Hello,

I have an issue with my Power FC, when I installed it I noticed I do not get any primary boost pressure at all. Essentially the car runs without pressure up til about 4500 RPM and then when the secondary transitions over it builds boost to 10 like normal.

However, if I switch it back to the factory ECU I get a 10-8-10 boost pattern just the way I should, with both primary and secondary turbos working fine. So then I had my tuner load my basemap into another Power FC, with no other changes done and it controls both the primary and the secondary turbos just fine.

So the problem is isolated to the Power FC unit that I have. I've tried using manual boost controllers, I've tried bypassing the hoses to the precontrol and WG solenoids, I've tried running them direct. We've tried changing the settings in the Power FC, but none of those have made any difference in making the primary build boost with my Power FC.

Additionally, when I shift under the 4500 RPM band it does not give any woosh sound from the BOV, because the air is obviously being recirculated to the secondary or being dumped to atmospheric or something. Another bit of info is that this is something the ECU is controlling for sure because when the SECONDARY opens up past 4500 RPM and if I let off the throttle and let the RPM's drop down to say 3000 RPM, then it'll start to build boost on the secondary, albeit slowly, to say 5psi until it's in it's power band and then it'll build to 10.

I did research the issue and some time ago I found a thread that mentioned that the problem was that one of the solder points was bad on the PFC board and that would cause the precontrol to not work or have no primary boost, but I cant find that thread anymore. I guess my question is, is there a diagram out there that shows what controls the precontrol on the board so I can see if the point is broken? Better yet is there another way to get around the ECU controlling the primary so I can at least get mechanical control and build boost?

Here's 2 threads I found that discuss these issues too, the first one is the same problem I'm having but it had no resolution. The second thread discusses a similar problem but also has no resolution.

https://www.rx7club.com/power-fc-for...t-pfc-1106992/

https://www.rx7club.com/power-fc-for...wer-fc-656097/

 

I would say that the Pre-Control circuit of the PFC is BAD.
Go to Manual Pre-Control and maybe even manual Boost Control.

If you purchased the PFC used, now you know why it was sold!

 

I have almost the same problem.
I have primary boost and also sequential boost the first run to redline. But if I coast down below 4500 rpm and floor it I have just a few psi and I can hear boost venting. After 4500 rpm I have full boost again. If I shift to another gear primary boost is back.

Charge Control Actuator is working (tried key on key off several times). But maybe the problem is at the Turbo Control Actuator, vacuum or pressure side. Vacuum and pressure tank holds vacuum/pressure.

Using a Power FC.

 

Take a look at this autox I did in May. At the start in second gear I have full boost on primary. Then at the hairpin (about 43 seconds into the video clip) I downshift from third to second and boost is gone whenaccelerating from low rpm. So I guess that when rpm goes below ~3000 rpm the system dosen't switch back to sequential or something is stuck, as the boost is vented somewhere (probably through the charge relief).

I guess I'll have to hook up my boost gauge to the charge control actuator and the turbo control actuator and see what's going on.

What do you guys think could be causing this?

 

There has been posts about this downshifting problem before.
The fix was raising the Turbo Transition Low RPM to higher than 3000. Somewhere around 3500 I think. Not sure as I have been single since 2005. Search it.

 

You can raise the "Turbo transition low" setting from 3000 to 3500. That's something I have had good results with. That way it will be quicker to switch back to primary-only operation between shifts.

 

The odd thing is that I never had this kind of problem before, and I have owned the car for 10 years now. I have tracked that Superstage track so many times and never had that problem with low primary boost.

The Superstage race was the first one since I replaced my fault PFC with an older version PFC and then a re-mapp. So it could be either the PFC or the re-mapp.
With the PFC I replaced I had problem with oscillating secondary boost. That went away when I replace it with the older version PFC.

I will do some more runs and get back with better input data on what and when things happen at different RPMs and load.

 

Maldito X - Did you ever find the solution? I have the exact same issue