Setting the Cold Start and Warm-Up Enrichments

If it is cold out, you may have to figure out the cold start enrichments/warm up enrichments right away to keep the engine running until it warms up. If it is reasonably warm out, the default values may be sufficient and you may be able leave the cold start enrichments until you have the VE table and other parameters in a reasonable state of tune.

During cranking mode (defined as when the RPM is less than 400), MegaSquirt produces cranking pulse widths that are calculated by a linear interpolation of two end-point values defined by the user, one at -40°F and one at 170°F. these are set in the warm-up wizard under 'Tuning' in MegaTune. They are called Pulsewidth at -40°F (ms) (CWU) and Pulsewidth at -40°F (ms) (CWH).

A typical setting for a Chevrolet small block V8 with a Tuned Port Injection set-up and 30 lb/hr injectors is 2.0 milliseconds at 170°F and 10.0 milliseconds at -40°F. The optimal values for your combination are likely different, though generally should follow a similar pattern.

During cranking, MegaSquirt-II injects one pulse for every ignition event, so for an 8-cylinder it shoots out 8 times for 720 degrees crankshaft, with all injectors squirting. So with the above values, at 170 degrees, the effective amount of fuel per cylinder is 8 × 2 = 16 milliseconds. For -40°F it is 10 × 8 = 80 milliseconds.

Note that even in a 'piggy-back' application, do not set MegaSquirt's cranking pulse widths to zero. This will cause unpredictable pulse widths up to 13 milliseconds. Instead, set them to 0.1 milliseconds in that application. This allows very little fuel to flow.

Once the engine fires up (defined by engine RPM greater than 300 RPM), the engine goes into after start enrichment (ASE). The after start enrichment starts out at a user-defined percentage enrichment value (typically around 20%), and ramps down to 0% after so many ignition trigger events, which is user-defined (use about 200 for this number to start). This is an enrichment above the normal warm-up enrichment, which is temperature dependent.

I'm having a little trouble with my wolf, I find it starts after about 4 seconds of cranking, but about ever second time I start it from cold, it will have a backfire, sometimes small, sometime bloodly loud.. I'm thinking to much fuel, but havent played with it yet.

shh frank, dont tempt me

prob about 10% less fuel then idle, 18* timing

But there is a "cold crank" setting which is the amount of fuel on cranking. Ive set it at 65% now, but ive tried 0% and 100% but doesnt seem to make sfa difference

....f**k knows what x is