Rb25 Hks2535

[silva33]

I have an R33 GTST (S2 Motor) with the following mods.

full exhaust

PFC

Front mount

Boost controller

i am about to install a HKS 2535 with a bigger fuel pump but cannot decide if i should go for the Z32 AFM and injectors because people seem to be getting 250rwkw without the AFM and Injectors on about 1 bar..

Is it worth getting the AFM and injectors for the sake of the extra 3 or so psi and how much more power will it produce? i am having trouble finding RB25's running about 18-19psi with a 2535 and seeing how much power they produce.....

I know it is always worth going for the injectors for safety reasons but i was just curious on the power outputs...

Cheers..

[SeriesIIGTST]

Okay. I've got similar setup and have been running HKS2535 for quite some time. I run out of fuel (max injector duty out) at around 1 bar. This nets me around the 310-320rwhp mark but I never (well, hardly ever) wind it up that hard cause i'm on stockies. I do however have a Z32 AFM already and have a feeling that you'd find that even on boost below 1 bar, you'll probably max out the standard one pretty quickly.

One day, (I've just bought a house so no time soon) I'll get injectors and crank the boost up some more but for now, to be safe, boost stays around 12psi mark which nets around 300rwhp which is heaps of fun day in and out.

Enjoy!

[SLY33]

you can get away with std injectors and a fpr, but, you will definitly need the Z32 AFM. HPI did an article covering the swap from std to z32 AFM (my car the actual test car), and while the article conclusion was sh!t, the fact remains that with that turbo you will max out your std afm very easily.

Just to explain why the article was crap, they opened by saying that my car with its 2530 would max out the afm at 4000rpm at just under 1bar (or something like that). Hence WHY I WAS UPGRADING TO Z32 AFM. Then they conclude by saying its NOT really worth doing unless your pushing over 250rwkw or running really big boost. Well my car only made 227rwkw at the time, and i was only running ~1.2bar 'peak' boost, which makes their concluding statement wrong and contradictory to the facts, i.e. the car they saw max out the std AFM well under the criteria they recommended you need to change to z32!

sorry to go on, but it annoys me how they wrote the artice

[silva33]

ok then, so a Z32 AFM is a must but how much power will these turbos make on approx 18psi?

Is the $1300ish of injectors worth the power gain and is the power even usable on the street?

[SeriesIIGTST]

At 16psi (done once for shits and giggles), I pulled 252rwkw. Turbo was still going strong but engine wasn't liking not having any fuel. If you say approx 10rwhp for every psi increase, 18psi should see approx another 15rwkw bringing you pretty close to 270rwkw. However, as I've previously stated, I haven't actually done it and am guessing based on known outputs from my own experience.

Is this power useable on the road? Well, you tell me. I can certainly use 220-250rwkw on the road but when I do, I find myself breaking many laws in a very short space of time. However, higher gears, this turbo on RB25, lovely useable power to overtake/accelerate/etc.

[silva33]

SeriesIIGTST,

i have 185rwkw at the moment and am pretty happy with it as it pulls hard, how does they car drive compared to what u have now... in terms of straight line on boost and normal driving in the lower rev range...

I am thinking that while i am at it i may as well get the injectors and only have 1 tune but im thinking that if i am happy with 185rwkw then i may not need anymore than 220-230rwkw?

thanks

[Cubes]

You will always need more power.

185rwkw feels good, move to 220rwkw.. feels nice for a while, then ok, then hrmm i need more..

Could call it an addiction.

[Cool Hand Luke]

An addiction yes, but series2gtst is right... I had an 180 with 270rwkw and while an absolute blast to drive. You do have to be very mindful tho, its very easy to be doing 140 in a 60 zone in a short period of time, which would end your license for a few years.... Not to mention that unless your a good driver (and honestly) you'll more than likely find yourself in more trouble than from the law. Once you get used to the power it doesnt feel as fast either or until you drive a lightly modified car anyway

To give you an idea... i had a drag on the highway once, shifted from 3rd to 4th (about 135 in a 180) going around a slight bend, and the car wheel spun and crossed 2 lanes... That was with ok brand 225's on the back, so it wasnt like i was running stockies. Hmm but im not here to give you a lecture haha, i think my favorite was racing a hsv from the lights, taking off in 2nd and having the wheels spin till your past 100k's... it stops them from laughing at your bov anyway

That said though, i was just about to take the car off the road for some more mods, for sure its an addiction and a good one at that

[SLY33]

what i did, got my z32 and fuel pressure reg, got it tuned, AFR's were all good, so i didnt bother getting the injectors until i got a bigger turbo. My injector duty cycle was peaking at mid 90%'s though! this did worry me with all the talk it not being safe, but the tuner was happy, and it ran fine getting driven hard for 6 months, at which stage i went a bigger turbo and injectors.

not so sure youll get up around the 270rwkw mark with a 340ps rated turbo... It sounds simple upping the boost and getting more power, but you dont know for sure if boost will hold up top to get you that peak power figure. With smallish turbo's such as these on rb25's once you start to wind up boost youll often find a super midrange, but the the boost wont hold up top. My 420ps 2835 only makes 266 at 17psi, so to get that from a 2535 would really be pushing it..

Is the power usable?! yes and no. Depends on your tyres and suspension. On your average street tyres you wont be able to get traction in 1st or 2nd (and may even have trouble in 3rd if changing hard into it) without a very skilled right foot to feather the throttle, so you can forget getting off the line and just holding the pedal flat to the floor and feeling the slingshot. This is very frustrating when far lesser power cars can take you out 0-100 if you cant control the wheelspin. In my opinion, anything over 230rwkw in a rwd turbo setup like these should be on R-compound tyres, or the very top of the line street tyres at least. As mentioned above you can quite easily find yourself spinning out of control if your not careful, and i'd hate to think of myself when i was on P-plates driving the car i have now!!

At the end of the day, wheelspin on command is cool, but once you get sick of it, all you'll want is TRACTION!

[SLY33]

what i did, got my z32 and fuel pressure reg, got it tuned, AFR's were all good, so i didnt bother getting the injectors until i got a bigger turbo. My injector duty cycle was peaking at mid 90%'s though! this did worry me with all the talk it not being safe, but the tuner was happy, and it ran fine getting driven hard for 6 months, at which stage i went a bigger turbo and injectors.

not so sure youll get up around the 270rwkw mark with a 340ps rated turbo... It sounds simple upping the boost and getting more power, but you dont know for sure if boost will hold up top to get you that peak power figure. With smallish turbo's such as these on rb25's once you start to wind up boost youll often find a super midrange, but the the boost wont hold up top. My 420ps 2835 only makes 266 at 17psi, so to get that from a 2535 would really be pushing it..

Is the power usable?! yes and no. Depends on your tyres and suspension. On your average street tyres you wont be able to get traction in 1st or 2nd (and may even have trouble in 3rd if changing hard into it) without a very skilled right foot to feather the throttle, so you can forget getting off the line and just holding the pedal flat to the floor and feeling the slingshot. This is very frustrating when far lesser power cars can take you out 0-100 if you cant control the wheelspin. In my opinion, anything over 230rwkw in a rwd turbo setup like these should be on R-compound tyres, or the very top of the line street tyres at least. As mentioned above you can quite easily find yourself spinning out of control if your not careful, and i'd hate to think of myself when i was on P-plates driving the car i have now!!

At the end of the day, wheelspin on command is cool, but once you get sick of it, all you'll want is TRACTION!

To illustrate this point, the bling 19's you see in my avatar are sitting in the shed, and the car now wears 17inch jap rims with RE55s all round. If you ask me, the car was actually dangerous on ultra low profile street tyres with this sort of power, and it now pulls up in what seems like half the distance.

[ix9]

My 2535 maxed out my AFM at 15-16psi, I was running about 320rwhp @ 13psi, and when I cranked it up for "shits and giggles" i found it had a bery boring flat spot where the AFM maxed out.

But as SeriesIIGTST said, running on about 320rwhp day in day out, is a whole bagload of fun anyway

[Robo's]

I too with a 2530, are seeing about 95% max on the standard injectors. If i go bigger turbo, i will try to up the fuel pressure.

Im with SLY, too much power is good for bragging rights at the pub but useless for real world results. If you have 230rwkw plus, please get some "R" rated tryes otherwise you will be busted by most things off the lights. Last quick rex i ran from the lights i had to jump from the lights as i struggle for traction and short shift. Once under way though, its bye bye. But still it would be nice to have some decent traction.

[silva33]

so are people generally saying that winding the boost up on a 2535 will basically have the same gains as the 2530, i.e: more midrange but not much more top end... then again if people are already struggling to get traction with massive amounts of midrange is it pointless having anymore power... (without having to spend $$$$$ on suspension and $600 tyres that is)

so what is the most someone has got out of a 2535 on about 18psi, im guessing about 260-265ish rwkw?

[Robo's]

Id say the max you would get is around 250rwkw. Remember this turbo is only rated 20ps more than the 2530.

http://www.skylinesaustralia.com/forums/sh...&highlight=2535

[silva33]

that thread shows over 255rwkw at 1 bar... does this mean the extra power (like the 2530) will only produce more midrange rather than more peak power...

I think i would rather the midrange as these days unless you are on a track 90% of the driving will be using the midrange....

[ABuSD]

I just got my car back from the tuners with this:

Power FC

FMIC

3"turbo back zorst 3"cat and 3.5"rest of the exhaust

GTR pump

Fuel pressure reg.

HKS2835 (From SR20, 380ps?) mounted on a cast HKS low mount manifold

Trust Gate

224rwkw on 14 psi 85%duty cycle on injectors, u know what robbed me of my power?

MY CAT!!! :hellpisd: It was holding back power and not allowing me to boost it up, i cant beleive it i feel robbed, i was shocked when i found out. Ive been told that Z32AFM still arent needed when approaching 250, im considering injectors and hoping for abou 270rwkw and i dont plan on changing my AFM.

I tell you what though after driving it for 5 minutes i already cant wait for more power!!! MWAHAHAHAHA its soooo addictive!

(Fantastic drive, i thought it wa gonna be laggy)

PS Sorrys 2 wh0re but does any1 know if the Q45 AFM is even better than the Z32?

[Trust33]

So in your opinion the swap of a turbo with a t3 flange to a turbo with a t25 flange was all good.

The reason i am asking is because of the mixed emotions that i get when aking that question.That and they have never tried or known any1 who has tried it before.

The major hypothetical reasons that i get from them though,i.e.Why it is best not to run a t25 flange on the r33 gts-t,is that the t25 flange would restrict the ammount of flow possible.

Is this true.And are the exhaust turbines the same,from a t3 to t25 flanged turbo,size and specs only flanged differently?

[Trust33]

hmmm.

[Cubes]

Ive been told that Z32AFM still arent needed when approaching 250, im considering injectors and hoping for abou 270rwkw and i dont plan on changing my AFM.

PS Sorrys 2 wh0re but does any1 know if the Q45 AFM is even better than the Z32?

It is possible to stretch out AFM signal so to speak, you alter the % value in the afm section.. Its a little bodgy as you reduce your resolution but it works.

As a general rule.. When the stock AFM max's out (~220rwkw or so) you should really start looking at bigger injectors.

Increased fuel pressure to nudge 240-250rwkw is a worry, many RB25's have popped their ring lands doing so. Just because the AFR's are fine on the dyno when stretching injectors it doesn't mean 1 week later you will have one crap its self and decide run lean.