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Rb20 Wastegate Actuator Upgrade For R33

manuel

By manuel,
in Engines & Forced Induction

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manuel Community Regular

manuel

Posted
Posted

I would like some clarification on this topic.

I have been told that the rb20 wastegate actuator can hold 10 psi and the stock rb25 only 7psi.

I have had my car recently tuned with Greedy ebc profec 2 and power fc with stock turbo.

I am running 13.5 psi on high boost but would like to push it to 15psi on cold nights with 100 octane fuel which i use weekly. Car was tuned for 98 but runs better on 100 octane. I notice that when i up the boost it hits 14.2psi then drops off to 13.5psi.

If i change the wastegate to rb20 10psi spring, will i be able to hold 15psi on my turbo in the right environment with good fuel. i think the 7psi spring is letting me down

Your opinions greatly appreciated.

SKYPER Enthusiast

SKYPER

Posted
Posted (edited)

Boost dropping off could be BOV related (leaking). Factory BOV leaks past roughly 10psi. Aftermarket BOV might be worth it. Also I've noticed running engine lean can make boost level drop but hp increase.

Most fit a HKS or Garrett adjustable internal wastegate actuator (actuator arm is adjustable by 1.4psi or so) that has a higher spring pressure (around 14.7psi) when doing a boost up wth stock or aftermarket turbo. But might not solve the boost drop problem.

These are the rough healthy pressures in psi for stock Nissan R32, R33 GTS internal wastegate actuators -

R33 RB25DET 7.0psi-7.8psi. If tested you'll probably find it's roughly 7.5psi.

R32 RB20DET 11.4psi-12.8psi. Average on 2x RB20DET internal wastegate actuators that have tested is around 12psi.

I gather psi of internal wastegate actuator spring can vary from car to car (I assume it's why hp varies from car to car), so hard to say accurately that it would hold a certain psi.

Edited by SKYPER
Harey Veteran

Harey

Posted
Posted (edited)

Pretty much all of the standard turbo dyno graphs i have seen drop off boost towards the top end.

An actuator that is closer to the boost pressure you want to run can only be a good thing. There are some other threads on cars with bigger turbos that experience worse boost tapering off, their solution was a large can higher boost actuator. This solved the issue.

I strongly disagree that the factory BOV leaks above 10psi. There are many threads about how good the factory BOV is and there is no point in replacing unless its a really hardcore setup. Many 300rwkw cars running factory BOVs.

Higher boost actuator ftw

Edited by Harey
lachlanw Veteran

lachlanw

Posted
Posted

whats wrong with your boost controller ? and yes if you want 15psi you should run a wastegate actuator closer to your taget boost pressure .

also note to someone above , rb25det actuator is 5 psi

Harey Veteran

Harey

Posted
Posted
whats wrong with your boost controller ? and yes if you want 15psi you should run a wastegate actuator closer to your taget boost pressure .

also note to someone above , rb25det actuator is 5 psi

A boost controller can only do so much. It is limited by the wastegate actuator.

Geeze yeah asking a 5psi actuator to run at 15psi is a bit much to ask really.

SKYPER Enthusiast

SKYPER

Posted
Posted (edited)

R33 RB25DET has 2x different internal wastegate actuators.

Automatic R33 RB25DET internal wastegate actuator is around 4.8psi-5.6psi. But you'll probably find it's roughly 5.2psi when tested.

Both auto, manual internal wastegate actuators on R32 RB20DET have the same psi. Not sure why they changed it on the R33??? Don't know about R34 RB25DET, but could be similar to R33 RB25DET.

Manual internal wastegate actuator like where talking about above (he has a PowerFC which is manual ECU only) has a higher psi internal wastegate actuator.

How to find internal wastegate actuator spring pressure -

Remove internal wastegate actuator from turbo.

Get a boost gauge or compound gauge with T fitting, 2x 6mm ID vacuum hoses and plumb boost gauge T fitting into middle of 2x 6mm ID vacuum hoses and plumb one of the 2x of 6mm ID vacuum hoses onto internal wastegate actuator bulb.

Then slowly apply compressed air via a compressor to end of 6mm ID vacuum hose where nothing is plumbed in. Then see what psi on boost gauge that the internal wastegate actuator moves the arm. Then you'll have the spring pressure of the internal wastegate actuator.

Factory BOV is a push type BOV and valve gets pushed open under boost, leaks. When factory BOV is modified it doesn't leak as bad as it did without the stock BOV mod, but you have blocked the quick release part of BOV, so flutter sound (form of compressor surge) can be heard at lower boost levels (bad for CHRA on stock turbo). The flutter sound you hear is the air reversing direction, hitting compressor wheel and slowing turbo down.

Edited by SKYPER
Harey Veteran

Harey

Posted
Posted

I wonder then is 10psi from a stock 5psi wastegate too much for it to hold 10psi to redline?

I have never seen a stock turbo hold a constant boost to redline (above 10psi) on a dyno sheet. What are peoples dynos like that use the R32 10psi actuator?

SKYPER Enthusiast

SKYPER

Posted
Posted (edited)

Do you mean 12psi R32 internal wastegate actuator???

I wouldn't expect power, boost to rise above 6400rpm with stock turbo, stock ECU tune, as it's running off the edge of fuel, ignition maps on stock ECU. So ECU tune probably would be the limiting area as far as power, boost goes, not stock internal wastegate actuator or stock turbo.

Edited by SKYPER
Harey Veteran

Harey

Posted
Posted (edited)

I am saying even after a tune the stock turbo with stock actuator struggles to hold boost to redline. Mine dies off from 10psi to a bit less than 9psi.

My question is does an R32 actuator make a constant 12psi to redline on a stock rb25 turbo?

Edited by Harey
SKYPER Enthusiast

SKYPER

Posted
Posted (edited)

I don't think stock RB25 internal wastegate actuator is a problem at 10psi.

With ECU retune, tuner probably still used the stock map scaling on GTS ECU that only goes to 6400rpm. Only GTR ECU maps that I know of go to 8000rpm and can add more ignition timing, more fuel above 6400rpm to keep boost, power rising with stock turbo's. After 6400rpm, stock GTS ECU uses the last settings at 6400rpm for fuel, ignition until rpm needle hits redline.

My theory is more rpm = more air sucked in by pistons inside engine and air forced in by turbo + same amount of fuel injected by ECU at 6400rpm+ = leaner A/F ratio as revs rise and boost level drops. Also not enough ignition timing above 6400rpm, leaking stock BOV could be part of the problem.

If a RB20DET internal wastegate actuator is tested on bench and arm moves at 10psi, then there's something wrong with the spring inside bulb part of internal wastegate actuator or is not a RB20DET internal wastegate actuator.

Edited by SKYPER

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