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don't know to much about the rb motors but my wrx makes 320atw with a gt35.82 seeing full boost(25psi) at 4200rpm, I would have thought a 35r on 6 cylinder would be a good match and you would see full boost hitting alot earlier???

AGREED.

Pretty much the same situation with an 1992 VR4 RS.

320kw at the wheels, factory bottom end. GT3540, made 18psi at 4500rpm.

i think that a slightly bigger turbo or even the GT35.82 would be a near perfect matchup for the RB25

A GT3582R is definitely better than a GT3082R on an RB25 (or most things), one of my mates went from GT3082R to GT3582R on his EVO and the drive was much of a muchness - just made quite a bit more power. GT3076R is a fair bit of an improvement to drive, but a twin scroll GT3582R would be the dogs bollux I reckon.... if they were around when I was doing my turbo choosing I would have put a fair bit of consideration to one of those as an option.

Lasted 6 months... and the only reason it died was my laziness. Nothing else.

From my own experience, having a GT30 on my RB25, I think it is an excellent turbo. My car drives incredibly smoothe, power is incredible, delivery is excellent etc. But Mick at ovaboost would have to be the best RB tuner in WA. Tune is where its at! I'm sure any car would be a pig to drive with a poor tune.

From my own experience, having a GT30 on my RB25, I think it is an excellent turbo

Which GT30?

- Garrett GT3071R

- The GCG "GT3076R" with the .70a/r EC-1 compressor cover

- Garrett GT3076R with anti-surge compressor cover

- Garrett GT3082R

- some other combo?

They're all reasonably different beasts!

AGREED.

Pretty much the same situation with an 1992 VR4 RS.

320kw at the wheels, factory bottom end. GT3540, made 18psi at 4500rpm.

i think that a slightly bigger turbo or even the GT35.82 would be a near perfect matchup for the RB25

factory bottom end? thats a shipload of power for a standard bottom end, must of had some huge ass cams and only 18psi :D

don't know to much about the rb motors but my wrx makes 320atw with a gt35.82 seeing full boost(25psi) at 4200rpm, I would have thought a 35r on 6 cylinder would be a good match and you would see full boost hitting alot earlier???

EJ20?

Spool I very difficult one to compare as a result of gearing and how one tests where 'full boost' is.

My experience driving a few setups over the years...

GT35r .82 on an RB30DET top gear loaded up would see 17psi around 3100rpm.

Normal driving conditions in second gear leaving a corner it would punch hard around 3600rpm.

GT35r .82 on an RB25DET top gear loaded up would see 17-18psi around 3700-3800rpm.

Normal driving conditions in second gear leaving a corner it would punch hard around 4200rpm.

The biggest noticeable difference between the two setups was the 3ltr made more boost earlier providing a more linear power curve where as the 2.5ltr would go from what felt like nothing to everything.

your going to have to explain too restrictive to me. as in no top end?

It just limited the set-up overall.

Yes it'll bring on boost sooner, but the problem is the flow, you run into back-pressure in the turbine housing too soon when you take into account how much air the comp wheel flows.

It'll limit the amount of boost you can run so the turbo wont be making the most of what it possibly can.

If you wanted to go a .63, you are far better off with a hi-flow style R34/OP6 hi-flow of some description as the power output will be similar, response better.

This is all RB25/26 specific of course. Other motors, different dynamics

  • 4 months later...

Sorry to bring the post back up but I wanted to know if there was a difference in any aspect of the turbo if I get it with the S-style Anti-Surge compressor housing in/out is 4'' / 2''

Thanks for any info !!

Your calls but I would avoid the GT3082 like the plague - unless you can get the 50 trim compressor version which was the HKS spec one "GT3040" .

I cannot for the life of me see anything desirable about having a compressor wheel that's simply too big/much for the turbine to drive . The reason why they are lazy turbos is because they need a lot more exhaust gas energy (read higher WOT engine revs) to get them going .

I reckon if you need the sort of airflow that the 82mm GT40 compressor can pump then at least give it the GT35 turbine to drive it with .

I think its hard to go past a GT3076R on an RB25DET size wise , even these can be borderline laggy on the street but at least they are a reasonable wheel match and they are more than capable of frying road rubber .

There is no way I would accept a GT3082R for price reasons , I have and would not hesitate to pay more for the GT3076R knowing that it will give a better overall result and that's what makes you like driving your car on the street .

I know people think that HKS spec Garrett GT BB turbos have some sort of magic breathed into them but that's just garbage . What they did was have Garrett play around with wheel sizes and trims to optimize compressors to turbines so that they give good results on performance petrol engines . By good performance I mean a turbo that spools up and makes good engine torque over a reasonably wide range .

If you actually look at their spec turbos they often have a more minimalist approach particularly with compressor trims - look at these :

GT3071R - HKS 48/52/56T - Garrett 56T only . (HKS incorrectly called these GT2835 but they use a cropped GT30 turbine)

GT3076R - HKS 48/52/56T - Garrett 56T only .

GT3082R - HKS 50T - Garrett 56T only .

GT3540R - HKS 54T - Garrett 56T only . (HKS call their version GT3240 but the turbine is a cropped GT35 one)

Remember the pretty blue "Power and Response" tag ? Its because they aimed to make torque which is the thing that shoves you in the back .

I think GT3582R's are a real bitzer in that both ends don't use appropriate housings for their wheels , GT35 turbine in a GT30 turbine housing and GT40 compressor in a T04S compressor housing . I reckon it was all aimed at using biggish wheels in a small compact cartridge and ditto for the housings themselves .

I reckon its why you can sometimes achieve similar or better results using older T series BB turbos like the large frame BB T04 60-1 turbo . These use a T04 P trim turbine in a T04 turbine housing and a 76mm (3") T04 60-1 compressor in a T04S comp housing designed for a 76mm T04S compressor . Everything pretty much matches and you get 1001 T04 turbine housings in single/twin entry and T3/T4 mount flanges .

Years ago I saw someone that used a plain bearing P/60-1 turbo on a hotted up (head/cam/injectors) RB30ET Commode Door and he tore up the pavement everywhere on 10 pounds of boost . 1.00 AR TS T3 flanged T4 hsg BTW .

My bottom line for a street RB25 powered RWD car is a GT3076R , more than that equals more lag and you are beyond traction anyway .

A .

Edited by discopotato03

Well i am running a Garrett GT3071 By GCG . It runs the I/W Rear Housing with an A/R.82 Rear Housing and comes on full Boost at 3450 RPM and stays on the boost all the way to 7300 RPM . It's the only turbo i've put on my car but i would have to say its a very responsive street car and it does give you that big feeling when it comes on boost .

CHeck my post GT30RB for the dyno sheet

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