Quote:
Originally Posted by winders
Air temp is not a proxy for fuel temp. Fuel temperature affects fuel density so an EFI system monitoring fuel temp can compensate for changes in density. Changes in fuel pressure need to be compensated for as well.
A closed loop EFI setup can compensate for only so much variance. Changes in air density, air temperature, fuel temperature, and fuel pressure can easily exceed the limits of compensation when running in closed loop.
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I stand corrected, the MegaSquirt2 ECU has limited capabilities which in turn limit its capabilities to control AFR, see below from a quick AI search of the internet:
Fuel temperature and intake air temperature are often different in an engine's fuel injection system due to several factors:
Heat Transfer: Components within the fuel injection system, such as fuel lines, pumps, and injectors, are located near the engine's heat sources (like the engine block and exhaust system). This heat can be transferred to the fuel, raising its temperature.
Fuel Recirculation: Many fuel injection systems have a return line that sends unused fuel back to the fuel tank. This recirculated fuel has been heated by being in the engine compartment and can increase the temperature of the fuel in the tank and lines.
Intake Air Source: The intake air is drawn from the ambient environment, often through a cold air intake system designed to minimize its temperature, to improve air density.
Different Paths: Fuel and intake air travel through different parts of the engine compartment. The fuel path is near the engine, while the intake air path is typically routed to avoid heat.
Ambient Conditions: The temperature of the fuel in the tank is affected by the ambient air temperature, whereas the intake air temperature is directly influenced by the ambient air temperature at the point of intake.
These factors contribute to a difference between the fuel temperature and the intake air temperature, even though both can be influenced by the external environment. The ECU monitors both temperatures to ensure the correct air-fuel mixture is delivered for optimal performance and emissions control.