HELP on Arrows (or a Primer for the Arrow Challenged)

Dazed:
First of all, you shouldn't worry too much about this right now, much will come with time and experience.

But, since you asked, I'll do what I can to clarify some of the theory and practice of optimizing.

Over on the 2G-Yahoo Group there's been some pretty extensive discussion of the ways to optimize mileage. One of the key things the Japanese drivers have found to be effective (though I'm a tad doubtful) is what's being called "Dead Banding". The theory with this technique is that any transfer of energy to the battery and then back to the electric motor from the battery has inherent loss of energy and thus is less efficient than using power exclusively from the ICE to the wheels. Of course there's no way to completely prevent battery and motor use, but minimizing it supposedly improves overall performance. My belief on this is that although it's probably true that you can improve mileage significantly with this technique, that it is more due to the fact that you're using a relatively small ICE for power at very low rates of acceleration and, in the long run, you're going to become very frustrated (as will other cars on the road) with the slow acceleration and low power mode. IMO, that is not how the Prius was designed to work and essentially defeats much of the purpose of a hybrid--they could have just built an underpowered ICE driven car if that was the goal.

What I tend to do is this. I try to maximize "no arrow" driving. Think about it, when feasable coasting is the time where you are getting maximum fuel efficiency. You mentioned thinking that green arrows to the battery was what you thought would be most efficient. It isn't. The reason is that with green arrows to the battery (foot off pedal) the electric motor (MG1) is creating drag and recharging the battery. Although this is MUCH better than what happens with a traditional--non-hybrid--vehicle, there is still energy loss--you can't recapture all the kinetic energy during the transfer process. Also, you will slow down much faster than in a 'no-arrows' condition so you'll either have to wait longer to start coasting or you'll have to use power to maintain speed sooner.

Now, what really happens with the 'no arrows'. It's hard to maintain a no-arrows condition for extended periods. But what you can do is accelerate up to your desired speed (this all assumes relatively flat terrain--hills make it much tougher) then 'Feather' the pedal. To feather I lift my foot quickly but very briefly off of the accelerator then very slightly depress it. If you're on the Energy screen (and you should as you're learning to 'feel' this technique) you will see the arrows showing the usual power from ICE and HV battery to the motors and wheels, then when you feather the pedal you might briefly see green arrows from wheel to battery. But you're shooting for no visible arrows at all. Depending on the Battery SOC (state-of-charge) and your speed of travel you may or may not be able to attain and sustain that 'no-arrows' state. It doesn't really matter, as long as you're close. Often, at higher speeds and lower SOC what I'll achieve is a frequent back and forth and maybe even brief periods of arrows from the ICE (by brief I mean 1-2 seconds max.) You'll have a definite seat-of-pants feel of 'free-wheeling' rather than the usual slowing felt in the foot-off-pedal coasting. You can then very gingerly depress the pedal to sustain 'stealth or hyper-stealth (stealth above 41mph--the ICE will be on even if you can't see it on the Energy screen) on level terrain with minimal use of power from the battery for very long periods of time and little power drain.

You probably need to print that out and read it a million or so times then practice and practice to really get a feel for what I mean. It seems difficult and cumbersome initially, but it becomes second nature after a few thousand miles (I drove my Ford Expedition yesterday to pick up some furniture and found myself subconsciously using the feathering technique with it--didn't work so well!! :wink: .)

If you have a long hill near you I think that's a good place to practice and get a feel for the difference b/w coasting (foot off pedal) and gliding (feathering then foot on pedal to achieve no arrows). I have one particular long hill on my commute. It is in a 60mph speed zone and I'm usually right at 60 when I start the downhill part. If I'm coasting I'll usually slowly gain speed and at the bottom I'll be going about 64mph (give or take 1-2mph). If I glide on that hill I'm almost always at 69-70mph and can then continue the glide for another 1/2 mile or more before I'm back down to 60mph--I'll usually nurse in a little battery use to make the glide longer while trying to avoid the ICE. There's an uphill section shortly after and I replace any used battery charge going up that.

As you noted in your post, mileage will improve with experience and with time as the car breaks in. Be sure you've checked the oil level and that it is below the MAX level on the dip stick. Consider pushing tire pressures up to as close to the 44f/42r level as you're comfortable with. Turn off the AC when practical and keep the settings conservative when you do use it. Don't haul a bunch of junk around that you don't need. Really anticipate stop lights and glide/coast to them when you can--if you can avoid actually stopping that helps greatly too.

I think you'll start seeing better mileage soon with that.

Just for your own sense of reassurance, take a look at my mileage chart I have over at Jason's GreenHybrid.com site:

http://www.greenhybrid.com/compare/mileage...ils.php?cid=129

You'll see how my mileage has improved since I got to the 5000 mile mark. Warmer temps had a lot to do with it, decreasing or not using AC at all had a lot to do with it, but I think technique had the most to do with it.

Sorry to be long winded, let me know if there are any details I can clarify, and if you're unfortunate enough to be in SW Missouri any time soon give me a hollar and I'll take you out for a driving 'lesson' in my Prius!