Sequential control question
 

My car has been running bnr turbos in parallel mode since I bought it (12 years ago). As I was trouble shooting my vacuum leak issue last week, a couple club members pointed out that all my sequential components were still present. This made me want to try sequential. So I did.

The primary turbo makes boost fast and performs as it should. The transition occurs at 4500 as it should. The secondary comes on and reaches full boost as it should.

The issue is that once the secondary comes on, if I get off the gas and the RPMS drop below the transition point, to say 3k as an example, it will only make 1-2 psi. Then when the transition comes I get full boost. The system will reset if I come to idle. Then it will perform as it should. But then again this issue happens. This is repeatable every time. There is no variation of the issue. It remains consistent.

I think if this was the pre control (or the actuator or solenoid for it) the symptoms would be similar however I think rather than only making 1-2psi it would sort of act more like it’s stuck in parallel. It would build boost slowly and eventually reach full boost. However in my situation it’s only making 1-2 psi then when the transition occurs the secondary kicks in completely normal. No lag. It’s spooled.

So I think it’s more likely to be the charge control valve (or its actuator or solenoid). Basically it’s not resetting. It’s staying open and the charge is simply going to the secondary to spool it rather than be directed to the primary.

Does this make sense to you? I can bench test the solenoid but would rather start with the likely culprit.

Charge control valve BOV stuck open, or missing?

[Be careful with old BOV. A friend had new turbos installed and shop paralleled from the beginning, but left old piping/valves in place. One of the old BOV disintegrated and took out his new turbos with plastic bits.]

This sounds like a classic case of turbo control solenoid ‘E’ hanging; search on this term and you should find a lot of information about the problem and remediation.

It does does sound exactly like the Turbo control solenoid. Thank youi!

Especially considering that i am well over stock boost. It could easily freeze up a tired spring within the solenoid.

I am running simplified sequential and therefore some of my solenoids arent in the stock location. So i need to track the vacuum lines to fine the TC solenoid. With that said i am confused by the diagram. E signifies the TC solenoid. on the graph its labeled next to the F solenoid. But i also see it on thje top left. I circled both. Which is the correct one? I
https://cimg2.ibsrv.net/gimg/www.rx7...ea09070ab3.png

You want E in the rack, it is the pressure side of the turbo control actuator (the one on the acv is the vacuum side of the tca and rarely fails).

Get yourself two good vacuum tees and a good check valve and install the fix I described in the other thread. This will forever prevent the disallowed logic state that causes the problem in the first place—You’ll save yourself a lot of frustration and never have the problem again.

What the mod does is creates a pneumatic logic circuit the allows the TCA to discharge through the check valve and reset the system, and is no longer dependent on solenoid pintle spring to overcome the pressure in the TCA—which is the origin of the problem. (Note that the solenoid continues to be used to command Tca operation at the transition.

@Speed of light
Yes i want E. That is my question now. Not sure which one is E? Actually the diagram seems pretty confusing and i see this question pops up a lot. But it sounds like you are saying E is the one in the middle of the diagram i posted and basically connected to the "F" Charge control solenoid. Do we agree? it has a line from the pressure tank connected to it and the other goes down to the TCA. Do i have that right?

And yes i saw your post about adding a valve to reduce the stress on the spring to 10psi.

Thank god you showed me this though. Thank you. Once i know for sure the location of the solenoid ill see which solution i can accomplish.

Matty, E is the one on the right (above), further from the front of the car with the blue shading and lines that run down to the actuator that is under the turbo manifold. If you’re referencing my thread titled “FIX—sticking sequential turbos/TCA/solenoid ‘E’….” there is another diagram and photos depicting installation in the front where hoses transition into hard lines running down to the actuator. You should be able to install the mod without having to pull the UIM.

great. It’s one with the blue line that heads down to the small nipple on the tca and as you said not the one on the acv which also had a blue line but goes to the bigger nipple on tca.

I think I got it now.

so I’ll have to replace this e solenoid then do your mod. I didn’t fully read your thread in detail. I will do that tonight. I was focused on the initial thread where the problem was identities in 2004
great. It’s the blue

@matty No, you don’t need to replace the solenoid. Just add the mod and be sure the check valve is facing the proper direction.

The hanging problem with the solenoids is quite random and has been observed with brand new solenoids as well as those that are otherwise good.

You are adding a pneumatic path in parallel with solenoid E that releases the pressure in the TCA and allows the system to reset to primary operation, rather than hanging; so the solenoid becomes irrelevant for the release of the TCA. Since the pressure is bled off around the solenoid, it drops out and is again ready for the next transition. The solenoid’s only function now is to initiate the transition to secondary. And we all live happily ever after.

ok. I’ll leave it. My solenoid “E” is buried under the UIM deep. I know some cars aren’t this way. But mine is. BUMMER

I’ll study your thread tomorrow.i wanted to bench test the solenoid “e” bc my issue is slightly different then the way you articulate the issue. Once I transition and the rpm’s come down it doesn’t behave like a parallel setup as you explain. It only make 1-2 psi. And stays there. No spooling. Then at transition,boom, full boost. It’s weird cause the 2004 thread explained it exactly as mine. And his solution was the same as your mod or replacing solenoid E.

Keep in mind that when solenoid E sticks, the hot side [of the turbos] stays in parallel; however, the cold side reverts to sequential, closing the secondary and opening its bypass. So the net result isn’t the same as parallel operation; rather, it is much more lame.

@Speed of light Gotchya. That fits my situation great. Your mod is a no brainer. Really nice work with the diagram and such. I am just writing you a pm now.

Thank you !
 

@Speed of light your mod worked great. Car is boosting correctly now. Thank you very much for the details on the setup. It was an hour job. But only bc I had to remove fpr and lower the alternator for room.