Choosing Suitable Twin Turbos

[Lithium]

Hi all, I was wondering if someone could shed some light on this topic for me....

I notice when people go for twin turbo setups for "light tune" GTRs, they seem to go for things like disco potatos etc. Recently a mate of mine asked what would be a good turbo to go for on their Starlet GT, saying they wanted a good streetable turbo which would let them get ~270hp @ crank. He had been looking at GT28 style turbos, so I went and had a look at some compressor maps and made some wild estimates.

Something interesting I found, is that at least the way I was estimating the flow of the motor etc - SMALLER turbos seemed better suited to the 1.3, but at higher pressure ratios. Funnily enough... almost so much that a GT28RS would be a worse choice than a much smaller turbo for the same power level, as at the boost level required surge lines get precariously threatening etc - but the motor didn't look like it would breath enough in the "top end" to make the size of the compressor wheel at any given pressure ratio worth while.

I looked around at other maps, and feel apon the GT22 with 59.4mm 52trim compressor wheel - which for the same pressure ratios (up to around 2.5) SEEMED by my loose estimates to be a lot more sensible.

After that, I pondered the fact that half an RB26 might be a bit better flowing up top than a 4EFTE - but not HUGELY so. When matching a pair of turbos to a straight six, should you treat it like a pair of 1.3s? Because if my assumptions are remotely correct - that GT22 turbo could actually be quite a nice match to the RB26 for a mild upgrade over the stock turbos?!

GT22 Map

[danielson]

you cant really treat it as 2 1.3l motors, as the exhaust pulses are different, and the final inlet is merged into a common collector (plenum)...and the flow of a 8000+rpm 3cyl motor would not flow the same anyway.

[R31Nismoid]

whats you power aim?

[Lithium]

  R31Nismoid said:

whats you power aim?

Say around 550hp...

[Guest Mashrock]

if your after crank power with the 550hp, something along the lines of hks 25/30's or the largest sized r34 n1's possibly even gtss turbos.

but your also going to need some supporting mods to give them that top end in say the 34n1 and gtss.. i am not sure about the 25/30's tho as they are a wee bit bigger than the later two.

[Guest Mashrock]

p.s. thats for a streetable setup

[Tommyk]

Two of that turbo would not get you to 550hp.

You would be lucky to get around 27.5 lb/min out of it at a decent efficiency. That would give you no more than 500hp for a pair.

Look at the 2530 sized garretts (which I have for sale )

Theyre good for about 35lb/min of air, and are thus rated at around the 600hp mark (id say).

If you want something streetable, go the ss's. If you dont mind a bit of lag, the 2530s arent bad and give good power. Dont forget all your support mods to get to that power level !

[R31Nismoid]

Read the sticky thread at the top of this section

Would have linked you too this thread

http://www.skylinesaustralia.com/forums/in...opic=80624&st=0

cheers