Real world MPG not even close to Ford's Hybrid EPA MPG claims

[radioranger]

Don't forget the EPA runs the country now, you no longer get to make laws everything is done by un-elected officials making RULES, what's the difference, you dont get to fire them ,

[bwilson4web]

Hi,

If you get a chance, check my work?

I used the following from the EPA table:

• Target Coef A (lbf)
• Target Coef B (lbf/mph)
• Target Coef C (lbf/mph**2)

Using the chart, we would expected the same rate per second of fuel burn going horizontal.

~18hp @80 mph "Prius hatchback"
~18hp @67 mph "CMAX"
~18hp @67 mph "Prius v"

For example, our 2010 Prius gets ~39 MPG at 80 mph:

Now back of the envelope, we can estimate the CMAX/'Prius v' MPG by scaling for the slower speed ASSUMING the fuel burn rate per unit time are identical:

~33MPG = 39MPG * (67/80) ::@67 mph

The owner reports:

• 38MPG @65mph
• 33MPG @70mph

Close enough for my work.

The power vs speed chart of the CMAX shows rolling and aerodynamic drag consistent with the "Prius v". I've included the "Prius hatchback" for reference yet this is the EPA ratings:

City Hwy Model
47 47 CMAX
44 40 Prius v

51 48 Prius hatchback

What this means is any vehicle with coefficients listed in the EPA tables can have a power vs speed graph. Then if one has their own MPG vs mph chart, one can estimate the expected performance.

Your posting gave me the clue needed to do the power vs speed chart. The rest is simple math:

Originally Posted by Old Tele man

The "EPA testing" process begins with the manufacturer: (A) doing "coast down" tests to find a "road load hp (RLHP)" number for the vehicle. Then, they (B) come up with a supposedly equivalent "test load hp (TLHP)" for the dynomometer they used. So, errors in A propagate into B and so on...

The two equations:

RLHP = (A + BV + CV^2)/7.5 ...A,B,C coefficients for "road"

...where:

V = mph
A = lbf
B = lbf/mph
V = lbf/mph^2

TLHP =(A + 50B + 2500C)/7.5 ...F0, F1, F2 coefficients for "test" dyno

_V = 50 mph
F0 = 36.62 (rolling force)
F1 = 0.1461 (rotational force)
F2 = 0.01869 (aero force)

...example from GM data submitted to EPA:

TLHP = (36.62 + 50(0.1461) + 2500(0.01869))/7.5 = 12.1 "test" hp @ 50 mph

Thanks,
Bob Wilson

[Daox]

Originally Posted by radioranger

you're forgetting one big thing which is incredibly fit into the mold, Obama wants Ford to look bad, The media will NEVER want ford to look good . they bucked the bail out, you have to ,very sadly to say , look at darned near everything that way now, If it's not in the agenda it's not good for the Elite, it's downplayed by the media,

Please keep political banter off the forum. Thanks.

[Recumpence]

I can also add this to my personal experience (I currently have nearly 6,000 miles on my C-Max);

Yesterday I was right at 47mpg average until it began to rain and snow. My mileage dropped to 43.8mpg by the time I rolled into my driveway. This car is extremely sensitive to conditions......

My 70mph highway mileage is 41.5 to 42mpg. In town in warm weather (above 50 degrees) is 48mpg without any hypermiling, 52mpg if I hypermile it. Also, remember, I carry 300 pounds of equipment in my car all the time......

Lastly, my experience may be a bit biased toward the plus because of the type of driving I do. I drive in town and town to town to and from clients. I typically drive 30 minutes from one town to another on 40mph roads with some 25mph in town driving. Then after 20 minutes at the client, I drive 30 minutes to my next client. This 20 minutes of down time does not allow the engine to cool down. So, I am driving the way this car shines best (town to town driving under 50mph most of the time) without any significant time for the engine to cool down. This driving style may be skewing my experience to the positive. However, that is precisely why I bought this car. It has the perfect amount of interior space, is quite powerful, and excels at exactly what I need from it, mainly town to town driving.

So, bear that in mind........

I can tell you this, if you drive this car for 10 or 15 minutes and let it sit for an hour or more, then drive it for 15 minutes again, you are going to average 30mpg. The first 15 minutes of driving nets me about 30 to 35mpg in cold weather (40 if it is warm). It takes a good hour of driving to see 45mpg, two hours to see 50mpg.

Matt

[radioranger]

Originally Posted by Daox

Please keep political banter off the forum. Thanks.

why do you think they always report when Toyota does something wrong , or never report when hardly anyone buys a volt, nuff said but think about it .

[MetroMPG]

Political talk stops here, thanks. There are lots of forums where people can talk politics - this isn't one of them.

[bwilson4web]

Thanks Matt,

Originally Posted by Recumpence

. . .
Lastly, my experience may be a bit biased toward the plus because of the type of driving I do. I drive in town and town to town to and from clients. I typically drive 30 minutes from one town to another on 40mph roads with some 25mph in town driving. Then after 20 minutes at the client, I drive 30 minutes to my next client. This 20 minutes of down time does not allow the engine to cool down. So, I am driving the way this car shines best (town to town driving under 50mph most of the time) without any significant time for the engine to cool down. This driving style may be skewing my experience to the positive. However, that is precisely why I bought this car. It has the perfect amount of interior space, is quite powerful, and excels at exactly what I need from it, mainly town to town driving.

So, bear that in mind........

I can tell you this, if you drive this car for 10 or 15 minutes and let it sit for an hour or more, then drive it for 15 minutes again, you are going to average 30mpg. The first 15 minutes of driving nets me about 30 to 35mpg in cold weather (40 if it is warm). It takes a good hour of driving to see 45mpg, two hours to see 50mpg.

Sad to say, I'm flying blind without any OBD based metrics. The original poster over at PriusChat seems interested in resolving the problem but I don't get the impression he has much engineering expertise. So we try to talk him through what to do and . . . wish for the best.

Do you have CMAX aware OBD scanner that can report battery metrics or any metrics from the MGs?

Thanks,
Bob Wilson

[Recumpence]

Originally Posted by bwilson4web

Thanks Matt,



Do you have CMAX aware OBD scanner that can report battery metrics or any metrics from the MGs?

Thanks,
Bob Wilson

No I dont.

Honestly, I do not know what that is. Sorry for the lack of knowledge on that...

Matt

[gone-ot]

Originally Posted by bwilson4web

Your posting gave me the clue needed to do the power vs speed chart. The rest is simple math:

Thanks,
Bob Wilson

You are welcome!

[euromodder]

Originally Posted by YeahPete

I think Ford botched thier numbers. I read the articles. The MPG is off by 10 in this car while most others tested are off by 1-2.

Why would they botch the numbers ?

They CAN get these numbers, but that doesn't mean (most of) their customers can.

Hybrids (not just Ford's) are very susceptible to how they are driven.
Ford's engineers obviously know the inside-out of how the hybrid system works, how they can play it, and how they can get the best numbers out of it on a relatively short cycle.