my 93 rx-7 has a boost problem. It has a stock twin turbo that boosts up to 14psi.
here is problem! Turbo does not boost at 2nd gear if I have a full boost at 1st gear around 5000rpm. The same thing happens at 3rd and 4th gear.
I hear some metal scraching sound from the turbo when I boost high. Someone told me that is a wastegate problem, but I do not know. Any body knows about this problem? Please help me!

 

I would think you would be able to build boost pressure in any gear as long as you have load on the car. Thats a weird problem.

 

what do mean by have a load on the car? sorry, I am from Korea. How about the metal scraching sound?
thank you.

 

Metal scratching sounds bad, it could be any rotating part. Does it only make the scratching noise in 2nd gear, where the boost problem is?

Load, I mean as long as the wheels are touching the ground you have load (hell even sping the drivetrain may create enough load to build boost). In neutral you will not build boost, you will build 0 pressure (not in the negative), but it will not go to positive boost pressure.

 

That sound is very loud. few days ago, I met a blue rx-7 on the high way. We raced for a while about 120mph.
After that we talked a little bit. He said that he could hear the scraching sound from his car. yes, I can hear the sound when I boost high at every grear.
thank you again!

 

Check turbo control solenoid, vacuum chamber check valve. You sure it's metal scratching, and not air whistling? 2nd turbo problem usually points to vacuum chamber check valve or TCA solenoid. If you create a vacuum by letting off of the gas, and reapplying the throttle during your 2nd gear run, the boost should be back (2nd turbo comes online). If this occurs, you have a vacuum leak, TCA solenoid problem, have a vacuum chamber full of oil, or have a leaking vacuum chamber (cracked or bad hose connection).

Follow-up with what the cause and repair was for your boost problem, so we all learn from your experience!

 

A FD makes about 4psi in neautral if you go WOT.