renkenkyo

iTrader: (6)

So I was out at Autoclub Speedway a few weekends ago and on the second day I noticed I wasn't making any power at all! After the car go over 4.5K rpm my boost gauge showed the car would go into vacuum, so I figured it was just a popped off hose and I was losing air. The shop hasn't been able to find a leak either so I think the turbos are probably dead.

Now, the turbo has been leaking oil for awhile (not during driving, but only when it's parked), though only small amounts (probably 1/4 cup) everytime it's parked. Also, I wasn't able to get full boost on the last track weekend (max was around 6-7 psi).

Here's the dyno I ran after to confirm the lack of power:


I had the compression run about a month before and my numbers (while low) looked ok, so don't think it's my engine:

Front:86 86 73
Rear: 86 87 87

So are the twins dead?

potatochobit

iTrader: (1)

you should check the solenoids
do you hear any noises?
if the charge control valve is stuck open you might get 6-7 pounds at WoT
make sure the waste gate clip didnt come off as well

sc_frontier

iTrader: (3)

wonder if one is locked up...

renkenkyo

iTrader: (6)

I feels like the second turbo isn't spooling at all. The car makes a really weird studdering spurting sound when instead of the usual swoosh of air when you left of the gas/clutch/brake.

'Ryuji'

I've been having the same problem too for quite sometime. Been trying to troubleshoot but nothing.
http://www.youtube.com/watch?v=AzTYGG2E1Zk
Skip to 1:52, is that the sound you hear ? sounds like pewww

Narfle

iTrader: (16)

Check your CRV, PCA, corresponding solenoid, and the involved hoses. I'm in the same boat.

Primary works fine, secondary ruins the party and makes awful noises.
The very last suspect is the turbo itself. Of the many things that break on these cars, the stock turbos are not usually one. It's their supporting cast that is the culprit, luckily.

dgeesaman

iTrader: (7)

You're figuring wrong - your turbochargers are not the cause. You have primary boost and no secondary boost. I would strongly suspect the CRV system.

RENESISFD

iTrader: (13)

^ What is interesting to me is that after transition OP says the car goes into vacuum. To me that means the Charge control actuator and valve are working. It is possible the Secondary turbo is locked up somehow and all the boost from the primary turbo is being dumped out of the secondary.

Op it is easy to check if the secondary can spin. Just remove the secondary intake pipe from the turbo inlet and see if you can spin the turbine with your fingers. Other than that you will have to probably check actuators and solenoids.


John

scotty305

iTrader: (2)

I agree this is probably a problem in the twin turbo control side of things. It looks like the car makes the proper amount of boost in primary mode, but something is not working properly when the secondary is supposed to join in (around 4500-5000 RPM). I've created similar problems by screwing with the Turbo Control, Charge Relief, and Charge Control solenoid outputs using my standalone ECU, just to see what would happen.


There's a bunch of good links in the FAQ, under T for Turbo System Troubleshooting:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/faq-3rd-gen-other-useful-links-68640/

renkenkyo

iTrader: (6)

Thanks for the advice guys, I'll take a look at the solenoids and see if I can isolate the issue.

sc_frontier

iTrader: (3)

maybe the turbo actuator control is not opening up the big plate on your exhaust manifold. (actuator below turbos, big cylinder) Make sure the vacuum lines to and from are good, and if so you might have to start testing solenoids in the rats nest!!

twinsinside

iTrader: (34)

Yet another reason I'm glad I bit the bullet and got in on the custom solenoid rack GB. No more digging under the UIM for me!

alexdimen

iTrader: (13)

First thing that makes sense is the what barban said with the charge relief valve (CRV) sticking open. IIRC what happens at transition is the charge control opens up, when it had initially isolated the primary from the CRV. That would explain why pre transition you have boost and after the charge control opens at 4500, the pressure escapes through the open charge relief back into the airbox or atmosphere depending on what you have there.

In case you don't have them, take a look at the attached images. They have helped me. Good luck.

SonicRaT

iTrader: (6)

If you're good on the primary turbo up until the transition, then losing boost and have that strange sound, there's a relatively simple path to follow for diagnosing. The most likely cause I find is the Turbo Control actuator. If your turbos aren't smoking to the heavens and pushing tons of oil, it's probably control related.

Charge Relief Valve:
Disconnect the CRV's vauum line and plug your boost gauge into it's port, for now, you can plug the CRV into your old boost gauge's port. At idle/anything under 4500 you should see constant stable vacuum. Over 4500 it should jump to ambient/slight boost if in neutral. If you see this, the solenoid is working. Take it for a drive, do a 2nd or 3rd gear pull over 4500 and keep an eye on the boost gauge. Did you see positive pressure? If it's ~5psi and tapers off, your CRV system is likely working fine.

Change Control Valve
Connect your boost gauge up to chamber A's vacuum port on the manifold, rev the car over 4500 rpm and see if you go from stable constant vacuum to atmospheric or slight boost. If so, the solenoids working, reconnect and verify that when idling, the valve is sucked closed.

Turbo Control Actuator
This ones a pain, it has two solenoids in awkward spots for positive pressure, and vacuum. First and foremost, you should check and MAKE SURE that the actuator arm is actually attached to the door! This will give you all kinds of strange effects (and the weird noise on decel too), as the exhaust gases will hold the door closed, running the secondary only off the pre-control, eventually the primary turbo overpowers the secondary and bleeds the boost back out the intake path, and gives you that weird sound on decel. You can observe some of the solenoid function by watching the TCA while someone KOKO's the ignition. Otherwise, plug into each line on the rail just under the pressure chamber with the boost gauge and watch each during a drive. If you're getting good readings (10psi on the pressure side, good solid 20"+ on the vacuum side), then inspect the TCA for leaks.

Gringo Grande

iTrader: (97)

I seem to be having a similar issue but with a Rich Man's NS. I'll be using info in this thread and the link provided to test. Will hopefully have feedback after this weekend.