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What Turbo's To Use When Twin Turboing A 3.0l

tai_180sx
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tai_180sx Enthusiast

tai_180sx

Posted
Posted

ok i have done a search but obviously i can't find anything on this website regarding what i need to know.

and this isn't a topic like... what turbo do you think is best.

basically i have a VQ30DET motor and i am twin turboing it. i figure the power output would be very similar to an RB26DETT..

basically i want to know what turbo's will work, and come on boost at a respectable rpm and make big power.

i'm chasing somewhere aound the 500rwkw mark..

i already have a GT35 garret turbo with a .63 exhaust housing and i was thinking about using 2 of these turbo's but i don't think i will have full boost till after 5,000rpm and when they are rated at about 500HP each turbo then i think it might be a little overkill.

so are there any GTR's out there making something around 450 to 500 kw, i'd like to know what turbo's they are using and when they hit boost. the other thing is that the VQ30DET has a rev limit of 6500rpm, i may extend that to 7000rpm but i need to have some useable power.

also yes this is a single turbo engine, i am making twin turbo manifolds for it.

nfi Community Regular

nfi

Posted
Posted

I probably wouldn't want to use the term "come on boost at a respectable rpm" when your aiming for 500rwkw. RB26's are over square so that doesn't promote good boost response but I am not sure what VQ30's are. I would guess they are under square given the "lowly" 6500rpm limit.

Twin t67's will get you there. Keir wilsons gtr uses these but I doubt they will come on boost before 5000rpm on a 3 litre.

If the engine is in a 300zx you will have serious room issues as well.

tai_180sx Enthusiast

tai_180sx

Posted
  • Author
Posted (edited)

it is not in a 300zx.

when i say come on boost at a respectable rpm, i mean anything below 5000rpm. i dont' want lag. i.e no boost on gearchanges.

i'm still chucking up the idea of leaving one big single turbo, or twin turbo's...

i already have a Garret GT3540 with a .63 exhaust housing which i'm sure will make teh power with 2 of them, but can anyone tell me when boost might hit?

if you guy's can say what hp rating the turbo is and when they might hit full boost.

thanks guys.

Edited by tai_180sx
discopotato03 Grand Master

discopotato03

Posted
Posted

By my calcs you'll need ~ 67lbs of air for 500Kw (670Hp) so about 33.5lbs per compressor for 2 .

Something like a pair of 48 or 52 trim GT2835's should get there easily enough . I don't think I'd go beyond 52T GT3037's if the rev ceiling is 6500-7000 . A pair of GT3540R's could potentially do 800Kw but I don't know of any T28 flanged turbine housings for them which you will probably need to keep the turbos and manifolds compact .

Cheers A .

Actually would a VQ35 be a better option given the limited rev range ?

BHDave Grand Master

BHDave

Posted
Posted

Out of interest, what car will it be going into? I considered a vq30det swap about 18months ago but was put off by the lack of wiring information (and cheap bolt on manual gearboxes) at the time as i had limited time to take the car off the road to do the work.

BezerkR32 Veteran

BezerkR32

Posted
Posted

I agree, would be running 28/35s or or disco potatos, if you have the room you can run 25/40s, they are an upgraded gt28 with 0.7ar comp cover, 0.64ar exhaust housing. they will flow at a good rpm but retain throttle responce. Anybody telling you to run gt35/40s are kidding themselves.

By my calcs you'll need ~ 67lbs of air for 500Kw (670Hp) so about 33.5lbs per compressor for 2 .

Something like a pair of 48 or 52 trim GT2835's should get there easily enough . I don't think I'd go beyond 52T GT3037's if the rev ceiling is 6500-7000 . A pair of GT3540R's could potentially do 800Kw but I don't know of any T28 flanged turbine housings for them which you will probably need to keep the turbos and manifolds compact .

Cheers A .

Actually would a VQ35 be a better option given the limited rev range ?

tai_180sx Enthusiast

tai_180sx

Posted
  • Author
Posted

i'd like to stick to the garret range of ball bearing turbo's if i can...

so the only problem i am seeing is if i go internal or externally wastegated. ok so say i go for two GT2860R turbo's which garret say are good replacement turbo's for the GTR and they are rated at 400HP each. that should mean i would get 800HP worth of air flow, which would make me around 500rwkw at 20 odd psi... right?

so this is probably the biggest garret GT28 series turbo before the go into the GT30 range and run the bigger 0.7 front cover.

by the way this motor is in an extensively modified 180sx...

tai_180sx Enthusiast

tai_180sx

Posted
  • Author
Posted

i spose the biggest problem is that i'd prefer to got a bit bigger than a bit smaller if you get what i mean. i don't mide driving cars with big arse turbo's. as long as i don't get lag between gear changes thats all i want.

the more power the better, but it's already at the point where i'll have no traction on teh street anyway...lol

discopotato03 Grand Master

discopotato03

Posted
Posted

No , not all GT30 turbine based GTBB turbos need to run the large .70AR ratio TO4S comp cover . These are only used with the 76mm 7/14 blade TO4S dinosaur compressors or the 82mm GT40 compressors .

The GT3071R runs a 71mm compressor and can use the TO4B cover (like the 2871R's do) or the TO4E cover they normally get and like GT2835's do .

Compressor cover families go T3 T04B T04E TO4S . The basic GT25 ball bearing centre section is almost the same ftom the smallest GT2554R up to the GT3540R (GT3582R) and all that really changes is the flange on the compressor end of the bearing housing . The smallest compressor stages are 54mm and the largest 82mm so the bit behind the compressor has to grow to suit 54 , 60 , 71 , 76 and 82mm wheel families . Then you have an aluminium backplate or adapter ring to make what are basically "T" series covers bolt to modern cartridges , once they are internally profiled to suit the compressor wheel that is . This adapter ring has a groove machined in it and butts up against a lip on the compressor end of the bearing housing and is locked in place with a large internal circlip . It fits on from the front and has a O ring to seal it up .

Cheers .

tai_180sx Enthusiast

tai_180sx

Posted
  • Author
Posted

thanks discopotato been a big help, you obviously know what your talking about...although i don't understand all of it..lol

can i just ask one question..

if i go with twin 400HP GT28 style turbo's, what sort of rpm should boost come on and what power would i be able to pull at 20psi??

i realise its not a definate answer, but an educated guess would be fine.

BezerkR32 Veteran

BezerkR32

Posted
Posted

Would be guessing, nobody knows what engine mods you have. remeber you are running two turbos off half the engine capacity. basically a 1.5litre engine pushing each turbo. would be keeping exhaust housing small for this reason. You still get the combined volume which will see you good power.

thanks discopotato been a big help, you obviously know what your talking about...although i don't understand all of it..lol

can i just ask one question..

if i go with twin 400HP GT28 style turbo's, what sort of rpm should boost come on and what power would i be able to pull at 20psi??

i realise its not a definate answer, but an educated guess would be fine.

Sydneykid Grand Master

Sydneykid

Posted
Posted (edited)

OK here’s your problem. In typical Nissan manual gearbox fashion I bet you have around a 3,000 rpm drop on the 1st to 2nd gear change (ie; ~7,500 rpm to ~4,500 rpm). So you need a pair of turbos that make full boost at 4,500 rpm and at the same time have the airflow to support 7,500 rpm without dropping of boost. That narrows the search down somewhat.

When I was looking at twin turbos for the RB30, our turbo supplier (GCG) suggested a pair of Garrett 2871RS with the 0.64 turbine for circuit work and the 0.86 for drag. They come in T25 and T28 flange patterns. This was based on what the VG30 guys were running successfully (both 3 litres). Keep in mind we have largish cams, extensive headwork, 9 to 1 compression ratio etc etc. How this compares with your set up is important

:) cheers :)

Edited by Sydneykid
tai_180sx Enthusiast

tai_180sx

Posted
  • Author
Posted

yeah i talked to GCG today and they definately suggested 2 GT3071 turbo's with .63 externally gated turbo's. said they'd be on boost at 3500rpm and will make 450RWKW on 15psi. said they have done this before and know this for a fact. so i think this will be the way to go.

anything under 4000rpm is great for lag and can easily make the power i want.

what do you guys think about this?

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