Rb25det Swapped R32 Low Rpm = Low Boost Problem

[GTSTLOVE]

Ill cut right to it.

My R32 gts-t came with a S1 rb25det swap already done. it seems like they used the rb20 loom. I know with the rb25 wiring harness the 2 stage boost can be disabled by the solenoid ground wire attached to the body. how can i bypass the rb20's restricted boost (as the 20's didnt have a boost solenoid) and let the rb25det keep 7 psi at low rpms rather than 5 psi from 2500~4500 and then 7-8 psi through the higher powerband?

shorter story

I have a hallman MBC, but when i open up the spring, it doesn't give me any extra boost at all. am i limited until i get a haltech ecu? or can the rb20s boost limiter be disabled to allow more than 5 psi at low rpms?

[Ben C34]

Is the stock boost solenoid there? If it is bin it. Use your mbc only.

[Sinista32]

bought it off carsales very recently?

You'll need an SBC (electronic) if using oem ecu's.

Edit: If you use just the MBC your A/F mixtures will be off. In itself not a biggie but not the best way to go about things.

P.S. You should have had a look at the R32 4 Door - Just saying (its mine )

Edited April 29, 2016 by Anonymouse

[Ben C34]

bought it off carsales very recently?

You'll need an SBC (electronic) if using oem ecu's.

What is an sbc?

[Sinista32]

Solenoid boost controller

I may be assuming wrongly that MBS stands for Manual Boost Controller

Edited April 29, 2016 by Anonymouse

[GTSTLOVE]

When i purchased the car it had a direct line from the I/C to the wastegate. So if i put a MBC between the I/C and wastegate, i will run rich or lean? but it still won't increase boost at low RPM's?

and how can i run a SBC if its a rb20 loom. theres no plug because the rb20s didnt have a boost solenoid

also the ECU is supposedly a mines tuned refurbished rb25/20 ecu. i can't confirm this though. other than the 2 stage boost the car runs smooth and i haven't had any problems at all

Edited April 29, 2016 by GTSTLOVE

[GTSTLOVE]

and im also located in the united states. the united states forum is always dead, as the car is still somewhat of a rarity here.

[Sinista32]

my stuff up mate. Don't know what I was thinking.

SAFC II for the air fuel if your not considering replacing the stock ECU.

T-boost controller (Manual)

What is the internal wastegate used? and it's PSI rate?

[Ben C34]

If there's a direct line to the waste gate it's not possible to have 2 stage boost.

[GTSTLOVE]

i must have a vaccum leak or boost leak somewhere. I'm running a large FMIC without a BPV/BOV. I get damn near instant spool, but it stays 3-5 psi until 4500 rpm which leads me to believe the 2 stage is still active. This is with either a direct line to wastegate or mbc. im not sure if the wastegate is off a rb20 or 25. id have to research the differences between the 20/25 turbo before i can tell you which im running

[KiwiRS4T]

The RB20 has a direct line to the actuator which opens at about 10psi so no 2 stage boost. If you are using the stock RB25 actuator with a direct line also no 2 stage boost. If your manual boost controller is working and correctly plumbed you should be able to raise the boost to better than 10 psi.

Has your new RB25 got an internally wastegated turbo (stock) or has it had an external wastegate fitted?

[blind_elk]

If you use the wastegate controller for an RB20DET, then you will get around 10psi available right through the rev range. Then "open up" the dump pipe and you can get a couple more psi.

(this is how my RB25DET in R32GTS4 is set up. I also run the wastegate actuator from the fpr line, so I get full 12psi at the manifold, rather than at the compressor wheel)

[KiwiRS4T]

I also run the wastegate actuator from the fpr line, so I get full 12psi at the manifold, rather than at the compressor wheel)

You shouldn't run anything from the fpr line . Boost for actuator ideally comes from compressor or as near as.

[Dose Pipe Sutututu]

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