Eratic tach input

[Smithius]

Just got my efi setup running on my 1980 corolla with the original 4k motor and a supercharger of an aw11 Mr2, but I'm getting odd erratic tach inputs at idle.

The car will fire and idle but I will get an event where it will show really high rpm signals and then obviously it makes it run rather bad.

I'm running a Bosch hec715 coil and bim024 igniter with the corolla electronic dizzy, no coil control atm, just fuel control.

Megasquirt 2 3.57smd running msextra 2.21 I think.

Cheers
Matthew

[trakkies]

How is MS configured for the tach input from your stock ignition system?

[Smithius]

Pretty sure that its set up as basic trigger? Rising edge I think, I'd have to check but I'm pretty sure that's what it is.

What setting do you recommend

[trakkies]

I was more thinking of the actual hardware set-up - as there are different ways MS can accept the tach signal. Which wiring digram was used?

[Smithius]

I bought the setup from diyauto tune, so I just connected the white wire in the shielded cable, to the negative side of the Bosch coil. I don't have the black wire connected to anything. Should I?

[trakkies]

Basically, there are hardware alterations designed to overcome tach signal problems - if encountered. Without knowing exactly how your unit is configured internally it's difficult to make any recommendations. Have you approached DIY Autotune about the problem? Was the unit supplied for your exact ignition system?
The screen of the cable is normally left floating at the coil end.