the prices but very few question the results .

Ask him but I'm reasonably sure he'd suggest a Garrett GT4088R and has had a lot of success with them .

You get into a grey area with GT3582R's because there is no propper twin scroll turbine housing made for them - well not for the higher EGT petrol version of the GT35 based turbos anyway .

FullRace has used a turbo cobbled together by Turbonetics called F135R which you can see on his site but it's not a cash and carry from a local distributor here like the GT4088R is .

Geoff is one of the very few who has played seriously with single turbo RB26's in the US and I believe his opinions are well worth listening to .

Lets know where you go with it , cheers A .

Edited August 27, 2008 by discopotato03