Stock Tach with Megasquirt?

[csracer]

I have my car up and running on Megasquirt II with a 3.57 board and Extra code 2.1.0d.

Every thing is working great, closed loop stepper idle is ok, it needs tweaking but it will hold a good idle and I have been tuning it into boost up to about 7 psi so far and working up to 20psi. I removed all stock electronics, the SMEC is gone, and I converted the fusible link wiring to the under hood power distribution/fuse box from a 92 Daytona, it's very tidy :thumb:

I am running a 36-1 trigger wheel attached to the crank pulley with a Ford crank sensor and coil pack. The coil pack is directly fired by the megasquirt via dual Bosch BIP373 coil drivers.

Anyway, I got the stock tach to work by using the diode circuit that the megamanual recommends for wasted spark coil packs but its jumpy and erratic at 4000 RPMs and above. I have done countless hours of searching on the forums but there doesn't seem to be much info on this.

Any of you other Megasquirt guys have any ideas on how to smooth out the tach reading at higher RPMs? The diagram of the diode circuit i used from the Megamanual is below

http://www.csracer.com/megasquirt/tach1.gif



Chris Still
1989 Daytona Shelby

[glhs0426]

Use the tach setup (http://mnneons.net/viewtopic.php?t=197)the Neon guys use.

[risen]

You can enable a tach output pin on the MS and wire that to the tach on your car. I haven't tested it, but it should work OK. The only issue is that the tach may jump a little with key-on engine stopped. The omni uses EDIS which puts out nearly the same tach signal and the tach bounces when you first key-on. It's steady once the engine is running and through the rpm range, so I'd imagine the tach out function on the MS should work the same.

[csracer]

Thanks for the responses guys, I got the tachometer to work! :D I found a suggestion on a Euro Peugeot 205 forum where they got theirs to work by adding a resistor to the circuit. I created a drawing based on theirs to show how it got it to work and the components I used.

http://csracer.com/megasquirt/Tacho%20Adapter.gif


It revs clean to 6000 RPM and I ran a log to verify what I was seeing on the tach was the same in Tuner Studio.

I was trying to avoid the tach output mod to the Megasquirt board because I have the v3.57 surface mount design board which is harder to solder components to and dosent have a proto area. So it pretty cool that this is working. Hopefully this can help others running a similar setup and trying to get the stock tach working.


Chris Still
1989 Daytona Shelby

[csracer]

Hey Risen, did you use Pin 11 CTO (clean tach out) on your EDIS for your your dash tach? I have a buddy running FAST XFI with EDIS 4 on his Daytona and I need to help him get his tach working next.

[BadAssPerformance]

Good to hear you got it up and running on MS Chris :thumb:

Are you or Mike running an MSD box? The tach out on the box usually works... well at least with the FAST classic on both my car (MSD DIS-2 box with Autometer Tach) and Tommy's Shelby Charger uses the MSD 7AL2 tach out on his stock tach.

[csracer]

Nope, neither one of us are running an MSD box but that is good to know that it word on both Tachs, Mike is running an Autometer tach.

[BadAssPerformance]

OK, w/o a box... which eDist are you running? According to the paperwork I got with mine, the FAST eDist uses pin C15 with a light green wire as Tach out.

[csracer]

My meagasquirt II directly controls and fires the coil pack with dual Bosch BIP373 coil drivers. Mike doesn't use the FAST eDist, he went the Ford EDIS-4 module route, which interfaces with the FAST but the EDIS-4 Module controls and fires the coil pack.