Thanks, I am certainly learning far more about this car than planned.

One of the jobs that I planned when the engine was out was to install an AFR gauge to make sure the engine was running properly. I ran the wiring for the wide band sensor through the tunnel while I had access but that was as far as I got. Now that the car was running again, I got back to the AFR gauge. I couldn’t decide on where to mount the gauge, seeing them mounted in the clock position seemed like a good idea. But I also like the idea of turning that into an additional air condition vent, so I went with the ashtray location.

http://forums.pelicanparts.com/uploa...1666313692.jpg

I used the exercise as an opportunity to clean up the stereo wiring, adding in the gauge power with a molex connector and an inline fuse.

Before:

http://forums.pelicanparts.com/uploa...1666313692.jpg


After:

http://forums.pelicanparts.com/uploa...1666313692.jpg

The lighting wire was tapped into the ashtray light and the RPM wire was tee’d in to the back of the tachometer.

http://forums.pelicanparts.com/uploa...1666313692.jpg

I bought an Innovate PSB-1 gauge that also has a boost gauge. I connected the map sensor by replacing the brake booster connector with one from a Porsche 924 that includes an additional port. I made a bracket to mount the boost sensor on the brake reservoir bolt

http://forums.pelicanparts.com/uploa...1666313967.jpg

http://forums.pelicanparts.com/uploa...1666313967.jpg


I added the oxygen sensor bung to the cat delete pipe. Rather than take it to an exhaust shop and have someone competent weld it. I decided to try stainless flux core wire. It did the job but I’m not brave enough to share pictures of the aftermath of my welding/grinding effort. There were also some holes in the muffler that I plug welded and ground down.

http://forums.pelicanparts.com/uploa...1666314048.jpg

http://forums.pelicanparts.com/uploa...1666314048.jpg

http://forums.pelicanparts.com/uploa...1666314205.jpg
http://forums.pelicanparts.com/uploa...1666314205.jpg

The gauge came with an 8ft cord that wasn’t quite long enough to reach. I soldered in an extra two feet of wire to get the required length.

http://forums.pelicanparts.com/uploa...1666314205.jpg

http://forums.pelicanparts.com/uploa...1666314205.jpg

After it was all connected and I’d been through the calibration sequence, I took it out for a drive with my laptop connected and logged some runs.

http://forums.pelicanparts.com/uploa...1666314297.jpg

I was surprised to see that the cruise AFR stays around 15.8! It drops quickly when boost builds and gets down to 10 when making power. The car has always felt under powered at less than 3000 RPM. I originally just thought that this was the off-boost lag that everyone talks about but now I see I’m not getting enough fuel. Further searching lead me to find that the frequency valve is not working….On to the next repair.

http://forums.pelicanparts.com/uploa...1666314510.png

I played around with the data from testing. Having the time and RPM meant that I could calculate the speed I was travelling as long as I knew what gear I was in. Taking the slope of the speed plot meant that I could calculate the acceleration. And from there, knowing a few other parameters such as co-efficient of drag and frontal area meant that I could calculate the HP. I used the calculations from “Analysis techniques for racecar data acquisition” and came up with a sort of power vs RPM plot to compare my car with other cars. I can’t put any claim against the accuracy of the numbers but the overall trend seems to look right. At the very least it will let me know if fixing the frequency valve and getting my AFR’s better will make a difference in the off boost performance. I found a picture of a dyno run of a stock car and overlaid my HP plot with that. It does seem to show that I'm low in power when the car is running lean.

http://forums.pelicanparts.com/uploa...1666314831.png

http://forums.pelicanparts.com/uploa...1666314944.jpg

I tell everyone to get an AFR gauge, then you will see how perfect your perfectly running car really is..

I did not know a 930 uses tapered roller bearings in the rear instead of the split race press in style bearings used by the non-turbo cars. Interesting.

Any idea why?

I’m with you..! News to me as well.

It was quite a surprise. If I had to guess I would have thought it was running too rich based on the spark plugs. My only concern now is that I'll be constantly tinkering with it trying to get the perfect mix.

I'm not sure. I wasn't aware that this was different to the non-turbo. I searched rear wheel bearing diy in the 930 forum and was brought to an excellent DIY that was written by dap930.

From my last update I had discovered that my frequency valve was not working and that my car was running lean below 3000rpm.

I started off by checking the wiring diagram for my car as well as other post on the forum. The first item to check was the oxygen sensor power relay. I checked it by placing it in the horn relay socket and hitting the horn. I was greeted with silence. I checked a few other relays while I was there and found that the rear fuel pump relay was bad too. The pump still runs with the relay removed so I’m ignoring that for now. I was concerned that the WUR and AAR and well as ignition power for the oxygen sensor relay comes from the rear fuel pump relay but whatever rewire of the rear pump was done, it maintained that connection.

I replaced the oxygen sensor power relay with a known good one and checked to see if the frequency valve now buzzed. It did not.

I checked the pins on the oxygen sensor power relay socket and found I had good ground on pin 85, power on pin 30, pin 87 had continuity with the frequency valve. But Pin 86 wasn’t getting power with the ignition on. So, I jumped pins 30 and 87 but still no joy.

I started performing continuity checks on the wiring. Starting in the engine bay I disconnected the 14pin connector by the rear shock and checked each pin had continuity to its respective component. I found that the 35C switch was not connected; I saw the terminal was hanging nearby so I connected it. I am assuming that I missed this connection during the recent engine out work. All the others were good pins were properly connected.

Next, I started looking at the three boxes under the driver’s seat. One of the things that I noticed while driving was the AFR (and drivability) is good from ~3000RPM and up so I first checked the speed relay. From the wiring diagram, I believe that I should have continuity between 9 & 12 for the 3000RPM switch and 1 & 2 for the 7000RPM cutoff. I had neither! I checked the grounds were good and that the ignition power was good. I opened it up expecting to find a dry solder joint but instead was met with this burnt mess!!!

http://forums.pelicanparts.com/uploa...1667092066.jpg

http://forums.pelicanparts.com/uploa...1667092066.jpg


I’m starting to think that this was the reason for rewiring the fuel pumps but I’m sure I’ll find out once I try and repair that mess of wiring. Surprisingly, if I supply power and ground to the appropriate pins to the relay, both sides activate. So it appears that the damaged part is part of the RPM input.

I added wires to bypass both speed relay circuits in addition to the oxygen sensor power relay and still the frequency valve is silent. I have a MSD CDI now so the 7000RPM over-speed relay is not needed. The only part not working is the oxygen sensor below 3000RPM.


http://forums.pelicanparts.com/uploa...1667092119.jpg

Next up is the fuel enrichment relay. This one has seen some work in its life. The wire colours don’t match the circuit diagram; there’s short sections soldered on the end of the existing wires and there’s one green/black wire that’s not connected to anything. The pins also don’t line up with the wiring diagram for an 86 turbo. It looks like there was an updated design that used a different connector and the wiring was changed to that.

From the label on the relay it appears the new wiring is correct. The alpha 35 pin connects to the 35C switch; The LL pin connects to the throttle switch labelled LL and so on. I don’t know if the T50%, T75% and Pu connectors are correct though but I don’t have any reason to believe that they’re not.

Does anyone know what the Green/Black wire is for and why it’s not needed in this new relay?

http://forums.pelicanparts.com/uploa...1667092142.jpg


Next was checking the connections between the jetronic box and the fuel enrichment relay. It took a bit of figuring out now that the enrichment relay was rewired but eventually, I concluded that all of the connections between these two boxes were good.

The next step was to verify the wiring between the 14-pin female connector by the rear shock mount and the connectors under the driver’s seat. This is where it started to get interesting.

I start by checking pin 1 which should be connected to pin 3 of the speed relay……. and find that there is no terminal in pin 1 location. Off to a good start with this one.

Check pin 2 and its good.

Check pin 3 and there’s no continuity to pin 1 on the speed relay.

Pin 4 is good.

Pin 5 should be connected to the jetronic box but again it’s not. I start poking around in the other terminals to find that Pin 7 is connected to the jetronic box. Then I go back and check which pin is connected to the pin 1 of the speed relay….. It’s pin 5 not pin 3 of the chassis connector.

I go through the rest of the terminals and slowly realize that all of the odd numbered terminals are off by one position.

1->3
3->5
.
.
11->13

So it appears that the female terminal has been opened up at some point. I carefully move the odd number terminals one hole over and then reassembled the connector. Another continuity check to make sure everything was where it should be and all terminals passed.

Before

http://forums.pelicanparts.com/uploa...1667092287.jpg


And after, all pins back in their proper position

http://forums.pelicanparts.com/uploa...1667092287.jpg

Another continuity check to make sure everything was where it should be and all terminals passed.

Pin 14 should provide ignition power to terminal 86 on the oxygen relay but there seems to be a break in the wire somewhere. For now, I jumped ignition power from the yellow relay.


http://forums.pelicanparts.com/uploa...1667092379.jpg

With the male connector inserted; the speed relay bypassed; and the oxygen sensor power relay jumped, I turned to key and finally heard the frequency valve sing the song of its people.

Turned the key a bit more and the engine fired up. After a minute or so the AFR gauge read 11, with the engine warm it rose to 12. Before this repair, it was at 16. I got for a short drive and instantly can feel the change in power off the line. I can finally pull away from a junction and keep up with traffic. I took a 3mm allen key with me and stopped off at a shopping center once the car was up to temperature, then I played with the mixture and idle until I had an AFR of 13.5 at 950rpm. I’m sure there’s more tinkering to do to get the mixture right throughout the operating window but this one fix was a big jump forward. Hopefully in the next few days I’ll get the chance to log some more runs and check out the AFR’s in all operating conditions

Sweet! I agree with the others - drive and enjoy it!