Ford test-protocol error causes EPA ratings revision

  • 12-Jun-2014 05:10 EDT

VP of Product Development Raj Nair said Ford engineers identified the issue last October, when FE data from the physical testing of a Fusion Hybrid did not match the engineering model.

An error in a key vehicle fuel-economy test protocol caused Ford to lower its U.S. EPA fuel economy (FE) ratings for six 2013 and 2014 model year Ford and Lincoln vehicles, most of them hybrids and plug-in hybrids. In a June 12 conference call with Automotive Engineering and other media, Raj Nair, Ford VP of Global Product Development, explained the cause of the issue and apologized to Ford customers.

The affected vehicles include hybrid and PHEV versions of the Ford Fusion and C-Max, and Lincoln MKZ, as well as the conventionally powered Ford Fiesta. Owners and lessees of those vehicles—numbering about 200,000 in the U.S. and about 13,000 in Canada—will receive a “goodwill” payment for the estimated average fuel cost of the delta between the original and revised FE labels.

The FE ratings changes average between 1-5 mpg, with the MKZ taking the biggest window-sticker hit: its city and highway FE values are reduced by 7 mpg in the revised rating.

According to Nair, the cause of the issue was an error in the process Ford engineers used to correlate wind tunnel testing into their Total Road Load Horsepower (TRLHP) factor that is key to the vehicle fuel economy models that are ultimately submitted to the EPA. Specifically, the cause of the issue was a “misapplication” in the transfer of wind-tunnel data to the model, itself the result of a recent process change, Nair explained. Ford engineers have implemented a robust solution that includes additional physical coast-down validation testing of prototype and production vehicles, he said.

TRLHP is the vehicle-specific resistance level used in vehicle dynamometer testing that determines FE ratings consistent with EPA regulations. It is established through engineering models that are validated through various vehicle tests including coast-down regimes. Wind-tunnel tests are typically used to generate coast-down data due to their repeatability and consistency in replicating certain physical tests such as cross-winds and broad thermal ranges that have inherent variability.

The TRLHP and related models are then validated through dynamometer and track testing of both prototype and production vehicles. Hybrid vehicles are particularly sensitive to TRLHP testing, Nair noted. He explained that the test-protocol issue was first identified in October 2013 during coast-down testing of the Fusion Hybrid. It was confirmed in March 2014, and Ford swiftly notified the EPA of the issue, Nair said. EPA participated in retesting of the vehicles, a process that included more than 100 laboratory and track tests since March.

Nair said EPA did not fine Ford for the mistake, which he said was “entirely from within Product Development” and thus his responsibility. For a video of Nair speaking to the issue: Corrected FE numbers for the vehicles involved are on the EPA-U.S. Department of Energy joint fuel economy site (

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