Gt28 Potential

[AngryRB]

Hey ive searched but not found my answer ..

i have a gt2871R with 56trim, it has r33 housings on it, ive been looking thru silvia forums and guys on there are getting figures of upto 260kw's using this turbo but in smaller trim and .63 turbine housing, so my question is if this turbo was fitted with a .86 housing (garrett)

and run on 18-20psi ( apparently its most efficient pressures) will it achieve upto 260kw or even more? if a silvia 2L can make 260kw with supporting mods with smaller specs can an rb25 make the same or more or will the bigger engine hit big exhaust restriction with the smaller 53mm turbine wheel??

also worth noting is hypergear uses 2871r and 3071r for its highflows ( correct me if im wrong) so anyone know what the full output can be on an rb with all supporting mods etc..

[The Mafia]

Dude you can't just whack a bigger rear housing on, wind up the boost and make it just make more and more horsepower.

The size of the compressor is the limiting factor, and in this case, I'm pretty sure anything past 260rwkw will be very difficult. I doubt you'd even make much more power anyway. The compressor will be choked up.

Solution? Get a bigger compressor. This means a gt30 series.

[D_Stirls]

The 56 trim wheel in the GT2871r is the same compressor as the off the shelf GT3071r but in this case its the turbine that restricts the turbo as it can't drive the compressor hard enough to reach it's potential. The 0.86 rear (probably 0.82 if It's a T3 housing) will help to not choke the turbine but you will still be around 20kw down on the same compressor mated to a GT30 turbine.

[AngryRB]

so it is the same 71mm compressor, i wouldnt expect the same as a gt30's output, was just curious to if it can make 250-260kw, the silvia's seem to be making it so i thought why not on an rb.. on the garrett website it says 475hp so that would be 280-290 , but im not saying it would do that..

maybe i should be asking, what is the max output on a gt28 housing with cams etc assuming it can hold high boost for short periods..

Edited September 25, 2011 by SliverS2

[AngryRB]

Dude you can't just whack a bigger rear housing on, wind up the boost and make it just make more and more horsepower.

The size of the compressor is the limiting factor, and in this case, I'm pretty sure anything past 260rwkw will be very difficult. I doubt you'd even make much more power anyway. The compressor will be choked up.

Solution? Get a bigger compressor. This means a gt30 series.

the horsepower i am talking about is what is quoted on the garrett page, 475hp apparently but i dont know what the real world figure is.

[hypergear]

GT2871 is ok for Rb20dets. it maxes 230rwkws on stock r33 housings and gets red hot. If you are looking for high flowing our current std or pu options will perform lot better.

[AngryRB]

GT2871 is ok for Rb20dets. it maxes 230rwkws on stock r33 housings and gets red hot. If you are looking for high flowing our current std or pu options will perform lot better.

isnt a .86garrett housing alot bigger than a stock r33 though, so maybe another 20 -30kws more

[Touge Kyousou]

My setup has a gt2871rs with .86 and maxes out at 245rwkw on a low reading dyno. Setup is in sig. Hth

[The Mafia]

Your forgetting that Garret's rating is fly wheel horse power. Not rear wheel horsepower.

[AngryRB]

My setup has a gt2871rs with .86 and maxes out at 245rwkw on a low reading dyno. Setup is in sig. Hth

that sounds alright, whats the top end like ? how much boost?

[AngryRB]

Your forgetting that Garret's rating is fly wheel horse power. Not rear wheel horsepower.

yeah its 475flywheel horsepower times 0.75 =356kws at the flywheel then - say minus 60kw to give 290kw at the wheels.. thats if the garrett site is accurate

is that calculation correct?

[T04GTR]

well, from what i have heard, the gt30 variant is better, more power with less lag. i only know them as the 49,51 and 53mm comp inducers. the tiny little gt28 turbine is a major bottle neck. much like the older gt2540r.

on a s15, the 51mm aka -10. came on at 3800, changed to gt3071 same comp wheel, came on at 3300. and made more power.

so if you are thinking of getting one, get the gt3071. great turbo.

[Touge Kyousou]

that sounds alright, whats the top end like ? how much boost?

Revs nicely to 7400rpm, doesn't really let off til 7100rpm - a lot of that is in the tune though of course (ignition timing).

Truth be told, my gate control is REALLY crap atm, real hack job so no doubt could be much better but other responsibilities now prevent full setup changes etc.

Boost is at a max of 1.34 bar so approx 19.5 psi.

But with the current offerings from hypergear, i know what turbo i would prefer! ( one of those ss1 or ss2 items for sure and almost full bolt on)

As for your calculation, 356kw at engine = approx 250rwkw after drivetrain losses. I'm assuming a drivetrain loss of 30% which i think should be about right considering the period of our drivetrains and age of the box etc.

I'm about to change over to caltex e-flex so expecting 275rwkw on the same low reading dyno with the tiny turbo lol and that should do me happy - 245rwkw was already spinning second if the tires weren't properly warm (245 ku36's but on 1.2 negative camber)

[JonnoHR31]

Your forgetting that Garret's rating is fly wheel horse power. Not rear wheel horsepower.

your forgetting 280kw isnt 475hp.

i dont see any reason a rb25 couldnt make a healthy ~260rwkw with the proper garrett housing, you'll need to run a little more boost than you would with a gt30 but thats no big deal.