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shifting from reverse to drive
- Thread starter orlando
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- Model S User Interface
steve841
Active Member
Though I don't speak from experience ... It won't hurt anything and there is programming (i recall reading here) to prevent a shift to reverse above 3-5 mph ...it would go to neutral.
Puyallup Bill
Member
And the car will beep at you.
Before I learned that you can get to neutral with a slight down pull of the shift lever, I would push toward N and often overshoot into R. Got neutral.
FWIW, hypermilers like using neutral in the LEAF and that requires holding the hockey puck shifter in position for a few seconds. The work around is to shift into R and go to N immediately. just ignore the angry beeps.
if you lift your "gas pedal" - regen is setting in, from an electric view this is in fact the same as setting the car in reverse while driving forward.
There would be nothing wrong about allowing shift to reverse while driving forward, as long as SW is handling this in a controled way - e.g. using regen down to 0 mph and instead of stopping regen, just contionue backwards.
There would be nothing wrong about allowing shift to reverse while driving forward, as long as SW is handling this in a controled way - e.g. using regen down to 0 mph and instead of stopping regen, just contionue backwards.
mknox
Well-Known Member
When I back out of my driveway, I've noticed that I can shift from R to D directly without coming to a complete stop and without touching the brake. It seems you only have to press the brake when shifting from Park.
ModelS1079
Member
Yes I noticed the same. At low speed only, as you noted. Every morning as I back out and pull a three point turn. Never stopped to think how nice this is compared with pressing the brake to change. Well-noted.
Puyallup Bill
Member
If you want to go to neutral while in motion, pull the shift lever down one notch. Might take a few practice tries - it is easy to pull through that spot, but not a problem if you do, as you just go back to D.
I play a lot. Shortly after leaving my home there is a long down slope on the freeway - 70-75 MPH when freewheeling. I shift back and forth between N and D. Sometimes I go to the touch screen and change the amount of regen.
Is it really that hard to put the MS in neutral while driving? On a road with a slight decline or to coast to a distant redlight using neutral would be the most efficient way to travel. Hyper milers do it all the time in hybrids.
NigelM
Recovering Member
I agree with Jerry. While there are some circumstances where this is useful, around here I'd find it dangerous to be slowing down without brake lights coming on.
A more technical question would be which is better and by how much: a) coasting in neutral to save power or b) using power for forward momentum but gaining back by using regen to slow to a halt?
My experience has been that there is no real difference between coasting in neutral and pressing on the accelerator just enough so that there is no regeneration or power used. I've found this to be true in both the Prius and the Model S. During 2012, the average mpg on the 2004 Prius was 69.2 over 16,212 miles, and on the Model S the average is 257 kWh/mi over 8,400 miles. Both used as daily drivers and about 25% of the miles have been vacation trips. Unless there is some evidence that far better results can be achieved using some other technique during daily driving (you can get far better using a pet course), I'm going to assume that pressing the accelerator the correct amount is equivalent.
Regeneration turns kinetic energy into electricity and heat so slowing without using regeneration will always do better. However, it appears that the Model S is far more efficient at regeneration than the Prius is so the difference is much smaller. This is because there is almost always some friction braking used with the Toyota system (see the graph I posted in the braking thread).
I try to do this all the time. If I'm accelerating, near desired speed, and I see the next light just turn red, I try to slowly come down in speed (hopefully getting to the light when it is about to turn green) by coasting and letting the wind resistance do its thing. I'm using the heavy regen option so just lifting the foot off the accelerator would decelerate too fast (distance between lights at my location is 2-3 city blocks).
The difficulty is that the accelerator is very touchy in the transition between actual acceleration and start of full regen. I find it difficult to get to this point quickly and frequently go into "lights on" regen by releasing too much. Even after getting close to the transition by feel, I find myself having to look at the screen to check that I'm actually not using the regen. I believe this is because once the car gets going approximately 75% of the accelerator range of travel is for acceleration and only about 20% is for deceleration/regen. It's hard to say precicely since the percentages seem to change based on speed.
I'm really hoping that Tesla will refine the acceleration algorithm in a future update to make it easier to control this crossover.
Note that the scale on the instrument panel is logarithmic. If it's showing a tiny bit of power or regen it's really only a very tiny amount. Doing it by feel should give you very good results.
in real life the far trickier thing would be determining the exact distance where coasting will bring you to a stop at the exact point you want anyway. Because I believe applying a constant amount of regen to stop is better than coasting and then having to use more regen to stop at the end. I find the Model S coasts for a really long ways.
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Hybrids have this issue too. But it is easy to just slip the gear shift to neutral. Hypermilers do it all the time when air and rolling resistance is all you need to slow or maintain speed at a certain rate. So an easy to use neutral would really help efficiency.
1. There isn't anything unsafe about it. I do it all the time. Hyper milers do it all the time. People with manual transmissions do it all the time.
2. The post above says it is hard to modulate it. Which is it?
Seems to me it would b easier to give your foot a rest and not have feather the accel all the time to stay in neutral without generating any wasteful regen or accel when you don't need it.
NigelM
Recovering Member
I think it depends where you live. FL has it's fair share of senior drivers and most accidents seem to be rear-enders with an elderly driver saying they didn't see the car in front or didn't realize it was slowing. No, I don't have stats for that but personally I want my brake lights to come on back there. If it works for you then fine.
The brake lights have nothing to do with whether you are in neutral or feathering the accelerator. The brake lights are based on accelerometers, so their behavior should be exactly the same.
If you want the best view of the brake lights, press the Tesla logo on the MCU. That picture is a good view.
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