okay. i'm a noob at tuning.. the more i learn, the more questions i have. hopefully my questions will help others, as well. question for today:

exactly why is more fuel needed at startup? without doing any corrections for ECT or air temp, my car used to run at 10.5:1 and works it's way up to 14.7. i feel that is too rich. how much fuel is needed?

 

Cold engine, also there is no fuel at all coming into the engine.. When its idleing you need a little bit of fuel but there is plenty of airflow to carry it.. When its not running there is no airflow and when cranking there is hardly any so you need more fuel to make sure it gets there..

Same reason that carb'd engines use a choke, instead of adding more fuel they just cutoff alot of the air so that the little bit of higher velocity air is mixing with all the fuel..

 

plus chamber temps are low which means more air molecules per cubic inch.

 

Liquid fuel can't combust (at least not within the normal parameters of ICE operation), only the vapors are combustible. Fuel doesn't vaporize, atomize, and then mix with air as well during cold-start conditions. To ensure that there's enough vaporized fuel to burn, we enrichen under cold-start conditions.

After the engine has had time to run, the engine and fuel are warm enough to more fully vaporize the fuel as it's injected into the air stream.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IN VTEC &raquo;</TD></TR><TR><TD CLASS="quote">Liquid fuel can't combust (at least not within the normal parameters of ICE operation), only the vapors are combustible. Fuel doesn't vaporize, atomize, and then mix with air as well during cold-start conditions. To ensure that there's enough vaporized fuel to burn, we enrichen under cold-start conditions.

After the engine has had time to run, the engine and fuel are warm enough to more fully vaporize the fuel as it's injected into the air stream.</TD></TR></TABLE>

that's what i was looking for. thanks. so, though the a/f is rich, that is not actually the amount of fuel that is burning. i see. so, no matter what, you have to have an excessive amount of fuel at startup. cool. got it.

so, if my A/F was 14.7:1 at startup, i'm actually only buring enough fuel to be equivelent of about 17:1 ( just a random number for illustrative purposes ). is this right? so that would make the car stutter and want to die because, though it reads 14.7:1 it's not burning that much fuel, it's running much more lean.