Anyone out there still running a MSD 8731?

Billy, you are going to have to tell us more about the setup. Probably the easiest thing is for you to email me the 8973 setup file so I can look at it. Send it to mike.c@mindspring.com. Do you have a file saved from before you changed the timing and one when you changed the timing?

Questions
1. How is the Launch Retard Graph setup. Do you have zero degrees in it or what?
2. How is the Run Retard Graph setup. Do you have zrero degrees in it or what?
3. Do you use any Step Retards or Launch Retards
4. Do you use the Time Retard graph
5. Is the MSD 8973 dark blue wire hooked up to your clutch switch?

If you hook a laptop up tto the 8973 and turn power on to the 8973 then what retards are showing "ON" in the Monitors in the upper left corner of the screen?

 

Billy sent me his file and I looked at it and this is what happen. Don't feel bad because you are the second person today that has had this problem.

You put your timing retard change all in the Run Retard Curve Graph. Let me explain the Launch Retard and Run Retard Curve graphs. It would actually would have been easier if MSD had called the Launch Retard Curve Graph the First Gear Retard Graph and called the Run Retard Curve Graph the 2nd & 3rd Gear Retard Curve Graph. The Launch Retard Curve is only for first gear and when you shift to second gear the 8973 switches to the Run Retard Curve. The problem is that when you start the car up it is automatically in the Run Retard Curve (don’t know why MSD designed it that way). When you hit the transbrake or push in the clutch pedal you apply 12 volts to that dark blue wire in the 8973 and it resets the 8973 into what I call the “Ready Set & Go Mode” which is resets the shift lights into first gear and switches from the Run Retard Curve to the Launch Retard Curve. The 8973 then uses the User set Shift Light RPM for the Shift Light and the User set Drop RPM to know it has shifted and switches to the Run Retard Curve when you shift.

So what happened is that you put all 7* retard only in the Run Retard Curve and 0* in the Launch Retard Curve. So when you started the car you had the 35* minus the 7* so you had the 28* you wanted BUT if you hit the transbrake and the 8973 switched to the Launch Retard Curve it jumped back to 35* because you had 0* in it. So if you were going to launch with the expected 28* you didn’t and you had the 35* so you overpowered the track.

The other problem is that because you are using a shift light not on the 8973 you have the Shift Light RPM in the Data Editor set to 12500 RPM and you never got to that RPM and the 8973 thought you were in first gear for the whole run. So you actually never changed from the Launch Retard Curve to the Run Retard Curve and the whole run was done at 35*.

Recommendations.
1. If you want to be able to pull timing out for the entire run then take one of the three Step Retards and hard wire it to the same 12 volt switching power for the 8973. Now anytime the 8973 is turned on then that Step Retard is active. Say you wired Step Retard 3 to 12 volts. Now you just put 7* into Step Retard 3 and it will pull that out of the box for the whole run or you can adjust it quickly to any retard. Also if you check the timing and you find it is 1* off then adjust the amount of retard in the Step Retard so you don’t have to change the crank trigger or the mag everytime. It is probably better in your case to put 2* in the step retard and then set your timing to 35* so you can adjust the timing either side of 35*. You use that Step Retard like a plug in timing chip.
2. Put 0* in both the Launch Retard and Run Retard Curves so it is not looking for a shift to change curves.
3. If you do want to use either the Launch Retard Curve or the Run Retard Curve then you are going to have to put your shift rpm into the 8973 Data Editor Shift Light so it know you are shifting.
4. If you do use either or both the Launch Retard Curve or the Run Retard Curve then before you check or set the timing with a timing light you need to hit the transbrake once or push the clutch pedal in once.