RX7Wishing

I have checked and rechecked all vaccum lines and solenoids for cracked/broken nipples. I replaced the TC/WG solenoid with a known good set. Here's the deal. Boost is fine on the primary when secondary comes in i get about 11psi witch tapers to 7 psi till redline?? If i let off the gas and i gun it again i get an incrediably slow buildup of boost. Im at a lose on what the cause can be. I tested the solenoids and they all passed (heated them up in oven as well). What failing that is causing me to tamper down to 7psi when secondary comes online.. If i boost on the primary i get a perfect 10psi. Secondary sucks :T.


My boost pattern is 10-8-11-7


power mods are DP,CB,Apexi intakes.

silver93r1

if i were you i would get change them to nonsequential and not have to worry with all that

trini

iTrader: (2)

did you check the precontrol vac lines? also check and see if the rod that controles the gate in the exhaust manifold is in place it could also be that little butterfly in the y pipe is sticking after the transision.. if all else fails just go non sequential . you will get rid of most the vac lines and rats nest /boost problems. i am actually doing it now for my buddy. manny34711

RX7Wishing

If i had the time and resources to go NS (not poor mans) i would.. TRUST ME!

flyboyjuge

i had nonstop probs with mine...i just bit the bullet and went single...no problems now, and quite a bit more hp

rynberg

clogged cat is a possible cause

RX7Wishing

^ very true.

what would you reccomend as a replacement? what brand? highflow?

WaLieN

Let me get this straight. So, you make 10 on the primary, 8 on transition with a spike of 11, then immediately back down to 7psi until redline?

WaLieN

BTW, this is pretty horrible advice for someone who almost has a working sequential system.

jeffrored92

Sounds very normal, I vote clogged cat. If your still in the upper RPM range when you get back on the gas, boost will be a little sluggish to build up because the turbo control actuator will still be open, meaning you gotta spool both turbos. If you let the revs drop under 3000 so the ECU closes the turbo control actuator, do you get 11psi nice and quick on the primary?

DaveW

Could be a restriction anywhere in the intake/exhaust system, but, I agree, a clogged cat is a likely suspect.

RX7Wishing

Boost goes something like this.... when engine is warmed up... below 4500 rpms 10psi fairly quick.. i can be in any gear and hit 10 pounds. as soon as secondary comes online i get a dip to 8 psi quick pop to 11 psi then a drop to 7 psi till redline. the dropt o 7psi is almost immediate

dgeesaman

iTrader: (7)

At first crack, the loss of boost above 4500 sounds like a clogged cat.

The slowness of response on respooling the turbos resembles this case:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/weird-boost-issue-341534/

- which Dave found was caused by sticking/lazy turbo control solenoids. The TC Pressure solenoid in particular is under the highest such loading, and can cause intermittent/slow secondary response.

Keep in mind, that what rpm you let off and resume WOT at can affect whether the ECU tries to engage again in parallel or primary-only mode. In parallel mode there is more lag.

Dave

DaveW

Are you still using the stock control setup? 7-psi is a strong hint that there is no pill in the WG actuator line from the Y-pipe, or that the WG solenoid is not functioning or the line to it is blocked off.

dgeesaman

iTrader: (7)

The wastegate controls primary boost also, I suspect that since that reaches 10psi, that's not the problem. So it would have to be malfunctioning in a way that it still works when the primary is active.

I wonder if the stock BOV is venting when it shouldn't - try unplugging it from the airbox for a bit. It should be quite loud when disconnected, and only make noise after letting off the throttle - if you hear it venting during secondary boost (when it drops to 7psi) that indicates the BOV or solenoid connected to it has a problem.

Dave

jsplit

Non-Sequential is your friend

F0RSAKEN

Only the Charge Relief Valve has a solenoid attached to it. The Bypass Valve is connected directly to the UIM, and is controlled by the vacuum/pressure it recieves from there. My Bypass leaks at part throttle (not sure if its supposed to) so try unhooking both of them, one at a time, and seeing if either of them vent when they arent supposed to.

silver93r1

well i was just thinking about less headache and more power but whatever

DaveW

From one of the turbo trouble-shooting sites:

"With only the Primary Turbocharger in operation, the Wastegate is NOT actively controlled by the ECU. Once boost pressure reaches about 10 psi, the Wastegate starts to open to bypass some of the exhaust around the Turbocharger, thus slowing down the Turbocharger. The Wastegate is not actively controlled by the ECU when below 4,500 RPM."

So I still think my statement below is correct:

"7-psi is a strong hint that there is no pill in the WG actuator line from the Y-pipe, or that the WG solenoid is not functioning or the line to it is blocked off."

dgeesaman

iTrader: (7)

It also says:

"The size of the pill to the Wastegate Actuator in conjunction with the fixed 95% duty cycle of the solenoid controls the maximum Primary Turbo boost pressure."

Since the primary is working, that suggests the pill must be there, and the wastegate is at least working to achieve 95% DC. If it were blocked/missing a pill/not functioning, primary boost wouldn't hit a clean 10psi.

There are a couple other references in that site that suggest a wastegate problem does create a 7psi maximum but that it affects both primary and secondary. I'm not trying to sound really contrary, but I believe it's ok to assume the wastegate is working for now, unless of course it's easily reached for inspection. That said, all of these things should be inspected carefully if it's not too much trouble.

Fortunately, the ACV and CCV are pretty accessible, so checking them is the easiest first step.

Dave

DaveW

Hmmmm...

DaveG, I think you got me there

WaLieN

I agree in that non-sequential *would* be nice if he had a full exhaust and a REALLY messed up sequential system atm, but he doesn't. ATM, he can easily recover a working sequential system again.

Back on topic, I agree with the others that it could very well be a clogged cat. Some others have mentioned it could be a leaking ABV(aka BOV), but I would really doubt it since it loses boost the way it does. You *could* try switching the two valves (though they work a little bit differently) to see if you get a change in secondary boost.

I know it also may sound stupid and probably an unlikely culprit (since the boost loss is so quick), but I would also check all of the pressurized hoses (actually take them off to inspect).

At the moment, the easiest thing to do is to replace the main-cat with known working one. It's an easy job and will at least cross that out of the list of culprits. You can check the link below for some sequential troubleshooting, it has helped me quite a bit when I was working on my sequential system. If you need further assistance, feel free to contact me on AIM. Happy hunting!

http://www.autosportracetech.com/RX-7/rx7stuff.htm

RX7Wishing

Thanks for help guys.

I dont think it s aleaking bov per i dont hear it leaking and it hold fine on primary. Im going to attack my midpipe this weekend to see if it fix's the issue.. if it does.. then i know what the issue is.

BoostFrenzy

just try the daleclark check valves...

RX7Wishing

^ i already did that