MONTREAL, Que. — Relying on fuel efficiency data provided by the engine electronic control module (ECM) may not be good enough when making decisions regarding fuel economy, a new technical report from PIT Group has revealed.
The report examined fuel consumption data from the ECM on several vehicles then compared it to actual fuel consumed. Significant variances were discovered.
“The ability to measure fuel consumption accurately and precisely and defend the results is critical for writing vehicle specifications, for establishing effective maintenance practices, and for training drivers to operate vehicles as fuel efficiently as possible,” said Yves Provencher, director of PIT Group. “Our tests show that engine ECMs present different levels of precision and accuracy, and that ECM data should be used with caution for evaluating the impact of a fuel saving technology or operational practice.”
The study was conducted in the fall of 2014 using 14 different vehicles with engines from four manufacturers. Actual fuel consumed was measured using the Joint TMC/SAE Fuel Consumption Test Procedure Type II protocol. Key findings included:
• Cummins (four vehicles were tested for a total of 24 tests): accuracy from -5.4% to -6.2%, precision from 0.18 to 0.81%;
• Detroit Diesel (seven vehicles were tested for a total of 27 tests): accuracy from -2.6 % to 2.1%, precision from 0.37 to 1.09
• Mercedes (one vehicle was tested, nine tests were conducted): accuracy of -0.9%, precision of 1.59%
• Volvo (two vehicles were tested for a total of 29 tests): accuracy of -3% and 0.9%, precision of 0.25% and 0.84%.
For all engines except the Mercedes, the ECM indicated lower fuel consumption than the gravimetric measurement, PIT found.