Methods and systems for determining effective steady state flow rate for fuel injectors

1. A method implemented in a fuel injection system comprising a plurality of injectors coupled with a common rail, the common rail coupled with a pressure sensor, and the pressure sensor coupled with a processor, the method comprising:

identifying, by the processor, one of the injectors to calculate a pressure change rate of the common rail associated therewith;

receiving, by the processor, pressure measurements of the common rail from the pressure sensor before and during an injection event within a measurement window;

using, by the processor, a pre-injection mean pressure of the common rail to determine a rail pressure drop range that is specific to the identified injector; and

calculating, by the processor, the pressure change rate associated with the identified injector based on the pressure measurements of the common rail taken during the rail pressure drop range.

2. The method of claim 1 , further comprising:

estimating, by the processor, an effective steady state flow rate of the identified injector based on the calculated pressure change rate associated with the identified injector.

3. The method of claim 2 , further comprising:

calculating, by the processor, a plurality of pressure change rates associated with the plurality of injectors; and

estimating, by the processor, a plurality of effective steady state flow rates of the injectors based on the plurality of calculated pressure change rates associated with the injectors.

4. The method of claim 3 , further comprising:

calculating, by the processor, an average effective steady state flow rate based on the plurality of effective steady state flow rates; and

using, by the processor, the average effective steady state flow rate to determine an error in the estimated effective steady state flow rates of the injectors.

5. The method of claim 3 , further comprising:

using, by the processor, the effective steady state flow rates of the injectors in an injector control algorithm.

6. The method of claim 1 , further comprising:

estimating, by the processor, a percent change in an effective steady state flow rate of the identified injector relative to a nominal steady state flow rate of the identified injector based on the calculated pressure change rate associated with the identified injector.

7. The method of claim 1 , wherein the rail pressure drop range is determined using a first pressure drop and a second pressure drop greater than the first pressure drop.

8. The method of claim 1 , wherein the pressure measurements of the common rail are taken in a non-hovering zone of the injector in which an injected fuel amount thereof does not initiate hovering of a lower plunger in the injector.

9. The method of claim 1 , further comprising:

determining, by the processor, that a suitable condition is met to receive the pressure measurements, wherein the condition includes at least one of the following:

(1) an engine coolant is within a required temperature range,

(2) a pressure of the common rail is above a minimum threshold,

(3) an injected fuel amount is above the minimum threshold, or

(4) any potential pumping events which would overlap with the measurement window are disabled.

10. The method of claim 1 , wherein the pressure measurements are received at a frequency which provides the processor with enough datapoints to identify a sufficiently linear pressure decline in the pressure measurements for calculating the pressure change via a linear regression.

11. A fuel injection system comprising:

a common rail;

a pressure sensor coupled with the common rail;

a plurality of injectors coupled with the common rail; and

a processor coupled with the pressure sensor and a non-transitory computer readable medium storing thereon instructions that, when executed by the processor, cause the processor to perform the method according to any one of claims 1 through 10 .

12. A vehicle comprising:

a fuel injection system according to claim 11 ; and

an engine coupled with the fuel injection system and comprising:

a crankshaft, and

a plurality of cylinders coupled with the crankshaft via a corresponding plurality of connecting rods, the plurality of cylinders including a plurality of pistons configured to cause the crankshaft to rotate via the plurality of connecting rods in response to receiving fuel from the plurality of injectors.

13. The vehicle of claim 12 , wherein the processor is an on-board processor physically coupled with the pressure sensor.

14. The vehicle of claim 12 , wherein the processor is a remote processor communicably coupled with the vehicle via a wireless communication network and is configured to receive the pressure measurements of the common rail from the pressure sensor via a secondary on-board processor physically coupled with the pressure sensor.

15. The vehicle of claim 14 , wherein the non-transitory computer readable medium is a remote data server.