Ok, to make a long story short, finally got my car running after engine overhaul, along w/ a few upgrades, engine runs fine, had my car dynoed and tuned @ top speed and it yields 327hp/277tq @ 14 psi. Now here is my problem. Day after the dyno, I noticed my secondary turbo will not come on. I will have full boost on primary until it hits 6K rpm, and the car will not rev. past 6 in any gear, and I can hear my boost will drop and sounded like a vacumn leak. I then did some troubleshooting and found out a check valve from the dbl throttle to the upper intake manifold failed. I replaced it w/ an OEM check valve from Mazda, and instantly, the secondary came alive and everything runs fine. The same exact problem happened again a day later, no secondary again..now I am puzzled...couldnt it be the check valve again? I just replaced it a day ago?? Any advise would be great.

Marco

 

I had a similar problem when I was on stock twins. It turned out that my wastegate actuator arm for the second turbo was lose and it would come off therefore not letting me boost at all.

 

Ok, previously I had a boost problem where my secondary would not come on, and 6K rpm cut off. Many forums member told me it was the turbo control solenoid went bad. So this weekend, I removed my UIM and tested all my solenoids underneath the manifold. All of them seemed fine when I tested them with 12v and did the blow test. I am running out of stuff to check as all the solenoid seemed fine. Someone told me might be a melt down CAT? I have an aftermarket high flow that I bought used from a member, could this be the case? Maybe spark plugs? Any help would be appreciated...

 

Don't start a new thread each time. If you still have the same problem, use the same thread so we don't have 10 incomplete threads hanging around which people might find in their searching.

 

Are you sure you did the correct test? There is a very specific procedure to test these solenoids...Make sure you test them the right way, which includes heating them to ~250 degrees....Try this link.. http://rx7.voodoobox.net/howto/solen...oid_check.html

Good luck, and welcome to the crowd of misbehaving stock twins!

 

As you read from the link above, Dave had a problem with his solenoids not acting correctly at higher boost. IIRC, the M2 SMIC has a drop pressure of ~1PSI @ the boost you're running. That means that your solenoids are seeing at least 15 PSI of pressure when you are boosting at 14PSI.

Try limiting your boost to ~8PSI to see if your boost problem persists. At least then you can somewhat verify it's not your solenoids acting up under high boost.

 

Update, took the car for a spin last night after checking all the solenoids upder the UIM, ( I am pretty certain it is a faulty TCS since I didnt do the real test w/ the vacumn reader and all) Anyway, the car seemed to be worst, no boost on first, second and third gear on both primary / secondary, under WOT on 4th, I get about 6psi on primary....weird, and my stock BOV does not seem to vent when no boost...any more advise...

 

update:
I replaced the TC solenold (3rd one from the front of the rats nest) as well as replacing all the check valves w/ Dale's new valves, and still has no secondary, there seems to be an air leak when the rpm reaches around 4-5k, and the boost will drop. Also the boost off the primary seems to occur intermittenly, seems like a valve is stuck open or closed or something...I think I have another faulty solenold somewhere to prevent the boost to transit from primary to secondary. Can someone tell me which Turbo control solenold controls the vacumn and which one control pressure? I have heard there are 2 turbo control solenolds in our car!! Advise please!!

 

Do the KOKO test. http://www.scuderiaciriani.com/rx7/boost_test.html I'd particularly like to know if the TCA is cycling. Do you have a Mityvac tester? There are a few other tests as well.

Your turbo control actuator is controlled by two solenoids - one vacuum, one pressure, set up to run the TCA in a simultaneous push/pull manner. If either one is sticking or leaky, it can affect the TCA function (which can screw up primary or secondary boost). The TC vacuum solenoid is mounted on top of the ACV, under the UIM and hidden behind the wg/pc solenoid pair.

Dave

 

I wonder if it would be effective to install a bleed valve between the pressure chamber and the check valve, to regulate the pressure chamber to 10 or 12psi.

The only drawback I see is it would be a boost leak, but I'm guessing it would be so small as to not matter.

Dave

 

Just solved my secondary boost problem (only when hot).

The turbo control solonoid ( the 2 nipple one attached to the acv ) was the problem.

Symptom was ok boost when cold. Sluggish primary boost, no secondary boost when hot.

 

did you get secondary boost when cold? Also can you explain more about cold? How did you find out it was the TCS near the ACV? Did you do a test w/ the mityvac? Did it pass the test described on the shop manual? I tested all my solenoid described from the shopmanaul, all of them pass the basic blow, 12v test w/ flying colors...

 

The problem is those solenoids sticking and not releasing pressure or vacuum. The FSM tests are too forgiving. The blow tests only have atmospheric pressure pushing against the solenoid - in reality it can be much more. The same thing is true for the check valves - you really need a Mityvac to apply a useful pressure.

See this test, which can be done with both pressure and vacuum to see if a solenoid operates under the full range of real-world loads. You will need a Mityvac and 12v power source.

Dave

 

A bleed valve would possibly work, but it would leak an unmeasure amount of air all the time. You answered the question yourself (look at the bold words ). A pressure regulator is more appropriate as you can set the maximum pressure that the solenoids will see.

 

OK, fine - I guess blow-off valve is the proper term instead of bleed valve. You know what I meant

Dave

 

rotorypolo

Diagnosing my problem was kind of easy because I replaced the turbos, check valves, and all the solonoids in the rack.
When I still had the problem after all of that, I realized there was one solonoid I didn't replace.
I had ok boost when the car was first started and run. As soon as the engine got up to temp, I lost secondary boost and even primary boost on occasion. So I knew it had to be a heat related problem with a solonoid.

 

I am going to replace my vacumn TCS tonight near the ACV. BTW, my symptom is a little different than yours considering I will get intermitten boost regardless of heat. BTW, I have replaced my other TCS already.

 

Have you tried running with a lower boost setting such as 7PSI?

 

ok, I replaced my other TCS, so both of them are new. However, I still get the same sympton, the seems to get better boost, however, I can still feel the air leak between 4-5K rpm transition, and the boost will drop. Any other advise? could be a bad secondary air switching solenold?

 

Ok, what "exactly" is your current boost pattern?

 

1) Agree with Mahjik, the exact boost pattern is important info

2) Please run the KOKO test - if there is a bad actuator or tank this should detect it.

Dave

 

My boost is ~9psi on primary, when it hits transition, it will go down to around 4-6psi and decrease.. no secondary!.but the car is set for 14 psi when it was running correctly

 

Ok, so you have zero after the transition. Have you tested to see if the CRV is closing?

 

crv stands for?

 

charge relief valve, ala the "other" bov that vents until 3500 behind the BOV, should close altogether at 3500