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Idle Spark tables/ HPT?

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Old May 13, 2007 | 03:33 PM
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Country Boy's Avatar
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Default Idle Spark tables/ HPT?

What table is used at idle the most? Is it the HO spark table or the "Idle spark advance" table? If its the latter, then why are there so many cells, when "Idle" can only be but maybe the first 2 rows and 5 columns? Also, when does the switch to the idle state occur, is it when the motor reaches its target idle RPM or speed based?
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Old May 13, 2007 | 04:25 PM
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idle to humans is a state. to the computer it is an 'area' of airmass, map, rpm, speed and other stuff... look around for other parameters and you'll find the paramters that have to be meet for the computer to identify as the idle state. usually it's when the car is under 2-3mph with 0% TPS. that means the coming to a stop but still moving counts as idle. it needs to know which state it's in to decide which tables to use. once it's in idle state it uses things like RAF and cracker and follower to get info about airflow, and then uses that airflow to determine airmass, which determines spark from the idle spark table. but because of idle's special needs it also uses commanded rpm vs real rpm to figure out if it's under or overshooting, and then it can use spark to correct it.

just look around in the editor and just see how many more tables there are for idle, and what are the triggers that officially mark the 'idle' state. it's also a good set of parameters to know to filter out data for VE tuning if you come to a stop, as the airflow is dictated by more than just the VE table.

the fact that to you idle is just few cells, it doesn't mean it would be the same cells for others. obvieously my z06 cammed stock cube motor is going to idle at a very different map/rpm than a race only big cube motor. thanks to the bigger, more flexible tables with a large range of values, you can hopefully describe whatever conditions you experience in your setup.
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Old May 13, 2007 | 04:36 PM
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Thats why I was curious because the idle spark tables use the whole VE range and up to 4800 RPM, I was curious as to why such a big area for just the idle regions. Also, when the RPM corrolates to the same idle condition ( MAP and RPM are "Idle state" such as a 6 speed) but the speed is above 2mph, I wasnt for sure what table was used, but I see now. ALL idle requirements have to be met to be considered "idleing".

I know different combinations are going to need different idle parameters, but I was just unsure exactly when Idle spark tables were used, if it was RPM, MAP, or speed based.
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