It seems as though WickedESI, Gilee_8, and I have had spark problems using the MSnS code with the MSI ECU on a V3 board sharing the crank sensor with the stock computer. The engine will run ok with just fuel, but hook up spark control and the engine bucks like crazy at 2500+ RPM. The RPM will drop out, spike, and generally freak out when the engine bucks. This seems to happen whether you have internal coil drivers (VB921) or external coil drivers (4G63 transistor). A noisy tach signal (likely related to the stock ECU and unsheilded stock wiring) is probably to blame. More sheilding, different grounding, capacitors, and other fixes don't seem to help. So what is a person to do?

1. Unhook the "TACHSELECT" to "XG1" jumper
2. Unhook the "OPTOOUT" to "TSEL" jumper
3. Build the VR sensor input circuit on the board per the standard V3 assembly instructions (if it is not already installed)
4. Jumper "TACHSELECT" to "VRIN"
5. Jumper "TSEL" to "VROUTINV"
6. Turn the R52 potentiometer (middle of the board) counterclockwise until it clicks (minimum hysteresis)
7. Turn the R56 potentiometer (bottom of the board) counterclockwise until it clicks (setting crossover point at zero)
8. Turn the R56 potentiometer clockwise 8 1/2 turns clockwise (setting crossover point well above zero)

All of this tricks the VR sensor input circuit into reading the stock hall type crank sensor. No software changes are necessary versus using the hall/opto sensor input circuit. The engine should start and the RPM shown on the MS should be accurate and stable. If the engine won't start at all, you should first try to turn R56 counterclock wise a turn. If turning it counterclockwise a couple more turns doesn't do help, you better check out your circuit. If the RPM doesn't read right, but the engine starts, you probably hooked up "TSEL" to "VROUT" instead of "VROUTINV". That makes the RPM display jump in between a normal RPM and twice that number. If you did all of this right, you should not see any tach spikes or drop outs at any RPM or load point. At least for me, I tested 500 to 7500 RPM and 20 inHG vacuum to 15 psi boost. No hiccups, no nothing! Hopefully this works for others.

Corbin

'95 ESI-T
Now with more power and fewer leaks



Gimme fuel...Gimme fire...Gimme that which I desire