Ford Motor Co. is trying to turn the tables in a controversy over fuel economy ratings for some of its new hybrids, suggesting the problem is how the government ratings for such cars are calculated. I must say at this point, as the writer of the BLOG I have to agree---the ratings can be misleading. Specifically Ford’s C-Max hybrid wagon and Fusion hybrid are rated 47 mpg, using the method developed by EPA, Environmental Protection Agency. But in road tests by Consumer Reports magazine, the C-Max and the Fusion are rated 37 and 39 mpg respectively. Ford said the EPA test may require modifications to more accurately reflect a hybrid's fuel economy.
In EPA-designed tests, a vehicle’s wheels sit on giant metal spinning drums that run through a driving cycle meant to capture city and highway scenarios, including stops, starts, heavy acceleration and highway driving speeds. Most of the highway testing is done at an average speed of 48 mph, below the 62 mph threshold of the Ford vehicles. However, most customers typically drive faster than 48 mph on the highway and accelerate faster than required to keep the car in the electric mode, eliminating or reducing much of the hybrid’s benefit.
Consumer Reports test vehicles on rolling hills and at constant highway speeds of 65 mph, eliminating some of Ford’s all-electric benefits. The EPA, in 2006, acknowledged that its test is less effective in capturing the real-world performance of hybrids and may understate the efficiency of diesels compared to gasoline powered cars.
COMMENTS—It seems part of the questions about test results is caused by how the battery is recharged (or not recharged) depending upon hybrid OR hybrid+PHV operation. In the hybrid only mode recharge energy comes from burning gasoline in the ICE. In the PHV modes the recharge can be direct by plug-in OR via running the ICE. The Consumer Reports type testing tends to force recharge by using the ICE and causes a pessimistic mpg calculation. One change to the Consumer Report scheme would be to include PHV recharges to simulate the daily driving mode of electric only during driving and recharge from the 120-240 Vac house power source overnight. In this mode the ICE is NOT normally used UNLESS you drive extended range each day.
It seems the idea the PRIUS and now VOLT are now pushing, is gaining a foothold. The presumption is that the vehicle will be used for LOCAL driving and will go as far as it can on Electric only. In the VOLT case this is 40+ miles. If the day driving is less the ICE need never start. Should the day driving go over 40 miles the ICE becomes the range-extender. The Ford C-Max and the Fusion function nicely in this mode and I think the car manufacturers see the market moving toward that direction.
INTERESTING--
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