I'll admit to not understanding the concept of D and N beyond the facts, D is drive where you are connected to the engine, and N has only braking, but no conection to acceleration.

So I've read here about using N while in parking lots to maximize roll since the regeatize brakes won't engage, so wouldn't that also work going downhill?

I tried using N while on declines both on backroad and highway driving recently to see if I could maximinze the distance gliding before needing to shift gears and hit the gas. But when traveling at speed the mpg display rapidly lowers when in N? Does only D shut the valves while gliding downhill? Is N just for slow to idle speeds? Any help explaining would be appreciated

 

Once you learn to feather your foot, you'll improve your overall FE by leaving it in D. When you switch to N, you disconnect the engine crankshaft from the wheels, preventing you from using regenerative braking (whether by coasting or with foot on brakes) to moderate the speed you gain going downhill, and leaving only brake pads. By leaving it in D, the ICE will still shut off, the valves will seal along with it, but when you start accelerating from gravity, you can recapture that energy by lessening foot pressure and diverting energy into the IMA>NiMH.

 

When you release the accelerator while in "D" (say, coasting downhill or anticipating an upcoming stop), the fuel supply is shut-off to the injectors. For this reason, you'll see your mpg display read maximum (you're moving but using no gas).

On the other hand, when you attempt to coast while in "N", this tells the powertrain that you want to disconnect the transmission and "idle" the engine (assuming your foot's off the accelerator). In this case, your mpg display will show less fuel efficiency because you're both moving and using some gas to allow the ICE to idle.

The car will not shut-off fuel, close the valves, or auto-stop when in "N" (or "P", for that matter). So, even though you can't choose a "no regen" mode while coasting in "D", it's still the most efficient way to drive.

 

In my opinion, it is better to stay in D. When coasting in N, your engine will not regen and thus coast further. This is why some people want to coast in N. However if you coast in D and step on the accelerator just enough to stop the regen, you will be coasting and no fuel will be flowing into your engine. Getting the pedal position right takes a little bit of practice, but once you get used to it you will do it w/o noticing.

 

I went last summer to the new hampshire where there are a lot a big mountains. I have tried many strategy. For Downhills:

D. All the time. I regenerate the batteries consumed in the upwill then goes in the stealth mode (no assist/no regen). That give good FE and most the mpg lost in the uphill was recover in the dowhill with a SoC at max for the coming uphill.

N. All the time. With A Forced AutoStop (FAS). Give a excellent mpg but you might not have enough SoC for the coming uphill. So that's ok for one or two downhills only. Conclusion. Not suggested. Yes you can make N without FAS but the ICE will consume fuel and your FE will be less (as said above). Not suggested neigher.

D + N : D : I regenerate the batteries consumed in the upwill then goes in N, make a FAS and downhill like a jet. A got tremendious mpg with a SoC at max for the coming uphill. I will not say it is my suggestion since FAS can be illegal some places. I would not invite you to make illegal things after all.


PierreM

 

Well D it is then. Good too because I'm lazy and hate shifting gears. Tiptronic as about as far from automatic trans I'd go

 

I know this may sound like a dumb question, but how do you do a FAS? I've never done it (at least I don't think I have)

 

Shift to N, turn off the engine with the key. Illegal in some states/localities.

 

*Could be dangerous if not done right, possibly illegal*

Forcing an AS in any vehicle (other then an Fas , takes these limits out of the equation. Shift to N, let the Tach stabilize, [b]key back to IG-I (shuts down the ICE via key to IG-III, release to IG-II, and engage transmission with a rev match to continue on your way. Source:cleanmpg

PM

 

Anybody have any thoughts on shifting to 2nd down a hill? I live at the top of a hill where I'm quite often at about half charge when I leave in the morning, while the car's cold. Unfortunately, the hill's not steep enough, nor long enough, for the car to get fast enough to engage the charging.
But, if I drop the car into 2nd for a second after I've built up a little speed I get 2-3 green bars, and engine breaking is strong (which isn't bad, since I have to stop at the bottom of the hill anyhow).

What are your thoughts on this?
-Mo