SpeedracerRX7

I looked through some of the past threads on boost but I haven't really found anything on this particular problem.

Ok here is the scenario. If I am at full throttle in any gear the first turbo comes on strong up until when the second turbo is supposed to kick in around 4000-4500 RPM. At this point one of two things happen 1. the second turbo kicks in and carries it right to the redline or 2. the boost drops to 0. If it drops off in most cases all I have to do is lift off the throttle and mash it in again and it sometimes comes right back to 10 psi. Sometimes it takes 2-4 blips to restore boost.

I talked to Brian at Rotorsports where I recently have had my engine replaced and the vacuum hoses done and cable tied. (May I add that they did a wonderful job) He thinks that the white check valve with the green top might be failing or not working. I have no reason to doubt him but I just wanted some other input because I won't be able to get the car to him so that he can properly diagnose it until late next week.

By the way I did take the black vacuum box off and was not able to find any loose vacuum hoses or anything like that. Thanks in advace for any help in this matter.

SpeedracerRX7

bump

RotaryKnight

I had the same problem when i had stock turbos. Something to do with either the turbo control solenoid or one of the check valves. Never did get it fixed cuz i went single a month later.

jr

Your vacuum chamber isn't holding vacuum. When you lift off the throttle you build vacuum which allows the 2nd turbo to operate. Could be a few reasons for this, but the most common would be a bad check valve in line to the vacuum chamber or the vacuum chamber itself could be cracked. Check those first and then come back if you still have a problem.