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Correction factor for coolant temperature

EFI Tuning Fundamentals

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Is there a phormula to calculate the correction factor in accordance with the coolant temperature?

for fuel or spark or...?

Hello, the correction it´s for fuel .


The short answer is, you need a sophisticated model that accounts for the geometry of the port, temperature, spray pattern, etc. It's not worth the trouble trying to calculate it and you're better off using a known good basemap as a starting point.

The detailed answer is, it varies a lot with the fuel and the injection method. You could broadly categorize the correction factor as accounting for two things:

1) poor vaporization of the fuel, especially on port injection. Extra fuel sticks to the walls and you need to account for that somehow.

2) extra fuel needed to stabilize the combustion because the engine doesn't burn so well when it's cold.

If you have a port injected engine you are going to need a lot more additional fuel, especially with high ethanol content (E85-E100 is known for poor starting and cold idling due to poor ethanol vaporization). If it's just port injection of normal E0-E10 fuel you still have to account for some seasonal variation in fuel blend. If you have direct injection there's no real concern for vaporization due to the high fuel pressures.

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