Hey all. I am running a zetec on bike carbs and using esc for the ignition.
I am taking the feed for the rev counter from one side of the coil pack and am using an old smiths rev counter.
I am only getting what i believe to be a half reading on the rev counter though. What have other people done to get their rev counters to work and has
anyone else had problems?
I believe you can take a feed from both sides of the coil pack and then use diodes to join the signal wires but i can't seem to get hold of the
diodes to do this so am a bit stumped.
Thanks, Mark
Try Maplins for the diodes Maplins.
Doesn't the esc have a tacho output?
Stu
I've tried maplins and can only get hold of 2 of the diodes, the diodes i need are
2x 1N4004DICT-ND
1x 1N4746ADICT-ND (hard to get hold of)
the esc i am using doesn't have a tacho output, it came off a 1.3 mk5 escort with no tacho, although i do also have a esc set up off a 1.6cvh mk5
escort (slightly different) and the loom is untaped in places and the tacho feed just seems to be wired to one side of coil pack which is why i done
mine like this 
what ign have you got. the only way i could get mine to work with megajolt was from a pin on the edis4.
Any 18v or so zener diode will be fine, this is not a critical circuit. The idea is that the zener blocks the 12v from the un-energised coil, since the tacho needs to see the voltage swing down to zero, or thereabouts. Since the flyback voltage from the coils will be of the order of 200-300 volts, a few volts difference on the zener isn't going to make any difference.
maplins do 1n4004 (forget the other numbers); do a search and this comes up as rectifier diode; also shown are 1n4001, 1n4002, 1n4003 - as far as
your application is concerned, all are interchangeable. (difference being the max reverse voltage).
1N4746a is a 18V zener - it shouldn't be necessary to use a zener.
1N4004 is the minimum spec, 1N4005 to 1N4007 are all ok as well. Anything lower in the series and reverse breakdown voltage is too low for ignition
coil applications.
Zener is usually needed, without it the voltage never reaches zero since with wasted spark there is always 12v on at least one coil.
quote:
Originally posted by MikeRJ
Any 18v or so zener diode will be fine, this is not a critical circuit. The idea is that the zener blocks the 12v from the un-energised coil, since the tacho needs to see the voltage swing down to zero, or thereabouts. Since the flyback voltage from the coils will be of the order of 200-300 volts, a few volts difference on the zener isn't going to make any difference.
Probably small casing difference. Nothing to worry about
[Edited on 12/6/09 by Macbeast]
Would this diode be ok as an alternative to the 1N4746ADICT-ND...
1N5352 BRL from maplins site
it just says it's 5w and is 15v, would this be ok?
i have also found some 18v zener diodes on the maplins site but they are 0.5w or 1.3w, i'm getting confused do i need the 18v diode or the higher
wattage?
what should i go for?
thanks for any help 
Out of interest, we sorted out our rev counter yesterday (It's for the Acewell).
We connected the yellow wire from the Acewell dash to pin 11 on the EDIS 4. Hey presto ... instant Revs
quote:
Originally posted by Mk1_Mark
Would this diode be ok as an alternative to the 1N4746ADICT-ND...
1N5352 BRL from maplins site
it just says it's 5w and is 15v, would this be ok?
i have also found some 18v zener diodes on the maplins site but they are 0.5w or 1.3w, i'm getting confused do i need the 18v diode or the higher wattage?
what should i go for?
thanks for any help