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Choosing Suitable Twin Turbos

Lithium

By Lithium,
in Engines & Forced Induction

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Lithium Grand Master

Lithium

Posted
Posted

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

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danielson Proficient

danielson

Posted
Posted

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.

Guest Mashrock

Guest Mashrock

Posted
Posted

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.

Tommyk Veteran

Tommyk

Posted
Posted

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 :P)

gt2860R_707160-5_comp_e.gif

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 !

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