im installing an aftermarket rev counter and need to find the negative wire that comes off the coil.

the engine is a fiesta rs1800 and its running off a fiesta rs1800 loom the 3 wires coming off the coil are green with red stripe , black and green with a yellow stripe. so which 1 of these is the negative ??

also on the rs1800 loom theres already a wire for the standard rev counter (engines now in a ka) so i connected this up to my rev counter but does not work , what signal would this put out and for what type of rev counter??

any help would be greatly appreciated

cheers

 

The two outer wires on the solid state coil packs are the trigger earths, the center is the coil live.

So pick up on either outer wire and set your rev counter to work on that.

 

cheers for that bud

what do you mean by set the rev counter up ??

the only thing adjustable on my rev counter is to change it from 4 cyclinder to 6 cylinder or 8 cylinder ??

 

yes thats it, swap it around till it reads correctly, its not as simple as just setting it to 4 cylinder on wasted spark.

 

why would that be mate ?

sorry for all the questions just tryin to understand it

 

Because its wasted spark, it doesnt just fire once per cycle on each cylinder like a normal coil set up,
wasted spark gets it name from firing twice, as it fires cylinder 1 and 4, then 2 and 3 in pairs, it will fire once as normal on the compression stroke, but also once on the exhaust stroke which is wasted.

(IE, if cylinder one is one the compression stroke and gets spark, the coil is also firing cylinder 4 which is on its exhaust stroke).

The coil pack is basicly two coils in one unit.

If you run into rev counter issues, you can also make a diode pack to run from both sides of the coil to feed the rev counter.

 

cheers for that mate , ill give it a nudge and report back

 

ive got it working it revs up fine but on tick over it sitting at say 900rpm but every few seconds it flicks up to about 1200rpm , by that i mean it just shoots from 900rpm to 1200 rpm and then back instantly and does that every few seconds when reving up its fine

any idea's?

ive also read about the diode thing , you have to put a diode on each of the negatives off the coil and them connect them together to go in to one signal wire , is this correct or have i got it wrong??