rev counter on a pre cat

[stoker302]

Having taken my rev counter out the car to see if the thing has burnt out, as its not working. Took the glass front off to find everything looks ok. A friend is going to test this but needs to know what type of signal do I need to put onto white wire to test rev counter, what voltage do I apply to red wire. help much appreciated.

[PeteGriff]

Hi Alan, I have not had the need to test or look into the TVR RPM Counter, but typically on the electronic units there is a system feed (i.e. +12V DC), Earth and a signal feed. As the Griff is an 8 cylinder there will be 8 pulses per revolution, this will increase in frequency of course the more Rev's the engine does. Therefore at 1000 RPM there will be approx. 133Hz and at 3000 RPM 400Hz. Though I do not know the signal voltage, it would probably be safe to use the low outputs of a signal generator as used to test Hi-Fi for example. On the older type of electronic RPM units used on say the MGB or other cars of that ilk, there was a return feed from the low tension terminal of the coil which fed the points, this gave an induced emf pulse picked up via a coil around the feed wire in the RPM counter itself.

Hope that is of some help. Regards, Pete

[stoker302]

Cheers Pete, I will pass that info on.