Jump to content
SAU Community

Rb25Det Overboosting - Creeping, Not Spiking

Brent

By Brent,
in General Maintenance

 Share

Recommended Posts

Brent Enthusiast

Brent

Posted
Posted

Hi guys. Just as the title says, I've got an RB25DET in my R32 and whatever I do, the boost will NOT stay steady.

The motor is 100% standard. Standard turbo, intercooler, dump pipe, blow of valve, everything.

I have tried a few configurations though and nothing makes any difference. Have tried an RB20 actuator, t piece boost controller, aftermarket dump pipe and just recently a brand new GReddy Profec B Spec 2.

So like I said, even with stock parts, the boost level to 4000rpm will stay steady at 4.5ish psi, then gradually climb to about 8.5psi by redline.

It does it in every gear, although I found if you launch hard in 1st then the boost stays down a bit for some reason.. Whereas if you're on the freeway in 3rd or 4th then it will climb more noticeably.

I have checked the wastegate flap and moves very freely and does not get stuck at all.

What the hell is the problem?!

Brent Enthusiast

Brent

Posted
  • Author
Posted

I've tried two different standard RB25 ECU's, both have the same affect.

The car is standard. Fully standard. It has to be something broken or not functioning correctly, but what?

Marcus89 Proficient

Marcus89

Posted
Posted

If the actuator isn't opening properly then he would be having massive boost spikes. Would be more a case of the actuator not holding closed properly but then like someone posted above if he is still running the stock boost control solenoid then it could just be normal

Brent Enthusiast

Brent

Posted
  • Author
Posted

The solenoid is non existent and the actuator and wastegate are both working CORRECTLY. The actuator has also been swapped out for one which has been proved in another car to be working properly.

Today the car stalled on me while coming off higher revs and putting the clutch in. To me this indicates a leak of some sort. I am getting a smoke/leak test done this Saturday to see if that is the case. The turbo to exhaust manifold gasket is brand new and there are no leaks there. I'm thinking the leak may be coming from the actual manifold to head gasket...

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

Smoke test came up sweet. Noticed the TPS was stuck on 0% according to ecu. Checked and found the signal wire has a short to ground. Ran a new signal wire now TPS works.

Ran it up on the dyno with boost controller turned off. Ran 5psi then creeped to 8psi up top 177kw

Tried playing with boost controller with no rise in boost.

So

Turned it onto high boost and held a flat 10psi 201kw.

Next run te same. 3rd run boost dropped back to gate pressure. Suspect his boost controller is faulty

Brent Enthusiast

Brent

Posted
  • Author
Posted (edited)

And Jez has done it again. Car now runs perfectly!

I completely removed the Profec B and switched back to the RB20 wastegate and now the car holds 10psi all the way to limiter. Stoked :D

So it looks like for some reason the RB25 actuator would not hold the same pressure (although I had the same result with another RB25 actuator), the 'brand new' boost controller was faulty (will have a word with who I purchased this from), and the TPS wiring (I had the R32 RB20DET > RB25DET loom made up by someone reputable) were all significant factors as to why my car would run how it did.

Other things which improved with how the car drove were brand new AFM and OEM o2 sensor.

Was definitely a bitch to get this motor running how it should, but worth it in the end.

Thanks again Jez!

Edited by Brent

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Duncan
      What accelerator cable can be used with greddy plenum

      By Duncan · Posted

      I was 99% sure the standard one is long enough to get there, you might just have to change the throttle orientation. If not, I remember someone having used an r31 cable instead, but that is probably harder to find than r33 by now...
    • V36
      What accelerator cable can be used with greddy plenum

      By V36 · Posted

      HELP   Hey all, Is there an accelerator cable from another Nissan that can be used on the R33 GTST RB25DET with a Greddy forward facing plenum?  Thanks in advance  Rob 
    • ARB26
      RB26DETT Sketchy boost mod?

      By ARB26 · Posted

      Or do we think it was installed to give 1 bar of boost max, all day, everyday?
    • ARB26
      RB26DETT Sketchy boost mod?

      By ARB26 · Posted

      So could it be assumed it has been installed intentionally with potentially a power FC boost controller kit? 
    • Gareth87
      What should I do next to hold the head on

      By Gareth87 · Posted

      Had my rig on Matt's dyno at PITS the other day. After a few years between tunes I added a few sensors and swapped intercoolers. Result. 553hp at 26psi. Not bad for an FJ20 that was built in 2007. The problem.. It filled the overflow bottle on hard runs which leads me to believe the head gasket isn't sealing. I have a coolant pressure sensor which was reading cap pressure at 22psi and occasionally overrunning to 23/24 psi on deceleration after a pull. It was not spiking. It has arp2000 head studs and a cometic gasket. As its been 18 years in service, I pulled the engine out and head off. Everything looks good but we obviously have an issue. Where I'm at.. Years ago I had the same issue, I checked the stud tension and they were all over the place. Some at 60 to 70 and some up near 90. I nipped them all to 100ft lbs and this stopped the water push until now. I believe this compromised the gasket back then. What do I do? 2 options are..  1) I bought arp 625+s, which I could put in with a new gasket. Thinking Kameari this time, reassemble and try again. 2) strip the block, get fire rings machined in with copper gasket and try that. I do not want to push it more than 28 to 30psi. I think the turbo will be out by then anyway. (G30-770). My other concern is the long term ability of a copper head gasket. Are they streetable for years? I feel like a new gasket with the new studs will probably suffice, but I don't know. Any thoughts welcome and advice on copper gaskets and fire rings. Thanks!
×
×
  • Create New...