glemmers

I have been trying to troubleshoot a 10-5-10 boost pattern for a few months now (late last fall and so far this spring), with no success.

The lowdown on the car; it is a ’93 R1 with 73,500 miles. The turbos were rebuilt at » 68,000, (second turbo was leaking oil into the compressor) as well as a full silicone hose job with spring clamps on all connections. The car has the original motor, which idles at 15 in-hg at 750 rpm (has been since I purchased the car with 63,000 miles), a bit low, but has been verified on 3 different vacuum gages. Despite the low idle vacuum, the car seems to run excellent, doesn’t stall at idle, and pulls really hard under boost. Other pertinent mods are: removed double throttle, removed throttle body coolant, eliminated EGR, K/N filter, and McMaster Carr intake hoses. I have also verified the TPS is in spec and reset the idle air adjustment. The car also has stock exhaust, except for an installed downpipe.

I am running a pressure regulating boost controller (similar to Dawes device) on the wastegate and am using the precontrol solenoid to spool the second turbo up. I have verified that the precontrol actuator works by applying pressure, with a pressure pump, to the actuator and visually watched the actuator rod move. I have also played around with the precontrol pill, even removing the pill for one test, and can get the primary turbo boost to drop to 9 psid max (with the pill removed), but the transition boost remains low at 5 psid. Since I am not using the wastegate solenoid, for one test I swapped the precontrol and wastegate connectors and plumbed the precontrol actuator to the wastegate solenoid, and got the same results, ruling out the precontrol solenoid. I am currently running a #61Holley main jet in the precontrol line and have the precontrol actuator plumbed to the precontrol solenoid.

I have teed into the pressure and vacuum sides of the TCA, CRV, and the pressure tank and went test-driving. Below are the results.

Accelerating
TCA Vacuum Side
< 4500 rpm = 0 psid
> 4500 rpm = 15 in-hg
TCA Pressure Side
< 4500 rpm = 0 psid
@ 4500 rpm = 5 psid
> 4500 rpm pressure rapidly builds to 13 psid
CRV
< 4000 rpm = 20 in-hg
> 4000 rpm = 0 psid (no boost)
4000 – 4500 rpm = 0 psid (under boost)
> 4500 rpm = 13 psid (under boost).
Pressure Tank
< 4500 rpm = 14 psid
@ 4500 rpm = 5 psid
> 4500 rpm pressure rapidly builds to 14 psid

Decelerating
TCA Vacuum Side
> 4000 rpm = 15 in-hg
< 4000 rpm = 0 psid
TCA Pressure Side
> 4000 rpm = 13 psid
< 4000 rpm = 0 psid
CRV
> 3500 rpm = 0 psid
< 3500 rpm = 20 in-hg
Pressure Tank
Holds @ 14 psid

Unfortunately I could not test all the above at the same time, so I do not know if a timing critical event is awry(?). Also, I did not tee into the Charge Control Actuator, but I did verify that it cycles with the key. The pressure and vacuum tanks also hold with the car shut-off. Form the above tests, only one thing jumps out at me; the low (5 psid) pressure in the pressure tank and pressure side of the TCA at transition. Does anyone know if this is normal?

Is it possible that after replacing all the vacuum/pressure hoses, the volume is large enough that the pressure tank on the car is not large enough to hold adequate pressure for transition? Has anyone else had/heard of this problem?

I’m running out of ideas, any advice would be greatly appreciated.

Thanks for your time,

Glenn

technonovice

If you teed in at the line behind the 1" charge relief 90 deg bend (to monitor the second turbo's activity) you should see nothing at first, boost builds at 3500 rpms, and holds. If not then your precontrol is with little doubt the culprit and it will just be a matter of determining what part is failing. You should see numbers close to these below:

3rd gear - WOT

2000 RPM - 0PSI
3000 RPM - 0PSI
3500 RPM - 0PSI
4000 - 4500 RPM - Roll up to 8 PSI +-1PSI
4500 + RPM 10PSI

What is happening: Page F-84 in the manual

0-4000 RPM -
Precontrol controlled by ECU,
CRV off (Venting)
Charge Control Valve on (closed).
Turbo Control off

4000-4499 RPM -
Precontrol Optimized by ECU,
CRV off Charge Control Valve on (closed).
Turbo Control off

4500 RPM -
Precontrol fixed (5% open)
CRV on (closed) and Charge control valve off (open)
Turbo Control on

If you don't see any pre-spool before 4500 then the precontrol is not working.

technonovice

Possible pre-control culprits:
The Wiring
The Solenoid
The Lines (those brass tubes can get clogged with crap too)
Actautor
Clip at the pre-control rod
Rod not adjusted properly
Pre-control valve
There maybe others that I am forgetting or ignorant of. Sometimes it is a subtle partial thing... like a line leak (or clog) that allows only partial operation or works with the Mity Vac but not in real operation.

glemmers

I apologize, what I meant by "teed into CRV", was I teed into the CRV control line (the line from the CRV solenoid to the CRV), not the second turbo output.

I also checked the adjustment on the precontrol rod, and it is set right (1/2 overlap of hole in rod and pin on precontrol door).

technonovice

See what you get from the secondary. I'm not sure if there is a pill in the precontrol line that would matter...any smart guys know?

How quickly does boost build? Slowly build to redline, and obviously quicker in higher gears? This would make look at the Turbo Control.

However, if it drops to 5 but then builds right away it is likely your turbo precontrol.

weaklink

have you seen this site? http://home.istar.ca/~dvandit/turbocharger.htm

technonovice

I think that is the old site. Here is his new one:
http://www.rx-7tt.freeservers.com/rx7stuff.htm

2 hott

iTrader: (4)

Which way is open for the CCV?

technonovice

The rod pulled in (actuator on) closes the valve.

2 hott

iTrader: (4)

Thanks

glemmers

Technonovice, thanks for your help. I had forgoten to check the second turbo output rpessure. It turns out that I a mot prespooling the second turbo prior to transition. So, apparently I do have a precontrol problem.

I disconnected the rpecontrol solenoid from the wiring harness and hooked a volt meter to the harness, and went driving. The ECU is definately PWM the solenoid, so it doesn't appear that I have a wiring or ECU problem. I guess its time to take a closer look at the precontrol solenoid, actuator, and plumbing.

Again, all help was greatly appreciated.