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So what's this I have been hearing about keeping the Prius ICE running at 1700RPM for maximum efficiency? Inquiring minds want details. ;)

Hmmm, I thought Hobbit had determined it was more like the 1800-2300rpm range. I've been focusing my driving to keep accelerations in that range as much as possible for the last month or so and have had some pretty impressive mpg numbers (esp. considering that it is winter). I got nearly 60mpg in December and am currently at 64.8mpg.

I think he based it upon some vacuum efficiency or something?...sorry, I know I sound like an idiot with that comment, but that's what stuck in my head.

Ah ha!
Greenhybrid thread:
http://www.cleanmpg.com/forums/general/t-throttle-control-915.html

Hobbit's Page:
http://techno-fandom.org/~hobbit/cars/sweet/

Pretty Picture (from Hobbit's site):
http://techno-fandom.org/~hobbit/cars/prius-curves.gif

I realize hobbit already has the Prius answer, but for the rest of us, I wonder if ScanGage could find the answer on the other cars?

i didn't realize how flat my torque curve really is... for this tank i'll be a faithful ye old 1700 rpm max dude!

maybe 2300 rpms on some days... those are magic numbers for now!

With the ScanGauge re-mounted in a more prominent location, I kept a closer eye on RPMs on my trip home. One thing for sure, if the engine switches to a less-efficient intake profile (or something) at 2300-2400RPM then there are significant implications for driving style.

Keeping it under 2400 wasn't too tough, but it requires a fair bit of DWL on the highway if there are any hills involved. Anything more than very light acceleration or attempting to maintain speed over a moderate grade results in engine speeds closer to 3000RPM. It's very easy to get into that range if you aren't paying attention, as engine speed is quite "slippery" at speed. On the other hand, it's incredibly cool to be cruising at 60mph+ at low load with the engine turning at a cool 1500RPM. I would have killed for that kind of gearing in the Accord. Maintaining low RPM is quite a bit easier around town. Since you don't have all of that aerodynamic drag, more engine power at low RPM is available for acceleration.

My initial anaylsis is that driving for maximum highway FE in a Prius might look quite a bit like the routine that the MT Insight pros describe in their quest for lean-burn. We're looking at low-ish speeds and a very light tough on the accelerator to keep from breaking free of that low load/low RPM ICE state.

Now I'm having fun. ;)

i tested the 1700 rpms theory here is what happened on my usual 9.3 mile commute (15 km?)

6.5 L/100 km for the first 5 minute bar (35 mpg)
then 2.5L/100km for the last 20 minutes! (92 mpg)

need I say more? I pulsed and glided all the whole way! And the amazing thing is I caught up with my boss which she left 5 minutes earlier than I did and has no idea how to hypermile! Now that's efficency folks!

dropped my score from 4.4L and now sitting at 4.2L/100km with 104 km on the MFD

even climbing up hills I managed to keep it at 1700 rpms, it seems with your car brick its more engine rev happy.

Also another thing I noticed the 1700 rpms sweet spot is usually enough for the engine to handle on its own, so current is at a measly 1 or even 0 at times, ignoring the conversion losses! As well the Instant FE was displaying usually at 7.5L/100km when I'm pulsing with 1700 rpms in mind, its only a matter of time when it becomes second nature!

data graphs for my NWH11 prius, thanks Bob!

http://hiwaay.net/~bzwilson/prius/pri_power_eff.jpg
http://hiwaay.net/~bzwilson/prius/pri_power_MPG.jpg


edit: after looking at those graphs one more time.... 1700-1800 rpms will be my sweet spot and when I do punch it 2700 rpms will be my king