Transition is supposed to occur at 4500rpm, right? So what senses the rpms and sends the signals to the solenoids? the ecu? something else?

 

The ecu decides when to prespool and transition.

 

Thanks. So when you get an aftermarket ecu, it is programmed to transition at the same place?

My transition occurs late (5500rpm). Is it more likely that there is a problem with the ecu or with a sensor somewhere. Does the ecu read the rpms off the same signal as the tach?

 

My guess is the ecu gets its rpm from the crank trigger, but I am not completely sure. Are you sure you are just not slow to transition? As in is the entire vacuum solenoid and actuator system functioning correctly?

 

Hehe, good point. I have done many tests to make sure everything is working correctly. It's complicated by the fact that I'm at 7000ft. If your interested (or just bored), you can read all about it here...

http://www.geocities.com/laracers_vr..._problems.html

One specific test I did was to drive in 3rd gear WOT up to 4500rpm and just hold at that rpm. I was testing to see if my actuators were just slow. It never transitioned until I increased the rpms again to 5500. I've also tested all the actuators with a vacuum pump and they all work well. All the solenoids work fine. I'm almost certain it must be an electrical type of problem, but I don't know where to start looking.

This is not a life-and-death type problem. The car is very driveable. It's just been bugging me that its not perfect, and I'm thinking that maybe an aftermarket ecu will cure the problem.

 

bump

 

^

 

One more bump...

So where does the ecu get its rpms from? Same as tach? Is there something else electrical I should check (besides all the solenoids - like I said, done that)?

 

Has anyone tried to mess with the transition point? What else might control it other than the tach?

 

2 little gremlins control the transition. They are located in the "rats nest" and pretty much just do what they want. Also if you haven't paid the trolls you can't get the second turbo...

I couldn't resist.

Jeff

 

I can relate. My gremlins will get it one of these days.

 

You could always have a sticky solenoid somewhere preventing the transition from taking place when it is supposed to.......

 

there is a pre spool line on your turbos that will control the pre spool time. So if you put in a manual boost controler you can mess with that line so you can cut the boost spike at 4500 down. Im not exactly sure how it works but Im thinking thats also what your looking for. If you go to robinettes site and look at his boost controler how to, youll see it there.

http://www.rx7turboturbo.com/robrobi...controller.htm

Check that out. maybe thats what your looking for.

 

Well, thanks for the comments guys (and I'll even take smart-*** help over no help)...

turbojeff: I think I fed my gremlins after midnight and now they're mad at me.

Flybye: No sticky solenoids or actuators. I tested them all.

actionhank: I have needle valves on the wastegate and precontrol actuators that I use to correct boost for my high altitude. Changes to these valves do not affect transition point, only boost pressure. Good thought though.

Any other ideas (or smart-*** comments )

 

Under light load, transition occurs at 5500 rpm. Could be coinsidental high altitude effect ... take a trip to nearer sealevel. Could also be that a high load condition is not being recognized, possibly TPS signal problem.

 

Ahh, now that's the kind of thing I've been looking for. Thanks alot KevinK2. I'll look into a possible TPS problem...

 

The Mazda Service Highlights manual details all the signals involved. I'll take a look at it and update everyone when I get home late tonight.

 

I'm not sure I understand this correctly...you floor it until 4500 and "hold it there" (obviously not WOT anymore and not under boost any more)...once the load is taken off, it won't transition at 4500. You can take your car to redline without transition if you wanted too. I'm not sure that is a valid test for anything??? So does you car not transistion until 5500 under WOT (without pauses in throttle)???

 

And I assume you've been here:

http://www.autosportracetech.com/RX-...leshooting.htm

Are you sure you are getting both pressure and vacuum signal to the turbo control actuator?

 

I was kinda thinking the same thing. Glad you confirmed it for me: that test tells me nothing... Yes, transition happens at 5500 when WOT 'till redline, no pauses.

 

Hehe, I have that site pretty much memorized now .

Well, I know I'm getting both pressure and vacuum by 5500 because I definitely feel the transition (I'm sure I wouldn't feel it unless the TCA was moving). I get pressure at the TCA for sure by 5000 (did a T-test). I never did a T-test for vacuum, but I assume it comes some time before 5500. See the link I posted earlier to see all the other T-tests I've done...well, I'll just summarize the results here:

1) charge relief valve closes at 3500rpm
2) precontrol valve opens at about 4000rpm
3) turbo control valve opens at 5000rpm (probably just a little higher than that)
4) charge control valve opens at 5200rpm.

I assume it's the CCV that I feel at 5500 (just a little delay I guess while the air gets moving?) I think I better check when the TCA gets vacuum, just to complete the picture. It won't be for a while though; it's snowing right now .

Thanks for the ideas. Anyone else want to chime in?

 

Geeze go non-seq and get rid of ALL the acranyms (sp?) you just spout out!

And both your twins will be online before 5500 for sure

 

Direct from the 1993 Service Highlights: The crank angle sensor, TPS, and pressure sensor are all used to vary the duty cycls from 5 - 95%. Basic output duty comes from the crank angle sensor. The TPS determines target boost pressure. The pressure sensor determines real boost pressure. All of this feeds the ECU to control the turbo precontrol and wastegate control. To be on secondary boost, the turbo precontrol must be at 5% duty (fully open), The wastegate control must be in duty control (wastegate opened). The charge relief valve must be on, the charge control valve off, and the turbo control valve on.

Looks like switch-over is controlled by engine speed, load, and primary turbo boost pressure. Are you getting correct boost on the primary turbo? The TPS must be in full range as well...

 

Awsome info rotary-tt. Thanks.

I get 10psi on primary, so lack of boost shouldn't be the problem. However, maybe the pressure sensor is not functioning correctly.

The crank angle sensor is giving the rpms, right? Is that what the tach uses also? If so, then I have to believe it is working since my tach is working.

I need to do some reading on how to test if the TPS is working correctly and how to adjust it. Same for pressure sensor.

Thanks again.

 

I believe the crank angle gives rpms but I have to check. Looks like all your transitions are occurring too late (as you already know). The shop manual shows how to test the TPS and pressure sensor. Is the vacuum chamber or lines leading to it leaking? That might cause it to take longer to build up pressure and start the whole switch over process...