Rev counter signal

[Dum-Dum]

Hi all, what sort of signal does the crank sensor give out?

Is it a 12v pulse every revolution or is there a break in the signal every revolution.

Only asking as i want to fit a rev gauge to my NAD

[Toby]

I believe the sensor itself is a Hall Effect sensor, which means it would send a signal with each revolution.

[samass]

It is a hall effect sensor, which sends a pulse signal every time it passes over a tooth on the reluctor ring. There will be many pulses per rev, you'd have to count the reluctor teeth to work out rpm.

[Ruan]

There's two marks on the flywheel... And it's a hall effect sensor, so a pretty small voltage increase every 1/2 rotation I think...

[samass]

Most have a couple of teeth missing, or half missing, this is to tell the ecu when tdc is. The many teeth (normally around 60) allow the ecu to work out rpm with out the engine having to do a full rotation.
I just did some coursework on reluctor rings and hall effect sensors, ill dig out the relevant parts when im next on a uni pc

[Ruan]

Except there's no ECU as it's a Mechanical Diesel... Infact even the early 8v XUs use this arrangement for the tacho reading, then another 62-2 on the flywheel for the ECU to determine crank position.

HDis and GTi6s have a 62-2 tooth flywheel and the revs are read from a pulse from the ECU... As do lots of other cars...

[darrenjlobb]

As Ruan said, these mech diesels that pug make literally just use two notchs in the flywheel, with a sensor over the top, are you planning on trying to make a set of perv 106 clocks work? Or an aftermarket tacho?

Getting the stock clocks to work would probs be very difficult unless you removed the tacho mechanism from the back of a set of 306 diesel clocks and fitted it to the back of a set of perv 106 clocks...

In terms of making an aftermarket tacho interpt the fly sensor, its very hard, best bet would probs be a proper diesel tacho that works from the alternator extra terminal, and calibrate it with a laser rpm gun....

[Dum-Dum]

Suddenly hunting for a set of 106 diesel clocks with a tacho seems like an easier option. They are rare as flying pig shit but do exist (and theyre listed as NFP on service box so i aint getting a set from pug)

[darrenjlobb]

Yeh, that would by far be the easiest option