Sequential Problems
 

I figured I'd post this up while I have the car apart for diagnosis. The problem first started when I would take a WOT run in say second gear, then when I'd shift to third and go WOT, it would fall flat on its face 0psi and no power. Then eventually the problem got worse. Now when I take a WOT run, it will hit 4500rpm and fall flat with no boost or power. My buddy suggested trying the poor man's non-sequential, but then I got boost spike up to 14-15psi. And I'd rather run sequential anyways. I've done lots of research and tested the obvious stuff like the CRV, but figured someone might have experienced similar problems.

Just to confirm what you are describing:
-You do at WOT run
-Primary spools up fine until 4500rpm?
-Then at the transition, you lose all boost and the car sits at 0 psi from then on?

Yup, you are correct. Its a fairly new motor I put in and did all the vac lines and rats nest stuff. The sequential system only worked properly for about a month. I also tried installing two MBCs to bypass the boost control solenoids, but that didn't help. I have the UIM off now and am going through all the lines and solenoids.

Too me it seems like the charge control valve, so the 'flapper door' inside the Y-pipe isn't opening. So no air is getting to the secondary turbo.

(You said you've check the CRV, but that just vents secondary boost back into the intake).

Either that or you have a giant boost leak somewhere, but you would generally hear a swoosh sound then...

Have you looked at this yet?

http://www.fd3s.net/boost_problems.html

Might help you diagnose the problem.

i pretty much have the same problem and cant figure out whats wrong....i might just have to go non sequential! oh and i also get that BHEYW sound when i let off the gass!

Awesome, thanks for the link. So I think I found one problem yesterday. My Precontrol actuator doesn't seem to hold the pressure. Also, I've tested the control solenoid via the FSM and it seems to function properly.

Try the poor man's non sequential first to make sure you like it. I hated it, so I'd rather get the sequentials working.

im going to be going 1jz gte pretty soon....soo i want to enjoy any sort of boost with the rotary for a bit!

That could certainly be part of the problem, but I would think that even if the PRECONTROL wasn't working right, you should still make boost on the second turbo, since that is controlled by the TURBO CONTROL. It probably just wouldn't prespool?

Just thinking out loud here.

But, if the TURBO CONTROL wasn't working, then the manifold would be closed off for exhaust gasses for the secondary turbine, meaning no boost.

Or, if the airflow to the compressor for the secondary turbo is closed off by the CHARGE CONTROL , then you wouldn't get boost either.

so what is the boost pattern when it worked vs when it is wrong

After 4500 the primary turbo should still be producing boost though right? I tested the Turbo control via applying pressure to the side port and the arm functioned properly. The boost pattern when it was working was 13-10-14 Spike a little on the secondary, but between 12-14. I went through all the lines under the UIM and got it back together today. I'll take it for a spin tomorrow and see if there is any change.