I have always had an occasional hard start issue. Not knowing exactly what was causing it, I went around in circles changing settings to try to isolate it. Finally I went back to the manual, not realizing that it has been revised a few times since I last read it.
Went digging around in the (revised) Megatune manualfor a solution to this problem, and after reading for a while I finally found something.
Basically, I had the tolerances set way too low, and so while cranking and starting, MS was throwing out too many signals, making it really hard to start reliably.Next Pulse Tolerance (%) (PulseTol) is the tolerance during which the next pulse is not allowed to count as a 'true' pulse, and is counted as a false trigger. These allow the code to have some way of knowing that the tach pulses are not arriving in a manner consistent with the configuration. The tolerance is a check on the percentage change in times between tach pulses, or between teeth if using an M-N missing-tooth wheel.
The next pulse tolerances are designed to 'catch' errors and adjust the tach/tooth count (or reset the ignition) when an error occurs. Note that unlike the next pulse tolerances, the time and percentage masking above is designed to prevent false triggering that would create additional tach events that were false.
So if the time between the last two events is X, then if then next pulse occurs within X-PulseTol, it is rejected as a false trigger. If a pulse is NOT received after X+PulseTol, a tooth is assumed to have been missed. This only occurs after the first few pulses (as specified in the Skip Pulses). In later versions of the MS-II code, the next pulse tolerance can be set under three different conditions:
Cranking: This is the next pulse tolerance while cranking (enginebit=3) - it should be set fairly high. This is because the starter motor speed can vary quite a bit, depending on the compression and which cylinders happen to reach firing conditions first, etc.
After-start: This is the next pulse tolerance while afterstart enrichment is active, and it should be lower than the value while cranking.
Normal Running: This is the next pulse tolerance once afterstart enrichment ends, and it should be the lowest of the three (since the engine speed is more stable in normal running conditions - there's more rotational inertia, and fewer variations in things like air/fuel mixtures. As well, if you have a VR sensor, the signal is stronger, etc.)
I have had much smoother starting with the following settings
Cranking % = 95
Afterstart % = 90
Normal Running % = 85
Somehow I misunderstood these settings and had them reversed. I had cranking set to 30, Afterstart set to 20, and running set to 10.
My theory, so far seeming true, is that the stock CAS produces very little noise, compared to a VR wheel or possibly even a Hall sensor, so only a small percent of the signal should be considered noise. Almost anything that comes across the signal should be considered a true trigger event, due to the design of the optical system.
I have not attempted using a 100 % setting yet, but I doubt that it would have adverse effects.
I have not noticed any adverse effects to having these settings set this way on my car So Far, but Please use your best judgement before changing your settings. Hope this helps someone
Happy tuning