c00lduke

If i run though all the gear like i'm racing i get 12 in 1st and the 3lbs on all rest, if i dont full throttle it in 1st i get 12lbs in both 1st in 2nd but still only 3 lbs in 3rd. Each gear by itsself can run a 12-10-9 boost pattern. It is the same if i shift at 5000rpms or 7500 still only get 3lbs of boost in the next gear up. Any ideas?

Thanks
~Luke

7-sins

Backwards check valve maybe.. what mods do you have?

c00lduke

intake and thats it, which one of the check valves would it be, cause pretty much here's hows it goes, run it up to 5k cause my boost starts droping around there and then shift up, let engine wind down to 3k and kick it cause if i dont i will only get 3 lbs of boost.

7-sins

It sounds like there is a control problem on the 2nd turbo. Your not getting that much boost after the 4500 trans. point so you shift and since the rpms are above 3k the car relies on the 2nd turbo. When your rpms are back under 3k the car switches back to the first turbo. It is hard to point out a single place to start... just do some trial and error. Check out the check valves you can see w/o the UIM off. If you feel like pulling the UIM off it would be a good place to check for some mixed up hoses or bad solenoids. Checking the TCA - Turbo Control Actuator, might be another place... but it sounds more along the lines of the solenoids that control the TCA.

93TTRX7

doesn't second turbo work 4,500 rpm and up only?

mr_jonboy

Yes, but I believe it doens't kick off until the rpms go below 3000.

Do you notice this problem when the car is pretty warm or is this problem all the time. I believe I have had this problem before. I got an aftermarket boost controller and it fixed it. The controller replaced the solenoids that are on the front of the UIM. You could check those to see if they are working. The problem I am currently having is heat related and I have found that the TC solenoid (vacuum side) goes bad after awhile under extreme heat (with others help on this). Check those, you might find something.

P'cola FD

I had the same problem. For me it was the charge control and charge relief solenoids not getting a boost signal. It was a reversed hose on the turbo side of the extension manifold. That's probably not you're exact problem, but it might be similar. The TCA has opened the door sending equal exhaust gases to both the turbos. But if the CRV is open and the CCV is closed then you only have the boost that your primary turbo is producing. Until I figured it out I always shifted before 4,500 rpm. But ever since I can't believe that I didn't fix it sooner.

technonovice

What is your full boost pattern in third gear?
Cruise steady at 35 mph floor it have someone watch the boost and note the boost pattern.

You should get:
rpm psi
3,000 10
4,500 8 (as 2d turbo comes on)
4,500+ 10 (recovers almost immediately)
6,000+ 8 (and holds to redline)

Let me know what your numbers are.

Garrett

It's about darn time, thanks a million for this thread

I am having the same exact problem, no boost when I shift into second but I still have boost in second when I am easy on first

Hey cool duke, e-mail me or submit a reply to how your problem played out and how you fixed it, loosing that boost is really making me frustrated

we are in the same predicament

technonovice

To test the vacuum tank:
Tee into the vac tank with the vac gauge at either the vac tank itself, or the hose that goes to the solenoid rack. Same effect.
Run gauge into the cockpit.
Start car, go for a drive. You should see vacuum build up once the car starts and HOLD.
Then, the actual test is to find a hill and go up it in a higher gear where you won't gain much speed but will stay on boost for at least 10seconds.
Vacuum should remain high. If it drops, the first thing to check/replace is the check valve that feeds the vacuum system. Next would be hoses and looking underneath the plenum. Lastly would be a faulty charge
control/relief solenoid.

Another test to find out what is going on with your car is to tee your boost gauge into two locations:
1) The line that feeds the pressure tank, and tee into it before the check-valve: see boost build, drop at 3500rpms, build again and hold
2) The line behind the 1" charge relief 90 deg bend, which is the second turbo's activity: see nothing, boost builds at 3500 rpms, and holds. You should see numbers close to these below:

3rd gear - WOT

2000 RPM - 0PSI
3000 RPM - 0PSI
3500 RPM - 0PSI
4000 - 4500 RPM - Roll up to 8 PSI +-1PSI
4500 + RPM 10PSI

What is happening: Page F-84 in the manual

0-4000 RPM -
Precontrol controlled by ECU,
CRV off (Venting)
Charge Control Valve on (closed).
Turbo Control off

4000-4499 RPM -
Precontrol Optimized by ECU,
CRV off Charge Control Valve on (closed).
Turbo Control off

4500 RPM -
Precontrol fixed (5% open)
CRV on (closed) and Charge control valve off (open)
Turbo Control on

If you don't see any pre-spool before 4500 then the precontrol is not working.