Shifting into neutral

I don't see any particular downside to using N under these circumstances. I personally use EV mode in similar conditions at the end of my commute. I drive about 8 miles each way, mixed 55mph freeway and 40mph urban, ending with low speed ~20mph pulse/glide through quiet neighborhood with speed bumps. Almost always end up turning into neighborhood with a little excess charge in battery (one bar from top) and typically use only one bar to get to the driveway.

I think most concerns about N voiced above relate to folks using it as part of their regular driving at higher speeds in traffic.

Rob

 

This is why it is still obscure to me. How do you know it is more efficient? Do you factor in the added time it takes to coast (not glide) to a stop? Have you compared mileages using an OBD reader? Having compared results, I would say that using N in other than very specific circumstances will result in lower mileage.

 

It is more efficient because the kinetic energy used to move the car NOT charging the battery it is good to reuse some of the energy if no other way but it is better to avoid it if circumstance allow.


Sure it takes a few more minutes to get home about 4 minutes longer but that is no big deal most.

Yes I drive with an SG and have detailed logs. Also some engineering explanation of the above was discussed on PC several time. The idea is the conversion of the energy from motor generator to battery and then back with the inverter motorgenerator again is substantial somewhere around 30% or even more.

 

Most of the discussions about the regen systems are wrong. In any case, that is not what I asked. Your SG will show that the car uses 1.5-2 amps at a minimum. That means that 4 minutes is about 20 watt-hours of energy. This needs to be accounted for. My car currently shows 64.7mpg with about 250 miles on this tank. I do not coast to stops. I do not use neutral. I am not saying that 20 watt-hours is a big deal, only that it is very difficult to pick out one small part of a driving system and use it in any meaningful way.

 

I think most would agree that gliding, whether in neutral or by pedal manipulation is more efficient than coasting (no pedal input in drive, regen dragging). In this low speed condition I'm not sure that there is any real difference between gliding in neutral and gliding in drive. The ICE should be truly off either way. I think what dryinsider is getting at is when gliding in N, you are probably still using some net charge out of the battery during your pulses and/or just from the overhead it takes to operate the vehicle. Gliding with very slight regen would offset that usage. It probably doesn't really matter unless you are significantly lowering the SOC of the battery by the time you get home. If you lower it by more than what will be made up for on the next warm up cycle, then you might be burning excess fuel on the next drive to bring the SOC back up to nominal.

 

Dangerous to coast in neutral. The logic of some really escapes me here. As a former truck driver I get the reasons why it's a bad idea driving a class 8 truck, but that's a whole different concept than what would apply to a car.

 

You are thinking in terms of modern cars. The laws were written several generations ago when cars and light trucks had the same limitations as the heavy trucks.

 

I shift into neutral any time I'm going through a car wash. Otherwise? I see no appreciable real benefit from using neutral.

 

Wayne Gerdes in a Prius hypermiling tutorial here, suggests Neutral at several points through the Video:

Personally I leave it in D, all the time, but if Wayne's advocating Neutral there must be a reason.

 

Neutral does not mechanically disengage anything. The disengagement is purely electrical - a computer mode if you will.
I have read some reports that the problem of overspeeding of MG1 has been eliminated in the newer versions - need to confirm before I am willing to do it much.
The warning about neutral has to do with overspeeding MG1 in some scenarios. If the wheels are spinning then either the ICE has to spin or MG1 has to spin - or both - even in neutral.

Do a search for this thread:

Use of "N" for coasting

It discusses what happens to the ICE and MG1 when in neutral. It's on page 4 of the posts that tests show that the ICE is burning a small amount of gas in neutral to keep the MG1 from over spinning at speeds above 40 mph.

 

Ok, after more investigating, it seems in GenIII the overspeed of MG1 and MG2 happens now at 61 mph. Above 61 mph retarding voltage is applied to the motors and the ICE it seems still has to spin with or without gas injected to stop overspeed of the motors. This all of course happens in neutral as well as drive since the motors and ICE are never disengaged from the drive axles.

All this to say it probably is ok to mechanically to run at speed in neutral. The computer monitors and adjusts things as needed even then.

 

I only cost in neutral only if the road is fairly straight and no more then 20% grade, then again i live in flatland and i hardly can coast in neutral.

 

That's exactly the reason I've been thinking of using N. After about a half hour of driving and finding that glide spot, my leg feels as though I've been highway driving for hours with no cruise control.

Just watched the video above. I'm a bit confused. Seems neutral was used a lot and no gliding. Is this because of the slower stop and go city traffic? In another posted video of his he seems to be doing nothing but P&G although it's in a much more rural setting. Also, I'm not sure if I understand super highway glide. The best I can do there, at highway speeds, is to have no arrows going to the wheels and a red arrow going to the battery.

 

This probably does not happen in neutral. It is a function of the Synergy firmware, which is disabled in neutral. You really need to understand what happens when you shift to neutral.

 

What happens? According to the video you are literally in "neutral". At least that's the way I understood it.

 

No "N" good bye auto car washes

 

This was a shortcut for training purposes during his limited time available for drive-alongs. Longer term, the students are supposed to lightly apply the pedal to make the HSI bar disappear (no thrust, no regen/synthetic engine drag). These sessions didn't have much time to practice that move, N immediately gives the same effect.

 

I will be trying N instead of glide at speeds under 40 mph. Seems like much less work than "jiggling" the pedal for glide.

 

i use the Nuetral to gain speed when the battery has been adequately recharged to pick up additional speed down Highway 14 from Lancaster, CA. I will go from SHM to (B)raking to Neutral to either gain speed to around 78 mph downhill in anticipation of going up the next hill, where i will trade speed for MPG. I use the B when i come up someones tail and need to slow down while charging the battery. Most of my driving is DWB not DWI.

 

The Prius has two systems that provide almost 70% of the fuel efficiencies that we enjoy- the regeneration systems and the Synergy drive firmware. Both of these are disabled by shifting to neutral. Why give up 70% of the car's potential when you can do exactly the same thing by backing off on the accelerator?