6-7 up to 4500 then it drops to 0 all the way to redline. I can't hear any boost leaks. I put it on the dyno and pulled a 163hp 168ft-lbs pull. It clearly shows on the graph at about 4500 the car just dies (just power wise, car runs great minus the boost problems).

I'm pretty sure the secondary is fried but shouldn't the primary keep pushing after the transition?

List of mods:

3" SS DP
3" SS Cat Back
3" SS Midpipe (stock cat is on the car right now, cat could be clogged)
Air pump removed

 

Nope. After the transition, primary is offline. Sounds like you're running NA over 4500rpm. Aren't you glad these cars are turbocharged???

I bet someone one here can tell you *exactly* what the problem is...but that somone isn't me.

Good luck and free bump.

 

Yep, it is driving me crazy, 163hp really sucks. I have a set of NS twins I just haven't done the swap yet (still waiting on a few parts).

 

Post-transition the primary is offline? As in both turbo's are not working together?

In my mind, I have always thought of the primary turbo as the small turbo, and at transition the second turbo is pre-spooled, and then added to the primary turbo to make your high end power.

I'm not sure why boost would drop to 0 at transition, perhaps some sort of massive leak when the system is opened to allow exhaust into the secondary?

*Hoping for another Rotary mind to chime in for clairty*

-Rotary4tw

 

First of all, your primary boost is low, so you actually have TWO separate issues. The low boost on primary most likely means a boost leak of some sort -- bad coupler, etc. The lack of all boost post transition is likely due to a problem with the vacuum line from the y-pipe to the pressure chamber (contains a check valve) or an issue with the charge control sub-system of the turbo control system.

Get your hands dirty and start troubleshooting -- here's a nice description of the various parts of the turbo control system -- http://www.autosportracetech.com/RX-7/rx7stuff.htm

 

both turbos are Hitachi H12s - identical size.
from my understanding the higher the RPM's the more 'real' air that needs to be supplied to the engine to reach any given pressure level. as you get past 4,500rpm the primary turbo starts to get beyond it's maximum rpm efficiency and starts to decline in it's performance.

thus, the secondary turbo comes online to 'fill in' the boost curve whilst maximising the efficiency of each turbo... genius!

i'd say you have a boost leak that is exposed by the secondary turbo charger and/or the transition surge... check all the couplings between the 'rear' turbo and the throttle body and also that the blow-off and charge releif valves are secure and functioning properly.

also, check the FAQ for turbo troubleshooting under T.
it seems strange to me that your primary disappears instantly... maybe that is your primary air intake hose collapsing which'd strangle the whole system?

 

I am waiting on my new vacuum line to come in and then I will get started on my Non-Sequential swap. I will check all the couplers and intake pipes then.