What is cranking RPM really?

bluetrepidation · Post by **bluetrepidation** » Mon May 22, 2006 5:44 pm

OK I've been pondering this for some time. What is cranking RPM setting on MSII? Is it the point where MS considers any RPM above this cranking? The manual mentions that above 400 RPM is considered running. I ask because my engine cranks at about 270 RPM. It always is hard to start. If I watch my PW gauge it never really transitions like I'd expect from the cranking PW settings. Maybe MS isn't seeing the engine as cranking? Though the cranking indicator does come on. My PW usually sits between 2 and 8 ms depending on how warm the engine is then suddenly jumps to 23 ms and sputters and gulps till it revs up. Maybe I should set my cranking RPM to 200? Or is it a single transition point where anything below 300 is cranking and above is considered running?

Thanks,
A.J.

Bernard Fife · Post by **Bernard Fife** » Mon May 22, 2006 6:10 pm

A.J.

Cranking rpm is the rpm below which MegaSquirt uses the cranking mode. In cranking mode, only the cranking pulse widths (based on the coolant temp) are used to determine the fuelling pulse width. Fuel is injected on every ignition event during cranking mode. It is also the only time flood clear is allowed.

Once above the cranking rpm, the running mode is used, and the MAP, IAT, VE table, etc. are used to determine the fuel pulse width. The fuel is injected based on the number of squirts and alt/simult..

If you engine cranks at 270 rpm, you might consider setting the cranking rpm to 350 or 400 rpm.

Lance.

bluetrepidation · Post by **bluetrepidation** » Mon May 22, 2006 6:58 pm

THANKS. Manual confised me. Cold starts are ok for me but warm is just a pain sometimes. People stare like my car is a POS. I'll take that over running a stock ECU any day.

A.J.

keithmac · Post by **keithmac** » Mon May 22, 2006 11:26 pm

Could be suffering from AIT heatsoak on a hot restart causing lean mixtures?