Ford to lower fuel economy rating on C-Max hybrid!

Agreed because:

• MPG = F(mph, temp_ICE, distance, temp_air, speed_fretting, altitude_change)

There is never going to be a single number that predicts the MPG for a trip. However, "mph" is a primary determinant followed by the other factors:

• temp_ICE < 50C, distance ~= 1.5 mile -> 30 MPG
• temp_air -> aero drag proportional to air density, a function of temperature
• speed_fretting -> more operations, lower MPG, ~10-15% impact (unless Top Gear)
• altitude_change -> with distance, the grade is the determinant

But given how powerful speed is in determining MPG, it is enough to get a good, first approximation. But the two EPA numbers are at best a poor approximation of what an accurate, "mph vs MPG" chart provides.

Bob Wilson

 

+1

Absolutely. What we can do is have multiple tests that give us a good idea, and we can make these tests more like Americans drive in 2013. There is no reason for the epa not to publish all 5 tests on their website. They should at a minimum have the data on a server (including whether it was 5 tests or 2, if it was derived from another vehicle, etc). It only takes web development, which given the importance of the information will be a small cost.

In 2008 only 1 additional route was added. The federal test protocol (ftp) retained the old city and highway tests that were based on much older driving information but established in 1977. Fix the routes and publish all the numbers on the web would get rid of a lot of the misinformation. I was quite surprised to find that car makers were able to choose to use their calculators instead of testing, but I found this out months ago when car and driver published it.

Instead of using proper speeds as the key, the epa started relying on math, which doesn't really do a great job in aerodynamic cars. Given variable trip distance, mpg at speed once warmed up is not a major component of gallons used per year, unless all other things are equal. A ford focus and prius might be only 20% appart with cruise control on at highway speeds, but its how it does accelerating to those speeds, and its performance at lower speeds, that give the prius so much more of a real world advantage.

I do like this supplemental information. I especially like how tesla puts it out, giving you a calculator to figure out distance for fuel (miles per charge, but mpg would be great for hybrids) at different temperatures, different tires, and different speeds. Toyota, Ford, GM, VW etc probably have most of this information. Ford put out a little bit during this c-max controversy. I don't think we can ask the epa to police it, but it would be great if the manufacturers from pressure from other car manufacturers would provide this. I am sure the good folks at clean mpg would be willing to test if car makers loaned them the cars.

 

Glad to hear Ford finally awoke from the stupor.

 

Actually the EPA does provide the core determinants, the raw, roll-down coefficients. This provides the rolling drag force but lacks the vehicle overhead and engine-overhead at the corresponding points. The first step is to have a good, trustable math model and it isn't that hard to do.

Bob Wilson

 

+1

I did not realize they published this data. Is it easily accessible. We do have some strong evidence that the epa math to go from 2 cycle to 5 cycle does not work well for efficient vehicles. I don't think you can get good ac or cold start overhead from the 2 cycle test.

 

The 2 cycle to 5 cycle conversion fudge factor was probably based on Prius and Civic hybrid of last gen. Those cars were lighter and Prius had dedicated hardware to speed up warm up.

C-Max is much heavier and it does not have anything to speed up the engine warm up. Those are probably the cause of real world disparity.

 

Compared to the Fusion ?

 

Compare to Prius or Prius V.

C-Max is a very heavy hybrid for it's size -- about the same weight as Escape SUV hybrid it replaced.

 

If I read the c&d piece right, the prius and civic were tested by the epa on the 5 cycles. It is likely that their current generations also did 5 cycle testing (We know the doe did 5 cycles on the gen III 15" wheel prius). The fudge factors were determined by other cars. If you read the earlier epa response, they think the ford software and higher speed battery assist helped on the highway test.

Here are some slides of the prius on the 5 cycle test along with charge and discharge on the high speed test
http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2012/veh_sys_sim/vss065_lohsebusch_2012_o.pdf

Especially if you don't do the cold cycle of the test.
http://scholar.lib.vt.edu/theses/available/etd-11092011-115101/unrestricted/Meyer_MJ_T_2011.pdf

I don't see any reason not to require hybrids and small turbos to do all 5 cycles. The epa obviously can't do 1 set math formulas that works for SUVs, economboxes, hybrids and turbos.

 

Yes, starting from 2008 model. However, per-2008 was done in 2 cycle, I believe. EPA added 3 more cycles in 2008 in response to the hybrid models available at that time. Those models were light and frugal on accessory power consumption.

C-Max hybrid is much heavier with no compromise in driving characteristics. Cabin cooling and heating did not have Eco mode either. The updated firmware added eco to help achieve the new 43 MPG, otherwise would have gotten 41 MPG.

 

I'm skeptical.

The test sets the acceleration.

 

Funny how they thought "Oh it weighs about the same as the Fusion hybrid so they'll get similar mileage." The Fusion Hybrid is so much more aerodynamic. Whoever's rating the cars' mileage needs to go back to go back to physics class. At least Ford is compensating people unlike a certain Japanese brand that faced a class-action lawsuit instead.

 

Fusion hybrid real world is no where near 47 MPG.

 

exactly

 

2-cycle test plus the ability of software to take advantage of the test. Reports were that the initial software did well on two cycles but glided and charged too much for the real world. We can assume that the 17" tire model cars with the new software will do better than currently reported mileage which is skewed lower because of larger tires and less efficient software. I assume that if 5-cycles were really tested we would get a 44-46 combined mileage, but it would have been lower because of software when released. I think it would still fall short of these possible tested figures, but it may be much closer than the current numbers indicate.

Some interesting things about the 5 cycle study.
http://scholar.lib.vt.edu/theses/available/etd-11092011-115101/unrestricted/Meyer_MJ_T_2011.pdf
First is they judged that on a hybrid the math conversion on from a 2 cycle to 5 cycle, would make the city mileage lower, but highway mileage higher than running the test. The research was available before the ford hybrids were tested, so ford must have known this before choosing the 2-cycle test with math, wanting higher freeway mileage.

Other interesting findings, in 5 cycle simulation dropping the weight by 150kg (330lbs) on a hybrid in the 5 cycle test would increase city mpg by 7.1% and highway by 3.8%. Dropping the cd from .30 (c-max) to .25 (prius) would increase city mpg by 3.6%, hwy mpg by 7.7%. The 5-cycle test makes aerodynamics much more important than the 2-cycle test.

Finally the 5-cycle highway plus fudge factors seems to underestimate fuel economy on highway drives as long as they are not short (start up penalty). The 5-cycle city seems to still overestimate fuel economy. This appears to be a problem with the 3 tests (ftp75, cold, and air conditioning) all are based on the old test route. These definitely could stand to be updated. Here is a description of where this profile came from.

Until that procedure is updated, there will be variation from real world numbers. The fusion hybrid seems to be able to take better advantage of that route than the camry hybrid.

 

I would bet that Sonata hybrid started the trend of using the 2 cycle to beat Toyota figures.

 

From the link in my previous post, the large majority of cars were tested on 2 cycle with math adjustments instead of 5-cycle in 2011 and 2012. Its a practice that should be stopped when going from a fusion ice to hybrid, or even a focus natural asperated engine to small turbo charged. It is probably fine if you go to a less efficient vehicle like from a 4 cylinder camry to a 6 cylinder one.

 

I have looked at the data file before but do not know what to look for, to determine 2 or 5 cycle. Will have to check it again.

If I read that right, perform 5 cycle test first. Then compare the emission data with the 2 cycle regression line. If it is within 4-5%, they can use 2 cycle fudged MPG figured?

 

Just downloaded the file, I didn't know it was there. Column BT shows if it was tested or fudged in the 2013 dataset.
Derived 5-cycle in that column means they only tested the 2-cycles then used math to derive the other cycles.

The rule as I understand it says something like this. You have to test the main model, in the fusion/c-max case that is the fusion 2.5L gasoline in all 5-cycles. If the city mileage is within 5% and the highway mileage is within 4%, then you can use the mathematical method on2-cycle all of the fusions. A different rule allows the fusion number to be used on the c-max without ever testing the c-max. It sounds like the epa will get rid of that second rule, but is still deciding in the 2-cycle test fudge method is good enough. That 2-cycle fudge method also helps small turbos and vehicles like SUVs that are not aerodynamic get better highway fuel economy on the sticker.

The US06 procedure in the 5-cycle test is problematic for hybrids, as the state of charge is unlikely to be the same before and after the test. Virginia Tech though found that this should amount to less than 1 mpg in the case of the prius even without adjustments because of the other parts of the math to compute mpg. The accord and ford hybrids may have bigger differences, so the EPA and DOE are likely looking at some adjustments based on change of state of charge. This may be partially responsable for the c-max getting 40 mpg hwy on the 5-cycle test.

 

Ford didn't cheat they just changed the laws of physics.