From the October 2016 issue
The EPA uses dyno cells like in the image above for tests from 20-degree cold starts to 86-degree highway runs. A separate cell with high-intensity lights simulates the solar load of a sunny day for the high-temp tests.
Recent cases of ?misstated? fuel economy involving Ford, GM, Hyundai, and Mercedes-Benz have this in common: All were caught by the EPA during audits of data submitted by the manufacturers for certification. That?s because the EPA?lacking the personnel, facilities, and funding to test every vehicle?lets the manufacturers largely certify themselves and just submit the data.
All automakers follow the same set of procedures designed to generate comparable mpg numbers, but manufacturers have obvious incentive to exploit gray areas and loopholes to produce higher ratings. The goal is to net the best window-sticker numbers without netting ones so good that they raise suspicions. It?s a delicate dance, and engineers we spoke with described it as pervasive. These are a few manufacturer approaches: It?s a Drag
The EPA-prescribed dynamometer tests incorporate calibration settings intended to align laboratory results with real-world performance. Road-load coefficients?determined from a coast-down test wherein a car coasts in neutral from 80 mph?are programmed into the dyno to account for the energy lost to aerodynamic drag and friction. Recently, the EPA had to remind automakers to test cars on typical road surfaces and with critical compon...