I am trting to get rpm working just wondering if i go of the negative side of the trailing coil will this work on stock fd dials

Using Motec no additional outputs left so trying to find a way toget tacho working

Thanks

 

it should, its how the pre FD cars all worked

 

Ive red that a pullup resistor is needed few years ago but cant seem to find the link again
I just wanted to be sure as dont want to blow the dials up

Also does it matter if i use the trailing or the leading

As the leading fires a doble pulse ?
Thanks for fast responce



Dont no how usefull this mabe for fd tach

https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://www.hot-spark.com/tachometer-fix.pdf&ved=0CB4QFjABahUKEwjz8NTupPfIAhVCuhQKHdSxD RY&usg=AFQjCNHaxtLkC5qOjeGmkiBdkZ1aXBkaqw

 

Found this but does it apply to stock tach ?

https://www.rx7club.com/aem-ems-81/tach-signal-1025077/


My coils are aem smart coils triggerd by motec



Is this statment correct
NZConvertible , 10-20-03 08:59 AM
Each trailing coil (there are two) fires once per rev, but the tach signal from them is summed.

The leading coil (which is a single dual-post coil) fires twice per rev.

Thus the tach signal can be picked from either coil pack, because both give the same two pulses per rev, just like a 4-cyl.

 

Got rev counter working but its not correct speed its reading 1000rpm less not drove it yet but will give a full run at night mat sure its out by 1000rpm threw out the reverange if it is then i will just shift the needle


My only thorts is the needle is not correct ( i cant remeebr moving it )
Or the trailing ttl signal doesnot work it needs a leading signal ?
Any ideas ?

https://www.youtube.com/watch?v=bAqxySkqWvA&feature=youtube_gdata_player