Systems and methods for characterization of aged fuel for an engine cold start

A method, comprising:

• in response to an engine start request during a cold start condition,
• estimating a volatility of fuel stored in a fuel tank using a physics-based model;
• determining a confidence in the estimated volatility based on a duration of engine inactivity, the confidence being a probability that a current fuel temperature is within a determined range;
• and
• adjusting an injection amount and an injection timing of fuel delivered to the engine from the fuel tank based on the estimated volatility and the determined confidence, a degree of adjustment to the injection amount and the injection timing increasing as the determined confidence increases.

A system for a vehicle, comprising:

• an engine including a plurality of cylinders, each cylinder including a spark plug and a fuel injector for delivering fuel;
• a fuel system, including a fuel tank for storing the fuel;
• an evaporative emissions system in fluidic communication with the fuel system, the evaporative emissions system coupled to atmosphere via a vent;
• an ambient temperature sensor coupled to an intake passage of the engine;
• an ambient pressure sensor coupled to the intake passage of the engine;
• an engine coolant temperature sensor coupled to a cooling sleeve of the engine;
• and
• a controller holding executable instructions in non-transitory memory that, when executed, cause the controller to:
• determine an engine cold start condition based on an output of the engine coolant temperature sensor and an engine start request;
• estimate a vapor pressure of the fuel in response to the determination of the engine cold start condition using a physics-based model that relates a temperature of the fuel to an evaporative percentage of the fuel via an empirically determined fuel distillation curve, the empirically determined fuel distillation curve selected from a plurality of empirically determined fuel distillation curves stored in the non-transitory memory;
• and
• adjust a pulse width and/or timing of signals sent to the fuel injector and the spark plug based on the estimated vapor pressure and an engine-off time.