Hello Theo

How are you, the new software is very good , I have another question , I hope you may be able to help me with , do you know how the original system generates a signal to the dash pod for the fuel kilometers consumed , my electrical drawing does not show it , and cannot see on the electrical plugs where the electrical connection is ,as it has stopped working , it used to work well. My wiring is showing different to the manual .

Thanks in advance

Best Regards
John Gill
cell 0412 084 004
Fax (61) 7 3389 2508

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Hi John,
Yes, all is fine on our side of the pond. Just started to get warmer and spring is in the air.

The digital dash has a microcomputer inside. It uses car-speed from the speed impulse (sender depends on MY) and load from the ecu. I’d have to look which path the signal takes, but from head it is the load that is monitored. These are calculated and used to estimate the fuel consumption.

regards
Theo
1992 Porsche 928 GTS Midnight blue
The Netherlands
http://jenniskens.livedsl.nl
http://928gts.jenniskens.eu

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Thanks for that Theo

By load signal do you think it is voltage related , i.e. can be measured , I cannot for the life of see where it is taken from the ecu , it is certainly not in the place as indicated on the schematics.

Best Regards
John Gill

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Hey John,
Somehow I was at this station before… I remember looking for the same issue. Apparently you forget when you get older ?

It is not load but the actual injector pulse. It reads the injector pulse duration from the trigger point at the injectors (L89 , not #2, label N26) and that N26 is connected via the CEB (W12-Q23) to pin 8 of plug 4 where it says Jetronic. Nice …. They could have said “injector pulse for measuring fuel consumption” and a think Jetronic is a somewhat short version of that.
Yes, load can be measured, but is a 10uS impulse, so you need a scope for that.
The dash evaluates the injector pulse by looking at the PWM, Pulse Width Modulation. Clever device eh…?


regards
Theo
1992 Porsche 928 GTS Midnight blue
The Netherlands
http://jenniskens.livedsl.nl
http://928gts.jenniskens.eu