Adaptation of skip fire calibration to vehicle weight

1. A platform powered by a skip fire controlled internal combustion engine having a plurality of working chambers that provide motive power capable of moving the platform comprising:

a sensor or model that outputs a signal indicative of a weight of the platform; and

an engine controller that determines a skip fire profile which includes an operational firing fraction and a working chamber load, wherein engine operation at the skip fire profile produces an acceptable level of noise, vibration, and harshness and results in combustion conditions in fired working chambers closer to an optimal combustion condition as compared to any other possible skip fire profile, wherein the skip firing profile is adjusted based at least in part on the signal indicative of the platform weight.

2. The platform of claim 1 , wherein the platform is selected from a group consisting of a motor vehicle, a tractor trailer, a tractor, a delivery truck, a locomotive, a ship, and an aircraft.

3. The platform of claim 1 , wherein the allowed working chamber load increases as the platform weight increases.

4. The platform of claim 1 , wherein the skip fire profile delivers an engine output that substantially matches a requested engine output.

5. The platform of claim 4 , wherein the skip fire profile delivers the requested engine output at the best fuel economy of any possible skip fire profile.

6. The platform of claim 1 , wherein the internal combustion engine is a spark ignition engine or a compression ignition engine.

7. The platform of claim 1 , wherein the internal combustion engine is located in a first unit and the first unit pulls a second unit, the second unit being connected to the first unit through a coupling that allows the second unit to track the first unit through turns.

8. The platform of claim 1 , wherein the model uses as an input a measured fluctuation in the rotational speed of a rotating element.

9. The platform of claim 1 , wherein the internal combustion engine is mounted to the platform.

10. A method of operating a skip fire controlled internal combustion engine having a plurality of working chambers that provide motive power capable of moving a platform comprising:

receiving a signal indicative of a weight of the platform; and

determining a skip fire profile which includes an operational firing fraction and a working chamber load, wherein engine operation at the skip fire profile produces an acceptable level of noise, vibration, and harshness and results in combustion conditions in fired working chambers closer to an optimal combustion condition as compared to any other possible skip fire profile, wherein the skip firing profile is adjusted based at least in part on the signal indicative of the platform weight.

11. The method of claim 10 , wherein the selection of the operational firing fraction is based on at least one table indicative of allowable firing fractions for a set of engine operating parameters and performing a vehicle weight adjustment of the at least one table.

12. The method of claim 11 , wherein a correction factor to the at least one table is selected based on the vehicle weight.

13. The method of claim 10 , wherein the selection of the operational firing fraction is based on a set of tables for different vehicle weight ranges and a selection is made of at least one table of the set of tables based on the vehicle weight.

14. The method of claim 10 , wherein the selection of the operational firing fraction involves selecting a lookup table, from a plurality of lookup tables, based on the vehicle weight.

15. The method of claim 10 , wherein the selection of the operational firing fraction is based at least in part on a system excitation model of a coupling of engine excitations into a vehicle cabin as a function of the vehicle weight.

16. The method of claim 10 , wherein the optimal combustion condition is based at least in part on operating the engine in the most fuel-efficient manner.

17. The method of claim 10 , wherein the optimal combustion condition is based at least in part on an air/fuel ratio or aftertreatment element temperature.

18. A method of adjusting a powertrain parameter of a powertrain whose value had been previously determined in a calibration procedure with a baseline vehicle weight comprising:

operating an internal combustion engine to provide a requested torque to the powertrain using a skip fire profile that operates all fired working chambers of the internal combustion engine at combustion conditions closer to an optimal combustion condition as compared to all other skip fire profiles that provide the requested torque and operate at an acceptable noise, vibration, and harshness level;

determining a current vehicle weight; and

adjusting the powertrain parameter based at least in part on the current vehicle weight.

19. The method of claim 18 , wherein the powertrain parameter is selected from a group consisting of a powertrain slip, an operational firing fraction, and a cylinder load.

20. A method of selecting an operational skip fire profile suitable for use in operating an internal combustion engine having a plurality of working chambers in a skip fire manner to produce a desired engine output, the method comprising:

determining a desired engine output;

monitoring a vehicle weight; and

selecting a plurality of candidate firing fractions from an allowed list of firing fractions;

calculating a candidate cylinder load for each of the plurality of candidate firing fractions such that the combination of the candidate cylinder load and each associated candidate firing fraction substantially yields the desired engine output, each such combination being a candidate skip fire profile; and

selecting one of the candidate skip fire profiles as the operational skip fire profile, wherein the selection of the operation skip fire profile depends at least in part on the vehicle weight; and

operating the internal combustion engine with the selected operational skip fire profile.

21. The method of claim 20 , further comprising:

determining which of the candidate skip fire profiles operates with a working chamber load closest to optimal combustion characteristics; and

selecting the candidate skip fire profile which operates with the working chamber load closest to optimal combustion characteristics as the operational skip fire profile.

22. A skip fire engine controller for an internal combustion engine mounted to a vehicle comprising:

a lookup table, wherein the lookup table is embodied in a computer readable media and includes table entries that indicate different maximum allowable cylinder loads at different engine speeds, transmission gears, firing fractions, and vehicle weights;

a skip fire profile module that is arranged to determine an operational firing fraction suitable for delivering a requested engine output using the lookup table to determine the operational firing fraction; and

a firing controller that is arranged to direct firings in a skip fire manner that delivers the operational firing fraction.