Twin Turbo question
Turbo Mini Forums

Quick question(hopefully). If I twin turbo a motor, say a gt12 and a gt17 turbo, the gt12 is good for about 8psi, if I have that spooling, will it hurt anything for it to be spooling and boosting, or should I have a bov set at the desired psi on that, and then a bov set at the desired psi on the gt17? I hope that's understandable...

-James

Okay, call me a total wank or what have you. I had a complete moment of stupidity and would appreciate if a mod could delete the evidence. I would need a bov of some sort to relieve the pressure either hot side or cold side, I've heard that it's better to have it cold side, so there it will be. One for each turbo. Let me ask a different question instead...
Would there be a problem t-ing the boost controller together for both, or should i have two boost controllers? Can something like the Apexi boost controller do two at a time?

Also, if I put in bov's cold side, do I need to connect them in any way to the manifold?

Okay, so I've answered my own questions I think through logic... blow off valves are t'd into the manifold line to provide the ms with a reading, as well as the gauge. Each turbo would have to have either it's own boost controller(manual) or a electronic one that can do both. Anything I'm missing or need to think about as well?

i think your getting waste gate and dump valve(bov to you )mixed up at least i hope you are, you should only need one bov to relieve the manifold pressure on lifting off, there is a lot of different ways to plub up a twin turbo setup, i cant see a need for more than one dumpvalve unless you want to run really short pipes on a recirculating setup ( would need a bov on each turbo)

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The reason I'm thinking two bov(and you're right, I was, that's why it was confusing the hell out of me) is because I'm having two different turbo's. I suppose I could still do one off the plenum I suppose... I'm wondering though, is it possible to run the intercooler pipes through one intercooler? Or would it be more efficient to have two smaller intercoolers and y the pipes together closer to the plenum?

You need to look into how OEM's do their staged charger setusp.

If something is worth doing, it's worth doing half of.

i think you need to draw out the design of our system as simple as you can, there is at least 3 types
true twin turbo,
sequential twin turbo,
compound twin turbo

i think the idea you have is a mix of 2 ie if 2 [different size] turbos are being directly fed and both pumping into a common plenum there will be problems

have a search for
skyline RB twin turbo system, this is a true twin turbo settup
supra 1JZ/2JZ this is a sequential system,
and lancia hf integrale (sp? maybe the wrong model too)
this is a turbocharged supercharged setup ( compound iirc)

a quick summery in my words lol

true twin, both same size turbos commonly fed and both pump into the same plenum, both spool at the same time, essentially the same as a single turbo system

sequential system, roughly the same as above, but ont turbo is shut off untill the first has boosted ,in the case of the supra it bleeds the waste gate gasses through the second turbo to pre spool it then at 4krpm opens up the exhaust system on the second turbo and opens a second butterfly in the turbo y peice allowing both turbo to boost, the turbos are the same size and the workload is shared ( again same as the true version)

a compound system, the first turbo- turbo charges the second that then turbocharges the engine i am researching this y self its quite complicated VW have made a good job of it in thier EUDM golf 1.4l super turbocharged engine, i posted a link earlyer in the week, vag compound boost or something have a look

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bollox, all that typing and i got sniped

Yes i moved to the darkside

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But the rb26 motor in the nissans is a split system as well, into one plenum. It's two turbo's, one on the front 3 one on the rear 3 cylinders. Same size as you said. I have been looking into compounding turbo's myself. Now, does the smaller turbo compound into the begger one, or does bigger go to smaller? as I think on the a-series a compound turbo set up would be more efficient than a true twin, unless of course you're using a 8 port head.

Or, if I wanted to do something similar to the nissan setup, I could run two gt15 turbo's? one exhaust off of either end, and a y split in the middle, sharing the two inner ports? Remember I'm using an 850, hence the small turbo's.

Where will all this fit?

In the 13's at last!.. Just

I'm thinking gt12 over the clutch, and gt 17 on the other side, as I'm moving the rad to the front. Or gt15 over clutch and gt15 on other side where rad was.

the RB26, is a split twin turbo, and the turbos are the same size and both take 3 cylinders each and both feed a common plenum, hence true twin turbo

i would feed the small into the big then have a bypas on the inlet side of the big turbo so once its singing its tits off it can get the air it needs instead of trying to pull it through the smaller turbo

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how would you plumb in the bypass, or rather, how would it be best to bypass it?

Edited by Brett on 22nd Jun, 2010.

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I'm thinking you're going to compound a supercharger and turbo?

To be honest i dont see what the gain will be in using two turbos on anything below 3000cc or less than 6 cylinders.
A "super turbo" maybe better with smaller capicity engine.
would however be impresive to see a twin turbo'd a-series and any results.

Edited by Brett on 22nd Jun, 2010.

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I'm hoping to have the mini back on the road by september, and then turbo'd soon thereafter.

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lol, I don't have to MOT mine!

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Hence my problem Paul. I'm trying to get low down boost for better use. I don't spend a lot of time over 4500 rpms... Sometimes I take it to 6, but if I don't get boost until 5k I'll never see it. Hence, thinking if I have a small turbo(gt12) for low spool, and a gt17 or gt15 for when I do take it over. Problem is, there is no real efficient way to twin turbo the 5 port, as you'd have to y the middle two exhaust due to the siamese nature and I think that would make it more like having one giant turbo, as the exhaust wouldn't spool as quick. So, I'm not sure if it would be better to have a twin turbo like that(y-d inner 2 chambers) or a single small turbo.