Primary turbo boost issues
 

Relevant modifications:
- Stock twins, ported wastegate
- Midpipe, downpipe, catback
- Intake
- Viton check valves
- HKS EVC VI boost controller
- PFC - controls pre-control
- New silicone vacuum hoses

My problem is that when I punch the throttle from low rpm, the car will only reach ~7 psi. It will hold 7 psi until transition starts. After transition, the car will hold 12 psi (or whatever I set my boost controller to) until redline.

I have tried a number of things to fix my issue:
- Checked vacuum routing. I am running simplified sequential, so I do not have the EGR solenoid, the two solenoids for the ACV, nor do I have the FPR solenoid. Also got rid of the double throttle solenoid (and the associated butterflies). I cleaned up the routing of some of the lines that were left, replaced all the hoses that were not connected to solenoids. As far as I can tell, everything is hooked up correctly.
- Checked rods for the Turbo Control, Wastegate, and Precontrol actuators. All gates are closing/opening completely as far as I can tell. It was pretty damn hard to get those rods back on once I took them off...
- Checked functioning of actuators. They are all within spec.
- Messed with gain (called offset on the EVC). Changing gain only affects the max pressure after transition on my car, I will get 7 psi on the primary regardless of gain.
- Checked for play on the primary turbo. Seems to be fine, just like when I got them ~40k miles ago, with 40k miles already on them. They shouldn't be going bad, right?
- Even though I'm using the EVC VI to control the wastegate, the PFC controls the precontrol. I have tried changing the duty values with the commander, to no avail. Same behavior as stated.

I have not:
- Checked the solenoids for functionality.
- Other things you guys can think of.

I did search the forum for fixes, in case any one was wondering. I found a few promising leads (like the precontrol possibly being slightly open), but none of them panned out. It's strange; a lot of the problems I found were with getting no boost, or very little boost on the primary turbo. My primary is producing at least wastegate pressure, but it won't pass that.

I'm open to retrying things I've already done. Chuck Westbrook and I have been trying at this for months, I just want my sequential system working again.

My impression is that your precontrol solenoid is not functioning and that your precontrol actuator is operating off spring pressure.

To test this, you can vent the precontrol actuator by pulling the lines off the precontrol solenoid (or actuator). If you do this, the EVC should regulate primary boost to your 12# setting using the wastegate. The caveat being that the transition will likely be wierd without prespool control; however, it will not hurt anything.

That was my thinking too. The fact that I can regulate boost after transition makes me think the precontrol is staying open all the time.

Thanks for the suggestion, I'll go try that out and update the thread sometime tonight.

This is exactly what the problem was.

However, instead of just taking the lines off of the actuator and testing it that way, I tee-ed the precontrol actuator into the line from the boost controller to the wastegate. Bada-bing, perfect boost pattern.

Thanks Speed of light. :icon_tup:

Still having some issues.

As stated in my last post, I have a valve between the prespool actuator and its pressure source. I can completely open and completely close this valve.

I logged boost pressure vs rpm, starting with the valve completely open, and eventually completely closed it. I made 8 runs from 2.5k RPM to 6k RPM at different valve settings, with NO change to boost pattern. AT. ALL. Not sure if I still have this log, but there was maybe .1 psi of variation in one cell on one of the runs... that's it. I consistently made 10.2-8.7-12.1 psi (boost controller set to 13psi target).

I also tried it using the precontrol solenoid additionally, with no change at all to the pattern.

So no matter how much pressure the prespool actuator receives, there is no change to primary boost and transition.

Did check the wastegate and precontrol actuators... both were within spec. Same with the solenoids.

Running out of ideas of what to check, or what could be causing the problem. It's just wierd... I can only get 10.5 psi at most on the first turbo, but I can basically achieve whatever target pressure I want on the second turbo (I can hold anywhere from 10.5 psi to 14 psi with almost no variation, till redline).

Any more ideas?

Nobody? :(

I dont know if this helps but check: https://www.rx7club.com/showthread.p...=primary+boost

I'll check that when I go single turbo this summer. The system is working well enough for now.