Right, as above really. I need to know what the input into the rev counter is on my fiesta 2.0 zetec (mk3)si. I have an idea for a rev counter accessorie but dont know if the input it a pulse, i.e 6k per min pulses at 6krpm, or like 6v for 6k rpm, or if its done on resistance or what. if someone could enlighten me, and give me a few rough numbers that would be awsome.

cheers

 

the signal is a switched earth, usually on the LT side of the coil

 

Erm....? Basicly im getting a mate to make the thing up for me, as im crap with electrics, so have no idea what you just said! I get its done by like a missing tooth type thing on the flywheel sending a slat spot in a wave thing, but does this go through something else before being sent to the rev counter?

 

no its controlled by the LT signals which also fire the ignition coil.

 

Ah ok, right. Do you have any idea what this signla looks like? I know which wire it is, im just wondering what the signal looks like as it will be going through a basic processor that a mate of mine will write some code for, but i need to tell him what signal he will be getting so he can write the code for the desired effect.

cheers dude

 

being as its just switched its a square wave

 

So its a square wave that goes straight to the rev counter, so 6krpm would be 6k...... im forgetting its over a min, so it'd be like 100hz(3krpm 50hz)? would it be a 12v signal? or as its got 4 spark plugs would this have to be multiplied by 4?

 

cheers btw

 

Well no not necessarily, different rev counters are calibrated accordingly, if the car is running coil packs then it could be running wasted spark or a coil for each plug!!

How could it be a 12v signal i said above it switches earth

 

Soz, im crap with electrics, dont get what you mean by it switches earth???

 

Switches the negative side of the coil, so 0v.