Engine Manufacturer Variables: Notes

Engine manufacturers create variables that affect engine ECM data. The definition of idle time, time in high gear, and time in cruise control vary among manufacturers. (They may even vary from model-to-model or year-to-year for engines from the same manufacturer.) Depending on the manufacturer, ECMs may or may not be able to measure the time a vehicle travels above the company-specified speed limit. The presence or absence of a real-time clock creates data sets that may be difficult to compare. For engine ECMs with real-time clocks, time setting is another variable (e.g., Central Standard Time, Pacific Standard Time, Eastern Daylight Time, etc.) Power Take Off (PTO) time and deceleration rate (panic stop) are other variables that are also defined differently by manufacturers. Fuel variables directly impact ECM data also. Engine manufacturers may not correct for fuel temperature, fuel viscosity, air in the fuel, or fuel energy content in the same manner. The possible variations among different engine manufacturers' corrections may significantly affect comparisons based on ECM data.