Hks Gt-rs Turbo Analysis For Rb-25 Engine

[simpletool]

Equinox - That dyno chart is fine assuming you mean run about 1bar at manifold, 2.25 ratio. Remember the compressor charts are a ratio of output pressure/input pressure at the compressor housings (after losses).

output pressure = pressure before losses through piping and intercooler plus normal atmosphere (estimate 2psi loss = 16.7 + 14.7)

input pressure = pressure after vaccum loss to air filter and piping. (estimate 12.7psi, ie. 2psi vacuum relative to atmosphere)

Ratio =

(16.7 + 14.7)/12.7 = 2.5

(brackets are guestimates - I do not stand by them at all)

Not being a smart arse just trying to create some clarity for those using compressor charts.

Ohh and I agree GTRS would be my turbo of choice (if I wasn't so broke). HKS quote 225rwkw at 0.9bar I beleive on RB25, seems to be on the money.

Edited July 17, 2008 by simpletool

[and3_3]

On the topic of turbo upgrades, i would like a gtrs turbo but im not to sure if i need a z32 afm.

Is it absolutely essential for that sort of power range?

[PM-R33]

To get the most out of the turbo then yeah you will need a AFM upgrade.

[GtstCoupe]

I will have mine tuned early next week.I will post results

[SkyDragon]

Looks like this is shaping up to be a GTRS vs 2835 Pro S thread.

I am installing a 2835 Pro S in around 2 weeks. I went through the whole turbo analysis phase and came down to a choice between these two. My requirements where 250-280rwkw on stock internals (I have all other supporting mods) whilst maintaining response. It was a hard choice, but I had heard more positives from people who had a 2835, hence I went for that!

Surely the .68 vs .64 A/R would make a minimal difference in response? I have heard 2835 users state boost comes on as early as 2.5k rpm?

[discopotato03]

Don't forget that the GTRS uses a HKS enhanced GT"28" turbine housing where the Pro S turbos use HKS enhanced GT "30" turbine housings . If you had the turbine housing off a T3 flanged (RB spec) GTRS and a 0.68 A/R Pro S one sided by side you could see a marked difference .

Personally I suspect it's a price thing going on here GTRS vs 2835 Pro S , if the price was line ball I'd go for the 2835 every time .

What would be interesting for comparison price wise would be a GTRS kit supplied with their dump pipe and all the extras to get it on an R33 GTS25T .

As for SR20's , they use T28 flanged exhaust manifolds so you could fit either a 0.64 or a 0.86 A/R GT28 turbine housing to a GTRS . Neither Garrett or HKS made T3 flanged 0.86 A/R GT28 turbine housings , Garrett do the 64 and the 86 in T28 flange and HKS do the 64 in T28 and T3 flange to suit CA/SR or RB engines .

A .

[paulr33]

a bit out of left field but what about using the twin spec turbo in a single spec setup?

that is, using say a 2835 from a twin GTR kit on a single turbo setup.

troy (roy) has a twin trust turbo setup, but is only using a single turbo on his rb20.

it has one of the best curves and setups ever seen on an rb20.

there's a 2835 kit in twin form for the GTR with twin external gate.

i dont think you can order a 2835 in single form with external gate.

any ideas / ball park on the specs of the 2835 ex gate version from the GTR twin kit?

[discopotato03]

I would have to check Paul but often the larger HKS spec (larger that GT28xx) twins use smaller (than 56) trim compressors like from memory HKS GT2835's for RB26's used 52T 71mm compressors , I think some 3037's were the same deal . Their GT3240 is just a cropped GT35 turbine (cropped to ~ GT32 dimensions) and the compressor was a 54T version of the GT3582R's compressor .

The GTRS (GT2871R 52T) was a later addition to their line up and its 71mm GT35 compressor is 52T as well .

That's why I was always keen on 3037 52T's in the past . It's not always easy to get maps for the smaller trim compressors but the usual trend is (all else being equal) as compressor trim falls turbine efficiency rises .

Brett at GCG reckons all bets are off between HKS and Garrett now and their altered spec cartridges should be available - maybe special order though . Trouble is you probably won't get HKS's housings from Garrett and Garrett don't do T3 flanged turbine housings for the cropped GT30 turbine .

You may be able to rat up a second hand GT2835 Pro turbine housing and buy a 52 comp trim cartridge for it .

Information is scarce but there may have been a 48T version of the 2835 intended for Subaru or Toyota , I can't remember which .

Anyway HKS catalogs show 48 and 52T versions of 2835s and 3037s .

Cheers A .