if i go from a dead stop and hit the gas to wot i get good boost patterns in first and second. but when i shift to third it seems like i can't get the boost to come above 4. whenever i take first or second gear to ~6000 rpm then this happens. any ideas? from a roll if i punch in second gear i'm okay, might take a sec, but boost climbs to 12. same thing if i'm going from a roll in third. mods are below. car has 65k miles on it. usual boost pattern is 12-7-8(i know it's not supposed to be like that, still haven't got the needle valves dialed in right) nick

 

I believe it is from a bad one way check valve connected to the pressure chamber on top of the engine. Remove the black chamber in front of the upper intake manifold and you will find a green/black check valve going towards the turbos. Take it off and blow hard in the direction against the arrow on it. If you can blow through it it is bad. It is only supposed to blow one way (with the arrow).
You might try just disconnecting one of the hoses from the chamber, you should hear a "whoosh", if you don't you are loosing pressure needed to operate the turbo controls correctly.

Frank

 

thanks for the help frank. i went outside, disconnected a vacuum line from the chamber and heard the sound of air escaping.
so any other ideas??
nick

 

Check all the control actuators. Old and damaged pneumatic actuators can cause irratic boost behavior. Make sure all the c-clips are there.

 

Have you solved the problem? I just finishied a hose job and mine is doing the same thing.

 

haven't figured it out yet. my clutch started to slip so now i'm getting ready to put a new one in. in your case did this happen before the hose job? if it didn't then i would think you maybe forgot to connect a hose or switched up where some hoses go.
some suggestions i got was a bad solenoid (maybe charge releif solenoid-valve) or a clogged cat or pre-cat.
nick

 

you should hear that sound. its a presure chamber

 

if you read this today, stop up at jims. we will do what i talked to you about. just to try...

 

Check out this page, if you haven't already.

http://www.autosportracetech.com/RX-7/rx7stuff.htm

It might not solve your exact problem, but it should help with understanding how many of the systems work.

 

wish i could, but i have school all day and i've already skipped too many classes. i'll catch up w/ you another time.
nick