Finally got my boost gauge mounted, and guess what I saw...

13-5-6 with transition at 5500rpm

A search turned up alot of great threads to help me diagnose the low secondary, so I won't ask about that. I'm more concerned about the late transition since I have never heard of this before. Might it have something to do with the fact that I live at 7000ft? The weather is prety cold (~45F) and dry too. Does that make a difference?

Any ideas?

 

should switch at 5500, but with light load only. could be tps fault, among lots of other stuff.

 

Sounds like your TURBO-PRECONTROL actuator is not working - The HIGH primary boost is a clue, the TPC also acts as the wastegate for the primary by bleading exhaust to the secondary turbo, If it does not open the secondary won't Prespool and you get a very slow transition and low secondary boost as the second turbo never gets up to full speed. Also you might have a plugged Pre-cat causing high back pressure and limiting your secondary boost

 

maxpesce: makes perfect sense. Thanks.

 

Ok, I'm trying to isolate the problem, but I'm still a complete noob so I could use some advice...

I T'd into "the nipple that is on the back of the Y-pipe just behind the Charge Relief Valve's (CRV) hose connected to the Y-pipe" as suggested by spooledUP7 in this thread:

https://www.rx7club.com/forum/showth...rbo+precontrol

Apparently, what I should see is:
(3rd gear - WOT)
0 - 4000 RPM: 0psi
4000 - 4500 RPM: Roll up to 8 psi +-1psi
4500+ RPM: 12psi

but what I saw was:
0 - 5200 RPM: 0psi
5200+ RPM: 7psi

I think this clearly supports maxpesce's theory that my pre-control is not working (while the turbo control is fine).

I figure the problem can now be narrowed down to one (or more) of the following:

1) pre-control solenoid not working
2) pre-control solenoid not getting power
3) leak between pre-control solenoid and actuator
4) pre-control actuator not working

I have tested the solenoid as explained in the shop manual (closed with no power and open with power), and it is fine. I'm about to start checking the other stuff, but I just wanted to tell you guys what I am doing so you can (a) stop me if I'm doing something stupid, (b) tell me if I'm missing something simpler, or (c) give me any tips/advice on checking these things.

Thanks for ANY input

 

Anyone?

 

I'm still trying to figure out exactly where the problem is...

I T'd into the side of the pre-control solenoid that goes to the actuator. Here's what I saw at WOT in 3rd

0-3000rpm: 0psi
3000- ~5000rpm: rising to 2.5psi
>5000rpm: pressure falling to 0psi

Now, according to the shop manual, the precontrol actuator requires 10psi to move. Should I be concerned that there is only 2.5psi going through the solenoid, or am I missing some information?

I haven't tested the actuator yet (tonight hopefully), so I still haven't ruled that out as a problem.

Can someone who knows about this stuff PLEASE give me some advice.

 

I want to bring this thread back to life because when I searched turbo transition at 5500, only two threads came up and neither had a conclusion. I used to boost 10-8-10 w stock 94 touring w cat back. But now im getting 10-8-8 at 5500-5800 transition. Any one had successfully resolved this issue?

 

Yea I am having the same issue with transition at 5500 and lower boost!

 

Zombie thread!

Sucks that people are still dealing with this. Here are some other discussions that might help.

http://www.geocities.ws/laracers_vr_..._problems.html

http://www.nopistons.com/3rd-generat...ansition-8657/

I tried to document every test I did and what the results were. I made a *lot* of WOT runs in 3rd gear, with my boost gage T'd into various parts of the system. I tried to be very systematic and check the operation of every valve and solenoid, and then check to see what the pressure/vacuum levels were at various places in the system.

I did manage to get a more reasonable 10-8-10 pattern (with some valves in place of the pills), but the transition still happens later than 4500. About 5 years ago I took my car to a rotary mechanic for a clutch change, and he seemed to think my car behaved just fine and said that any deviation from the spec was from the altitude (I'm at 7000ft, and the mechanic was at 6000 ft). As of today (I still have the car, and it's still sequential) I still assume that my late transition (and the reason I needed valves in place of the pills) is my altitude. I've never driven the car at a low enough altitude to check this.

Good luck!

 

In fact, that first link is on an archived geocities website, and it might disappear one day, so for posterity, here's a cut-and-paste (if you're a fan of the sequential system, enjoy!):



My boost problem
---------------------------------------------
It will be hard to understand this unless you understand the sequential boost system on a 3rd gen RX-7. Check this for a quick explanation (http://www.autosportracetech.com/RX-7/rx7stuff.htm)

Here's the boost pattern I get at WOT in 3rd (TEST 1)

0-5500 rpm: boost steadily decreasing from 13psi to 10psi
5500 rpm: 5 psi
5500 rpm-redline: 6psi


----------------------------------------------
Tests I've run to diagnose the problem
-----------------------------------------------

I T'd into the nipple that is on the back of the Y-pipe just behind the Charge Relief Valve's (CRV) hose connected to the Y-pipe

Apparently, what I should see is:
(3rd gear - WOT)
0 - 4000 RPM: 0psi
4000 - 4500 RPM: Roll up to 8 psi +-1psi
4500+ RPM: 12psi

but what I saw was: (TEST 2)
0 - 5200 RPM: 0psi
5200+ RPM: 7psi

This suggests that the secondary is not being prespooled
----------------------------------------------

I T'd into the side of the pre-control solenoid that goes to the actuator. Here's what I saw at WOT in 3rd (TEST 3)

0-3000rpm: 0psi
3000- ~5000rpm: rising to 2.5psi
>5000rpm: pressure falling to 0psi

----------------------------------------------
I T'd into the hose that connects the precontrol solenoid to the precontrol actuator (on the solenoid side) and also to the short hose that connects the actuator to the y-pipe. The first test was a repeat of the one I talked about before where I got 2.5psi. I got the same this time. The second test (TEST 4) was different. I got over 10psi at around 4000rpm (easily enough to open the precontrol valve). This test is about as close to the actuator as you can get. Conclusion: the precontrol IS working.

----------------------------------------------
Ok, the first thing I checked last night was the charge control actuator. The shop manual says it should move with 1.9inHg applied. I had to apply 5inHg to get it to move all the way, so maybe it's a little sticky. I need to T into that line while driving and see what the pressure is; maybe this difference is insignificant.

Next thing I checked was the charge relief valve - works perfectly, tested it exactly as the shop manual said. I even tested it again using the hose it connects to in the rats nest to rule out a leak between there and the valve.

I also checked the charge relief solenoid. It works fine.

The vacuum system is fine. I hooked a vacuum pump to the hose on the front side of the check valve and the system held 15inHg steady for over 5 minutes. I also checked the check valve.

I checked the TCA by hooking a pump to it's hose in the rats nest. It worked fine (watched it move from under the car when the pressure was released). I think the only actuator I have not yet checked is the wastegate.

----------------------------------------------
T-ing into the line between the charge relief solenoid and charge relief valve (CRV): (TEST 5)
<3500rpm: 15"Hg (valve is open)
between 3500 and 5200rpm: 0psi (valve is closed)
>5200rpm: 7psi (valve is still closed)

(I just now double-checked this result by T-ing into the vaccum hose right at the CRV)

----------------------------------------------
T-ing into the pressure line between the turbo control solenoid and the turbo control actuator (TCA) (TEST 6)
<5000rpm: 0psi (valve is closed)
>5000rpm: 6.5psi (valve is open maybe - I haven't checked the vacuum side yet)

----------------------------------------------
T-ing into the vacuum hose right on the charge control valve (CCV). Here's what I got: (TEST 7)

<5200rpm: 10"Hg (valve is definitely closed)
>5200rpm: 7.5psi (valve is definitely open)

So the CCV appears to be working fine.

----------------------------------------------
Removed CRV, just to see the effect on prespool. Since the T-test on the CRV (above) shows the CRV closing after 3500rpm, I thought maybe that was affecting my prespool. After removing the CRV, there was still no prespool, as measured in the secondary side of the y-pipe (still 0psi to 5200rpm then 7psi).


Current Theory and Resolution

In my thread at nopistons.com ((http://www.nopistons.com/3rd-generat...ansition-8657/)
Tom93R1 suggested that my boost problem was caused by the high altitude (7000ft) I live at, Thus, I installed "home depot boost controllers" in place of the precontrol and wastegate pills. After some adjustment of these new valves I managed to get very close to a 10-8-10 boost pattern, although transition still occurs at 5500 instead of 4500rpm. I'll continue to attribute this to altitude until I learn differently.

 

Thanks for zombie thread.
I think boost level could be affected by altitude, but I doubt if the late transition could be affected too. Because all the valves have no idea what altitude you are at if the proper boost level is fed to them. Just what I am thinking though, everything is a possibility until proven wrong.

Just bought mityvac, I will start teeing into stuff.