Slow & Go vs. Constant Speed

[corncobs]

I was looking at my pictures and noticed something between the last two trips home. As you might know I can get 55 MPG on my way to work but I only got 42.7 MPG driving home today.

 

Here is yesterday's result

 

 

Now today's result under similar weather conditions at around 85F and AC on Auto at 79F.

 

 

You can see even when today resulted better EV and regen numbers the MPG # is quite a bit lower.

 

I actually blame today's traffiic for the bad results especially on the interstate traffic was less fluent than yesterday triggering EV mode more often. You might think that should be a good thing unfortunately it's not because it drains the HVB forcing the ICE to recharge when speed resumes.

 

The result you can see above a less constant speed at or below 65 MPH will hurt your MPG # because the ICE needs to work more often to recharged the pack before you see the 40+ instant MPG with a full charged HVB going 65 MPH again.

Edited July 11, 2013 by corncobs

[lolder]

In ICE mode, the drivetrain has about 5% loss, in EV, more than 20%.

[djminfll]

I was looking at my pictures and noticed something between the last two trips home. As you might know I can get 55 MPG on my way to work but I only got 42.7 MPG driving home today.

Here is yesterday's result

Now today's result under similar weather conditions at around 85F and AC on Auto at 79F.

You can see even when today resulted better EV and regen numbers the MPG # is quite a bit lower.

I actually blame today's traffiic for the bad results especially on the interstate traffic was less fluent than yesterday triggering EV mode more often. You might think that should be a good thing unfortunately it's not because it drains the HVB forcing the ICE to recharge when speed resumes.

The result you can see above a less constant speed at or below 65 MPH will hurt your MPG # because the ICE needs to work more often to recharged the pack before you see the 40+ instant MPG with a full charged HVB going 65 MPH again.

I have found the same thing... Being in heavy traffic may allow more time in EV, but it drains the battery, and once you get out of traffic, the car stays in ICE mode longer, and drains whatever gains you made in EV that much faster.

[rjent]

In ICE mode, the drivetrain has about 5% loss, in EV, more than 20%.

Where did you get this. Have a link? Interesting, I would have thought it just the opposite .....

[rjent]

I have gotten over 56 MPG over a 40 mile trip catching all of the lights and little traffic while maintaining 45 or so, I have also gotten 46 at 65 Interstate over a 70 mile trip, the problem (if there is one LOL) is that it is not consistent enough to determine what IS better. I drove from Las Cruces NM (70 miles) to Hot Springs (home) around town (5 mile trips max) for a couple of times, then to Albuquerque (160 miles) on the Interstate for 70 percent of the trip and only burned just over 5 gallons. I don't know about anyone else, but that is phenomenal any way you analyze it! It is just hard to determine what is the "best" way to drive it. I am heading out for California on Monday (about 900 miles). I will report my results..... :)

[lolder]

Where did you get this. Have a link? Interesting, I would have thought it just the opposite .....

Just engineering. When the ICE is propelling the car, it is directly through the CVT gear train which has only a few percent loss. In EV mode there is the loss in the generator, battery charging, batterry discharging and motor. In the Gen 1 FFH this was about 30 %. Maybe it's a little better in Gen 2 with the LiIon HVB. This is why at higher speeds you want to avoid EV. At lower speeds the ICE becomes less efficient if it is run continuously and going to EV-ICE cycling is overall more efficient even with the EV cycle losses.

[rjent]

Just engineering. When the ICE is propelling the car, it is directly through the CVT gear train which has only a few percent loss. In EV mode there is the loss in the generator, battery charging, batterry discharging and motor. In the Gen 1 FFH this was about 30 %. Maybe it's a little better in Gen 2 with the LiIon HVB. This is why at higher speeds you want to avoid EV. At lower speeds the ICE becomes less efficient if it is run continuously and going to EV-ICE cycling is overall more efficient even with the EV cycle losses.

OK, so you don't have any engineering numbers to work with. I was just wondering if you had any support documents from Ford ....

[lolder]

I recall a Ford engineer in an interview saying the EV mode was 70 % efficient. If you pulse and glide and modulate the pedal so there is no charging or discharging of the HVB, you will get 30 % more mileage. I have done this. You are avoiding EV mode in that way. Straight gears have always had only a few percent loss. The best electric motors and generators have about 5 % loss and the HVB charging and discharging each have about a 5-10 % loss so there's your 20-30 % loss for the EV cycle. Remember, in non PHEV HEVs, all the energy comes from gasoline and is produced at the output shaft of the ICE. How it gets to the wheels from there is the difference. In hybrids, the ICE is almost never run unless it is loaded up. The generator load is freguently higher than the motive requirements at lower speeds. Ford gamed the EPA tests by having a higher EV speed but perhaps with the consequence of lower economy in the 45-60 mph normal driving range. I wish someone would do a level road stable conditions comparison between the mileage at 60mph where EV cycles and 65 mph where it wont. Energy wise, the mileage at 65 should be 3 mpg. worse but I'll bet it's the same or better.