I noticed that the VE values (amount of fuel required for correct air-fuel-ratio) is different at night versus the day time. There are two possible reasons for this: voltage (lights on at night), or temperature. Generally when the weather is warm (extreme was the Abingdon track day where air inlet got to 52degC) the engine runs lean. This is the opposite of what might be expected and indicates that the ECU is correcting for temperature but over-doing it.
The view is that I have a problem with heat-soak into the sensor. Basically instead of the sensor measuring the air temperature it measures the air-box temperature. This isn't aided by the fact that my airbox is a chunk of aluminium behind the radiator. So, when the air-speed is high the air is much cooler than expected (and so denser) and hence the AFR is too high (which could cause engine damage if not sorted).
The gsxr600 sensor (from 2001-2003) is a solid brass affair which takes ages to warm/cool. This is not the best, and more recent sensors (especially for turboed engines) are designed to have low thermal mass.
I made a sensor based on a gsxr600 mechanicals, and maplin thermistor and some epoxy filler.
I recalibrated the ECU for this new sensor (resistance values in photo) and it seems to work fine. Note: don't try to upload to the Megasquirt unless your battery is putting out a decent number of volts.
I am keen to get tuning again and hopefully the AFR will be nice and stable.
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