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Old 11-05-2006, 12:21 AM   #1
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Default Ignition tables

I don't understand these MS ignition tables that are on some of the stock tables in the settings thread. How is it that all of your tables have values above 20 and sometimes 30. I though 10-15 degree advance was the most that was safe on pump gas. Also on my VE table at idle right now the cell is 57. I assumed thhat meant 57% duty cycle which seems rediculous. In my datalog the actual duty cycle is around 6%. Could someone explain to me how MS runs these tables?

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Old 11-05-2006, 01:39 AM   #2
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Well first off its great to see another MS miata, let me clear up some of your misunderstandings:

Timing: On our stock miata, you have heard that you can bump up the timing a bit for extra power but not more 15 degrees base timing usually on pump gas. The key word here is "base timing". That is how many degrees your spark plugs are firing before the piston gets to the top. In theory, there is a timing that is optimal for power and efficency, but it changes as rpm, load and other factors change. Sometimes that means 10* and sometimes that means 30* and everywhere inbetween.

VE Table: This is Volumetric Efficency. This literally means the efficency of the motor to pull in air, the higher the better. There are many, many factors involved and it is more complicated than you may imagine. As an example, smaller intake ports usually will increase VE on the low end of the rpm range because it will increase velocity, but it becomes a bottleneck at higher rpm. The numbers you see on Megasquirt are close, but not The exact VE of the motor.

Basically, get a wideband and tune for the AFR you want. Higher VE = MS believes more air is going in = More fuel put in at that point = you can make it a bit more rich at that point.
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