Hello all. The F3 controller has MSD etched next to the etched serial numbers, so I'll assume that it was produced for an MSD ignition output. The RPM signal is very erratic! Here is some data logging (engine speed should be ~4000 RPM) Speed Press Throt Cool Baro Air T Bat V Trim Inj T Range Time rpm psi % °F psi °F Volts ±% mS Bar 8000 4.6 58 126 12.6 144 15 0 10.75 8 17 00:09.3 8000 4.4 64 123 12.6 144 15.1 0 11.84 8 17 00:09.4 4100 4.9 69 123 12.6 141 15.1 0 11.9 5 18 00:09.6 8000 5 70 119 12.6 144 15.1 0 11.39 8 18 00:09.7 8000 4.9 70 130 12.6 148 15.1 0 9.79 8 18 00:09.9 8000 4.9 70 130 12.6 151 15 0 9.22 8 18 00:10.0 4000 4.4 70 134 12.6 155 15.1 0 8.58 5 17 00:10.1 8000 4.3 70 137 12.6 155 15.1 0 8.19 8 17 00:10.3 8000 4.4 70 141 12.6 158 15.1 0 7.81 8 17 00:10.5 8000 4.4 70 141 12.6 158 15.1 0 7.62 8 17 00:10.6 3900 4.6 70 141 12.6 162 15.1 0 7.42 5 17 00:10.7 8000 4.4 70 144 12.6 165 15.1 0 7.17 8 17 00:10.9 8000 4.3 70 144 12.6 162 15.1 0 7.23 8 17 00:11.1 8000 5 70 144 12.6 162 15.1 0 7.36 8 18 00:11.2 3600 4.3 70 141 12.6 165 15.1 0 7.1 5 17 00:11.3 8000 4.4 70 144 12.6 165 15.1 0 7.1 8 17 00:11.5 With the HEI (no MSD), I got some erratic RPM signal. Speed Press Throt Cool Baro Air T Bat V Trim Inj T Range Time rpm psi % °F psi °F Volts ±% mS Bar 4800 5.7 67 141 12.6 109 10 0 12.67 6 18 00:08.3 4800 6.1 68 141 12.4 109 14.1 0 13.44 6 19 00:08.4 4100 4.1 68 151 12.4 116 14.6 0 12.93 5 17 00:09.0 4500 5.4 66 144 12.6 116 8.5 0 12.67 6 18 00:09.1 4700 5.4 66 141 12.4 112 14.1 0 12.67 6 18 00:09.2 4800 5.7 66 141 12.4 112 10.9 0 12.16 6 18 00:09.3 4800 6 66 144 12.6 116 14.1 0 11.39 6 19 00:09.4 4800 6 66 144 12.6 119 15.1 0 10.88 6 19 00:09.5 4700 5.7 66 148 12.4 123 15.3 0 10.5 6 18 00:09.6 4600 5.7 67 151 12.6 123 15.2 0 10.37 6 18 00:09.7 4600 5 68 151 12.4 126 15.6 0 10.5 6 18 00:10.0 4500 5.4 68 151 12.4 123 15.5 0 10.56 6 18 00:10.0 4500 5.4 68 155 12.6 123 15.2 0 10.18 6 18 00:10.1 4500 5.7 68 148 12.6 126 15.5 0 10.18 5 18 00:10.2 4500 5.7 69 148 12.6 126 15.4 0 9.86 5 18 00:10.3 4400 5.2 69 148 12.6 130 15.4 0 9.15 5 18 00:10.4 4400 5.4 68 151 12.4 130 15.4 0 10.24 5 18 00:10.5 4400 4.9 69 151 12.4 130 15.5 0 9.73 5 18 00:10.7 4300 5 69 151 12.4 130 15.4 0 9.73 5 18 00:10.8 Any clues on how to fix this one. I'm using the HEI pickup in a SBC that is supercharged.

UPDATE:

Doing a data log with the engine not running but power applied to the Haltech and MSD is get

0
8000
8000
8000
0
8000
8000
8000
0
8000
8000
8000
0
8000
8000
8000

Hmmmm......

I'm guessing that the MSD is introducing some "noise" that Haltech is picking up and interpreting as RPM. The two boxes are a foot away.

Looked at the power supplied to both controller with an oscilloscope and didn't see any spikes.

Looked at the tach signal of the MSD box and is "square-ish". The wave form rams up to battery voltage, then there is a 0.5 volt dip for each spark, so the roof of the wave looks a little sawtoothish.

With an F7 Haltech, on can select the voltage level that the microcontroller will trigger on, which is 2.5 volts. The F3 Haltech has this capability built in so I'm guessing that 2.5 volts positive edge will trigger the Haltech.