Gt30r V's Gt35r

[boostn32]

I currently have a GT3040R .82 on my rb20 which i believe is a GT3082R?

I’m currently running 21psi and plan to screw in another 4-5psi, is this still in the efficiency map for this turbo?

at the moment the engine is making 10hp/psi and has made 371rwhp @ 7300rpm

at what point would you go a 1.06 rear housing or would you go a GT35R with a .82 rear. what is the difference from the obvious?

what are these turbos rated hp wise with the 3 different rear housing options?

what would the response/lag difference be between each combo

for a reference im making 5psi @ 4300rpm and ramps hard to 5500rpm making 17psi

what would be the next step with the turbo, my goal is another 50-70hp

Thanks Luke

[R31Nismoid]

On a RB25 i made 270rwkw @ 17psi with a GT3040 (600hp) in a .82

If you get a GT35, it'll be laggier, simple as that. Its a larger comp wheel so its going to be slower.

Given then 600hp GT30 should do 330rwkw, you need more boost.

[boostn32]

If you get a GT35, it'll be laggier, simple as that. Its a larger comp wheel so its going to be slower.

Given then 600hp GT30 should do 330rwkw, you need more boost.

yes will have more lag but just how much, 500rpm, 1000rpm for same boost.

330rwkw on a 25 or 20 and at what psi

[JonnoHR31]

25 psi will be fine for the turbo itself

[boostn32]

yes but thats only another 40hp, where to turbo wise after that

[R31Nismoid]

How do you know its not coming into another area of efficiecny and so on where the power gains are more than 10hp/psi?

IMO much below 24-25psi and the turbo isn't really in its happiest place given i should have been running closer to 20-21psi on a 2.5ltr

[TiTAN]

the next step up is the GT35, in 0.82 form it will do 350-380rwkw.

that is going to be very laggy on a little RB20, you will have ~1000-2000rpm of full boost before you have to change gear again. if its just to get the number is it really worth it?

[R31Nismoid]

the next step up is the GT35, in 0.82 form it will do 350-380rwkw.

that is going to be very laggy on a little RB20, you will have ~1000-2000rpm of full boost before you have to change gear again. if its just to get the number is it really worth it?

Nitrous, E85 - two much better ways to get that little bit more power

Or just alter the dyno setting, for 40hp I'm not sure the need for the hair splitting...

[boostn32]

maybe e85 and 28psi will do the job

[R31Nismoid]

It'll more than do the job.

Most cars see 30rwkw or so JUST from the fuel.

More boost, more fuel, you'll get what you want and more, much more.

[boostn32]

but will it do another 100hp.

[GTScotT]

but will it do another 100hp.

Probably, if your motor can.

Whats done to your motor? Your coming in fairly late with only 5psi by 4300, I know the gibson RB20 had powerband between 6 and 8 yet a 1:1 bump on the static CR and a 3 psi drop in boost saw it with usable power between 4 and 8... MASSIVE difference.

Tell us more about your motor.

[boostn32]

40thou over size arias pistons, spool rods, ported head, 264 cams 8.5mm lift, 8.7cr. high mount 3040, rb26 intake and throttles,

changing intake to 80mm tb and new plenum on half standard runners to make a little more torque. cam gears set at odeg atm.

720cc injectors, toda light weight flywheel,

[R31Nismoid]

but will it do another 100hp.

100hp, 70kw

Considering just fuel alone you get at least 30RWKW, pretty obvious you'd make what you want probably just on the fuel without anymore boost.

[boostn32]

450-500rwhp out a a 20 would be nice.

[GTScotT]

Leave the throttle, try get the gears dialed up. For interest sake I would also try dialing them with the stock intake cam.

Your motor sounds like it can make the power, just need to push the turbo into efficiency along with the tune to match. 25PSI and a good dial on the gears should get you the power Ash is talking about (30rwkw) if not more IMO.

[GUN_METAL_GTR32]

y dont u go the 35r with a .63 rear housing and twin waste gates to make it spool faster

[R31Nismoid]

Because his top end will still be choked with a .63 regardless?

[discopotato03]

Nismoid the Garret turbine maps actually show the flow rates of the 0.82 GT30 and the 0.63 GT35 as having similar maximums though IMO the GT30 0.82 is the better map , these are with the T3 flanged GT30 turbine housings BTW because the 30 and 35 both use them .

Not my project and don't think I'd build such a top endy RB20 but to each their own .

Now there is another option in the GT3082R family and its what used to be called GT3040 in HKS speak .

What it is is same deal as the Garrett GT3082R/GT3040 but with a 50 trim rather than 56 trim GT40 compressor wheel in it .

My old HKS list shows its good for 20 more PS/Hp than a GT3037S/GT3076R 56 trim .

I have a compressor map of a Garret large frame plain bearing GT4082 which uses this same compressor wheel and it shows the the maximum airflow rate at the bleeding edge of about 57 lbs so potentially 570 Hp if you go by maximums .

This is in a 0.58 A/R GT40 compressor housing which is crudely speaking of a similar size externally to a T04S o.70 A/R one , maybe a smidge smaller but port shrouded .

It may even pay the OP to look into Mitsubishi turbos because they tend to use reasonably big wheels in smaller trims than Garrett does sometimes and that could pay off when you want power over as broad a range as possible .

BTW what does the OP want to do with this RB20 ?

A .

[Wheezy]

Looking at the engine mods and response / power output it seems crazy not to look into a TD06.....