classic smiths 6 cylinder rev counter, electronic, in a car now powered by a 6 cylinder bmw E36 TDS.
The bmw engine loom plug, X20, pin 20 is engine speed. I am hoping I can use that wire to power the smiths/ jag rev counter.
If I understand correctly the original jag signal powering the rev counter comes from/ goes back to the coil, does not `plug into` the rev counter but a small loop in that wire is clamped against the back of the rev counter and induces a signal inside the rev counter through proximity- which is then amplified to operate the rev counter.
I am wondering if I can use pin 20 from the BMW ecu to dash output `engine speed`, and loop that against the back of the jag rev counter.......but need advice before doing it not being very good at this (although I did manage to strip out the bmw engine, ecu, ews and key and install that in the jag!).
Q, to try and see if pin 20 can supply a BMW ECU signal to the jag rev counter, should I `earth` the end of the X20 pin 20 SWTD wire to complete a circuit, after looping it against the back of the rev counter in the same way the original jag loom powered the rev counter ? Where does pin 20 wire `go` when it goes into the bmw rev counter ? Does it go to earth or to some other electrical component ? Might I damage the ecu if I run pin 20 to earth vire the jag rev counter?