Rev counter
Turbo Mini Forums

Hi just woundering if anyones having the same problem or nos a cure, currently got bmw 16v with megasquirt using the three diode circuit but the rev counter goes back to zero after 5000 rpm as soon as your below this rpm it jumps back to its proper reading apart from this it tallies up with megatune and my timing light.
pre injection clocks and running ms2

any helps great.

Edited by turboestate on 12th Jun, 2008.

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I suspect that the signal that the tacho is seing from the diodes is too noisy above 5000rpm. Just a guess.

My mate had his tacho recalibrated so that it could read directly from one side of the coilpack as he couldn't solve a similar problem.

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Hi,
Try a different voltage for the zener diodes, or change to zener if they're not already?
Don't ask me for values, I'm just thinking out loud...
Cheers,
Gavin :)

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Was thinking that myself cant remember what voltage zener i used, am i right in thinking theres an output from the edis unit for the rev counter something else to try if all else fails.

love that straight cut scream!!!
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Hi,
Yes there is, I don't know which pin. Also there's rumours not all edis units have this output...
Cheers,
Gavin :)

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Yes you can use the edis output, that is what I have always used.

It is Pin 11 that is the tacho output. This is always blanked off. All you have to do it strip down the plug, drill out pin 11, push out pin 2 and put it in the hole for pin 11. It is easy, honest.

I am sure you have seen this http://www.megamanual.com/ms2/EDIS.htm
it may be some help.

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http://www.hillclimbandsprint.co.uk/default.asp

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I did exactly what Ben H describes and modified the edis plug but it still wouldnt' drive my rev counter (Smith RVC type).

In the end I took a feed from the PIP line which works perfectly.

Edited by mlarj on 14th Jun, 2008.

Yes, some rev counters don't like the pin 11 signal. The pip signal can be used, but again some counters don't like that either.

Basically, keep trying different ways until one works.....

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Up date lads took a wire from pin 11 on edis works a treat rock steady rpm exactly the same as megatune and my timing light thanks guys

love that straight cut scream!!!
______
/___|_____
_ (@)___(@)

The edis module I got from a K reg cvh Escort has the tacho pin and wire in already.