Thursday, May 19, 2011

There's no right way to drive the thing - trip record to work

68.3 real mpg at the least from the Scangauge (this would read about 72.7 mpg on my Prius' display) over about 27 miles.

I am insanely ecstatic at this result. This route, even with warm temperatures in the past few months, always presented me with mileage challenges I couldn't quite meet. It would be common to see 60 mpg on the display, if I even got that high. High 50s were commonplace and a struggle. Hills galore, and most of it over the threshold for a Prius glide - the engine runs most of the time on this route.

The "discovery", or rather what others have known for a long time but which can only be found out through personal experimentation, is that there's no "correct" way to do it all. There's no one highway technique, and there's no one RPM or kilowatt setting at which you accelerate. I used Super Highway Mode and Warp Stealth, hard accelerations and light accelerations, no EV and some EV, all depending where I felt it was needed.

In some cases I accelerated much more lightly during pulse and glide. I've always *guessed* (though can't prove - anyone??) that turning the engine on and jumping directly to a good burn at 1600-1800 RPM can waste some energy. You know, when you hit the gas and you see instant numbers in the teens, then twenties, maybe if you're lucky 30 mpg by the end? At the beginning you just hear the engine rev on and get no torque - just seems like gas blasted into nowhere. So today I would turn it on gently, and aim for, let's say, 30 mpg (light engine, in other words) for the length of two telephone poles, and then try to glide for at least 6 more, for segment mileage of 120 mpg. The result was that my first 20 minutes looked like this one from the other day, even though today I was driving in rush hour, and the picture you just saw was from empty roads on a Sunday morning.

This also counteracts the nasty habit of hard accelerations in pulse and glide to slowly drain the battery (longer glide time = more battery use), until your accelerations are wasted giving 15 or even 20 amps to the battery. Higher state of charge, better mileage - what's next, free apple pie for Prius owners? :-)
EDIT from the next day:

Another awesome run on a totally different trip using same ideas. I've never done anything like this. 75.8 mpg over 20 miles, which would have read over 80 on the display!

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