Actually, it doesn't matter if battery charge is on level ground or a hill, and almost doesn't matter if it is downhill as well. The power drawn from the ICE by MG2 during charging is not available to the wheels for motive power or to MG1 for control, so it can be related to a certain amount of fuel per Kilowatt regardless of where that activity takes place. The only "free" charge is from charging while coasting (and you spent the gas to get up the hill) or regen braking (and you spent the gas to accelerate in the first place).

There is not a free lunch -- unless you consider two very minor points:

1. There may be some small fuel reduction acheived by reducing the number of engine cycles (stops and starts),

2. There may also be some small fuel savings realized by "making it" in "N" vs. "not making it" in "D" over a very small hill after coasting because of the difference in rolling resistance due to MG2 generation for battery charge. This would be a very small difference is a very few situations.

Also there could be a few potiential downsides to using "N" to coast in very cold conditions because the ICE shutdown means that it cannot maintain the catalytic system and/or cabin heat. That would mean that the engine is cold on restart, and would require a richer mixture from the ECU which could be detrimental to FE. Also, the loss of regen braking at lower speeds while coasting in "N" will increase brake wear.

 

It seems you took some of that quote out of its context and it seems as you did not read all of it as well. (I included more of the relevant text). I never said there was a "free lunch". I'm just describing the "cheapest lunch" possible.

Which scenario do you think is better (from a fuel economy perspective)?

1.) Coasting down a hill (ICE off) without assisting or charging. The slope is just right so that the desired speed is maintained.

2.) Going down the same hill (ICE off) while charging. Of course, you lose speed and either have to add battery assist or restart the ICE to maintain your desired speed.

The correct answer is 1. If you are coasting and you do not need to come to a stop or slow down, charging/regen is not a good thing to do from a fuel economy perspective.

Small fuel savings over short distances translate to large fuel savings over long distances.

Unless you actually want to slow down after you take your foot off the accelerator, it is pointless to go into regen mode. Shifting to Neutral eliminates this.

Let's stick to reality here. How long do you really think I'm suggesting people stay in Neutral? In my conditions, the most I can ever stay in Neutral is maybe 2 minutes maximum. It's usually much less than that.

 

Do you use your block heater during the summer months? Just curious, since for me a block heater has always been associated with letting my car start on a cold winter morning. I never thought about it as being useful to shorten warm-up time for FE.

 

Now that I have it installed, I have been using and will continue to use it every day I am going to drive. It is probably more beneficial to Toyota's HSD vehicles than most.

 

Thanks for the tips Mr. Kite and others. Those are good suggestions.

 

I'm also in the Denver area and hadn't considered a block heater... I may do just that. I wonder what real-world difference in economy it creates?

Anyway, Senior Kite, thanks for all the insight. I will begin experimenting immediately!

 

From some of the comments I have read, I get the impression that some HiHys can be started in Neutral instead of just park. Is that correct, or do all HiHys require you to be in park to start?

For Mr Kite, reading throught the states that a prius can be in, and assuming the HiHy is similar I do see a lot of similarities. However, I noticed that if I manually put my car in neutral, I seem to revert back to stage 3a. Have you notice similar or this either a new function or just my imagination?

Thanks.

 

I cannot speak for all, but mine can definitely not be started in Neutral. It can only be started in Park. I think this is always the case.

I have not noticed that behavior. Are you saying that the engine kicks on when you switch to Neutral? It was my understanding that the engine state cannot change when shifted to neutral (i.e. if the engine is off, it stays off when you switch to N; if the engine is on, it stays on when you switch to N). Also, this is what I observe through the ScanGauge II I have hooked up to my HiHy.

 

I was experimenting with high speed coasting. I don't have the full nav/monitoring system, and the limited one on the dash indicates that when going down hill over 40 mph, the batteries feed power into the system (I'm not sure if thats to prevent damage, to actually cause decerlation, or just a display anomoly).

Any way, when going down any signifigant hill (say longer than 15/20 seconds), I shifted into neutral to prevent battery power feeding in. The display seems to indicate this works. However I frequently notice a change in the point where ICE kicks in. When the car is heated up, but I haven't done the long stop which I'll assume allows the car to enter state 4, I usually can't go faster than about 32/35 mph on a flat without the ICE. At some point (usually after a long stop), that changes and I can go upwards of 40/43 without ice on flat. Actually, I think the limit at that point is around 45, but to maintain enough power for a steady speed, I have to use power electric power than is allowed.

By the way, can SGII, actualy monitor this state, or is it, as far as known, unmonitorable?

 

I filled up 2 days ago and have been trying use all the techniques that Mr Kite imparted to improve my fuel economy. Thus far, I've gotten it up about .5 mpg..... Yes. A HALF mile per gallon increase.

I coast in neutral often, I am really easy on the gas. I don't know what else to try. I'm at 23 mpg. My commute is about 10 miles, all stop-n-go 40 mph roads.