13brv3

Hi again,



I still think the lack of a transition at 4500 is a big clue, that should be investigated. Have you T-ed into the charge control actuator on the y-pipe? That will tell you when the charge control actuator is being told to open. If you see transition on the vacuum port, but don't see it on the boost gauge, then maybe the actuator is sticking closed. If the vacuum signal doesn't change until 5500, then we'll have to look deeper into why. While I was T-ing into the charge control actuator, I'd also put the vacuum tester on it and make sure you see it actuate.



Another thing that would be interesting (and you may have done this already), is to T into that nipple that's on the secondary side of the y-pipe. It would be interesting to see what the gauge sees at that point. This will give you some additional info on whether the secondary turbo is pre-spooling, and whether the charge control is opening.



Ain't sequential fun



Cheers,

LAracer

Greetings





This test I have done. It read 0psi up to 5200rpm (or at least, until slightly before 5500rpm), then it jumped very quickly to 7psi. Apparently (according to this thread: http://www.rx7club.com/forum/showthread.ph...rbo+precontrol) I should be seeing a smoother build up of pressure, corresponding to the precontrol opnening. This is one of the tests that pointed me to the precontrol in the first place. This makes it look like the charge control is opening, but just late.



It also makes me think that there is still one piece of the precontrol puzzle that I did not check. I did not check that the valve is opening, even though I know that the actuator is moving and it is connected to "something" with a c-clip. If the valve really is opening, I should see something at this nipple before 5000rpm, right? Have you done this to test on a working car before? If the precontrol valve itself is stuck or broken, how can I tell?



As for the charge control actuator, I have not tested it yet. When I get off work I will T into it, as you suggested, and see when it gets its vacuum?. And I'll also verify that the actuator moves under vacuum.



Thanks again 13brv



I thought debugging computer code was fun - the sequential turbo system makes fortran look easy

P'cola FD

I'm with Rusty on this one. Start T-ing into vacuum lines of things which occur around transition. Like the CRV, the CCV, the TCA, the vacuum tank, and the pressure tank. If you have a leak in the vacuum chamber, that could cause a late transition, due to the pressure side of the TCA having to do all of the work. Your theory on the wastegate not working doesn't make much sense to me, because until the transition, the precontrol is doing the boost control, not really the wastegate.

LAracer

Ok, I'll hold off on messing with the wastegate then. I'll do as you guys advise.



What is the simplest way to check the vacuum tank (the pressure tank is easier to check since it isn't connected to as many solenoids)?



Thanks.

P'cola FD

Just "T" into any of the lines that use the vacuum chamber. I "T"ed into the one coming directly off of it, but you can go in anywhere before the solenoids.

LAracer

Ok, the first thing I checked last night was the charge control actuator. The shop manual says it should move with 1.9inHg applied. I had to apply 5inHg to get it to move all the way, so maybe it's a little sticky. I need to T into that line while driving and see what the pressure is; maybe this difference is insignificant.



Next thing I checked was the charge relief valve - works perfectly, tested it exactly as the shop manual said. I even tested it again using the hose it connects to in the rats nest to rule out a leak between there and the valve.



I also checked the charge relief solenoid. It works fine.



I didn't check the charge control solenoid yet since it requires removing the UIM and so far I have managed to avoid this. Still, I am running out of things to check so it might be time to go deeper. I may wait until my y-pipe and dp arrive.



I need to verify that both the CRV and CCA are working when the car is running, but this morning there was 6" of snow on the ground, so that'll have to wait.



I haven't checked the vacuum chamber yet. I T into any vacuum line, and then what? should it hold vacuum? I tried this, but some of the solenoids must be open. Should I try again with the car running (or just turned on?)? what should I see?



Thanks.

13brv3

"I need to verify that both the CRV and CCA are working when the car is running, but this morning there was 6" of snow on the ground, so that'll have to wait."



Ack, snow.... I need to drive my car to let the PFC "learn" not to hunt for my idle speed, but it's barely 60 degrees out, brrrr :smirk:



Operational tests of your CRV and CCA will be interesting. I'll look forward to hearing about the results next Spring :stickpoke:





"I haven't checked the vacuum chamber yet. I T into any vacuum line, and then what? should it hold vacuum? I tried this, but some of the solenoids must be open. Should I try again with the car running (or just turned on?)? what should I see?"



The vacuum chamber is just to the drivers side of the alternator, and it only has one hose going to it. To test the chamber, just pull some vacuum on that hose to the chamber, and see if it holds. You just want to make sure the chamber isn't cracked. When you're under boost, that chamber is the only source of vacuum to anything that needs it.



Cheers,

LAracer

Sounds simple. I guess I just try to make things too complicated :redface: .



I just had another thought (scary, I know). Remember I mentioned I did the test on the nipple on the secondary side of the y-pipe and got 0 to 5200psi and jumped to 7psi after? Well, here's my thought: What if the charge control was working, or at least, was opnening at 5200, but what if the secondary turbo was not spinning? Wouldn't this give me that kind of result? i.e., the pressure I'm seeing is the primary charge air flowing backwards through the charge control valve! This would mean, though, that the secondary turbo did not spin under precontrol either. This would be a serious problem.



Any thoughts on how far up the BS-o-meter this theory ranks?

13brv3

Maybe not as far as you'd like it to be



Rusty

P'cola FD

I don't think that the CCV will open unless there is boost on the back side of it. I could be wrong, but I "think" that for it to open, there has to be equal boost pressure on both of its nipples. And I "think" that its other nipple gets boost from the secondary turbo. I would recommend not checking your vacuum chamber with a pump, but rather checking the entire system by "T"ing into the line Rusty is talking about, starting the car for long enough to build a vacuum, and then turning the car off. If you lose much vacuum at all, no matter how long the car has been sitting, then you have a leak. That leak could be your problem.