N - Should we? When? And Why?

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mwalsh

Well-known member
Leaf Supporting Member
Joined
Apr 22, 2010
Messages
9,781
Location
Garden Grove, CA
So a couple of times, as I've been shifting from D into ECO and been too slow, I've found myself in N. And you know what.....the car just coasts along in N. Really. There is more drag on the engine in D, just like there is most manual transmission cars in the highest available gear.

Now, I've already got myself convinced that's probably not a good thing to do, but I'm wondering if you agree? Or if you could see N being useful in any way when it comes to managing range and/or performance?
 
mwalsh said:
So a couple of times, as I've been shifting from D into ECO and been too slow, I've found myself in N. And you know what.....the car just coasts along in N. Really. There is more drag on the engine in D, just like there is most manual transmission cars in the highest available gear.

Now, I've already got myself convinced that's probably not a good thing to do, but I'm wondering if you agree? Or if you could see N being useful in any way when it comes to managing range and/or performance?
If you don't need regen and you don't need to accelerate, then why not use it? It's not even like an ICE where you can't accidentally press the accelerator and rev up the engine! :D

Looking at the service manual I can't see where any harm would occur as long as the vehicle is on and you are intentionally going to and from Neutral and into Drive... Reverse might be a problem, but I'm pretty sure the vehicle won't let you go into reverse when your traveling over a certain speed (I need to find that again in the service manual)...
 
I would not advise driving in N, and using the drive shifter constantly while driving will likely cause extra wear. What is the point of using N, there is a N point in the pedal position in every drive mode, It seems like a pointless distraction with no real gain other than parts wear. Lear to drive the EV the way it was designed and learn pedal position and you will become a far more efficient driver.
 
N is useful just as in any other car. If the car is dead and you need to move it, you'll need N. If its dead and you need it towed, you'll need N. Neutral is not useful in any way for managing range/performance. Its not supposed to be used when driving.
 
I wouldn't use N. If you need to accelerate quickly for some reason, you wouldn't be able to do that - unless switching from N to D becomes second nature.
 
For all of us Prius drivers out there - we know that when you take your foot completely off the gas pedal you actual impart some drag on the car as regen kicks in. On one of the dash displays, you can clearly see how much you need to push in the gas pedal in order to coast - no power, no regen. This state is essential the same as Neutral, except of course if you move your foot you either get gas or regen immediately. It's a better solution then putting your car into Neutral all of the time imho.

Is there a similar display on the Leaf which tells you that you are essentially coasting - no regen and no power? Does it seem as accurate as on the Prius?
 
LakeLeaf said:
For all of us Prius drivers out there - we know that when you take your foot completely off the gas pedal you actual impart some drag on the car as regen kicks in. On one of the dash displays, you can clearly see how much you need to push in the gas pedal in order to coast - no power, no regen. This state is essential the same as Neutral, except of course if you move your foot you either get gas or regen immediately. It's a better solution then putting your car into Neutral all of the time imho.

Is there a similar display on the Leaf which tells you that you are essentially coasting - no regen and no power? Does it seem as accurate as on the Prius?


Yes, but Nissan made all gauges broad based and not accurate, you can see use and regen but the increments are debatable.
 
DarkStar said:
If you don't need regen and you don't need to accelerate, then why not use it? It's not even like an ICE where you can't accidentally press the accelerator and rev up the engine! :D
I don't know about other states, but California law puts an important restriction on use of neutral:
21710. The driver of a motor vehicle when traveling on down grade upon any highway shall not coast with the gears of such vehicle in neutral.
(By the way, "highway" in California law is any public road, including city streets.)

So it might be legal to use neutral while slowing down, but never while maintaining or increasing speed.
 
Ohmie said:
N is useful just as in any other car. If the car is dead and you need to move it, you'll need N. If its dead and you need it towed, you'll need N. Neutral is not useful in any way for managing range/performance. Its not supposed to be used when driving.
I believe this is not true - "N" in the Leaf does not disengage any gears or anything, since there aren't any gears to engage in the first place. I'm pretty sure that "N" just turns off power to the motor, letting it spin freely. If the car is truely "dead" (battery, not say... tire problem), you're not going to be able to switch into "N" anyway.
 
as a Prius driver, i use N occasionally, but its rare cases that it can be useful. the rolling hills scenario that has been discussed is one as long as the hills are not too steep or too long.

but that goes back to the discussion of how much charge does it take to climb a hill now if allowed to gain speed to go faster than your target speed, that momentum is going to take you part way up the hill until you are able to slow back down to your target speed which in effect reduces the elevation of the hill climbed

well that is speed gained from gravity only so its "free range" in a sense in that regen would have regulated your speed much more while gaining a charge to do so, but the charge gained is very insignificant in a Prius (less than 5%) and i am guessing that will be the same in the Leaf.
 
DaveinOlyWA said:
well that is speed gained from gravity only so its "free range" in a sense in that regen would have regulated your speed much more while gaining a charge to do so
And it's not even totally free, since air resistance as a function of speed applies whether you are coasting or applying power.

Is it legal to coast downhill in Washington, unlike California?
 
DaveinOlyWA said:
as a Prius driver, i use N occasionally, but its rare cases that it can be useful. the rolling hills scenario that has been discussed is one as long as the hills are not too steep or too long.

but that goes back to the discussion of how much charge does it take to climb a hill now if allowed to gain speed to go faster than your target speed, that momentum is going to take you part way up the hill until you are able to slow back down to your target speed which in effect reduces the elevation of the hill climbed

well that is speed gained from gravity only so its "free range" in a sense in that regen would have regulated your speed much more while gaining a charge to do so, but the charge gained is very insignificant in a Prius (less than 5%) and i am guessing that will be the same in the Leaf.

Yeah - I'm waiting to use the argument to fight a speeding ticket. Yes your honor, I was just using the forces of gravity to gain additional momentum so that I could crest that next hill without slowing too much below the speed limit and while preserving my energy usage and therefore our planet.

Speed limits don't (yet) acknowledge hybrid and EV driving practices. :D
 
mwalsh said:
So a couple of times, as I've been shifting from D into ECO and been too slow,
I've found myself in N. And you know what.....the car just coasts along in N. Really.
There is more drag on the engine in D, just like there is most manual transmission
cars in the highest available gear.

This is a very good question, but from other posts it looks like the LEAF's OEM
instrumentation is not sensitive enough to allow a power flow-based decision.

The Prius is a case in point. One of the conditions that a driver can achieve with
the accelerator, "go-pedal," is commonly known as a "no arrows glide." In this
condition, the OEM instrumentation would lead you to believe that no power was
flowing to or from the HV battery or MG2 to drive the wheels. But folks with more
sophisticated instrumentation, CAN View IIRC, found that there is a very small
power flow from the HV battery to MG2, about . 75 HP. Sorry, don't know the
electrical equivalent. They also found that in Neutral, there is no such flow.
Also in Neutral there is no regen or direct ICE to HV battery charging.

This has two consequences:
* The Prius' surprising ability to glide long distances is not just the result of very
good aero, but some electrical "augmentation" as well.
* If you are very, very seriously committed to getting max FE, with the Prius you
can save a really small amount of SOC and it is better to glide in Neutral than
"no arrows glide."

Is this true for the LEAF?
At this point, I'll bet nobody but engineers/testers at Nissan know. This unfortunate
situation isn't likely to change until a serious e-geek/techno-type decides to get
some real power flow readings.

Also, in a post or two you'll be hearing from folks who say it is illegal in their state
to drive in Neutral. The laws go back to the '30s'. Probably issues with restarting
while moving. Wholly out of date with contemporary computer managed power
systems. What can I say?
 
planet4ever said:
DaveinOlyWA said:
well that is speed gained from gravity only so its "free range" in a sense in that regen would have regulated your speed much more while gaining a charge to do so
And it's not even totally free, since air resistance as a function of speed applies whether you are coasting or applying power.

Is it legal to coast downhill in Washington, unlike California?


the way i do it, its illegal no matter what gear you are in.

i have a road i drive on occasion. the speed limit is 50 mph and its rolling hills for about a 10 mile stretch. on a good day (which means no traffic) my speed runs from 40 mph cresting hills to as much as 75 mph at the bottoms. while doing this i almost never or only for a very short duration do i apply more power than what is required to do about 50 mph.. typically this period of power output is about 70-80% of the uphill leg. so for the entire cycle traveled, the power output is equal to 70% of half or about 1/3rd of the distance. i start applying power when i hit 55-60 mph. that only slows my rate of decceleration i dont feel that i take unnecessary risks and the road is pretty straight so speed is not really a factor.

and speed is a factor directly related to energy and there is no free lunch, but there is a HUGE difference in the types of energies involved the the level of efficiency in capturing and using energy.

if you can imagine a rolling hills scenario shaped in a perfect sine wave that runs from 0 to 360º with zero being the apex of the hump. so a cycle runs from hump to hump.

each area would be divided by two areas essentially 180º with the first half going down, the 2nd going up.

with a target speed of 50 mph, lets assume a value X is needed to maintain constant velocity. "free" regen provides a value we will call -y (we say minus because its power being restored to the batteries)

now, i dont know this, but i am guessing that y is very small as compared to X in absolute terms. maybe a 1 to 5 (i doubt its that high) we will say.

so if looking at a power output verses time chart.

you could have -y from 0 to 180º possibly generating a speed slightly above 50 mph. but almost immediately requiring power to ascend the 2nd half of the leg as soon as your speed drops to 50 mph. which would be most of the 2nd leg.

but suppose we decided not to regen (which is essentially coasting) so our power output was not -y, it was zero. but we are still gaining power thru much more kinetic energy due to gravity. the greater speed we obtain which will be significantly above 50 mph will propel us much farther up the hill before reaching the same 50 mph threshold.

so the power required to drive the hill is always the same, but in the 2nd scenario, we have removed the inefficiencies of regen and more effectively used gravity instead.

**edited for clarity**
 
Dave,

Well said. There are fewer losses when converting potential energy (top
of a hill) to kinetic energy (velocity) than by converting
potential to mechanical to chemical (in the HV battery] and then chemical
to mehanical later.

I know you know this but others may not: air resistance increases as the
square^2 of the speed, power needed to offset the air resistance increases
as the cube^3 of the speed.

"Fewer losses" does not include the $$$ losses from getting a ticket for
speeding though.
 
the law is something one must contend with all the time but we cannot ignore the archaic regulations on the books that must be in place for people who ignore safety. that is essentially what speed limits are for, its simply for people who dont know any better.

the road i mentioned above i should say that the average speed for a lone driver is probably 60-65 so the scenario i am describing is by no means risky or dangerous in any way. now there is always the risks associated with higher speeds, but with the lack of cross traffic, full visibility, etc. the risk is minimized.

the road is to a popular recreation area for boating, fishing, etc. so its very normal for people to pass car/boat combos that are doing the speed limit at 65+ mph.

now, i am not condoning the practice and about once every 2-3 years we have a head on despite the rod straight roads and the increased visibility (no excuses when you can see traffic a half mile in front of you) but people seem to be stupid enough to pass going uphill near the crest which would be the only time you cannot see what is coming...
 
The CA law, as "quoted" or described above, seems to say that having the gears in neutral & going downhill was illegal.

The LEAF does have a gear pair between the motor and the wheels, but using "N" does not put that pair in neutral.

But, the "flavor" of the law might prevail, however be very difficult to prove against a LEAF driver.
 
garygid said:
The CA law, as "quoted" or described above, seems to say that having the gears in neutral & going downhill was illegal.

The LEAF does have a gear pair between the motor and the wheels, but using "N" does not put that pair in neutral.

But, the "flavor" of the law might prevail, however be very difficult to prove against a LEAF driver.

"Honest, officer! I was too busy drinking my beer and texting on my phone while speeding to even NOTICE if I was in Neutral!!"
:lol:
 
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