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View Full Version : Tach. robing spark?


Giga Shadow
07-24-2004, 05:59 AM
I was wondering if my tach could be robbing some power from the coil since that's were it gets it's is signal and power from. :?

If it does will I get less spark or still the same as normal?

Thanks allot poofs. :wink:

http://mortalkombat.metropoliglobal.com/Fart.jpg

bimmerjim®
07-24-2004, 06:08 AM
its possible. some tachs and shift lights will cause a non contact ground. where the tach uses a siganl that is ground pulses. and ifthe tach has some sort of feebback, then becaseu all the tach signal lines are conected the tach could be feeding the ground signal some positive voltage, just enough to throw things off.

this shouldnt happen if ou have an msd box and your using the MSD tach signal off the box.

Giga Shadow
07-24-2004, 06:19 AM
this shouldnt happen if ou have an msd box and your using the MSD tach signal off the box.
I only wish I could spend on a MSD :( ($85 shipped from schwartz)

the tach could be feeding the ground signal some positive voltage, just enough to throw things off.

That's true!
It could throw the valtage back in the coils face.
Can I test this thery out? I'm pretty dumb when It comes to electrical.

Would getting the power from another source like the ignition switch fix this posable problem?

bimmerjim®
07-24-2004, 01:26 PM
you would need an ocsilloscope to SEE that it was happening.

i say this because when i put in my shift light, the light would sometimes light up at random while i was flooring it, because i had all the tach signals from one source. tach signal is a ground. but if all those wires running to the stoco tach, aftermarket tack, MS and whatever else arnt sheilded, or if they run near a power source, and electromagentic feild can give it just enough feedback to mess up the signal.

i had the turbo timer, the shift light, the MS, and the stock ECU all reading off the same tach source. i switched my shift light and turbo timer tach signal slource to the insturment cluster rpm signal and it was fine then. but before all were conected to the coil.

swartz
07-24-2004, 01:37 PM
at least someone saw my parts for sale. ill take $75 shipped come on they are like $160 new

they have a tach out. so u would just plug the wire into the box instead of off ur coil

bimmerjim®
07-24-2004, 02:09 PM
no i conected the tach signal from the turbo timer and the shft light to the tach signal at the stock instrument cluster. and then only had the MS and the motronic conected to the coil.

swartz
07-24-2004, 02:20 PM
i have the ms and shift light coming right off the coil