rb25/26 600hp GT30 or 35?

[Clint32]

I currently deciding on what turbo im going to use for my car, chasing 600hp form my rb25 built up with rb26 crankrods and forgies, cams, headwork and have all other support systems in place, cooler, ecu, injecotrs, exh are all over adequate. Car will be used for drags, circuit work and anything else so dont wont heaps of lag.

Whats going to work the best out of these two choices

GT30, .82 exh housing, rated at 600hp or a GT35 with a .82(or even .63) housing. im leaning to the gt30, but what is the real difference in lag between the two, any experience. cheers clint

[Clint32]

using details from this page

http://www.gcg.com.au/technical/garrett%20...ng%20turbos.jpg

[R31Nismoid]

GT 30, same thing i am using, and many others.

Great results

[N I B]

GT30 for 600 is a little small a 35 would be better.

[Bl4cK32]

Yer im using the gt35/40r for something like 350rwkw. Its got the 0.82 rear on it....but that is on the 3Lt

[Clint32]

How would the GT35 perform with the 0.63 housing to help reduce the lag.

also the manifold i have is low mount and im worried that the extra size of the GT35 would mean it will not fit. Also the engine will be run in and fully tuned on the engine dyno so it will get a very good tune to get the most out of it and find out what it realy makes

[Bl4cK32]

Steve had a .6 housing on his 3037 on the rb25, and boost came on like a switch, if i remember correctly....

[Roy]

What sort of cams/head will you be running. With an A/R of 0.63 i suspect that you could possibly run into surge problems running such a big compressor (what A/R compressor and turbine with the GT35)

Maybe do a search around US sites , some interesting combos of turbos there, Supra and all...

[Freebaggin]

I currently deciding on what turbo im going to use for my car, chasing 600hp form my rb25 built up with rb26 crankrods and forgies, cams, headwork and have all other support systems in place, cooler, ecu, injecotrs, exh are all over adequate.  Car will be used for drags, circuit work and anything else so dont wont  heaps of lag.  

Whats going to work the best out of these two choices

GT30, .82 exh housing, rated at 600hp or a GT35 with a .82(or even .63) housing. im leaning to the gt30, but what is the real difference in lag between the two, any experience.  cheers clint

600HP is alot and if you want that much you need a very big turbo and therefore lag.

I have GT30 with "600HP" rated compressor wheel with 0.63 exhaust housing and internal gate. I get 280rwkW at 1.2bar, but I think if I was game (stock pistons ATMO) and ran 1.5bar I would easily get over 300rwkW. From what I read that's about 360kW at the flywheel which is "only" 480HP.

You know approx my setup Clint.

Even with nice aggressive cams and head work that I assume you are doing to get to 600HP I reckon you'd surely need the GT35 with the 0.82, run 1.5 at a min and use lots of revs.

[Clint32]

272 cams and just a mild port job/cleanup nothing major but enough to make a difference.

re the surge roy thats what i was worried about also, GT35 has a 0.7 A/R with a GT40 comp wheel 82mm, so its pretty large.

[Clint32]

600HP is alot and if you want that much you need a very big turbo and therefore lag.

I have GT30 with "600HP" rated compressor wheel with 0.63 exhaust housing and internal gate.  I get 280rwkW at 1.2bar, but I think if I was game (stock pistons ATMO) and ran 1.5bar I would easily get over 300rwkW.  From what I read that's about 360kW at the flywheel which is "only" 480HP.  

You know approx my setup Clint.

Even with nice aggressive cams and head work that I assume you are doing to get to 600HP I reckon you'd surely need the GT35 with the 0.82, run 1.5 at a min and use lots of revs.

thanks for your numbers mate, i would settle for 550hp but how much of a restriction is the internal gate/exh on your setup compared to a 0.82 external gate turbo, i hate these decisons

[Freebaggin]

272 cams and just a mild port job/cleanup nothing major but enough to make a difference.  

re the surge roy thats what i was worried about also, GT35 has a 0.7 A/R with a GT40 comp wheel 82mm, so its pretty large.

Head work etc looks good.

Don't worry about surge, basically I have a GT3040 CHRA with the 82mm comp wheel but with 0.6a/r comp housing plus the 0.63a/r exh housing.........it does not surge at all, it's fantastic actually.....but it won't make 600HP. The compressor wheel size is good for 600HP (better with a 0.7a/r) but you'll essential need less restriction in the exhaust side to achieve that number so that's where the GT35 comes in + maybe a 0.82a/r, but it's more important to have a big exhaust wheel (particlarly a big outlet diameter) to prevent back pressure at high revs.

If you aimed for say 520HP then a GT30/40 would do it with ease with the right support gear on the motor and with less lag ....... but that's the compromise eh.

[Freebaggin]

thanks for your numbers mate, i would settle for 550hp but how much of a restriction is the internal gate/exh on your setup compared to a 0.82 external gate turbo, i hate these decisons

Yeah, no doubt with an external gate it would be a bit better for flow and I would go with that setup as it's optimal compared to mine but my original aim was "only" 250rwkW and it's doing it easy.

Mate, it all comes down to the ultimate power you want and why...for bragging or for dragging or do you want a circuit/Adel hills beast.

For me 2.5L and 600HP in the hill would be just too hard to handle and not "fun", torque band is just too narrow. But for draggin and braggin, that's a different story.

If it were me I'd go slightly smaller in wheel size and just run more boost, particularly if you have nice forged pistons. Nothing wrong with 1.5-1.7 bar if the motor and coolling system can handle it.

So I'd recomend a GT3040 CHRA with 0.7 comp cover and 0.82 exhaust and simply see what you get. You'll have a much higher rev range than me so don't worry, you should have a nice big tourque band to play with

[Clint32]

yep thats my thinking to, not worried about boost, illl run as much is it will efficiently and always run good fuel, eg elf lms. I

[N I B]

Paul ( GTStVspec) has 450rwhp in his GTS running a GT30 with stock head and cams but GTR rods and Arias pistons and Greddy intake with the fuel pump at its limit so we dont know if there is much left.The power curve is the best ive seen.

Magic1 has the same set up but stock intake but 256-264 cams,His pump died at 435 but has 365hp by 4500rpm.Both cars rev past 8000 with out the power falling of and run modest boost.Still think 35 is needed for a tru 600 but the average power wont match the 30.

[Cubes]

Let me know how it goes Clint.

From the results of Freebaggin I think I am seriously going to look at his setup but with a .82 exhaust a/r, a small .6? exhaust a/r on the 3ltr may make throttle control impossible. I don't know..

[Freebaggin]

Let me know how it goes Clint.

 

From the results of Freebaggin I think I am seriously going to look at his setup but with a .82 exhaust a/r, a small .6? exhaust a/r on the 3ltr may make throttle control impossible. I don't know..

Joel,

The 0.82 will be good for the 3L.

Will you just get an off-the-shelf complete Garrett turbo and then fabricate a manifold + ext gate or go for a Tim or XTR style int gate hybrid like mine. To be honest, all the effort you are doing with motor mayeb better to go ext gate and fully designed manifold. My power drops off when I go past 7200-7300, might be internal gate restriction in exhaust???????

Steve-SST,

Do you remember what "moderate" boost was for 435rwhp?

[Cubes]

Freebaggin'

I really don't think its got anything to do with the internal gate causing a turbulence issue over 7200rpm, if anything it is the stock cams and or the small exhaust a/r. Most likely the exhaust a/r.

Do you have a split dump that rejoins later down the front pipe?

Taking all things in to consideration making peak power hence power dropping off over 7200-7300rpm isn't too bad for a stockish setup.

Shaun was telling me of this bloke who has a 3ltr in his R32.

Its using a hybrid RB20 highflow thing. It made around 240rwkw on 16psi but power noses over at 5000-5500rpm. The power nosing over, he is definate it is due to the small exhaust a/r.

Shaun went on to say that that same bloke is doing or is getting done (I'm unsure) the same type of turbo as you have but with some diesel internal gate .8? exhaust a/r.

He is confident it will make 300rwkw with no problems.

A while back when I was talking to Tim he mentioned your turbo.

I questioned him regarding the exhaust a/r size and 300rwkw.

He said it would 'just' but appeard a little unsure.

I mentioned the VG30 non-BB (can be machined to suit) .82 exhaust a/r's, he thought it would be a good idea on the 3ltr.

[Cubes]

Sorry to hijack Clint.

[sky30]

joel

yea i had the hiflow rb20 turbo on a 3.0l at shauns, pulled hard as to 6000, then nosed over real bad. Have just finished putting on my 35/40 but having problems controlling boost with the small int gate, hits 24-25 psi when reving past 5500-6000. I gota make my gate bigger b4 i kill the motor.

The .82 housing is definately alot lagier then the RB20 unit about 800- 1000 rpm.

I was gong to use the VG housing, but the ex wheel hung out the back (to big for housing) .

Freebaggin,

What specs A/Rs is your turbo, and what motor?