Hello, I have been struggling with a no secondary boost problem for awhile. Boost drops down to 3 psi past transition. I did all silicone hoses and new solenoids and verified all of my actuators are moving and holding with a mityvac.

I tee'd into my CRV and it got 11 psi at transition.

I tee'd into my TCA boost side and it only got 6 psi at transition.

I tee'd into my TCA vacuum side and it only got about 6 psi as well.

Im aware these readings are low and are probably why I'm not getting any secondary boost. What should these readings be on a functioning system? Thank you.

 

The actuator itself should hold ~10+ psi, until the secondary side matches, then the spring will open the valve naturally. Off boost, chamber A will receive vacuum, holding it shut.

https://www.rx7club.com/3rd-generati...r-work-902735/

Past transition sounds like my issue, a TCA with a shot bushing, so the valve never fully closes or is slow to open. Imported a new TCA, and you could hear and feel the difference when actuating by hand.

 

Upon further inspecting that psi on the Charge Relief Actuator comes from the secondary turbo behind the Charge Control Actuator. If I’m seeing 11+ psi on that line (CRA) and it isn’t making its way into my system then my CCA isn’t opening right?

 

The CRV and CCV both get operating pressure from the secondary turbo discharge, CCV opens when the dome side of the actuator gets boost pressure, equalizing the pressure across the diaphragm. You can test the solenoid by turning the key on with vacuum in the reservoir. The solenoid should energize when the key turns on, closing the CCV, and if it doesn't your solenoid isn't working or it isn't getting vacuum. If it moves with the key on test but it isn't opening under boost, it's losing the boost pressure that should be getting to it through a broken or disconnected hose. If the CCV isn't opening and the CRV closes, there will be a surge condition on the secondary turbo which may be audible and is not good for it.

There is a fairly detailed DaleClark thread somewhere on the forum about troubleshooting the boost control system, and a section on it in the service highlights which includes this chart that helps describe what should be happening when things are operating correctly.

 

Thank you for that information,

I just got done going through the rats nest and checking all of the solenoids, vac lines, pressure/vac tanks, check valves, and actuators. To my surprise, I didn’t find anything wrong which is frustrating. Going to solenoid port to actuator/tank verifying routing was correct and it was. It’s always when I start to get confident in troubleshooting a system it throws a curve ball lol

I’ll attach a video of me driving and the sound it makes when I get past 4500. It sounds like a boost leak but I smoke tested it and my primary turbo pulls hard.

 

 

Sounds like your CRV is sticking open or part of that system is leaking allowing the secondary to just vent. Are you sure that CRV hose isn't cracked somewhere? Those are some of the first ones to get hard and when you start moving things around back there they split but will hold in place because they are hard.

 

I have all fresh hoses and vacuum lines. I tee’d into that line and it was getting vacuum and then boost when it was supposed to.

The million dollar question! Where is my boost going!?

this all started 2 years ago before I put the car into storage. I had a broken y pipe o ring and I never got the chance to drive it after it was replaced. The car was put into storage for a year and when I got it back it had that same sound. I thought to myself, they must have forgotten to put that o ring back in. When I got time to look the o ring was in place. For ***** and giggles I just put in a new o ring.

When I smoke tested my system nothing came from that connection but I’m not counting out anything now.

 

That just sounds like a bad leak, surge has an oscillatory or chirping sound and a turbo generating boost against a closed CCV and CRV would surge badly. I'd pressure test the CRV off of the car with a leak sound like that. I know the CRV can be quite loud on cars with aftermarket intakes that don't recirculate it into an air box.

 

I recall having this problem myself once after having replaced one of the oil injectors….

Looking through my notes I found a notation about “no secondary boost; found cracked hose pressure side of solenoid F.” So this is the control circuit for the CCA/CCV.

The CRVs close progressively so it’s normal for some leakage from them; it doesn’t take much to make a lot of noise. Mine made a moo-ing sound.

It also sounds as if TCA and transition are ok; you would not have measured the 11# against the CRV if it were not. Keep in mind that the CCA is operated by differential pressure so I’d be looking for anything that affects that: the CCA control circuit and the CRV control circuit.

Iirc, the CRV is supposed to close, surge the 2nd turbo, the CCA opens a moment later as pressure spikes. The CCA is closed by pressure when pri >> sec and is opened by a spring when pri is approx equal to secondary. The pressure the CCA sees for secondary operation is dependent on solenoid F.

I hope this helps.

 

this was very informative thank you.

CRA passes with flying colors with the mityvac. Vacuum open and pressure closed. So it seems the system for the CRA is functioning. Spiking pressure when under 2nd boost and vacuum when under 4k.

Are there any tests I can do to isolate a system. I.e disconnecting a line or manually applying pressure or vacuum while driving? I feel as if I have looked everywhere already to no avail.

I want to keep the sequential because it’s great when it works but it seems like I’d save time and headaches if I went non-sequential.

 

There's a terminology issue here, when you say CRA are you talking about the Charge Relief Valve (one of the two plastic body blowoff valves) or the Charge Control Valve/Actuator (the two port actuator controlling the butterfly in the Y-pipe), it reads like you're talking about the CCV.

You can swap the CRV with the ABV (the front one) for a function test to isolate it. Pressure testing it on the big hose going into it is more important than testing whether it moves when you put vacuum on the chamber, because the valve internals could be moving but not sealing/getting blown open by boost pressure. If you're getting a 10-?-3 boost pattern there are only a few things that can cause this and you've confirmed that your CRV gets the 11psi it should at transition to close it but if you haven't verified that it actually holds boost pressure on its large ports that may be the problem.

It's worth triple checking every vacuum hose involved with boost control against the diagram. It's easy to get an adjacent vacuum hose swapped somewhere and wind up chasing your tail there are plenty of threads where simple mistakes have caused problems that stump guys for weeks. I got all of the hoses right then forgot the pills in the old hoses and had low boost because I forgot they existed. It was a quick fix but I spent years tuning other people's cars, fixing their mistakes, doing detail oriented work like building wiring harnesses and ECUs... Dumb thing to do. It happens.

You have full boost then low boost after transition and a hiss. This would say to me one of the following.

• Boost leak, CRV
  • Mechanical failure of the CRV
  • CRV control (you've confirmed this gets 11psi in the OP, ruling this out)
• Boost leak, CRV hoses or installation
  • Hose not seated correctly or split (you say they're all new, ruling this out)
  • CRV installed reversed (hose barb should face the firewall)
• CCV not opening and boost continuing to vent out of the CRV
  • Verify CCV hoses are hooked up correctly
  • Verify CCV is actually getting boost pressure on the FWD port, chamber A, when it should with a Tee-in
• Boost leak, rear Y pipe segment flange
• Intake hose collapsing, secondary turbo

Long shot, not sure how it would hiss unless the primary turbo's boost is escaping from the secondary in surge: turbo control valve isn't opening, so your secondary is making enough flow to power its charge valves but not enough to produce appreciable boost after transition.

Links:
https://www.rx7club.com/3rd-generati...s-how-1153111/
https://www.rx7club.com/3rd-generati...-stuff-802060/

 

Sure sounds like there’s a problem with the CCA/CCV; solenoid F, or line routing.

And based on your last remarks above, it seems as if the charge relief valve (CRA or CRV) is working. (This is the external secondary blo off valve.)

Did you perform the key-on, key-off (KOKO) test that was described in Varg’s post above? That is your quick test to see if the CCA is functioning: be sure your vacuum chamber is charged and have someone turn the key on/off while you watch the CCA and you should see the actuator pull in and rotate the valve’s shaft. (The TCA underneath the exhaust manifold will also move with this test, so you will hear that click as well)

in any event, if the CCA passes the KOKO test, then you most likely have a problem with the secondary pressure reference signal routing or making it up to solenoid F.

Be advised that there are known errors on some of the published vacuum line diagrams that are commonly used for reference.

 

KOKO test passes, I don’t see any movement of my TCA but I have heard it doesn’t work on PFC.

verified vacuum, pressure (2nd turbo port), and the main nipple of solenoid F.

This originally happened out of the blue not after maintenance. Troubleshot and found a bad TCA vacuum solenoid (no resistance on pins) decided to redo everything, new lines, new solenoids, and bench tested every actuator. Yet this issue remains. How odd. I know yall don’t care about the story, just on fixing the car but I don’t have any friends that understand this turbo system. It’s not that complicated it can only be so many things. We got this.

Tomorrow I will get my mityvac and apply vacuum/pressure to the CCA to see what happens.

 

Just throwing this out there, what kind of intakes do you have? Airbox or cone filter types? If you have the cone filter types, it is possible for the cone filter to be pushed on too far for the rear turbo and have the front part of the cone essentially plugging the intake path to the turbo. This can act and sound similar to a boost leak for the turbo that is being plugged.

 

I have HKS racing suction intakes, and I have ran the car without the second intake since this problem has arisen

 

Non sequential works.

used a metal hangar to hold my exhaust flap open and bridged the nipples on the y pipe for the CCA.

damn did it feel good. Got up to 13.5 psi. Guess I didn’t do a good job porting my wastegate.

that brings us to solenoid f again. Why isn’t it working

 

have you tested continuity from the solenoid connector pins to the ECU? There maybe a bad wire. What kind of shape is your harness in?