MSII (3.57) Coil Neg Triggering Question

[Tennesseejed]

I installed MSII (v.3.57) yesterday in my NA '75 280Z. The car has a Stage III cam and stock bottom end. 240SX throttle body. GM IAT and CLT sensors. No MAP sensor. LC-1 wideband installed. Fuel algorithm is set Alpha-N.

 

I am trying to run fuel only off of a coil negative trigger. Ignition is MSD 6A. I have spark. Plugs are dry.

 

I have comms with the MSII box and have burned a startup .msq including all of the known variables. Req_Fuel is 10.9 on turbo Z injectors. TPS tests correctly. Sensors have been calibrated (though my IAT temperature reading is 30 degreees high).

 

When I crank (set to 300), I do not get a tach reading on MegaTune. I have tried different variations on wiring the MSD 6A box. I have not wired MSD 6A according to Megamanual because I am not using MS to run ignition. MSD 6A is triggered off of dizzy VR and is wired to drive the coil directly. Tried using the MSD 6A tach output to signal MS without success.

 

Despite searching, I have not found in the literature what signal MS is looking for when triggering on coil negative. I suspect it looks for 12V going to ground when an ignition event happens. And I believe the problem is that the MSD box does not put 12V on the ignition coil until an ignition event. I ran MSD 6A with the stock FI box using a MSD 8910 adapter last year. However, this set up does not effectively trigger MS.

 

I am also uncertain if I should to use "Fuel Only" or "Basic Trigger" in the Tach Input/Ignition Setting box.

 

I'll try to attach start up datalogs, but right now I'm getting an error that says I can't upload these kind of files (XLS).

 

Appreciate any thoughts.

 

Edit: I wired coil neg to Pin 2 on DB37, but did not wire the positive side to Pin 24. Is this required? There is very little in Megamanual about running fuel only off of a coil negative trigger. The stock FI box ran off a coil neg input only, so I didn't think MS would require wiring Pin 24.

Edited May 23, 2010 by tennesseejed

[Zmanco]

I'm not sure I follow all of your description but I think you said you're using the MSD box to drive the coil and only want to use MS for fuel. Correct?

 

The problem with triggering MS off of the coil in your setup is that MSD generates multiple sparks per ignition event at lower RPM. (MSD stands for Multiple Spark Discharge).

 

Try using the tach out wire from the MSD box (white wire IIRC) to trigger MS. Dig around on the MS site to find how they recommend you build the input section of the board. It's been a few years since I ran that way and I'm afraid I don't remember the details.

[Tennesseejed]

Thanks for the reply Zmanco.

 

I'm not sure I follow all of your description but I think you said you're using the MSD box to drive the coil and only want to use MS for fuel. Correct?

 

Correct. I was originally going install EDIS, then MS3X came out. I couldn't find a MS3 board to buy, so I'm going to run fuel only and transition to sequential fuel and spark down the road.

 

The problem with triggering MS off of the coil in your setup is that MSD generates multiple sparks per ignition event at lower RPM. (MSD stands for Multiple Spark Discharge).

 

Even so, I was getting no tach signal in Megatune or Tuner Studio.

 

Try using the tach out wire from the MSD box (white wire IIRC) to trigger MS. Dig around on the MS site to find how they recommend you build the input section of the board. It's been a few years since I ran that way and I'm afraid I don't remember the details.

 

I had tried MSD tach output without sucess. What I did incorrectly, though, was to wire the tach output to Pin 2 (sensor - ) and not Pin 24 (sensor + ). After your response I wired the MSD tach output to Pin 24 and was able to get the car started.

 

Thereafter the car ran - badly - for about 5-8 minutes at very high idle. I've got a mechanical timing issue because my friend was not able to see the timing mark while the car was running. I'll tackle that tommorow.