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Old 07-11-2008, 09:52 AM   #1
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Default Idle valve frequency settings???

I keep rereading the section of the manual shown below, & reading posts that mention Idle valve frequency, but I can't seem to find or understand how to know what this setting should be.
The formula's seem to refer to how to do everything except determine what the "desired frequency" should be.

From manual: @
Idle valve frequency This is generally something most people will not need to mess with, however, different idle valves are designed to work best at specific operational frequencies. Note that the Frequency of actuation is 1000 / this value (255 is a good starting point)

Please Note: true DUTY CYCLE% = Lower or Upper dc * 100 / Idle Valve Frequency value example Freq value - 200 = 50 Hz operation, a DC value of 80 = 80*100/200 = 40% true duty cycle

While most valves operate at 100 hertz, some older style 2-wire valves will work better at frequencies as low as 39 hertz. There is an inverse relationship between frequency of operation and control precision because of the algorithm Used to control the PWM output. Lower frequencies have more steps between dc values. 100hz operation has 100 steps and therefore has 1% control steps. 50hz operation has 200 steps and has 0.5% duty cycle steps and that is why the duty cycle values put into MT need to be double the true DC% value.
Some valves may emit a buzzing sound which can be eliminated by increasing the frequency above 100 hertz.

There is a formula for modifying the idle valve frequency. The formula is '10000/desired frequency = x where x is the variable you input in MegaTune. For example '100' would be 100 hertz, and '50' would be 200 hertz
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Old 07-11-2008, 09:53 AM   #2
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i would start with what Diyautotune has loaded in their base maps.
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