Driving in L (Low)

[Russael]

Has anybody ever tried driving their Hybrids or Energi vehicles in Low mode?  I've been digging around trying to figure out if that gives a more aggressive regen once your foot is removed from the accelerator, sort of like how the Tesla Model S works.  With that car, ALL regen is based on the accelerator pedal, not the brake pedal.  A lot of people have learned to drive that car without touching the brakes at all.  The brake lights actually come on if you fully release the accelerator while travelling at speed without touching the brake pedal.

 

If this is the case in Low mode... I'll probably wind up driving in that.  I prefer the idea of a more aggressive regen upon release of the accelerator.  The brake pedal while driving the Focus Electric was rather touchy.  I didn't even think to try driving that in low.

 

I couldn't find much to see if the car regens while coasting either, but I've seen enough youtube videos to figure out that it does (shows the up and down arrows over the battery display).  But there is nothing on low mode.

[meyersnole]

My neighbor does that with his Volt, I wonder what that would do to the range though.

[Russael]

Personally, I would think you'd get greater range since you know you're not losing anything to the friction brakes unless you press them.  It'll be something to experiment with.

 

As far as it doing anything to speed... the owners manual says you can switch to low at any time and at any speed, so I don't think it does anything to the 'gearing'.  I'm curious, especially since there's nothing about it anywhere.

[bibolton]

I would think that it would hurt the overall gas mileage but sure would be interested in your results. I have been able to put 2 miles back in my battery by using "hill assist" on a good down grade. It is much better for charging than braking on down hill slopes.

Edited April 23, 2013 at 01:42 PM by bibolton

[jsamp]

"L" is exactly as you describe - a more aggressive regen.  It is not any more efficient, it just does the job of slowing the car down faster.  In my Escape Hybrid, it will sometimes cause the car to increase the RPM of the gas engine (on a hill) and use it as a brake when the regen can't keep up.  That would not improve the mileage any.  I'm not sure if the Fusion will do the same or not.

 

Using the brake regen conservatively will accomplish the same thing as "L", as long as you don't press so hard as to engage the friction brakes.

[Russael]

When I test drove the Focus Electric, it was difficult to feather the brake to keep from engaging the friction ones.  I'm hoping I can get the most agressive regen from L and only touch the brakes when I need to.  The car does creep, so I'd need to touch the brake pedal at an intersection, but rolling up to it in L should take the guesswork out of whether I'm on friction brakes or not.  That's what I'm hoping for.

[Scooter80]

...  In my Escape Hybrid, it will sometimes cause the car to increase the RPM of the gas engine (on a hill) and use it as a brake when the regen can't keep up.  That would not improve the mileage any.  I'm not sure if the Fusion will do the same or not.

 

...

The Fusion will not act the same. An Atkinson cycle engine mated to an eCVT is not physically capable of being used as a brake.

[Russael]

The Escape Hybrid is an Atkinson engine with an eCVT and the Fusion Energi should act exactly the same, just the battery is enormous in comparison.  If the engine comes on once the battery reaches capacity if you're in a down grade, at least that'll keep you from cooking your brakes.  When I go down hill with my Expo, I just take it out of overdrive to keep my acceleration under control.  I'm guessing hill assist does pretty much the same thing since eCVTs have 'infinite gears' and L increases that even more.

 

Anyway, this is something I'll experiment with.  I'll try putzing with hill assist, try driving around in L, and driving around in D to see what results they yield.  I've been promised my car THIS YEAR! :)  hahahaha

[murphy]

The Fusion will not act the same. An Atkinson cycle engine mated to an eCVT is not physically capable of being used as a brake.

My 2010 Fusion Hybrid had an Atkinson engine and an eCVT.  Going down a steep hill in L caused the engine to rev up to where it became quite loud.  The explanation given was that it didn't burn any fuel and was acting like an air compressor to provide braking.

[Scooter80]

I tried L on a good down-grade last night. I felt the regen brakes grab harder, but the engine stayed off. Had half the battery left (in EV mode, not hybrid) so it would be interesting to see what'd happen if the battery was full. Everything I've heard of this new generation of Ford's hybrid drive is that the ICE will not provide braking. I could certainly be wrong of course.

[rprobst]

I'm confused. When should you use the down-grade button on the shifter and when should you put it in 'L'? Are these the same, just 2 different ways of putting the car in the same state? Or are there 2 different situations and one is good for one and the other for the other?

[murphy]

Page 176 of the Owner's Manual describes Grade Assist and the use of L for engine braking.

It says that L provides maximum engine braking.

[rprobst]

So the down-grade button and 'L' both do the same thing but 'L' does more of it? How much more? Has anybody built up enough experience to comment?

 

It would be great if we knew that pushing the down-grade button was (say) 1/3 or 1/2 as effective as driving in 'L'.

[murphy]

How about shifting to L and turning grade assist on at the same time.

[Scooter80]

So the down-grade button and 'L' both do the same thing but 'L' does more of it? How much more? Has anybody built up enough experience to comment?

 

It would be great if we knew that pushing the down-grade button was (say) 1/3 or 1/2 as effective as driving in 'L'.

In my experience of some moderate (for my area) grades, the grade assist button on the shifter prevents any speed increase due to a down-grade. L is just like driving your previous vehicles in a lower (though still auto) gear (the 1 and/or 2 past D). And while grade assist seems to do nothing (as intended I'm sure) for acceleration, L certainly does. L does change "gearing."

 

Despite driving in L for some time on a downhill run, my ICE never came on in a braking behavior. It simply "geared" the electric motor lower, requiring higher rpm's of the motor for the same distance travelled. And L slowed the vehicle in the descent where grade-assist only did not, it only kept the speed constant.

 

Also, despite being described the same as the L on my nightly ride (a new Ford "Taurus") the L on the Fusion does not act the same per say because of the extra "engine" that is the electric motor and the eCVT as opposed to the conventional auto trans in the "Taurus." But I don't see how driving in L would ever be better for fuel or EV mileage. You are essentially losing your overdrive "gears" (and more). In a conventional ICE car, the repercussions are clear. In a hybrid they are less clear, but still there. While you might get more battery charging from a descent, that power is not free. And keeping it in L for everyday driving seems really silly to me. Having the motor do more work (spinning faster for the same distance) is a waste of energy. Even if you do get a little more back from the increased braking effect, you will still have lost energy due to inefficiencies in the drive-train, the regen brakes, the charging equipment and the batteries themselves.

 

I will, however, now eat crow as far as my previous posts on the engine not providing braking. So much for Car & Driver being experts in their field.

 

From the manual (Transmission section p174):

 

"Grade assist:

• Provides additional grade braking with a combination of engine motoring and high-voltage battery charging to help maintain vehicle speed when descending a grade.

• As the vehicle determines the amount of engine motoring and high-voltage battery charging, you may notice the engine speed increasing and decreasing to help maintain your vehicle speed when descending a grade.

• The grade assist lamp in the instrument cluster is illuminated.

E144523

The grade assist lamp will appear in the instrument cluster when grade assist is turned on.

Press the transmission control switch again to return to normal D (Drive).

L (Low)

• Provides maximum engine braking.

• The transmission may be shifted into

L (Low) at any vehicle speed. "

Edited April 29, 2013 at 10:33 PM by Scooter80

[rprobst]

Thanks, scooter, a really helpful post.

 

Just one thing:

 

In my experience of some moderate (for my area) grades, ...

You live in Chicago, right? There are grades in Chicago?? :)

[Scooter80]

Thanks, scooter, a really helpful post.

Just one thing:

 

You live in Chicago, right? There are grades in Chicago?? :)

Lol, no there aren't. I'm far n/w suburbs so we have a few up here, but I also took a trip into mid Wisconsin to see my folks. Some hills to and from and a really decent one by them allowed some tests.

[rprobst]

Ahh, I remember the Wisconsin hills fondly. I was born in Evanston and grew up in Northbrook.

[bibolton]

California has an area on Interstate 5 from LA north to the valley known as the "Grapevine". The descent drops about 2300 feet in 6 to 7 miles. Just using hill assist, it kept my Fusion Energi at 60mph and put 5 miles back into the battery. I did try a shift to low but it slowed me too much so I shifted back to drive within 15 seconds. At no time did the engine engage and my milage reading came up to 54.1 mpg. Gotta love this car!!!! Even if I never reach the goal of 100MPGe I'll take 50 any day.

Edited May 6, 2013 at 06:10 PM by bibolton

[jsamp]

It would be interesting for one of you to try going down a grade in L or hill assist with a full battery.  I'm pretty sure that is when the ICE will kick back on to aid in slowing the vehicle through compression.  Once a battery is full, it can't take any more charge so either the electricity has to be dissipated in a resistor (like diesel-electric locomotives) or something else has to take over like the ICE.

[Energized]

It would be interesting for one of you to try going down a grade in L or hill assist with a full battery.  I'm pretty sure that is when the ICE will kick back on to aid in slowing the vehicle through compression.  Once a battery is full, it can't take any more charge so either the electricity has to be dissipated in a resistor (like diesel-electric locomotives) or something else has to take over like the ICE.

 

http://www.fordfusionenergiforum.com/topic/800-engine-on-for-grade-assist/

[Ekpsych]

I am wondering if driving with hill assist on at all times will help extend ev range. I'm going to give it a try and report back.

[Russael]

I'm still not 100% certain on how Hill Assist works, but I kind of felt that it worked in conjunction with the cruise control to maintain your speed while on a decline.  If you're not at risk of accelerating faster while your foot is off of the accelerator, it shouldn't do anything at all.  Thing is, it still works even if you don't have cruise on, so it may still work if you're going downhill on a steep grade, and it won't let the car accelerate any faster than when you took your foot off the gas, up until the battery reaches full capacity.

 

Driving in L keeps maximum electric engine braking on full.  I like to mess with it from time to time to try 'one foot driving' which is cool, but it doesn't activate the brake lights when rolling up to an intersection, so I use it sparingly.

[BadRock]

I believe hill assist works in conjunction with data collected from the on board gyroscope. Depending on the angle of descent the car will apply appropriate regenerative braking to attempt to maintain the speed you were traveling when your foot left the accelerator. If you are traveling at 0° grade no additional braking is applied. 10°+ grade regenerative braking is fully applied. I use this often and it works rather well.

[Nherring]

I've been focusing on the following two methods of using L.

 

1) when driving at moderate speeds, drive in normal mode but switch to L when approaching traffic lights, stop signs, steep downhill sections and traffic congestion ahead.

 

2) when driving in heavy stop and go traffic, leave in L and control speed solely with the accelerator.

 

3) at high speeds, use cruise control and inactivate during downhill stretches, causing regen in normal mode, even if it causes modest speed loss; re accelerate as approaching level at the vase of the hill.

 

4) at moderate speeds, back off accelerator when approaching the top of a hill and allow the car to coast over the top, ain't wining a fir speed for those behind you.

 

Be more aggressive on regen if nobody's following closely. Slowing by 10 mph under the right conditions can really add the regen, assuming you don't use it up by heading up a steep hill immediately.

 

As a result, my overall regen has increased dramatically. For example, my commute is ~ 55 miles each way. Initially I typically drove 28 miles on battery/regen and used .85 gallons of gas. As I've improved, I'm now at 33-34 miles battery/regen and using an average of .65 gallons of gas. At the current rate, it'll take me two weeks to use a tank of gas, I'll get a total of 1,250 miles and average 90 mpg. I have an L2 charger at work so my drive is similar both ways.

 

I'm still improving. 100mpg is possible, I think, although only rarely, due to heavy traffic most of the time.