R34 Boost Upgrade

[ztune_R34]

Hi,

I've just installed RB20 wastegate actuator on my R34 25GTT.

I've got a standard boost gauge which was reading 0.7 Kg/cm2 with standard wastegate actuator (approx 10psi) but now it goes off the scales, that is over 1Kg/cm2 (approx 15 psi).

In terms of modifications all I have is 80mm cat back exhaust that came with the car from Japan, that's all.

My question is - did anyone perform this mod on their R34 25GTT and is it safe setup for a stock turbo and stock engine?

[Howie]

What was wrong with the factory wastegate actuator? Boy i wouldn't be sitting it on 15psi for very long.

[rgr34]

you should get an aftermarket boost gauge.......15psi is abit much for stock turbo....i was told by a tuner 13psi would be the safe limit......

[ztune_R34]

I see,

There was nothing wrong with factory wastegate actuator. I've read somewhere on the forums here that RB20 is runnung higher boost then RB25 and that a cheap ($50) and safe (in terms of not getting boost spikes) boost upgrade for RB25 would be to get RB20 wastegate actuator from R32. Those discussions were based on upgrade of R33 ebgines not R34. So I wander if anyone has done this upgrade on R34's and with what results.

BTW RB20 wastegate actuator is a perfect fit on R34's no mods needed (maybe a little longer vacc. hose but that's it).

[ztune_R34]

BTW does anyone know what's the stock boost level on R32 GTS-T???

[1400r]

Im guess your still running the solenoid as well

so 10psi plus what ever the solenoid adds over 3,500rpm

[ztune_R34]

I see.

Yes the solenoid is still there.

I did not remove anything except that I just swaped the actual wastegate actuator.

[rgr34]

hows the car go running that much boost??

[ztune_R34]

You can notice difference straight away.

When it starts boosting it's as per normal, you can feel it but when it goes over the standard boost threshold it feels like a second turbo kicks in, acceleration is improved compared to standard.

Well what can I say it's a lot more fun than before and one more thing Bye, Bye STI

But it's noticeably hungrier when on boost than before.

[rgr34]

sounds good but id be getting a after market boost gauge......when i changed my exhaust the stock gauge didnt read much different to stock.......i installed a aftermarket gauge that reads in psi and it was boosting at 9psi...... ur probly overboosting bad........

[ztune_R34]

maybe it is, I'll have to follow it up with a cheap boost gauge just to see but I will eventually buy a whole centre console nismo cluster ($370) with 1.4 bar boost gauge.

I thought that all skylines or at least 33's and 34's had an overboost protection built into the ECU where it will cut fuel if boost levels will reach dangerous levels, is it correct?

[Howie]

I thought that all skylines or at least 33's and 34's had an overboost protection built into the ECU where it will cut fuel if boost levels will reach dangerous levels, is it correct?

No such luck there mate, you'll need an ebc with a boost limiter there.

[ztune_R34]

Oh then HPI magazine is full of crap.....

[1400r]

isnt 15psi already pushing it on a stock engine stock turbo?

you may want to disconnect the solenoid

[ztune_R34]

isnt 15psi already pushing it on a stock engine stock turbo?

you may want to disconnect the solenoid

I'll try disconnecting the solenoid and see how I go. what's the purpose of the solenoid anyway?

[1400r]

"Im guess your still running the solenoid as well

so 10psi plus what ever the solenoid adds over 3,500rpm"

errr adds psi

[ztune_R34]

Well I'll rephrase my question.

How does it add PSI? I thought solenoid either closed or opened therefore wastegate is either closed or opened which means that there is only 2 states in which wastegate can be not 3 like half opened wastegate and solenoid is there to control those two states (fully closed or fully opened), I might be mistaken. Can anyone shed some light on this?

[ztune_R34]

For those who is interested I did a little reseatch and here is what I found.

"In standard form the R34 runs a two stage boost control system 5psi to 4500 rpm then 7psi to red line 7000 rpm."

"turbo’s exhaust wheel is ceramic and they tend to fail if to much heat is generated. The amount of boost you can run with the stock turbo is debatable but I don’t recommend running more than 10 psi."

"R32GTST wastegate actuator is exactly the same as the R34 except the spring inside is set for 10psi.

R32 actuators can be hard to find but I think it’s the best option for this level of modification as boost spikes and boost creep are eliminated.

No mater which system you choose the 2 stage boost control system should be disconnected."

Therefore I will disconnect solenoid tomorrow and let you know how I go.

[ztune_R34]

Well I couldn't wait till tomorrow so I tried it now with disconnected soleniod. The boost came down to about 0.8 kg/cm2 which is just a little bit higher than stock so I still have minor improvement over stock but I'm a little disapointed. I'll still get an aftermarket boost gauge and give you exact boost figure that I'm running now with R32 wastegate actuator.

Huh well got to look for a steel turbine wheel now.

Can anyone recomend good workshop in Sydney that can change ceramic turbine wheel to steel wheel as I'm pretty satisfied with the stock turbo and connected solenoid.

Another option off course is to change the turbo, any thoughts on what's the closest to stock turbo I can get that has steel turbine wheel and will fit without any modifications?

[gts-4 dreamer]

are you sure you only have a cat back ?

your r34 smic is supposedly good enough for the limits of the stock turby so provided your intake piping isnt sucking closed only your turby will fail in time.

funny how you say your stock airflow restriction was pushing 10psi as opposed to something lower by half. You sound like you already have a larger or atleast better flowing exhuast than stock with the stock valve / gate setup registering 10psi.

from reading here you will be delaminating your turbo's exhuast wheel at an excellerated rate. So you should hear bits of brittle ceramics bouncing around your car provided you still have some guts in it. if not meh would just become dust and fly out anyway.

you dont get r&R ? While driving you get a noticable drop in power while runnig... hell you dont get a sound like your engy is arcing out through its coipacks ? miss fire from your plugs ? lucky bastard......

my s2 33 has 5psi gate with a 2psi hold on stock boost controller so it manages 7psi over 4.5k rpm.. dont know for 34 in this area... since i put a decent if not loud and droning exhuast i do make noticably better power and my boost is roughly 7psi with the stock control gear then roughly 10 over 4.5k. adding a 10psi gate with the stock controller would mean it would do roughly the same @ top end. You wouldnt think this would be the case that with a fixed gate and a controller made to bleed off an extra 2 psi worth that it would be exactly the same. The only answer I have ever gotten on this is the less restriction somehow does this.. without any form of explanation .. good like finding one on here.. I have looked many times without an answer.