Hey gang,
I'm scratching my head on this one, and forum search got me close but no cigar yet, so I'm hoping the hive mind can help me out.
Problem: Sometimes the primary turbo in my stock '93 FD will not re-engage if I'm going on-throttle and off-throttle more than a few times. The turbo won't re-spool until I let it rev down in neutral to at or below 2krpm, at which point I can gas it and it'll take again. Makes auto crossing kind of hard.

As an example, I was at an autocross recently and it went like this: gas on, come off throttle- brake- turn in; then back WOT (boost fine), coast-brake-turn in, then gas on again (no boost!), and I had to let it catch its breath before it'd boost again.

Other notes:
- Never happens for secondary turbo
- Doesn't happen regularly. Sporadicly haunts me.
- When the turbo doesn't re-engage, I really have to let it spin down to below 2k rpm before it'll catch
- The car has a brand-new OEM twin turbo with 2.5k miles on it
- That said, this also happened to the previous (original) turbo
- Compression is perfect, was recently tested by Nick at Flatout.

Thoughts? Sticky BOV staying open? Some sticky solenoid?

Thanks!

 

My guess would be you are transitioning to the second turbo and it's not transitioning back. If the turbo control door and /or charge control valve are open at low RPM the car will be a dog.

What is your typical boost pattern? What mods are on the car?

Dale

 

With the OE ECU, the transition back to primary will not occur until the revs drop to well below 3000 RPM, say 2700 or so. It's set up that way. Mine has had that behavior since new.

 

What you're describing could be a sticky "E" solenoid, which would mean not all the exhaust gases are routed to the primary after boosting hard and the revs have fallen.. more info on how your turbos behave during nominal conditions would be helpful (boost pattern, etc). Assuming your car behaves normally otherwise, you could try this and see if changes the behavior: https://www.rx7club.com/3rd-generati...ctive-1120259/

 

@photoresistor , you legend, I think you're spot on. I'll do that Tee mod and see if that does it.
Thanks!!

 

I had the same issue and the tee mod worked perfectly. In my case the primary wouldn’t come back for about 1 minute after being out of boost.