Trying to diagnose a twin turbo problem.

Relevant details:

1992 JDM FD3S
BNR Stage 3 sequentials.
Aftermarket solenoid kit (from a member of this site)
AVC-R is running the turbos. (with the AVC-R, I've pretty much tuned out the boost-dip at the transition)
Power FC
Car professionally tuned last summer.

The problem:

The car runs great and I get full boost (16psi) all the way to redline.
HOWEVER, if I'm cruising above 4500rpm with no boost and I stomp on the gas... no boost.
If I dip back below 4500 and then stomp on it, I get full boost.

Really short summary: No problem if I start accelerating anywhere from idle to 4500, but if I start accelerating from 4501+, no boost.

I have gone through the car and made sure all the vacuum lines are still properly connected, I have also verified that the charge control valve is operating properly.

Any ideas or pointers would be appreciated.

Thanks,

-Geoff

 

I've been out of the game for a while now, but seems I had something like this with my sequential BNR's as well long ago. I think I got rid of it by working with the turbo transition settings on one of the FCedit screens (do you have datalogit to tune your PFC?). May have been settings 1 screen . Anyway, you need to work the the TPS and RPM settings. There are some writeups on this in the forum. Sorry not more helpful. . .

 

Thanks for the pointer, but the PFC isn't running the turbos, they're being controlled by the AVC-R.

-Geoff

 

Sounds like you have a leaking solenoid or vacuum/pressure chamber. Also, I would ditch the AVCR and use the power fc to control the boost. You can use the AVCR solenoid and connect it to the stock wastegate control solenoid and the power fc will control it. It is the same solenoid that comes in the apexi power fc boost control kit and a few other controllers. Simpler and less chance of failure.

 

Solid advice. There's a good thread on here that describes everything you need to know to use an aftermarket solenoid with the PFC for boost control. It even lists part numbers for the plugs so you can connect it to your factory wiring harness.

 

Ok, so I unhooked the AVC-R solenoid and reconnected the precontrol and wastegate solenoids and made sure their vacuum lines are correctly routed.

I also checked the PFC and the boost settings there, which are 1.15 for both primary and secondary turbos with duty cycles of 75% and 78%

I'm only getting 7psi now. However I do get boost (7psi) if I accelerate above 4500 rpm when starting from a vacuum state.

Basically I solved the initial problem but now I don't get proper boost levels.

-Geoff

 

7psi is what you get if you're running on the stock wastegate actuator spring without any assist from the bleeder solenoid. If all the vacuum lines are plumbed correctly, it sounds like maybe the boost control solenoid isn't switching. There's a good thread on how to test the solenoids. If you find your BCS is dead, you can just wire your AVC-R solenoid up to the stock wiring harness and use that instead.

 

I've also confirmed that the precontrol and wastegate solenoids are in functioning order by using a 9v battery to test them. They both click when power is applied.

-Geoff

 

I also hooked up the AVC-R wiring harness to the stock wastegate solenoid and left the engine harness hooked up to the precontrol solenoid and I still only got 7psi.

-Geoff

 

Regardless of what you use for boost control, you need to confirm your check valves, vacuum chamber, and pressure chamber are ok.

 

I guess that'll be today's work.

I assume my check valves are ok. They're all brand new and they're not factory, they're the ones Dale Clark sells in his kit. I do have extras, so I can attempt to diagnose.

How to I test the pressure and vacuum chambers? These are both original factory parts, I assume they could be wearing out.

-Geoff

 

Well, I think I figured it out.

Crawled under the car and upon close inspection, it seems the arm for Turbo Control Actuator has come off the lever it attaches to.

How is this normally secured? Is it a C-clip or a nut?

Thanks everyone for the input along the way.

-Geoff

 

So, final update in case anyone ever stumbles across this thread having the same problem.

It's fixed. The issue with no boost over 4500rpm while accelerating from vacuum while being over 4500rpm was that the arm from the Turbo Control Actuator had disconnected from the lever that open/closes it.

A 50 cent clip from the hardware store fixed this issue. 3/16ths is the size of the clip.

Thanks again to everyone who helped along the way.

-Geoff