saxyman990

Endless searching.... to no avail.
Heh heh heh, gotta love the good ol' twin turbo system. With out diagnosing turbo problems, how would I find fun ways to spend my weekends?

Anyway, hoping for a few ideas or thoughts concerning my odd condition. Just let me know if I'm on track or if you have any better ideas. Here's the situation:

About 6 months ago, had a problem with the secondary turbo not wanting to come online. I fixed that when I did a hose job (turned out to be a bad Turbo Control Solenoid). Now my secondary turbo comes online perfectly!

The problem is, that anytime I hit transition, and then upshift or back off, the system doesn't want to switch back to just the primary turbo. When that happens, turbos don't spool until about 3800 RPM, and then both will kick on. I've noticed that the exhaust is much lounder, too. Then, after about 30 seconds or so (different amount of time each time it happens), the system will switch back to completely primary turbo. This lead me to believe that the turbo system doesn't want to switch off the sequential mode.

So, here are my current thoughts on it. The two main things that cause the secondary turbo to come online are the TCA and the CCA. Obviously, those guys are getting the proper amount of vacuum/pressure under an acceleration load, and the 2nd turbo switches on perfectly. However, for some reason, one of these actuators must not want to close after I back of the throttle. This means that I'm still getting vacuum and pressure into the actuators when I shouldn't be.

Tryed WD40 on the actuators... no luck. I thought about the check valves, but that doesn't make sense to me, because the upside transition is fine. So now i'm thinking sticky solenoid. It opens fine, but it just doesn't want to close. I'll have to tee into the lines going to the TCA and CCA, to see what kind of pressures I'm getting.

Anyone else have any other thoughts other than sticky solenoid? Thanks for the input!

Hopefully, this thread may help someone that has a similar problem

Rob

spurvo

Just wanted to restate for my noob brain...

OK, so you accelerate hard enough long enough that you engage the second turbo (say 10 psi to 4500, dip, then 10 psi to 5500), then press in clutch, drop throttle (so boost goes to vacuum, probably 22 inches if anything like mine!), shift to next gear, let off clutch, and shove the throttle (a little early to get 'em spooled before the clutch fully engages so the accel is like a ******* airplane taking off! ) and you get no boost until 3800 rpm or so. Right? And if you keep out of the throttle after the upshift, but in enough that you should reasonably get the primary to push say 4 to 5 psi, you get no boost until ~4000 rpm? But after driving for 30 seconds with the system somewhere in vacuum (probably 10 to 8 inches to keep steady speed), you get primary spool at 2500 rpm, and normal operation.

When you have no boost, do you really have no spool up (i.e. no whistle) or just no positive pressure?

saxyman990

spurvo - exactly! After I reread my post, i realized that it wasn't exactly the most clear post ever, but you got the gist of it.


Yes, and I actually thought it had to do with check valve originally because of this. So I tried backing off the throttle completely, and even pushing in the cluch, so that RPMs would drop to ~1000, and the vacuum would drop to ~18inHg. But that still wouldn't put the system back into Primary-only mode. Basically, I just have to wait until it feels like switching back. On average, it seems to be around 20-30 seconds. But sometimes its immediate, and sometimes it takes a couple of minutes of cruising.

If this happens, and then I bring the car to a complete stop, then the Primary turbo engages again. Not sure if it is just coincidental or not...


When I have no boost, I have zero positive pressure. I can hear the turbos spinning, but they are much louder than usual (as is the exhaust), so I am assuming they are still running in non-sequential mode. There isn't enough exhaust energy to get them spinning together until ~4000 RPM. At least, this is my take on it.

saxyman990

By the way, in my first post (and the title), I meant to say non-seq. My bad.

Just to clarify. I am still operating in the stock seq mode. But every once in a while, the car likes to go non-seq (without asking me first).

SpeedracerRX7

I dont' know if it is the same thing that you are talking about but I know that when I went to a track day I had a similar problem. What happens is that after I took the car over 4500 RPM it would transition to both turbos but if I backed off to below 4500 RPM it wouldn't give me primary boost until I let it drop below 3000 RPM. I was told by a number of RX7 enthusiasts that this is normal and that the way the control system works won't allow for the primary turbo to re-engage without the RPM's dropping below 3000. I hope this helps but if it doesn't maybe somebody can give us all some insight.

saxyman990

Yeah, similar kind of problem, but unfortunately, even if I bring the RPMs below 3000, the system won't go back to primary only (I even tried popping in the clutch and letting RPMs drop to idle). Thanks a lot for the insight though.

Thats why I think that there are some more evil forces at work here than meets the eye.

I'll check out the CCA and the TCA tomorrow, to see what kind of pressure readings I'm getting.