Uphill vs. downhill makes the biggest difference

For what is worth:


I'm a great believer in route planning. Have you used Google Earth or Google maps to find alternate routes that may allow slower speeds ascending the hill(s)?

It would be especially helpful if you could give some Google Earth coordinates of your route (we don't need your home address but say a corner.) Then start a daily log from a reset trip meter. This may give some clues to how to approach a hilly commute.

Thanks,
Bob Wilson

 

I have observed the same thing over a longer drive. I work from home nearly 100% of the time but a few weeks had to go into to work for the first time with my 2010 Prius. My mileage on the 33 mile drive going in was very good, as in something like 64 mpg on the car. I reset the B trip meter for the drive home and was well under 60. I also felt on the way home I was doing more uphill stretches than on the way in. I had never noticed this in my previous car when I drove in 5 days a week. I looked up the elevation of the "from" and "to" locations and found they were almost 600 feet apart in elevation. This is only from one observation but I believe the elevation difference can add up quickly. It probably affects non-hybrids as well but not as much as the hybrid since it has been optimized to maximize mileage and anything working against this goal is felt.

 

PriusRos,

You have come upon two of the fundamental truths underlying getting
really good FE:
* route and topography make a difference. Sub truth; out-going
routes and returning routes for best FE are usually different. Good hills
have short, steep climbs and long, low-angle declines.
* one way FE figures are not truly indicative of overall FE. You have to
look at the round trip to get meaningful numbers.

I am speaking from Gen II experience, but I believe it is relevant to
the Gen III in this situation.

Recognizing that your home-going trip is a long uphill climb leads to
the beginnings of bringing your MPG numbers up. That said, pulling
your car up the garage ramps in EV probably has a significant
contribution to your low going-home FE. The car draws heavily on
power from the HV battery during the start-up engine/catalytic
converter warm-up period. It can easily result in SOC falling 10 or
15%. Rolling down the ramps in regen does not recoup this drop. You
may also notice that even though you are in regen, the engine is
running, even though it is making no contribution to the movement of
the car and wasting gas.

Finally, it will take quite a few miles to recover the SOC. During this
time the Power Split Device PSD will be diverting power through MG2
rather than directly to the wheels for the most efficient propulsion.

Just something to consider as you find what works best in your
specific driving environment.

 

PriusRos,

It may be better to come down the ramps in EV!

This is counterintuitive, but when you consider how the HSD works it
makes enough sense at least to give it a try.

Disclaimer: my experience is in my Gen II with after-market EV
switch. I hope it is relevant here.

As soon as the ICE starts, the HSD's first priority is to get the car
operating to produce minimum polution. It does this by running the ICE
rich which ultimtely leads to quick warm-up of the catalytic converter.
So, like it or not, the first minutes and miles produce very low MPGs.
One way to work with this unpleasant truth is to set things up so that
you are at least making some mileage while the MPG numbers are
low.

I don't know if there is a discretionary use EV switch in the Gen III.
If there is, engaging EV mode to get out of the garage will suppress the
engine coming on and you won't be using either fuel or SOC and your MPGs
don't take as big a hit! :rockon: It works for me anyway.

As soon as you get out of the garage, drop out of EV so you don't run
down the SOC and incur the attendant recovery costs.

 

Thanks for sharing, I am having very similar observations - great mileage legs and horrible mileage legs. Hills are work for this car. I have a gentle long uphill to the foothills where I live (1-2 miles up up up). The top of the HSI, the last pixels where I can keep the ECO lit before the power area, yeilds me very very slow acceleration and speed. There are 2-3 stop signs and trying to keep ECO lit can only get me (very slowly) to maybe 16 - 20 mph in this 30 mph zone. I do it if no one in behind, but that is rare.

Is it better to just use the gas to get up to the speed limit in the pwr area on HSI then back off to maintain, or to do the long, slow acceleration whe ECO lit?

Can anyone shed more light on the pwr area of the HSI? What does that tell us other than lots of engine work?

I am averaging 46.8 mpg over the life (only 750 miles total - basically break in period) and now 54 mpg on my last tank reset that includes a couple of work round trips. This, honestly, has been a combo of learning technique, working hard at it, and totally blowing it off for traffic and habit at times. To me, it seems the car will get exactly as advertised on the EPA sticker - for folks like me without consistent great technique (the general public).

I had one work round trip at 60 mpg - but more miles on that trip meter quickly averaged that down. This one trip had very little traffic that forced me to worry about being too slow, or under the speed limit, etc.

My best mileage seems to come on the long, gentle freeway downgrades where I go to glide mode (no HSI bar at all).

I just share for anecdotal data points - I am anxious to learn and slowly grow my MPG. It is funny to become obsessed with MPG up at this level after driving a 5.2 Jeep V8 at 12 mpg for so long. This is the best!

 

There is an EV switch/mode, but discretionary is up to the car, not the driver. There are many conditions where the car does not allow it - one of them is when cold. I can never get it to work first thing after a long cooling off period.

 

This is an area of interest for many of us who have contributed to Hobbit's thread. I've been able to map the power generated at 50%, 75% and 100% but I don't have the instrumentation to map the field, brake specific fuel consumption. This is coming but not here, yet.

There are some other aspects that have me wondering what is going on. For example, my "off the lot" performance was significantly better than recent numbers. Some of this may be lubricant related and I should have some data on that in about a month. Some may also be due to traction battery settling, a phenomena not yet throughly understood. It is an interesting time to have a new Prius.

Bob Wilson

 

Well, there you have it. General Gen II knowledge doesn't always map
across to the Gen III. I hope that I haven't wasted your time.

As Bob Wilson has pointed out, you are in the first days of discovering
the minutiae of how the Gen III operating algorithms work. In all the
years of the Gen II thre are still many questions and mysteries despite
the work of Bob, Hobbit, et al.

To all the Gen III explorers, investigators, and de-mystifiers, keep up
the good work.

 

No waste of time, I like all the help and understanding I can get. There will be many here trying to learn; some stuff old news to most others here, and some stuff new to Gen III.

TeamPrius showed the demographics of sales here.... lots of first time hybrid owners with the gen III (I am one).

 

Much like the OP, I live in an area that's very hilly - in both the side-streets and the highways. I've managed to increase my mpg from what I started with at the dealership (40mpg) and have it hover around 41.3-41.9mpg. The constant need for acceleration on the uphill climb is what I've discovered that drops the mpg. Also, it doesn't help that the on-ramp to the freeway heading to work is a long uphill climb.

I'm going to try and see if I can increase my mpg today by avoiding the freeway altogether and using the side streets heading home as the uphill/downhill isn't as bad. I'm curious to see how the mpg would react to this change.

 

EV can work at start up, if you have enough charge. The car will need a few secs to initialize before the EV will engage. So I just keep pressing the button every sec or so until it lights up. Just be sure to engage it before the ICE starts warming up. No going back after that happens. Then, you just have to make sure you're going less than 10mph on those garage ramps. It will kick you out of EV if you go over 10, although I haven't tested that limit with a no-gas free-roll condition.

 

Going to work today, which has a few hills going up including a pretty good sized one (for a city area), I got 43mpg. Coming home we got 65mpg.

 

Yup!
My mpg for the tank is finally out of the 30's and is now 42. Tomorrow I am going to track our whole commute together.

 

This is a very good thread. I have about 1,500 miles so far and usually drive short distances (with AC on almost always) and notice that because of the ICE running to heat up the catalytic converter my MGP is fairly low for half the trip which so far results in around 45-49 MPG.

But on longer trips, like 100 to the airport, I can easily get 52-55 MPG. I really think the warm really hurts MPG but once you get beyond the warm up period great milage is possible.

PS - First Prius, absolutley love it.

And the members here are so loaded with great information. Thanks to all.