hks gt2530 vs 40 on rb25

[curbsurfer253]

which turbo would you pick for an rb25? is the 2530 a little less laggy. what kind of wheel horsepower is each on these good for?

[lwells]

Mate, try a search. This has been gone over in a lot of detail previously. From memory the concensus is the 2530 is a much better buy, and the 2540 is generally considered pretty crappy.

LW.

[SeriesIIGTST]

I settled for the middle ground, 2535 on my rb25. All I have to say is woohoo. Spool is marginally slower (like only a few 100 RPM) than stock but when it does come on, look out!

[SLY33]

curbsurfer, ive been playing with a 2530 for a while, and IT IS TOO SMALL FOR A RB25!

The very most you will see is 230rwkw, and you wont be able to run more than 14psi at the top end as the rb25 has too much exh gas flow in the high rpms making the compressor spin out of efficiency and boost drops off, and intake temps increase and detonation increases. It is not correctly matched for this engine, and suits an RB20 perfectly, not a 25.

That said it is still fun to drive and spools like nearly stock, but after your used to the extra midrange torque, the lack of top end kick makes it a bit boring.

a 2535 should give you 240rwkw and the 2540 250rwkw. HKS japan website has dyno graphs for these turbos on a rb25 and you can see that overall the 2535 looks like a great match. The 2540 ove been told is the best if you are going to fit cams to boost the midrange a bit.

[mose]

I have a HKS2540 (running 18psi) on a r33 GTS-T. It pushes 272KW at the RW, But will not go much higher than that.. Its still a lot of fun though...

[snake]

272rwkw hey, thats not a bad number, do you run different cams? Hows it drive?

[mose]

Its pretty awesome, It doesn't have cams though.. Full specs are in the For Sale section.. It is a real blast to drive on the street.

It also has the stock plenum & stock manifold (the 2540 is probably the largest low mount turbo for the RB25DET) - Helps when cops pull you over...

check out www.geocities.com/r33forsale for under bonnet pics

[51jay]

2540 may be laggy on a completely stock R33.....but it isn't on mine its on solid full boost by 3000 with 7psi coming in around 1800....on less than half throttle

[SLY33]

51jay when you say it may be laggy on a stock r33, what have you done to yours that makes it not laggy?

also to mose, would you say yours is at all laggy?

272rwkw is a lot more than i thought it could make! thats a pretty big figure for a smallish turbo. Didnt grepin get only mid 270rwkw's out of a 2835proS?

51Jay what power does yours make at the wheels?

i was going to get a 2835proS, but if i can get 270rwkw at 18psi id be pretty happy with that!

[51jay]

51jay when you say it may be laggy on a stock r33, what have you done to yours that makes it not laggy?

also to mose, would you say yours is at all laggy?  

272rwkw is a lot more than i thought it could make! thats a pretty big figure for a smallish turbo.  Didnt grepin get only mid 270rwkw's out of a 2835proS?

51Jay what power does yours make at the wheels?

i was going to get a 2835proS, but if i can get 270rwkw at 18psi id be pretty happy with that!

Popular opinion seems to say it's laggy, It's not laggy in my car. I think a lot depends on how it is set up, mine makes respectable boost on 1/4 throttle and is very linier in it's onset coming on to full boost at 3000 or just under then maintains it up to 7500. I'm using the FC-Data Logit default tune as I have not yet got it to the tuners.

mods are

HKS adjustable camgear on exhaust retarded 4 degrees.... anyone who has this and hasn't got a big boost in low and midrange torque hasn't done it right...no argument!!

lightweight flywheel...6Kg

3" turbo back exhaust....pretty quiet...probably legal

600x300x75 fmic

modded plenum...front throttlebody R33

Apexi Super Suction pod filter kit cold air box

Sard fuel regulator, VN fuel pump

HKS2540 turbo split dump pipe

Power FC

E-Boost

I expect to have around 210 to 220rwKw when I finally get it tuned but i'm more interested in good power and torque right through the range than big peak power numbers

[SLY33]

51jay you should make 220rwkw in your sleep with that turbo if i can make 227rwkw with a 2530! I know that the 2540 gets lots of bad wrap, but i think this is mainly from tests done in twin form on GTRs. Ive never heard of anyone running a single one on an rb25 and complained of lag! How could one smallish turbo on a reasonable engine of 2.5 litres be laggy(?), is what i think! Im sure sydneykid has commented on it, but i cant remember his comments, and searching for a specific post from him would take me all day!

I am still wanting to hear from mose about his 270rwkw! either something is amiss or what he thinks is a 2540 is actually something bigger! because to me anything over 250rwkw from a HKS GT25series is so far unheard of!

[snake]

Im looking for 240-250 rwkws, if 2540 or even 2535 could do that with a reasonable spool up time id be happy. 270rwkw though is an awesome figure for 25 series turbo.

[Turbo Tits]

SeriesIIGTST what power do you make at the wheels with your 2535? at what boost?

cheers

[mose]

Its not too laggy at all, quite fun to drive actually.. While I had the engine built, I had a good look at the turbo, it is surely a HKS 2540.. I wanted a street car, not a drag car.. The suspension is very stiff in my car so when the turbo hits boots, all the torque hitting the rear wheels (with the stiff suspension) results in moderate wheelspin.. It is my understanding that Drag cars have much softer rear suspension, so when the turbo hits boost (in a turbo RWD) all the torque hitting the rear wheels is "cushioned" with the softer suspension... (Resulting in less wheelspin)

Personally I would highly recommed it (the 2540) as it a weapon on the road, especially in 1,2 and 3rd...

It is the best low mount turbo there is... I will post a pic of my dyno sheet up soon.. You WILL Notice that the turbo runs out of puff though at that boost setting. It hits 272rwKW then drops down about 8Kw... Keep in Mind that I run Low Boost (14psi = 254rwKw) and High Boost (18psi = 272rwKw) Not a whole lot of difference... I very rarely hit High boost, 254rwKw is still a bit of fun!!

[SeriesIIGTST]

Turbo Tits:

Having fuelling problems with mine at the moment and am waiting on my Nismo adj FPR. It would lean right off on anything over 7psi but I was getting 180rwkw @7psi even with problems (in Shootout Mode). Can't wait to wind the wick up when i get it all sorted. Stay tuned...

[Ezekrael]

Those are impressive figures mose... I've only managed 230rwkw's out of my 2540 @ 14psi. Need to replace the actuator to something heavier as I leak a lot of boost in the top end if I go much higher.

But yeah, congrats to anyone who comes even close to that on a 2540... I know I'd be more than happy.

[T0nyGTSt]

That's not far behind the 2835 if current verified figures are to be believed.

Be that as it may, there's several variants of the 2835 but this vindicates some of the bad press written about the 2540 nonetheless.

T.

[Sydneykid]

Hi Guys, I think you need to keep this table in mind when discssing 2530, 2540, GTRS and 2835

.....................Compressor......................Turbine

....................Trim...Inducer....Exducer...Exducer...Inducer....Trim

GT2530..........63____1.860____2.344___1.883____2.098____76

GTRS.............52____1.997____2.773___1.833____2.098____76

GT2835..........52____1.997____2.773___2.020____2.204____84

GT2540..........46____2.016____2.972___1.833____2.098____76

Note that the turbines on 2530 and 2540 are the same.

In my opinion, supported by experiences, the 2540 is badly mismatched between compressor and turbine (ie; either the turbine is too small or the compressor is too big). This mismatch exists no matter whether the 2540 's are used as twins on an RB26, or single on an RB25. It is my belief that HKS recognised their mistake with the 2540 and introduced the GTRS to fill the gap created by this failure. To achieve this they have simply used a 2835 compressor with a 2830/40 turbine.

So if a 2530 doesn't give enough power for your requirements, then I would go to a 2835 as they are a much better match of compressor and turbine.

[SeriesIIGTST]

Just to add and further strengthen Sydneykid's point.

A table showing the trim and compressor and turbine diameters can be found at:

http://www.takakaira.co.jp/performance/hks.../gtturbine.html

Here we can easily see here that all but the 2835 share the same compressor housing, and turbine wheel while the GT-RS and 2835 fit inbetween the 2535 and 2540 in terms of compressor wheel trim size. This demonstrates how large the trim is on the compressor side of the 2540 and perhaps explains why many people regard it as mis-matched as sydneykid pointed out.

Given that some people are of the opinion that the 2530 is a little too small on an RB25, perhaps for a mild increase in power while retaining near stock response a 2535 (340HP)would be the go while if you're after more power a 2835 (380HP) or 2835ProS (420HP)would be the way to go.

Just my 2c, plus i thought the link may be useful

[SLY33]

seeing as the 2835 "ProS" is the only variant that will bolt on, this is what i will be looking at upgrading to.

Mose:

im not saying your car doesnt have 270+rwkw, and i know that HKS's power ratings are conservative and rated at 1bar, but even with you running ~1.3bar i just cant see a 350ps rated turbo puting over 270kw at the rears!

Reading back over grepins 2835proS thread, he makes 275rwkw at 1.3bar, plus he has a plenum! I am thinking that there is a major dyno discrepancy here! what type of dyno did you use? please post the sheet up!