Hey guys,

I know you're probably tired of hearing about boost problems, but I'm terrible with searches and couldn't get a good search going. I know quite a bit about the sequential system anyways and I'm a little stumped.

I have perfect primary operation, but when the secondary comes on I drain to about 7psi and have a decent venting noise. I thought it was the BOV for the secondary turbo (I can't remember what it's really called), so I changed it out for one off another car that worked while it was still running several months ago. The hose seems to be in good shape as well, but I may try to change that out to. Anyways I still have the problem. There's absolutely no noise during primary operation, only when the secondary comes on. It's a big whoosh, like a coupling is off or something. Anyway if anyone has any ideas, I'd appretiate it.

Thanks ahead of time.

 

If you are getting good primary boost, then you probably don't have a leak. If you have not done so already, check the vacuum lines in front of, and under the UIM. Sometimes they pop off, and things don't work like they should. Pull the black pressure tank out of the way to check the lines.

Good luck

 

The BOV for the second turbo would be the Charge control valve. it's the little thing that sits on the y-pipe and controls the door that allows secondary boost to be added to primary.

If you're sure that one works, then it very well could just be one of the hoses or check valves that controls it is either disconnected or broken. A quick visual inspection should ensure that they're ok.

 

I'm going to check the lines next chance I get. Maybe something is just stuck holding that valve open so it vents all the time now.

Greg

 

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

those of you with turbo problems need to bookmark this link

the bov you're referring to for the secondary turbo is the charge relief valve. this allows the secondary boost to vent into the intake until the switchover rpm of 4500 is reached...the charge relief valve closes, the charge control valve on the charge control actuator opens, and the turbo control actuator opens the flapper @ the exhaust manifold, adding the secondary turbo's boost to the primary turbo's boost--sending you to full-tilt boogie

rx7joe, you sure you know quite a bit about the sequential system? after reading the above link, you'll know more than you thought possible...you may even claim yourself to be an expert after you solve your own turbo problem...

that's what i've done

 

...and don't forget to check the y-pipe coupling. That seems to be a very common problem. You need to inspect it carefully (i.e. take it off) to find any possible cracks.

Good luck

 

I pretty much know the sequential system inside and out. I have an efini y-pipe so the coupler is out. This is only in secondary operation anyways. The primary system works perfectly. I'm thinking a vacuum line or electrical problem. If the solenoid is stuck so that it's holding the releif valve open under secondary operation then it would just vent pressure. And it's venting a lot, not just some vacuum lline loose. I'm gonna have to dig around some this weekend or soon at least and see what I can find. It has to be coming from that releif valve. Nothing else could be making that much noise under only sequential operation.

Greg

 

Thanks for the link Sleepr1. I've already read that several times over a couple years ago though. It's printed and in a binder in my study so that I can just read whenever. It's handy. I think there is something else going on besides the regular boost problems, but I'll know more once I get a chance to look around under the manifold.

Greg

 

Well, if all else fails, you can get systematic and start T-ing into the vacuum lines of the various actuators. I did this and posted the results here:

http://www.geocities.com/laracers_vr_r1/boost_plots

But don't compare directly to my results; I'm at 7000ft and the sequential system goes all goofy up here .

(I'd still like to see someone with a healthy sequential system make a similar series of actuator pressure plots.)