my friend has a megasquirt in his fb and we can't get it to run right. he said the ecu keeps resetting itself and sometimes the tach signal will go crazy..we have the stock coils and we are running a wire from the ground on the coil to get a signal but i think it is getting too much noise. do we just have to buy a msd i don't know if the stock coils are making a strong enough signal?

 

Typically the Mazda coil (-) signal have been seen to be too strong (>300v spike!) with lots of ringing in it. Resistance inline on the tach wire has been known to effectively cure this. Linear taper 100K pot, adjust until no triggering at all, back it off maybe 20%, read this value and subsitute the nearest value fixed resistor. Done. I've never seen a dirty tach signal reset the MS, it generally false triggers as you've described. The resets may be another issue. Can you attach a log of the bad behavior?

-Mike

 

Make sure you are running the wing diode, and put a 30K 1/2W resistor in series with the coil negative coil.