NefMoto

What is the converted value range of the cold start factor map FKSTT? My definition says X/1024 (this is from a publicly available damos for ME7.9.10), which gives a factor of 34.5 for -30 degrees C up to factor 1.38 at 90 degrees. Is that right? I would expect a quarter of the values, if not 1/8, at least in the lower ranges. Confused a bit...

This thread is a perfect example of what happens when you have more experience with ECU's than engines.

The factor is completely right, at that low temperature barely any of the fuel atomizes. The majority of it simply makes a puddle and gets washed down the bore.

Probably true (about the experience), nevertheleas, my previous car had only 5 as much fuel at -40 compared  to warm for cranking, not 20+ like here, so the question is justified.

Almost every ECU I have seen has a huge factor at -40C, this is nothing to do with the engine or car, it is done with simple physics - at -40C only 5-10% of the fuel atomizes, the rest goes into a puddle.

I surely believe that, the maps I have seen for SAAB (I use them for E85 reference) give a factor of ~20 (this is still not 34 though :)) for freezing cold, 50 for E85 (50 being max I believe for those systems, because the map is 50 flat downwards of -10 C). From what I read E85 is a bitch to get the cold engine started on, essentially only the gasoline contained in it contributes.

What puzzles me now is how come the old ECU I mentioned (beginning of 90s technology) had only 5x injection time over warm, and the only conclusion I have is that it had a totally different start-up procedure and did not have per injection / engine speed gain based reduction, so I can only assume that starting at -40 would take a lot more of cranking than on a more modern ECU.

Anyhow, I sorted out most of the things I wanted to.