Down shifting drive to low.

5843 Views 23 Replies 13 Participants Last post by dsocks, Sep 20, 2015

dsocks

Discussion Starter · Sep 16, 2015

When driving in the mountains, what is the top speed at which you may down shift from drive to low in order to use the regenerative action rather than braking to control speed?

1 - 20 of 24 Posts

scottf200

· #2 · Sep 16, 2015

Any speed. It doesn't change any gearing ... just change how aggressive regen is.

Don't believe me. Just drive at any speed with a steady foot and shift multiple times between D and L ... you'll feel no difference.

I do this on test drives all the time to demonstrate L is not gearing just aggressive regen. (I've used L for 60,000 miles).

srmarti

· #3 · Sep 16, 2015

Like Scott says. Low isn't a low gear, just stronger regeneration. Drive 100mph in L and the motor turns at the same speed as D.

MrMischief

· #4 · Sep 16, 2015

On my test drive I slipped it from D to L and it surprised me at how aggressive the regen is at throttle lift off. Is there any "risk" in running in L? Extra heat generation maybe? I also wonder about inducing a slide if you do this on ice, or does the traction control system keep it sorted?

JeffC

· #5 · Sep 16, 2015

I usually drive in L all the time except on the freeway. Was driving my wife's Escape today and I actually found it annoying not having the aggressive regen slowing me down. It takes a few to get used to "feathering" the gas pedal to get varying amounts of regen braking, but once you get used to it you hardly use the real brakes for much more than holding at a stop.

canehdian

· #6 · Sep 16, 2015

MrMischief said:
On my test drive I slipped it from D to L and it surprised me at how aggressive the regen is at throttle lift off. Is there any "risk" in running in L? Extra heat generation maybe? I also wonder about inducing a slide if you do this on ice, or does the traction control system keep it sorted?

Zero risk to drive train. Many drive in L daily. Regular braking uses regen as well.

Ice can be tricky. If ABS is required/low traction flashes on the display, all regen stops suddenly. which can be scary. Same with downhill potholes.
Best to not use L in slippery conditions.

Mister Dave

· #7 · Sep 16, 2015

MrMischief said:
On my test drive I slipped it from D to L and it surprised me at how aggressive the regen is at throttle lift off. Is there any "risk" in running in L? Extra heat generation maybe? I also wonder about inducing a slide if you do this on ice, or does the traction control system keep it sorted?

Maybe a bit of extra stress on drivetrain bearings and CV joints, but so far no one has reported any repairs due to driving exclusively in L. There are a few folks tracking this, and plenty of guinea pigs.

MrMischief said:
I also wonder about inducing a slide if you do this on ice, or does the traction control system keep it sorted?

IIRC the manual has a caution about this.

linkim

· #8 · Sep 16, 2015

Mister Dave said:
Maybe a bit of extra stress on drivetrain bearings and CV joints, but so far no one has reported any repairs due to driving exclusively in L. There are a few folks tracking this, and plenty of guinea pigs.

Does the manual state that one should not drive exclusively in L and if so, why? Is there any numerical value to show the difference between D and L? The LEAF has two driving modes - normal and ECO - but there is mention of not driving in ECO exclusively.

Mister Dave

· #9 · Sep 16, 2015 (Edited)

linkim said:
Does the manual state that one should not drive exclusively in L and if so, why? Is there any numerical value to show the difference between D and L? The LEAF has two driving modes - normal and ECO - but there is mention of not driving in ECO exclusively.

IIRC it cautions about driving in L on slippery roads but I don't have time right now to verify that. It encourages using L downhill and in stop-and-go traffic to help keep brakes cool.

Edit: Okay, I took the time.....

Loss of Control
Skidding
-------------------------------
Try to avoid sudden steering, acceleration, or braking, including reducing vehicle speed by shifting to a lower gear. Any sudden changes could cause the tires to slide.

And later it slightly contradicts itself in the middle of this advice:

L (Low): This position reduces vehicle speed without using the brakes. Use L (Low) on very steep hills, in deep snow, in mud, or in stop-and-go traffic.

So don't use L on slippery surfaces, unless it's deep snow or mud? Pffft.....

Use the brakes on slippery surfaces. Your ABS will work then.

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llninja

· #10 · Sep 16, 2015

linkim said:
Does the manual state that one should not drive exclusively in L and if so, why? Is there any numerical value to show the difference between D and L? The LEAF has two driving modes - normal and ECO - but there is mention of not driving in ECO exclusively.

Many people drive in sport L all the time and there is no issue. Last winter I did some extensive testing driving on packed snow in al vs. D. Then the next day when a layer of ice was on top of the packed snow, I did it again. With packed snow without ice, driving in L was better than driving in d and tapping the brakes because the ABS would always kick in. I could not get any accelerator lifts in L to break the wheels loose. But on the day with ice on top of packed snow, I could get the wheels to break looks in al. But those conditions were extreme and atypical. But since you live in CA, this isn't anything you have to worry about.

Loboc

· #11 · Sep 16, 2015

'L' can get dicey if the TC gets confused. It will stop regen at once and seem like unexpected acceleration on a washboard road when stopping. Not enough ice conditions in DFW to test this behavior.

srmarti

· #12 · Sep 16, 2015

MrMischief said:
On my test drive I slipped it from D to L and it surprised me at how aggressive the regen is at throttle lift off. Is there any "risk" in running in L? Extra heat generation maybe? I also wonder about inducing a slide if you do this on ice, or does the traction control system keep it sorted?

The manual recommends using D in icy conditions. Handy thing that manual. It has answers to quite a few questions.

viking79

· #13 · Sep 16, 2015

The Volt uses two electric motors, some clutches, and a planetary gear set as a CVT transmission. The L and D are just software switch in how it behaves. They tried to mimic how you would use those in a traditional car.

There is no risk to the car running L 100% of the time. The difference between L and D is that L regen brakes when you let off the accelerator pedal and D the car still gives the motor some power to make it "coast" faster, and when you touch the brake pedal, apply some regen braking. I use L because it behaves like a manual transmission car when you back off the gas, the car slows down more rapidly and by the time I reach the brake pedal I have scrubbed off some speed and the weight distribution has already shifted to the front of the car.

Whenever the traction control thinks there is low traction it cuts regen braking. If you are relying on this in L, this is a bit disconcerting as the car suddenly stops slowing down as fast. This should be a non issue as you are presumably be moving your foot from the accelerator to the brake. In D it is less noticeable since your foot is already on the brake pedal when this happens.

To avoid this, don't over-inflate your tires for slippery conditions (I drop my tires to 32 PSI or so in the winter, mostly town driving). High tire pressures makes this much worse; the small bumps that trigger this condition are more severe and not as well damped by the tire.

This feature is a safety feature as it prevents loss of steering control in low traction situations while regen braking, but if you drive in L it might freak you out. I imagine this is why the manual recommends D for icy situations, although I prefer L (I just partly back off the accelerator pedal to slow down slowly).

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linkim

· #14 · Sep 16, 2015

With the regen paddle in the Gen 2 Volt, I assume the question of L and D is moot. Using the paddle and driving in D negates the need for L. Does that sound like a viable option?

MrMischief

· #15 · Sep 16, 2015

srmarti said:
The manual recommends using D in icy conditions. Handy thing that manual. It has answers to quite a few questions.

Sure would be nice if they gave those things out to all the non-owners so we can learn these things

scottf200

· #16 · Sep 16, 2015

MrMischief said:
Sure would be nice if they gave those things out to all the non-owners so we can learn these things

??? they are all here: http://www.chevrolet.com/owners/chevy-manuals.html

Paulacton84

· #17 · Sep 16, 2015

dsocks said:
When driving in the mountains, what is the top speed at which you may down shift from drive to low in order to use the regenerative action rather than braking to control speed?

101 MPH

you can shift to l or d or r at any time, including while driving backwards.

but you are mistaken when you say "rather than braking to control speed" the brake pedal on the volt is a deceleration control pedal- the cars computers apply the maximum amount of regeneration available for the brake pedal pressure you are applying.

This is one of the things that sets the volt apart from some other electric cars, which have mechanical braking only through the brake pedal. Use L or not, it matters not, but don't believe that you are increasing regeneration by using it.

canehdian

· #18 · Sep 16, 2015

Mister Dave said:
IIRC it cautions about driving in L on slippery roads but I don't have time right now to verify that. It encourages using L downhill and in stop-and-go traffic to help keep brakes cool.

Edit: Okay, I took the time.....

And later it slightly contradicts itself in the middle of this advice:

So don't use L on slippery surfaces, unless it's deep snow or mud? Pffft.....

Use the brakes on slippery surfaces. Your ABS will work then.

All of that sounds like legacy junk from as vehicle that actually has lower gears, and where 'L' limits power output/accel as well, not just slows the vehicle (like on my parents' escape)

saghost

· #19 · Sep 16, 2015

Mister Dave said:
Maybe a bit of extra stress on drivetrain bearings and CV joints, but so far no one has reported any repairs due to driving exclusively in L. There are a few folks tracking this, and plenty of guinea pigs.

IIRC the manual has a caution about this.

No extra wear, period.

What you have to remember is that under normal circumstances, showing the car by depressing the brake pedal lightly in D to get the same deceleration rate you get from get on the floor in L will result in the car not using the pads at all - the brake pedal also uses regeneration wherever possible, only triggering the friction brakes when the force levels rise.

MrMischief

· #20 · Sep 16, 2015

What is the logic behind always driving in L rather than D? The impression I was left with after my test drive is letting off the accelerator in D put the car into a coast (or near coast) while letting off the accelerator in L put the car into a deceleration/regeneration state. It seems that unless you need to be slowing at that rate, coasting in D where possible would be more economical than decelerating in L.

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