M104-AMG

iTrader: (8)

I have great primary boost build-up, but my patterns are as follow from 3rd gear @ WOT at 2500 RPM.

My boost pattern:
10-6, then a slow build-up back to 10 (about 4-5 seconds)

Sometimes I'll even get:

10-7-and then a fluttering 5-8 for 2-3 seconds, and then a build-up to 10.

I pressure and 12vdc tested all solenoids, and checked all hoses and check-valves.

The vaccuum chamber holds vaccuum, but I wonder if it is filled with oil since my track-days at Roebling Road, where I loaded up the intake system with oil on the long right hand sweepers.

Are these symptoms of them ?

If it is filled with oil, how does one remove the oil ? Or do I need to get a new vaccuum chamber ?

TIA,
:-) neil

dgeesaman

iTrader: (7)

I wouldn't worry about oil in the tank unless you see oil in the line leading to it. The stock green/black check valves are filtered to help stop this - my vacuum lines are bone dry. You'd need about a quart of oil to fill that thing anyway.

Unfortunately I think it's still a misbehaving solenoid. What kind of tests did you run on them? How many miles are on the solenoids total, and how long ago did you do the tests?

Another possibility is that the precontrol isn't getting the secondary spooled consistently - but that's less likely and more complicated to diagnose.

Dave

M104-AMG

iTrader: (8)

I did the Dave Disney test, where I add air pressure (with a Mityvac, pressure gauge, and pneumatic actuator for a source) and cycle the 12VDC to make sure the solenoids don't stick and that there is no leak-down.

I did this test five times.

The solenoids have less 2,000-miles on them total, and same with the Viton hose job.

How do you diagnose that the pre-control is getting the secondary spooled consistently ?

So weird, running/responding great until my day at the track . . .

TIA,
:-) neil

DaveW

The vacuum chamber enables with both primary and secondary actuation, but your primary is OK. However, the pressure chamber assists only with secondary turbo activation (turbo control actuator). If so, is something wrong with that (loose or detached hose, bad check valve, etc.), rather than the vacuum chamber? I had a hose pop off the pressure chamber once, and my symptoms were similar to yours.

Also, if any chamber were likely to fill with oil, it would be the pressure chamber, since it is fed by positive manifold pressure.

M104-AMG

iTrader: (8)

I think the autosportracetech.com RX7 troubleshooting document says the turbo-control solenoid, and turbo-control actuator use BOTH vaccuum and pressure.

BTW, all hoses are good (tested) and nothing popped-off.

:-( neil

DaveW

That is correct, but pressure is only needed as an assist to the vacuum (the TCA uses both) to get secondary actuation. Primary uses only vacuum.

dgeesaman

iTrader: (7)

I figured you had been so thorough, rats.

To rule out a solenoid issue, tee into the pressure and vacuum lines leading to the TCA and do a road boost test. (You should see about 20"Hg in the vacuum side line and 10psi in the pressure line immediately and consistently at 4500rpm).

To check on a precontrol issue, I would tee into the secondary with my Mityvac and do a road boost test. Use the green with red-dotted line on the diagram, and look to see if it consistently builds pressure (10psi?) to about the same level right up until 4500rpm.

I would do both of these boost tests with your boost gauge still hooked up as normal and a spare gauge or your mityvac reading off the tee. That way you can compare.

Dave

M104-AMG

iTrader: (8)

Sounds like I'll need two gauges to test the TCA.

Just to verify, the green w/red-dotted line is the line that is adjacent to the charge relief valve, correct ?

:-) neil

dgeesaman

iTrader: (7)

Yep, that's the line I was talking about. You should only need one extra gauge - just move the line and repeat the test.

Dave

M104-AMG

iTrader: (8)

As I was diagnosing, I thought I smelled some leaking exhaust, and I found the line between the intake manifold and the brake-booster line was torn. I also took apart the Efini Y-pipe and noticed that the O-ring was broken.

I replaced it, and re-tightend everything (Y-Pipe; intake from air-cleaner, etc.), and tee'd into the secondary turbo line (green w/red-dots) as suggested.

I noticed no vaccuum or boost until past 4500 RPM, at which it was 10-12 PSI all the way to red-line.

But, now I finally have a 10-8-10 pattern in all gears with very minimal lag between the 8 and 10 transition.

Could the broken O-ring do this ?

Since the lag is minimal, I didn't do the the TCA pressure & vaccuum test .

TIA,
:-) neil

dgeesaman

iTrader: (7)

Heh, you have a 10-8-10, who cares? (j/k)

I would believe the o-ring could do that, but I'm not sure exactly why. I'll test that green/red dot line today and find out for myself what it does. I remembered that it built boost before 4500, but I'll check that.

Dave

M104-AMG

iTrader: (8)

My understanding from the http://www.autosportracetech.com/RX-7/rx7stuff.htm RX7 write-up, is that the charge control valve is normally closed between the primary and secondary turbo-chargers. Since the green w/red-dot line is on the "secondary" side, we should see nothing until 4500 RPM and greater when it opens up.

Still, I'd be interested in what your results are.

:-) neil

dgeesaman

iTrader: (7)

I'm going from the literature here; I still haven't done my tests yet. I will shortly.

The green w/ red dot (GwRD :o)) line comes from the secondary side between the compressor and the charge control valve. It does not function as an output line, but an input line. It should always exhibit the pressure or vacuum coming from the secondary compressor.

This line feeds the 'on' side of the charge relief solenoid, which is on from transition+. The off side of the CR Solenoid is fed by vacuum, so if you monitor the output of the CR Solenoid, it's should be system vacuum up until transition, then secondary pressure (10psi) from transition+.

This line also feed the 'off' side of the charge control solenoid, which is off from transition and up. The 'on' input to this solenoid is the system vacuum. So its output also runs system vacuum from 0-transition, and secondary pressure (10psi) from transition+.

According to Vanditmars', this transition occurs at 4500rpm.

Dave

M104-AMG

iTrader: (8)

We are definitely talking about different lines. On my diagram, the line I Tee'd into did not got to either Chamber A or Chamber B of the charge control actuator/valve.

Rather it is one of the lines that comes off the intake and just to the secondary side of the Y-pipe.

:-) neil

M104-AMG

iTrader: (8)

Well, the slow secondary boost is back, esp. when the car is warmed-up.

I pulled the UIM, and checked all lines. I noticed that one of the lines to the Turbo Control solenoid (the one NOT down in the rat's nest), was pinched.

Could a slightly pinched line cause this ?

My hypothesis is that I got good 10-8-10 when cold, but as the VITON line warmed-up, the slightly pinched line became a fully pinched line.

Unfortunately, while trying to remove the lines, the solenoid was so brittle, the nipples broke!

I believe it is pn# N3A1-18-741

:-( neil

dgeesaman

iTrader: (7)

Possibly, but I suspect the solenoid is behaving differently when hot.

That would be the correct part number.

Dave

dgeesaman

iTrader: (7)

You can see in this picture how I routed those hoses to avoid kinking.

M104-AMG

iTrader: (8)

You'd man ! I didn't even think about routing it like that. I'm going to get a new solenoid regardless.

I hope you didn't pull your UIM just for me!

:-) neil

dgeesaman

iTrader: (7)

Gawd no, I pull it much more often for much less sensible reasons. (At least it feels that way - I pulled it 6 times this summer). I just cropped a picture from last summer.

Dave

DamonB

Both of those parts would function as boost leaks. Since the brake booster line comes straight off the UIM if it was split it would leak boost.

If your boost problem seems to come and go always suspect something electrical. A mechanical turbo or boost problem would be the same all the time. Once things seem to be caused by gremlins always suspect electrical (solenoids) first.