The first turbo will hold 11 psi but at 4500 rpm when the second turbo should come on the boost drops off as the first turbo runs out. The computer doesn't have any codes and no hoses seem to have come off or cracked. Also at one point neither turbo made any boost, but the first turbo made boost in the next gear. Need some help badly!

 

I have the exact same problem as you. The first turbo will push 10-11 psi then after 4,5-5k rpms you can feel the car lose power and see the boost gauge fall right back down to 0. It has been driving me nuts, I have pulled out half the engine bay trying to find anything. Just a little ago I found a torn hose, replaced it, got all happy because I thought I fixed it, put everything back together, no difference at all! The hose I replaced was the one comming from the charge control actuator. It looked fine untill I moved it and saw the rip. It's up on the secondary turbo portion of the Y pipe. I also know what your talking about with the different gears... if I let the rpms go past 5k when I shift to second sometimes it will only build to 5psi or no boost. Then when I shift back to 3rd and put more load on the engine it boosts back up to 10psi. THIS IS DRIVING ME CRAZY!!!!

 

Here is a link to an earlier post that may help.
Secondary boost help

 

Hey sin I'll you know if i fix he problem it sounds like you have the same problem. From what ive found it seems to be a check valve.

 

Thanks man, I will have to pull out the ol' vacuum pump and check things out. If I find anything I will do the same.

Chris

 

I checked the black and green check valve under the vacuum chamber. It works as a one way valve fine.. no leaks.. but the way it is suppost to blow it makes this weird whine noise. Should it be like that or should the air flow freely?

 

hey mate i had the same problem with my series 8 rx7 99 spec.the problem is the boost solinoid valve becoming stuck or it has **** itself, this is located directly under the plenum chamber, by removing this and apply a n electric current 12v to it it can free it self up, or you can sipply replace it, but as these units are pretty expensive as you cannot by indivially, but befor u take it all off do a simply check, just in front of the plenum chamber there is a small black box with two vacum lines attached to it simply unpug one if you dont hear any air come out the unit is not workin andy good luck

 

I'm in the same boat as you guys. I'll test this tomorrow when I get a chance. Good lookin' out andy69.