Eco versus MPH issues?

how can you lose mph? can't you step on the gas harder?

 

Yep - if you press the accelerator the same way on a given journey, Eco mode will definitely give you the lowest MPH and PWR will give you the highest MPH.

I assume you mean MPG (i.e. fuel use), rather than MPH (speed), though right?

All Eco, Normal, and Pwr modes do, is remap how much you have to press the accelerator pedal for a given amount of throttle.

The old adage of accelerating very gently (helped by Eco mode) isn't actually always the most economical way to accelerate in a hybrid. In fact, and this is backed up by your driving scores, you want to accelerate in accordance with the highest point of the accelerator guidance bar. In general, this means pressing the accelerator enough to bring the accelerator level to the top end of the blue part of the graph (i.e. just below the red PWR region) until you get to your chosen speed. This is how you get scores of, say, 95 to 99 for acceleration.

The main reason this is more economical than accelerating slowly is that by accelerating slowly you'll use up most of your battery. Remember, any energy that enters your battery originally came from your ICE (it sped you up before regen) and it incurred conversion losses of around 20%. It's better to use as much power as you can from the ICE, without it increasing its revs to an uneconomical speed (i.e. the red PWR area), so that you use less of your stored electrical energy, and hence are incurring less conversion losses. The electrical energy is best used to supplement the ICE in ways which allow it to run at its most economical speeds, or conversely keep the ICE speed up at its most economical speed by turning the generator and dumping the excess energy into the battery.

So, if you're a light-footed driver, Eco mode may not actually give you the best economy.

When I first got my Prius I always tried to use as much EV as possible. I'd get around 55MPG (UK MPG) on average. Now that I accelerate more briskly, I'm getting more like 60MPG on average, and that's been in the coldest months too.

 

This isn't a problem, it's a feature. @The Professor did a great job explaining it.

Eco, Normal, and Pwr modes map the throttle differently. So if you press the pedal down 25%, for example, Eco will not open the throttle plate as much as Normal and Normal not as much as Pwr. But they all open it all the way if you depress the pedal all the way to the floor.

 

after 9 days, i'm certain he meant mph...

 

My 2019 has a tad less MPG than my two 2016s. Maybe. Toyo tires could be a factor??

Also it is too early to tell but it appears the MPG display or the odometer/gas tank fills are suspect. I have three more tests to do to narrow the issue down to one variable. 2016's were pretty much spot on in all the calculations.

Highlander is spot on.

I need to eliminate tank fill issues from my gas station over two vehicles and 4 fills as well as pump issues as they have all new pumps.

As far as eco mode, I can do better (MPG) with my foot in normal mode but I always leave it in eco since someone else may drive it on occasion who has a heavy foot..

Same with cruise. Cruise control in certain situations can hurt your MPG.

 

i've felt that about all my hybrids on steep rolling hills, going back to 2004.
i think it's a combination of lack of power, regen braking and engine noise

 

Yeah, cruise on hills is unpleasant, not to mention extravagant fuel-wise. And every car I've had with a cruise control has been pretty abrupt. I wish there was a way to adjust the slack in the cruise so it wouldn't try to maintain the set speed goin up hill, but would slack off maybe 5 mph and get it back on the down hill side of the hill. I don't use the cruise in the hills.

 

It's a TOYOTA Cruise anomaly - work 2006 LandCruiser Diesel, work 2008 Avalon V6 were the same. I had a 2006 KIA and 2 later FORDS which were much smoother and kept the speed better.

 

Smoother is better, but I think I'd prefer an option to tell it to compromise between speed perfection and throttle opening consistency when traffic permits.

 

I had a 2005 Toyota Matrix that I drove almost always by cruise control. But I always had to cancel the cruise going up hills because otherwise it would surge like a rocket engine. When I test-drove 2019 cars to replace it (including the Prius I now own), when I hit the occasional hill I was impressed how much smoother the cruise responded.

But, I have stopped using cruise control completely on my new Prius. I feel like it must significantly depress MPG, since maintaining constant speed is never a priority when optimizing MPG with the accelerator pedal according to the Hybrid System Indicator display.

It's a bit ironic because the whole reason I started driving by cruise ca. 2005 was to smooth out the constant braking and accelerating I was doing, and I assumed the micro-adustments in the cruise control would be much more efficient (it probably was).

 

For the vast majority of drivers, Cruise will probably improve l/100km - I remember an article decades ago where Popular Mechanics (or was it Science) did some back to back tests.

Mainly because the computer on the cruise can detect small changes in velocity quicker than a driver. And back then, accelerator pumps on carburetors weren't as well regulated as the fuel systems of today.

2019 - we have better cars - but I'd still guess that the average driver would be better with cruise. Some have no idea what a Tachometer does - let alone the displays on a PRIUS. A hypermiler - yes, they'll beat the cruise when they can be bothered.

 

Cruise is probably best on interstates. You can personally do better on rolling hills. I haven't done many in my new Prime but in my Gen IIs the car would hold back on the downhill portion and lag recognizing the road ahead rose up. The resultant surge of power to get back to speed is a power waster. And of course as you crest the hill, the car lags recognizing that you are now going downhill and you go over set speed (presumably the speed limit) before it regen brakes to slow the car.

 

Precisely what mine does - and it annoys me. It used to annoy me on a work TOYOTA back in 2005 - a Diesel LandCruiser Wagon.

I had 3 Cruise Control cars before, and they held the speed much better under those conditions (KIA & 2 FORDS).