Hey guys, thought I could start up a thread relating to people having issues with their sequentials, or at the very least, a thread discussing my current issue.

I have a stock engine, running BNR stage 3 twins, sequential (obviously), with the azeknightz aftermarket solenoid kit, stock precontrol and wastegate solenoids, running powerfc.

For the most part, I had my car running right. I was making 17psi on the primary turbo, and we were running the secondary turbo a little bit lower (~12psi). I did a track day, all went fine. A couple weeks ago, I took the car out, and I was having some weird boosting issues. Sometimes the car would boost up to the 17psi, and other times it would only boost up to 10-11psi (on primary turbo). On top of that, if I took the car into transition, it would still be lowish boost (8-10psi), but as soon as I let off the gas (to shift) and get back on the gas again, it will only boost to 3-4psi. When it's in this 3-4psi boosting state, about a second after I let off the gas, it makes a weird squeal/howl noise. The following day I took the car out, and ever since then, the max boost I can get is 10-11psi. I hadn't changed anything on the car (other than messing with my oil catch tank)

So to be clear, my symptoms are:
Low boost on primary turbo (10-11psi max)
if I take the car into transition, it will still run around 8-10psi, but if I let off the gas, the next time I push the gas pedal down (while still in transition) it will only boost to 3-4psi.
When it only boosts to 3-4 psi, shortly after I let off the gas, there is a strange howl/squeal that I can hear.

crappy video of the noise:


I'd thought I found the problem when I got under the car and noticed the pre-control wastegate hose with the pill in it was badly ripped. (was using too small of a diameter hose, which has been fixed). But after I fixed it, the problem remained. Since then I've gone through just about as much of the car as I can. Boost leak tested it countless times. Triple checked everything. I had a theory that maybe it was a bad check valve, and the vacuum chamber was becoming pressurized and that howl was air escaping through the bad check valve. Unfortunately, I tested both check valves to the pressure and vac chamber, and tested the chambers, and they seem to be fine. I thought maybe the charge control valve/actuator was bad, because I have caught it not working before*, so I replaced that pipe and still the problem persists. I swapped out both blow off valves, that didn't help....

My most promising, remaining lead, which I will be able to test today (because I just got the part in) is a bad charge control solenoid. There was a moment where I experienced an issue similar to this about a month ago, while we were trying to get the car right, and I had noticed the charge control valve was not moving or changing from when the car was off to when the car was on, but it was just this one time. (ie. the valve was open even when the car was idling). On top of that, the charge control solenoid seems to get very hot, too hot to touch for more than a full second.

I'm worried that this solenoid won't fix the problem, and I'm making this post as a last ditch effort, as I've got a track weekend coming up tomorrow. I figure I'll post a video of the sound, and maybe someone will recognize it, or maybe someone has had a similar problem.

Any/all help is much appreciated. I feel like I have a decent understanding of how the sequential system works, but I'm ready to throw the towel in on this one!

 

The biggest tool in the arsenal to find a problem like this is a vacuum T and some extra vacuum line. Put the T in line with each component that you think could be the problem and have the line going to your boost gauge. If the part is supposed to get vacuum to actuate at transition you should see it happen, when you drop below transition it should go to atmospheric or whatever.

It's quite possible you have a bad solenoid. If it's getting hot it could be shorting internally. Is there a source to replace those solenoids?

Dale

 

great idea, I didn't really think of that. I guess I'd plumb into the charge control first, since that would probably be the easiest. as far as the turbo control, I assume it can/will work with only one of the two (vac and pressure lines), so both would have to be bad to be bad in order it to be causing this. so next would be what, charge relief?

I did get a replacement solenoid in today, which I will wire up/install tonight. (thanks to Eric) I'm just trying to have some back-up plans in case that doesn't fix it.

 

replaced the solenoid with no luck.

my leading theory is that the charge relief valve is sticking open when I let off the throttle, and i bleeding off boost. once i'm out of transition, it's probably still stuck open, but it doesn't affect anything since the charge control valve is shut. but that still doesn't explain the low boost on primary turbo..

 

I have BNRs and tackled a few boost issues... For the 3-4 psi issue on the secondary, try this:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/fix-sticking-sequential-turbos-tca-solenoid-e-cheap-easy-fast-effective-1120259/

You mentioned that you have aftermarket solenoids, but this solved nearly an identical problem for me.

For the low boost on primary, I'm not sure since you had good boost before, but definitely recheck the pills. I believe that they are different sized for the precontrol and wastegate. When I was running lines with no pills, it was impossible to make good primary boost because the ported wastegate on the bnrs and the precontrol actuator were opening from the higher input pressure. When you fixed the ripped line, did you mix up the pills or anything?

 

thank-you for the info. as for the pills, I did one line at a time, so I did not mix them up, but I'm 99.9% sure they're the same size anyway.

I could try that check valve fix, but the problem described in that thread is not the problem i'm having.
if I drop back down to below the transition, the car acts "fine" (as in it doesn't stick me with low boost) it only happens when I lift and get back on it while above transition.

so I have a bunch of stuff swirling in my head.
-I have to check logs to verify, but it does not feel like I am experiencing any more lag. the primary turbo seems to be making boost fairly fast. (hitting the ~11psi before I hit 3000rpm) that, plus the fact that I've boost leak tested the **** out of the system, leads me to believe that I don't have a traditional boost leak. so what would/could be regulating my boost to 11psi, especially since that's not really an achievable thing with the BNRs I thought.

-the theory of the sticking charge relief valve doesn't explain the low boost on the primary turbo. it also doesn't "stick" since I replaced it with another CRV and no difference.

-is the sound in the video compressor surge??? it certainly doesn't sound like it to me, but could that be what 3psi of compressor surge sounds like? what is that sound?! air moving through the bov? crv? a check valve? a coupler?

-when the car goes through transition, it makes kind of like a whippling sound. (not sure how to describe it) sort of like some weird conflicting turbulent air going on... pretty positive it did not sound like this when the car was running right. however, early on before this became a consistent problem, we would hear that happen when the car would have hiccups.

 

Finally had a chance to listen/watch the video, that does sound like compressor surge. Weird part is the BOV isn't solenoid controlled, it's just straight to the intake manifold.

The TCA does need BOTH vacuum and boost to actuate. If it only has 1 it won't work right.

Now, the charge control valve and/or turbo control actuator themselves could be bad. I have seen both with torn diaphragms. A Mityvac will tell you pretty quickly if they are bad - apply vacuum, it should suck in and STAY in.

Charge relief valve is pretty hardy, again try the Mityvac test. You can stick your pinky in the outlet side of the CRV and feel the piston inside move when you apply vacuum, if it moves and stays put with vacuum it's fine. If it slowly comes back to rest under vacuum the diaphragm is torn.

Dale

 

If you're like me you're just going to have to test each component individually and run down the list of culprits. The combinations of potential problems/symptoms are too complicated to try and troubleshoot any other way IMO. Test vac/press readings for each component on the car to make sure you are getting vac/pressure at the correct times and bench test the components to make sure they are actually working when given vac/pressure.

I have permanent tees with capped test ports for the TCA boost and vacuum signals as well as the charge control actuator vac signal.

This is an excellent resource: Troubleshooting

All that said, I've never actually had a bad solenoid or actuator. Found out my intake was collapsing under boost.

 

What sort of symptoms were you having before you figured out it was the intake? Just based on that resource I'm thinking that could be my problem - boost is good after starting up but I'll lose boost after a while especially if I take the revs past 6k or so, and once I lose boost I don't get it back until it's cooled off overnight.

 

Do you have a datalogit? Can you take logs? Click the button for "Advance" and "sensors" on the monitor window. I want to see the switching of your actuators and all your duty cycles. This could just be a tuning issue related to boost control setting and sequential transition settings.

 

Unfortunately no datalogit... I do have my turbos switched to the basic nonsequential setup as well.

 

you're wasting your time without a Datalogit, you have no idea what the turbos are doing.

 

Well guess it's time to pick up a datalogit then....

 

Basically just **** boost all the time. Max was 7 psi and of course the flow was garbage so I was making no power. Easiest way to verify your intake isn't collapsing is to detach the rubber inlet tubes from the turbos.

In my less experienced opinion a datalogit would help, but I've personally never used mine to diagnose boost issues. Even if the log shows that the actuator solenoids triggered I would think you still have to verify that they are physically getting vacuum or pressure by teeing into the line.

What I have done is verify TCA gets/holds vacuum and pressure at the right times while driving with an auxillary gauge teed in to the lines. I teed in right under the stock intake cross-over pipe. Then the same for vacuum on TCA. Next, I manually actuated the TCA and CCA with a mityvac on or off the car to observe them moving. That allowed me to rule out TCA and charge control plus their related solenoids.

 

If we can see the precontrol and wastegate solenoid duty cycles from the Datalogit, we can see if the boost control system is part of the problem. If the duty cycle is pegged high or low it will cause a drop, or if it is oscillating it can make for a weird boost curve.

 

Ah, that makes sense. I forgot I'm running dual hallman MBC's, so in my case I can always eliminate those from the equation when troubleshooting. I am thinking about switching back to PFC/solenoid based boost control when I get the chance, but these MBC's have worked so well for so long I am hesitant.

 

as mentioned check individual components, but definitely verify the turbo control actuator. Mine went bad late last year and would cause lazy boost response. Still made boost, but not much power and the response was slow. Was only working on the vacuum side and not the pressure side. I had cooked the diaphragm during track days.

 

just to follow up. I have tested all of the components with a mityvac.

turbo control actuator works and holds when you apply pressure at solenoid E, and returns right when you relieve the pressure. same when you apply vacuum at solenoid X.
charge control closes when it gets vacuum, and opens back up when the vacuum is relieved.
pressure chamber holds pressure, vac chamber holds vacuum.
tested for leaks in the lines, and ran my tests from right at the solenoid rack, so that should eliminate potential leaks.
check valves seem fine.

I'm going to do that T idea into all the components and run a boost gauge in the cabin and see what is actually happening.

sidenote: bought a new temp gun and the F solenoid is getting 30 degrees hotter than the other three solenoids on the azeknightz rack with just the key in the on position.

thanks guys

 

ps- datalogit of my issue (top: rpm, middle: wg/precontrol, bottom: boost)

 

so I did the T thing this evening, sort of impromptu, and tested 4 out of the 5 things I wanted to test (forgot to test charge control) but ended up finding out that the turbo control (E) solenoid does not seem to be doing anything. the pressure source from the rear part of the Y pipe is good, so I'm thinking it has to be wiring. I used some bullet style connectors where the original solenoid plugs were, and the continuity to the solenoid tests out. (shaved a little insulation off both wires close to the solenoid). with the key on both wires show 12v, so I'm going to check continuity from the ecu plug to the solenoid (the signal or trigger or whatever) and see what that shows me. I guess it could just be a bad solenoid too, I'll hit it with some 12v and see what it does.

thanks everyone

 

Cool, keep us posted!

Dale

 

soooooooooooooooooooooo


(theory is that while trying to troubleshoot/diagnose sequential issues, which I started doing months ago, that maybe the paperclip, I was using to probe the signal wires in the ecu plug, stretched out the pins?)

 

oh I skipped the part where after I did all that testing the other night, my charge control solenoid stopped triggering! so that's been a much easier problem to deal with/diagnose, since it should be triggered just with the key on. finally caught the bugger. (at least for now)

 

all fixed, and she rips again!

today's lesson: don't probe your ecu plug with a paperclip. take a grinding wheel and make the paperclip smaller first.

 

Sewing pins or needles might be better than a paperclip, they tend to be thin already and made from stronger metal. Glad to hear you got it figured out.