Few Questions about MAP display.

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Few Questions about MAP display.

Postby Nath88 » Sun Oct 22, 2017 6:20 pm

Is the MAP value shown by TunerStudio and in datalogs the instantaneous value, or is it the resultant value from the MAP sample routine?
Is the table switch status (switched on MAP) in the Microsquirt itself from the instantaneous value, or the value from the MAP sample routine?
Is the table switch status (switched on MAP) in TunerStudio from the instantaneous value, or the value from the MAP sample routine?

The reason I'm asking is that I'm using an 'exhaust pulse sensor' (piezoelectric microphone) on the MAP input of the Microsquirt to trigger table switching. It is calibrated so ADC 0V = 0kpa, ADC 5V = 100kpa. The signal with no input is 50kPa. When the engine fires, there is a rapid exhaust pressure rise and the input (inverted) to the microsquirt drops to between 0 and 25kPa depending on the strength of the pulse. When the engine misfires the peak is much smaller, somewhere between 30 and 50kPa. Table switching is set to >25kPa, so when the engine is firing VE1 is used, when it misfires VE3 is used, so I have 'firing' and 'misfiring' fuel tables.
See attached MAP logger screenshot, I later increased the MAP window from 30 degrees to 45 to sample the full pulse, but what is seen here is 2 firing pulses followed by a misfire. The exhaust port opens around tooth number 10.

20171022_205516.jpg
20171022_205516.jpg (127.08 KiB) Viewed 107 times


What I've noticed is in a continuous firing mode, the MAP logger shows the negative peaks consistently between 0 and 25kPa and within the sample window, as expected. However on the datalog, the fuel table switch bitfield swings between high and low, where it should be constantly low, and the MAP value varies between 0-90kPa, where it should be between 0-25kPa, so I suspect both values are not based on the values the MAP sample routine output.

For information it's a 2 stroke engine, when the engine is firing the airflow increases dramatically due to the wave energy in the exhaust system, so the wave amplitude is a very useful input to the fuel calculation, and changes from cycle to cycle.

Thanks
Yamaha YZ250 - Microsquirt V3 - Madhu PWM Fuel Pressure Regulator - 14point7 Spartan Lambda Controller 2
Nath88
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Re: Few Questions about MAP display.

Postby Matt Cramer » Tue Oct 24, 2017 6:47 am

Regular logs are post-sampling. High speed logs are pre-sampling.
Matt Cramer
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