Why are Energi gas-only MPG ratings lower than Hybrid's?

[esteinberg]

Greetings everyone. I'm in the market, so to say, and am having a tough time understanding something.

 

The EPA rating of the FFH is 44/41mpg, and the FFE is rated 40/36mpg. I am having a hard time believing that the extra weight of the batteries in the FFE can cause that large a difference. Is there some other technical reason that the FFE is less efficient than the Hybrid when operating in "normal" hybrid mode? Does this mpg difference actually translate from the ratings into the real world?

 

Thanks in advance for your input...

 

-Eric

[Jamone]

One other reason is that they have different final drive ratios 2.57:1 for the FFH and 2.91:1 for the FFE. I'm assuming this is because with the FFE running purely on electric at all speeds up to 85 mph it has drastic differences in the power curves compared to the FFH which was designed to use the ICE > 62 mph.

Edited July 18, 2014 by Jamone

[acdii]

Higher gear ratios translate to higher power input RPM to lower output RPM. Going from a 3:73 rear to a 4:11 rear makes an RPM adjustment from 1800 RPM @65 MPH to 2100 RPM@65 MPH in the F350 I had, which the end result was better fuel efficiency with 3:73 gears. Mine had 4:11 until I blew out the spiders taking off from a stop under full throttle, since I had to replace the gears decided to do front and rear at the 3:73 and gained 2 MPG.

 

Difference in ratio for the F350 was .38, difference for the Fusion is .34 so it makes sense that the MPG would be lower in the FFE vs the FFH. The E should be quicker off the line than the H, but the H could have a higher top speed.

[jeff_h]

It takes more energy to get that extra 300-lb of weight moving... but once it is going I don't see a lot of difference, I had a 2013 FFH for 35k miles then got an Energi to match my wife's... and just passed through Blacksburg last month on a road trip (long road trip on I-81 with cruise set on 68-70 averaged 49, 42, and 50 MPG on my segments) -- but aaronj1159 is in your area so he would probably help out with other questions if you PM him.

 

 

[esteinberg]

I had no idea that the drive ratio was different. I agree, that could make a difference in the MPG. It also makes me wonder if the FFE is going to be louder on long highway trips, with the engine running at a higher RPM.

 

So the other question is... are these particular ratings tracking well in reality? Obviously it's hard to compare since most people with Energi's are not reporting gas-only stats.

[acdii]

I doubt you would here the ICE at highway speeds, it is pretty quiet once you get up to speed.

[esteinberg]

Jeff, do you think your numbers there are skewed by having started your trip with a full battery, or would you say they are a mostly accurate representaion of "gas-only" mileage? Were you getting better numbers on long trips with your old non-plug-in Hybrid?

 

(long road trip on I-81 with cruise set on 68-70 averaged 49, 42, and 50 MPG on my segments)

 

 

 

[jeff_h]

Jeff, do you think your numbers there are skewed by having started your trip with a full battery, or would you say they are a mostly accurate representaion of "gas-only" mileage? Were you getting better numbers on long trips with your old non-plug-in Hybrid?

 

(long road trip on I-81 with cruise set on 68-70 averaged 49, 42, and 50 MPG on my segments)

 

The below is going from VA to KY with most on I-81, only the first segment of 185 miles had the initial full charge... however as you know, I-81 in that area has a lot of hills so I did not let the 'big HVB' (high voltage battery in an Energi is split into a large section of about 5kW, then smaller section about 1.1-2kW like the hybrid -- though these figures are just estimates only to illustrate the concept as someone will surely correct those numbers) go all the way to empty so I could regen some of it on those long downhills. So in that last segment of 173 miles, much of that was in coal country in KY with bigger hills and I got the big HVB charged back up all the way and then that helped later in other areas.

 

I do not get better numbers than I did with the 2013 Hybrid -- had a trip last year to Asheville NC (another long trip, this time on I-40 but similar terrain) and think I got 49 and 52 on that one. I think the MPG ratings for the Energi are rated about 8-10% lower than the hybrid, correct? In my real-life experience that has seemed about accurate.

 

Edited July 18, 2014 by jeff_h

[hybridbear]

The Fusion Energi rating is also lower because Ford ran the EPA tests for the C-Max Energi and applied those numbers to the Fusion Energi. Since the C-Max Energi was expected to be the better seller they were able to do this under the same rule that got them in trouble for rating the C-Max Hybrid at 47/47/47. They have not yet run EPA tests on the Fusion Energi to separate it from the C-Max Energi. Since the Fusion Energi is now the better seller it's possible that the EPA rules will require them to separately test the Fusion Energi at some point which would lead to it likely having higher EPA ratings than the C-Max Energi but still lower than the Fusion Hybrid.

 

Compare the C-Max Hybrid ratings to the C-Max Energi ratings to get an idea of the impact of the weight. I believe it's pretty small.

Edited July 18, 2014 by hybridbear