Ethanol detection with heated fuel injector in flexible fuel vehicles

1. A method of detecting a percentage of ethanol in fuel used by an engine, the method comprising:

initiating a heating cycle in a component of a fuel delivery system of the engine, the component including a heater;

monitoring the temperature of the heater as a function of time, the heater being operated during the heating cycle;

obtaining the heater temperature at a first time t 1 at which a slope of the heater temperature as a function of time reaches a predetermined threshold value indicative of fuel boiling;

obtaining the heater temperature at a subsequent time t 2 at which the slope of the heater temperature approaches a value of the slope prior to the time t 1 and which is greater than the predetermined threshold value indicative of fuel boiling;

calculating a difference ΔT between the heater temperature at time t 2 and the heater temperature at the first time t 1 ; and

determining the percentage of ethanol in the fuel as a function of the calculated temperature difference ΔT and the first time t 1 .

2. The method of claim 1 , wherein the heating cycle is initiated prior to ignition of the engine.

3. The method of claim 1 , wherein the heating cycle is initiated after a refueling event.

4. The method of claim 1 , wherein the component is a heated fuel injector.

5. The method of claim 4 , wherein the heater heats a body of the heated fuel injector.

6. A method of detecting a percentage of ethanol in fuel used to operate an engine of a flexible fuel vehicle, the method comprising:

initiating a heating cycle in a heated fuel injector of the engine, the heated fuel injector including a heater that is operated during the heating cycle;

monitoring the temperature of the heater of the heated fuel injector as a function of time;

obtaining the heater temperature at a first time t 1 at which a slope of the heater temperature as a function of time reaches a predetermined threshold value indicative of fuel boiling;

obtaining the heater temperature at a subsequent time t 2 at which the slope of the heater temperature approaches a value of the slope prior to the time t 1 and which is greater than the predetermined threshold value indicative of fuel boiling;

calculating a difference ΔT between the heater temperature at time t 2 and the heater temperature at the first time t 1 ; and

determining the percentage of ethanol in the fuel as a function of the calculated temperature difference ΔT and the first time t 1 at which there was a change in slope.

7. The method of claim 6 , wherein the heating cycle includes heating a body of the heated fuel injector over a period of time.

8. The method of claim 6 , wherein the heating cycle is initiated after adding fuel to a fuel tank of the flexible fuel vehicle.

9. The method of claim 6 , wherein the heating cycle is initiated prior to ignition of the engine.

10. The method of claim 6 , wherein a duration of the heating cycle is between 5 and 10 seconds.

11. The method of claim 6 , wherein the percentage of ethanol is determined by the following equation (1): % ethanol in fuel=C+αt 1 −β(ΔT).

12. The method of claim 11 , wherein C is 49.95±2.50, α is 5.22±0.26, and β is 2.8319±0.1416.

13. The method of claim 11 , wherein numerical values of the formula are determined based on an empirical linear regression using experimental data points obtained from known ethanol concentrations of fuel.

14. The method of claim 6 , wherein a margin of error of the determined percentage of ethanol in the fuel is ±15%.

15. The method of claim 6 , wherein the steps of the method are performed by a fuel heater control module of the flexible fuel vehicle.

16. A fuel delivery system of an engine, the fuel delivery system comprising:

a heated fuel injector including a heater and a body that is heated by the heater;

a fuel tank that stores fuel;

a fuel module that delivers the fuel from the fuel tank to the heated fuel injector; and

a fuel heater control module that controls the heater of the heated fuel injector;

wherein the fuel heater control module detects a percentage of ethanol in the fuel used to operate the engine by the method of claim 6 .

17. A flexible fuel vehicle including:

an engine;

a fuel delivery system that delivers fuel to the engine;

the fuel delivery system including a heated fuel injector including a heater that heats a body; and

the fuel delivery system further including a fuel heater control module that controls the heater of the heated fuel injector;

wherein the fuel heater control module detects a percentage of ethanol in fuel used to operate the engine by the method of claim 6 .

18. A non-transitory computer readable medium storing a program that causes a controller to execute a method of detecting a percentage of ethanol in fuel used to operate an engine of a flexible fuel vehicle, the method comprising the steps of:

initiating a heating cycle in a heated fuel injector of the engine, the heated fuel injector including a heater that is operated during the heating cycle;

monitoring the temperature of the heater of the heated fuel injector as a function of time;

obtaining the heater temperature at a first time t 1 at which a slope of the heater temperature as a function of time reaches a predetermined threshold value indicative of fuel boiling;

obtaining the heater temperature at a subsequent time t 2 at which the slope of the heater temperature approaches a value of the slope prior to the time t 1 and which is greater than the predetermined threshold value indicative of fuel boiling;

calculating a difference ΔT between the heater temperature at time t 2 and the heater temperature at the first time t 1 ; and

determining the percentage of ethanol in the fuel as a function of the calculated temperature difference ΔT and the first time t 1 at which there was a change in slope.