VR bad polarity gives what on PIP?

[doublegarage]

Hello - 1st post ever here.

Car is an Alfa Romeo 4-cylinder car. It's currently running with a distributor (yuk) and coil setup - trying to bring up the EDIS system alongside that and then cut-over to MJLJ forever.

Current status is:
- MJLJ talks to PC
- I see TPS changing and can calibrate it
- zero RPM ever on the PC when engine is running
- power and ground all good at EDIS connector (starred ground with MJLJ ground)
- see ~2.2volts AC from the VR sensor at the EDIS connector
- ocilloscope on PIP signal at MJLJ molex looks bad - it's 12 volts with about 2v ptp AC signal superimposed (i.e. +10 to +12 volt AC signal) - but seems to be correct frequency and increases with revs
- nothing on output side of MAX232 (i.e level shifter is not switching on 5volt side, so nothing into CPU)

Therefore 1st thing is probably to reverse VR sensor polarity - but before I do that...

I know you get no spark with inverted VR polarity - but would you expect that weird PIP waveform? In other words, is that why you get no spark? Or does this sound like bad EDIS module (shouldn't be..."new" from Boost)

Thanks for any help.

-Richard

[doublegarage]

you were probably thinking "why doesn't he just try it...?"
so I did (reverse the VR sensor polarity) and sure enough I got a perfect looking 0-12v square wave on the PIP signal and suddenly I see RPM on the PC etc.

Once I figured out the plug-lead order (2nd time lucky) the car fired right up and for the first time I had the excitement of using a PC to set ignition-advance - so cool.

Unfortunately my TPS doesn't work very well at all - The car has dual Weber DCOE carbs and there is no space to mount the TPS in the usual place on the end of the right (front carb) - therefore i made a bracket to mount it on the left, but now the TPS is reversed (clockwise instead of anti-clockwise) and seems to work very coarsely when operating backwards - I had thought it would be symmetrical, clockwise to anti-clockwise - but it's not even close - more thinking required.

-Richard

[brentp]

Thanks for the feedback- Truth be told we've never looked at the PIP signal with the VR sensor reversed. Odd that it has an signal superimposed on it- I figured it would just be a static signal .

Take advantage of that tunability- you'll be able to do things that were never possible with vacuum advance and spring loaded weights!

[alfadoctor22]

Hi Douplegarage...

If you use the old 1300/1600 intake manifold and a waterpump with 2 hose connection you can bolt on the original alpha TPSon the right side of the front carb. Only suitable for Weber and Dellorto btw.
You can get this item at. www. dellorto.uk

As soon as my system is running I will post some pics here.
I´m currently searching the spark....


Regards, Werner