How the EPA/Ford gets the C-Max fuel ratings

[fotomoto]

Here's a great article that helps explain the process and failings of the current EPA test cycle:  http://www.caranddriver.com/features/why-is-the-epa-so-bad-at-estimating-hybrid-fuel-economy-feature

 

Here are some excerpts for a quick summary:

 

 

We were impressed when Ford announced that the 2013 Fusion hybrid earned an EPA ­rating of 47 mpg for both city and highway driving. Here was a generously sized and relatively conventional-looking sedan rivaling the efficiency of the ­Toyota Prius.

Then we racked up a mere 32 mpg in our road test [December 2012]. That’s par for our foot-down driving style, but even when we drove more sedately, we had difficulty coaxing the Fusion’s trip computer to show any number that started with a 4. It turns out we weren’t alone.

 

The second cycle is called the Highway Fuel Economy Test (HFET), also established in 1975. Unless you live in traffic-besotted L.A., it’s laughably slow by modern standards, with a maximum speed of 60 mph and an average of 48. But, back in the day, Congress had also mandated a 55-mph national limit, and the HFET reflected the intent, if not the reality, of American driving.

 

these tests are irrelevant to contemporary real-world driving. For example, the maximum acceleration on either test is 3.3 mph per ­second. At that rate, it takes more than 18 seconds to hit 60 mph.

 

Another difference between hybrids and conventional cars is the effect of off-cycle driving. For example, propelling a base Fusion and a hybrid Fusion through the test cycles requires the same amount of energy. But the hybrid gets better fuel efficiency—both in the real world and during EPA testing—because a good chunk of its energy requirement comes from the electric power­train that receives a significant share of its energy from regenerative braking. What happens when you start driving faster? Both hybrids and standard cars require about the same amount of additional power to run at higher speeds. But on the hybrid, the extra power can’t be supplied by the electric motor because most hybrid power­trains don’t operate at high speeds, and there is less energy to recover through regenerative braking on the highway. So the hybrid’s extra speed comes primarily from its internal-combustion engine.

 

manufacturers are allowed to use their pocket ­calculators instead of actually running the three additional test cycles. Two scenarios enable such a certification. One is called the “mpg-based” approach, which, in many circumstances, allows the application of a mathematical fudge factor to those two hoary CAFE tests from the 1970s to adjust their results in a way similar to the three new tests. The mpg-based method looks like you’ve run all five tests, even if you’ve in fact conducted only the two old ones

 

Examining the raw data from the hybrid Fusion’s original FTP and HFET results, it appears that Ford used the “mpg-based” approach to determine its window-sticker numbers, a perfectly legal option. But while the “mpg-based” correction factor might do well projecting a conventional car’s five-cycle fuel-economy results based on the two basic CAFE test cycles, hybrids behave differently, as noted above. We believe that if you take the fudge factor derived from conventionally powered cars and apply it to hybrids, or even small engines with turbos, you will run into trouble, with on-paper results better than what hybrids can actually achieve on real roads with real drivers. That speed limits are going up in places such as Texas, which has a new 85-mph toll road, will only exacerbate this situation.

 

That’s government-speak for “Ladies and gentlemen, start your fudgy calculators!”  A lot of manufacturers are taking advantage of this strategy.

 

 

 

 

[RedLdr1]

 

"Examining the raw data from the hybrid Fusion’s original FTP and HFET results, it appears that Ford used the “mpg-based” approach to determine its window-sticker numbers, a perfectly legal option."

 

That one line says it all....especially the last four words. 

[plus 3 golfer]

Good article.  

 

The strategy apparently benefits Ford more than other manufacturers in two ways 1) Ford gets better mpg in the "actual" tests because the electric motor can propel the car up to about 62 mph with little use of ICE (slow acceleration speeds help this) and 2) Ford can then apply the "fudge factor"  for the other higher speed tests to get even higher EPA numbers.  

 

So the questions are 1) did Ford take advantage of the apparent EPA testing "defects" and cleverly develop ads / commercials to exploit this full well knowing the average consumer would not likely get close to the EPA numbers and 2) is # 1 a violation of any unfair trade and consumer protection statutes.

Edited May 2, 2013 by Plus 3 Golfer

[hybridbear]

Great article, thanks for sharing. I believe this will come back to bite Ford in the end even though it appears that they didn't break any rules. They have tried to get as close as possible to the line without crossing and that might have nasty consequences

[salsaguy]

regarding EPA testing ...

i posted this in another thread here but it probably makes more sense here:

http://www.automobilemag.com/features/news/1303_fuel_economy_numbers_gone_wild/

[SnitGTS]

Great article!  I have a question though, since the Energi gets to go up to 85 mph in EV mode, what is the drop off in mpg for it as it approaches 85 mph? 

 

The following excerpt from the article is very telling why a hybrid is so greatly affected by speed.

 

"What happens when you start driving faster? Both hybrids and standard cars require about the same amount of additional power to run at higher speeds. But on the hybrid, the extra power can’t be supplied by the electric motor because most hybrid power­trains don’t operate at high speeds, and there is less energy to recover through regenerative braking on the highway. So the hybrid’s extra speed comes primarily from its internal-combustion engine.

In theory, then, if a base Fusion needs 38.5 gallons to drive 1000 miles at test-cycle speeds (1000 miles/26 mpg EPA combined), and a Fusion hybrid needs 21.3 gallons (1000 miles/47 mpg EPA combined), what happens when the speed rises enough to require 20 percent more energy? We can assume that the nonhybrid’s consumption will increase by 20 percent—7.7 gallons—reducing its mileage to 21.6 mpg, a 17-percent drop. The hybrid’s consumption increases by about the same number of gallons, because the hybrid’s electric powertrain largely checks out at higher speeds, resulting in the engine shouldering more of the load. Thus, as a hybrid goes faster, it works its gasoline engine proportionately harder relative to the gas engine in the regular car. In our hypothetical example, the hybrid mileage falls to 34.5 mpg—a much larger, 27-percent reduction. Even if these numbers are rough estimates, you can see how real-world driving can reduce a hybrid’s fuel efficiency by a greater amount.

 

Drive a hybrid more aggressively in the city and the same thing happens. During harder acceleration, most of the extra power comes from the internal-combustion engine because the boost provided by the electric motor is limited. Furthermore, during hard braking, the hybrid benefits from only so much regeneration energy before its system capability is exceeded.

 

In cold weather, there are similar effects, compounded by the fact that batteries store less energy when they’re cold. Also, the hybrid system doesn’t shut down the engine as often because its heat is needed to warm the car’s cabin."

Edited June 8, 2013 by SnitGTS

[Noah Harbinger]

That article from Car And Driver has been thoroughly debunked. The "MPG-based approach" they refer to was only allowed on models that were sold in the 2007 model year and tested under the EPA tests in effect at that time, that would otherwise not have required to be re-tested in 2008. In other words, they weren't going to force every manufacturer to re-test cars they were already selling.

 

Those are the only vehicles that were allowed to apply a correction factor. That does not apply to the C-Max or Fusion, and thus the 2-test * correction factor method would not have been permitted.

[CNCGeek]

Great article, it should be read by anyone considering a hybrid. 

 

It does tick me off a bit though, and right now I feel like Ford can kiss my future business goodbye IF they used loopholes to "achieve" the EPA ratings on the C-max.  I used to have the quaint idea that the EPA test (though seriously flawed) is a standard, meaning the testing is done the same way to all vehicles.  Though it may be all legal to the letter, there is no doubt there is a marketing advantage to be gained if you can pick a higher MPG rating over one that is lower (but actually tested as opposed to being derived).  The term hypbrid seems fitting in such cases.

[CNCGeek]

That article from Car And Driver has been thoroughly debunked. The "MPG-based approach" they refer to was only allowed on models that were sold in the 2007 model year and tested under the EPA tests in effect at that time, that would otherwise not have required to be re-tested in 2008. In other words, they weren't going to force every manufacturer to re-test cars they were already selling.

 

Those are the only vehicles that were allowed to apply a correction factor. That does not apply to the C-Max or Fusion, and thus the 2-test * correction factor method would not have been permitted.

 

I did a quick google search to find the debunking and found this.  I did not read the whole thing, maybe if I cannot sleep tonight I will try, but I did find a description of when the 5 test and "mpg-based" numbers could be used - they seem to still allow the use of the "mpg-based" calculation, but there is a requirement that they compare them:

 

"Beginning with MY 2011, manufacturers are required to perform an evaluation using 5-cycle tests conducted for vehicle emissions certification that determines whether the models represented by the certification vehicle are eligible to use the less resource-intensive mpg-based method for determining adjusted fuel economy values. The evaluation consists of a comparison of 5-cycle and mpg-based 2-cycle fuel economy values to determine whether the mpg-based method achieves results comparable to the 5-cycle method. If the evaluation finds that the 5- cycle method yields significantly lower fuel economy estimates than the derived 5-cycle method, then the manufacturer is required to use the 5-cycle method for all models represented by the emission certification vehicle. Of course, a manufacturer may use the full 5-cycle method for any vehicles for which it is not required if they believe it produces better fuel economy results."

 

So that makes it seem possible, though unlikely, that they could have used the 2-cycle test values to derive the other results.

[Noah Harbinger]

I looked up the article cited in the federal register, and I believe that report misunderstands the published rules:

 

Federal Register: Fuel Economy Labeling of Motor Vehicles: Revisions To Improve Calculation of Fuel Economy Estimates

 

Let's take this quote (pg. 77882, 2nd column, last paragraph): 

 

Beginning with the 2011 model year, manufacturers are required to use the vehicle-specific 5-cycle method, but may still use the mpg-based approach on vehicles most sensitive to the new test conditions. Under the vehicle- specific 5-cycle approach, the fuel economy measurements over the 5 dynamometer test cycles will all be performed on (or estimated for) a specific vehicle in the current model year. The mpg-based approach uses historic fuel economy data over the 5 test cycles to estimate a fleet-wide average relationship between (1) FTP fuel economy and 5-cycle city fuel economy, and (2) HFET fuel economy and 5-cycle highway fuel economy. Under the mpg-based approach, a specific vehicle’s city and highway fuel economy labels are based on this fleet- wide average relationship, as opposed to that vehicle’s own results over the 5 test cycles. In other words, under the mpg- based approach every vehicle with the same fuel economy over the FTP test will receive the same city fuel economy label value. Likewise, every vehicle with the same fuel economy over the HFET test will receive the same highway fuel economy label value.

 

Since there is only one other vehicle in the Ford fleet with the same fuel economies as the C-Max Hybrid (the Fusion Hybrid), the only way I can construe this to mean that the mpg-based method could apply to the C-Max's fuel economy is if on the old Highway (HFET), old City test (FTP), or both, the C-Max scored the same as the Fusion, and based on that the Fusion's fuel economy was applied to the C-Max. 

 

Perhaps that is possible - the Fuelly.com average for the Fusion Hybrid is 2MPG higher than the C-Max Hybrid.

 

But it still renders bunk the concept that the fuel economy just 2-cycle test * adjustment factor. 

[CNCGeek]

I looked up the article cited in the federal register, and I believe that report misunderstands the published rules:

 

Federal Register: Fuel Economy Labeling of Motor Vehicles: Revisions To Improve Calculation of Fuel Economy Estimates

 

Let's take this quote (pg. 77882, 2nd column, last paragraph): 

 

 

Since there is only one other vehicle in the Ford fleet with the same fuel economies as the C-Max Hybrid (the Fusion Hybrid), the only way I can construe this to mean that the mpg-based method could apply to the C-Max's fuel economy is if on the old Highway (HFET), old City test (FTP), or both, the C-Max scored the same as the Fusion, and based on that the Fusion's fuel economy was applied to the C-Max. 

 

Perhaps that is possible - the Fuelly.com average for the Fusion Hybrid is 2MPG higher than the C-Max Hybrid.

 

But it still renders bunk the concept that the fuel economy just 2-cycle test * adjustment factor. 

 

Thanks for finding that, I saw it referenced in a few places but could not find it without having to log in somewhere. 

[nsteblay]

I am finding the EPA numbers to be accurate now that the weather is warmer.  I live in Minnesota in the Twin Cities and commute 42 miles per day mixed freeway and highway driving.  When at full speed on the freeway I typically travel 70-75 mph.  Not sure what my average speed is with congestion but it is definitely below 60.  

 

I have found Negative Split Mode (freeway driving above 63 mph) gets me low 40's.  Positive Split Mode / Electric Mode switching (in congestion or speeds below 63 mph) is getting me higher than EPA numbers. Combined I am getting right around the 47 MPG.

 

Really drops off in the winter - was only getting 35 mpg in cold weather that is well below freezing. I understand this is due to the need to heat the car and exhaust system, less battery capacity, and less traction on the road.  

 

I think for a yearly average I'll be right around 40-41 MPG average.

 

If anything the EPA should test in varying temperature for hybrids.  Cold weather really impacts the mileage. I can't comment as to whether this is true for all hybrids but I would imagine so.

 

My last 100 miles or so ...

 

 

My current tank of gas ...

 

[salsaguy]

if the car had to be ready to come off the line and into the dealer by June/ July 2012, then the EPA testing was probably done sometime in March-May ?? which would account for better numbers although testing is done inside a building on a dyno setup so not sure if they change ambient temps or not.

anyone know for sure when the EPA test was done for the cmax? Any way to find out?

[plus 3 golfer]

...

Since there is only one other vehicle in the Ford fleet with the same fuel economies as the C-Max Hybrid (the Fusion Hybrid), the only way I can construe this to mean that the mpg-based method could apply to the C-Max's fuel economy is if on the old Highway (HFET), old City test (FTP), or both, the C-Max scored the same as the Fusion, and based on that the Fusion's fuel economy was applied to the C-Max. 

 

Perhaps that is possible - the Fuelly.com average for the Fusion Hybrid is 2MPG higher than the C-Max Hybrid.

 

But it still renders bunk the concept that the fuel economy just 2-cycle test * adjustment factor. 

The Fusion Hybrid has a Cd of 0.275 while the C-Max is reported at .30.  That's over an 8% reduction in aerodynamic drag.  My calculation would indicate that at 45 mph, the the energy required to overcome drag for the Fusion might be 5% higher than the C-Max (at 20 mph, about a 2% difference, at 70 mph, about 6.5%difference.  This looks too coincidental based on the 2 MPG Fuelly difference and that Ford could have used the MPG approach based on the Fusion 5 cycle tests for the C-Max.

 

Edit: The above assumes frontal areas of both are same.  But height x width (excluding mirrors) shows C-Max is about 8% greater.  If this 8% approximates the frontal area difference. The energy required to overcome drag at 45 mph would be about 17% more for the C-Max.  Also, CR got 39 mpg with Fusion Hybrid and 37 MPG with the C-Max - a 2 mpg difference.

Edited June 16, 2013 by Plus 3 Golfer

[salsaguy]

i agree and always wondered how they got 47 across all three scores and the exact same for BOTH cars when we know and it is obvious the cmax is much bulkier and less aerodynamic than the Fusion.

this is the only place where im concerned about Ford. i don't think they cheated or falsified numbers but it is very strange indeed on this aspect of the data.

I'm surprised we haven't heard any updates from the EPA on this since is was around  Oct / Nov of 2012 when the outrage really hit full tilt and the articles said epa was investigating and Ford was assisting them to address why the numbers were accurate and true, which many of you HAVE equalled or easily beaten.

Edited June 17, 2013 by salsaguy

[hybridbear]

I'd guess that the numbers are the same because the time at high speeds is short enough on the EPA test cycles that the aerodynamic drag difference didn't have a large enough impact. In real world highway cruising there is probably a noticeable difference.

 

The EPA test cycles are temperature controlled. The EPA sets requirements for the temp in the lab when performing the test cycles