I have searched and read I think just about every post on the forum
regarding secondary boost issues. Many lead to dead ends.
I am running out of ideas as to what is causing my secondary boost problem.
Primary turbo boost fine 11psi then at the transition about 4500 rpm I will get 5psi
and boost will keep dropping until red line.
Vacum/pressure hoses have been
replaced on the engine already and I don't hear any unusual whoosing sounds.
Charge control actuator rod moves in and out with the koko test and if I leave
the key in the on position "rod in" and remove the vacum hose from the chamber
the rod moves out.
Both vacum and pressure tanks hold after the engine is turned off.
Check valves have been checked and I can blow in the direction of the arrows
and not the other way. Vacum side check valve arrows all point towards the UIM
and the pressure tank check valve points towards the tank.
Also if I do a WOT test and let off the gas to recharge
the vacum chamber and WOT it again still no boost or very little above 4500 rpm.
I have taken a look at the charge relief valve by starting the engine and checking
to see if I could blow threw the valve form the hose that goes to the air box and
I can blow threw it. After I remove the vacum line to the CRV and the engine is still
idling the valve closes and I can no longer blow threw the CRV.
I have pulled the UIM and replaced both turbo control solenoids and I have replaced
the turbo control actuator to no avail. I did buy the TCA and solenoids used so maybe
they were bad. I plan on pulling the UIM again and check these. I was able to find the
spec's for the solenoids on the rats nest in the service manual but not for the TCS
that is on the ACV. Does someone have the testing proceedure and spec's for this
solenoid?
Again, looking for some help.
Is there anyone in the Chicago area who enjoys a challenge and would like to help.
I'll buy the beer.

TIA

jaj1

 

how about the charge relief solenoid? do you hear the boost venting still above 4500?

 

Well, I just finished removing the UIM again, I'm getting pretty good at it. (g)
I checked the turbo control solenoid on the rats nest using 12 volts and it is
functioning correctly. I will continue checking some of the other solenoids tomorrow
i.e. charge relief solenoid, getting kind of tired.
Is there an ohm rating for the rats nest solenoids? I couldn't find one in the manual.
Can someone tell what the test spec's are for the turbo control solenoid that is located on the ACV?
All the hoses look fine.
I am at a lost as to why my 2nd turbo is not working right.
Any ideas from the forum will be appreciated.

Thanks

jaj1

 

Hmm... sounds tough. Try the troubleshooting guide on page F-193 of the service manual. My guess is ignition. Let me know what the problem is when you find out.

 

FDeez,

Why would you think the ignition would be causing my boost problem?
The car does not misfire even above 4500 rpm's.

jaj1

 

Does the car stutter or surge? If it stutters or surges, that might've been the problem, but if it's still smooth and just w/o boost, it might not be.

I had a similar problem after I had my engine rebuilt. First the mechanic thought it was the injectors. After getting new injectors, he figured out that it was the ECU. Maybe try to swap ECU's with someone.

 

The car runs smooth. The only problem in lack of secondary boost.
Idles at 750 rpm's. At WOT no studdering just lack of secondary boost.

 

Doesn't sound like injectors or the ECU to me...it sounds like your secondary turbo isn't coming on at all, and your primary turbo is working its *** off trying to make boost to redline, and is running out of breath. Keep checking the solenoids, I can almost guarantee thats what it is. It doesn't have anything to do with the CRV I don't think...I was testing mine out by using a friends for comparison and didn't tighten the hose down enough...it popped off on a wide open throttle run, and I lost ALL boost immediately, no boost in primary or secondary. Its possible its leaking a little, but that would not cause you to have that little boost only on the secondary. It would just make both turbos work a little harder to maintain boost. I had a leak in mine, it makes the transition longer as the turbos have to work harder to recover. It still maintained 14psi all the way to redline though.

 

the problem is that the door/valve on your Y pipe is not opening at 4500 so you are left w only your primary turbo.

tap into your secondary turbo to ascertain that it is making boost... you should see 10 psi or so.

if all is well, tap into the 2 lines (one pressure and one vacuum) that BOTH must work at 4500 for the secondary turbo output door to open. go for a drive w hoses connected to the 2 signal lines. at 4500 pressure should go to zero. at 4500 vacuum should go to zero. one of these events will not occur.

trace that side back and you will find your problem. it will be a leaking one way valve, hose or non-working solenoid. one way valves can be sneaky.... passing the blow thru test but not actually working properly.

good luck,

howard coleman

 

Are you the guy with silver Rx7 in chicago ?

 

Go to A-spec they will help you out

 

RX7-PL,

I have a Blk 93 Touring.
I know Steve and Shaun at A-spec. A-spec put in my reman engine.
At the time I also replaced my turbos with a used pair that were in good
condition mine had some pretty big cracks in the manifold. The thing is my
original turbos work perfectly.
After the engine was replaced and after the break in period I tested the turbos
and they didn't work. They thought it was the used turbos I bought.
So I did some looking around and found a shop rag in the bottom of my intercooler.
I put the plumbing back together and and did the 3rd gear WOT test and I had boost
11-6-11. I didn't notice that in 1st and 2nd I had only 5 psi on the secondary turbo
until later. Now I don't have more than 5 psi of boost on the secondary in any gear.
Anyway, the guys at A-spec are very busy and if I can fix my problem myself all
the better.

jaj1

 

I think I seen you once on harlem ave. i got blk one too. maybe we can meet sometimes and talk?

 

RX7-PL,

I live in Elmhurst. If you want to get together let me know.
I will be working on the car again on Monday.
I have been on Harlem many times usually getting off the Ike to go
to Russell's Bar BQ so it is possible.

Go Bears!

jaj1

 

the impression i got was that at transition his boost dropped quickly to 5 psi and fell from there. dont you think if the y pipe was not opening during transition his boost would just slowly trail off?... but if the crv stayed open he would loose a ton of pressure quickly when the y pipe.

 

Maybe I missed it in my reading, but did you check to make sure the rod is connected to the TCA? Those clips are known to pop off. I'm gussing you have already, but ,if not, since you are down there double check the presure and vac lines to the TCA.

I would tee in an inexpensive vaccum/pressure test guage or a boost gauge if you have an extra between the pressure tank and the check valve. Make sure you are gatting strong enough pressure to activate the TCA.

 

Well I think I solved, with the help of the forum, my secondary turbo problem.
I am posting this to close the thread.
After removing the UIM again I discovered
that the TC solenoid on the ACV was bad. I also checked all my check valves with
a Mityvac and not just the blow test, and I found one that did not hold vacuum.
The vaccum would bleed off slowly. I must conclude that the blow test for check
valves is not a good test. So after replacing the the TC solenoid on the ACV and the bad check valve my secondary turbo seems to be working properly again.
Thanks to all of you who did respond to my questions.

Another RX7 running fully functional sequential twin turbos is back on the road!

Thanks
again

jaj1

 

Glad you fixed it. However, you should have listen to me over a month ago:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/boost-problem-please-help-341685/



Enjoy your new found boost.

 

What does that make two FDs with fully functional sequential twins Glad to hear it worked out for you.

 

Make that three!

 

Im at work and I need to check this later so I'm subscribing to this, lol