Is the city mileage rating bunk?

I easily get 60 MPG in city driving, though most of my driving is highway.
I think the "city" rating generally means between 25 and 40MPH anything higher than that is considered "highway" speed.

The most efficiant constant speed for a prius on flat ground is 32MPH. Someone posted a graph on PC but I can't find it now.

 

You are apparently driving "incorrectly". I easily get or exceed 60 MPG in the city. There are plenty of driving tips on this forum. Personally, I use the cruise control whenever I can, and I coast and lightly brake as far as possible. That may piss off the guy behind me, but that's his problem. I don't subscribe to the "glide" method at all. Coasting at least puts energy back into the batteries. In my opinion, gliding wastes the car’s kinetic energy.

Funny thing – I parked next to another Prius owner the other day at Lowes and he asked me what kind of mileage I got. I told him 56 to 58 MPG, but only about 52 in the winter and he said that was an "urban legend". He was speechless when I showed him my MFD with 57.3 MPG and about 350 miles.

 

<div class='quotetop'>QUOTE(itstwowords @ May 11 2006, 07:27 AM) [snapback]253378[/snapback]</div>

That's awesome!

Windstrings - it's probably the length of your city trips that's the killer. On 1-5 mile trips the engine is warming up most of the time, instead of being off when you're coasting, and turning off promptly when you stop. So, with a fully warmed up engine in the city, 60 MPG is possible, but if your trips are generally shorter, expect much lower mileage.

I drive in rolling hills, stop and go style traffic 35-55 mph for 20 miles on my commute and last week when the weather was warm I was averaging 57 mpg. In fact, last week when I stopped for gas, I did it at the end of my commute about a mile from my house - and when I got home, I snapped this picture:

(of course - this was a fully warmed up engine, and a full battery and I used my EV mod for part of it - so it was pretty much cheating, but I've been waiting for the opportunity to post it!)

 

<div class='quotetop'>QUOTE(priusblue @ May 11 2006, 08:01 AM) [snapback]253387[/snapback]</div>

Shoot, I can get 99.9 MPG for the 1.5 miles from the gas station to my house. I travel at 55 MPH during two thirds of that and I don't have the EV mod.

What I have instead is a big long 55 MPH downhill between the gas station and my house. Since the MFD doesn't reset immediately, I've already accelerated up to speed by the time it does, then I'm just coasting downhill for most of the rest of the trip. I do have to go up a fairly steep hill going into my neighborhood, but I often have 7 green bars at that point and my Prius has no problems going up the hill on battery alone.

Of course, The next time I start the car up, it goes back down into the 40's and 50's.

As far as city driving goes, it really depends on how you define city driving and how long the trips are. I believe the EPA tests have an average speed of 28 MPH on flat ground with 1 to 2 mile stretches between stops. You won't get anywhere near that in real city driving that involves accelerating to 35 MPH between stop lights placed 1/8 mile apart with moderate hills.

Technically, my commute is "city driving". It's 15 miles with speeds between 35 and 45 and with few traffic lights. I get 53 MPG on it in the summer. It's got a couple of significant hills on it, and I would probably get closer to 60 MPG if it was flat.

However, when I drive down to Philadelphia and always manage to catch every red light, requiring me to accelerate and then stop every 1/8 of a mile, then I get closer to 45 MPG.

 

All of my driving is in Albuquerque, NM.

I tend to be mildly disappointed by 60 mpg in fair weaather, but I blame my wife.
My best results happened last autumn. I managed 75 mpg over 1/2 a tank, and ~ 69 mpg over three tanks.
My sig has the details.

 

I think the problem is with how you define "city". If you mean short trips, 15-30 max mph, stop-and-go, bumper-to-bumper traffic, sitting at long lights, that's one kind of "city". But, I find that I can easily get >65 mpg in what I would actually call "suburban" driving around here in the West Palm area, where you can maintain 40-50 mph, very few traffic lights, and nice traffic flow. I think the EPA driving loop was probably more like the latter than the former.

 

I thought about this thread while driving to work today and took a picture of my MFD during city driving. (I know you're thinking "Oh Gawd, not another MFD shot" But here it is.)

 

<div class='quotetop'>QUOTE(windstrings @ May 12 2006, 02:00 PM) [snapback]253954[/snapback]</div>

Above 42mph, you are getting worse mileage.
The 32mph peak is shown by Wayne's similator...
http://priuschat.com/index.php?showtopic=1...id=210092&st=26

The "no arrow" gliding is another story...
http://hybridcars.about.com/od/ownership/a/pulseandglide.htm

starting and stopping < straight crusing < Pulse and Glide below 42mph

Ken@Japan

 

All mileage ratings are bunk. That's why is says "Your mileage will vary".
The Prius should have its own system: SPG, "Smiles per Gallon".

 

I've had my Prius for 23 days now. The first tank my MPG was 43.1; 100 miles into the second tank my MFD says I'm getting about 48 MPG. The morning temp has ranged from high 30's to low 60's; homebound temp is usually mid-60's to high 70's.

My driving is mainly to and from work, 5 miles each way, 15 to 20 minutes total. My first '5 minutes' bar usually says 25 MPG, the next one around 50, and the third one closer to 75. If I take the 'main drag' to work (never home - it gets too crowded and stop/go), the speed limit varies from 40 MPH to 55 MPH, but LOTS of stoplights (4 in the mile or so with the 55 MPH speed limit). On the 'back road' the speed limit is generally 35-40 MPH. Either way, I have to go through a small town with 5 stop liights in about a mile.

So I'm not getting 55 MPG, but I'm sure it's because of the 'short trips'. Mid-40's is still twice as good as my old car <g>

 

<div class='quotetop'>QUOTE(Jeannie @ May 13 2006, 07:29 AM) [snapback]254401[/snapback]</div>

You're correct.

The main reason is the warming up fuel usage for the first 5 minutes..
The engine block heater will help you, warping to the 50 range at the beginning.

Ken@Japan

 

Remember the EPA standards are just a measure so you can compare cars. It was once based on how we drove a long time ago. It also does not take into account driving styles, terrain, weather, etc.

 

<div class='quotetop'>QUOTE(windstrings @ May 13 2006, 02:58 PM) [snapback]254625[/snapback]</div>

No, it isn't. It shows infinity MPG if you were in EV mode.

No, it isn't. It shows a crouising MPG number on constant speed, like using CC.
We know Prius runs by the ICE or sometimes by the motor on flat road on constant speed crouising below 42mph, then the data is shown at the graph under such conditions.

No, I have never seen such.
Why don't you make your own graph?

Ken@Japan

 

<div class='quotetop'>QUOTE(windstrings @ May 13 2006, 01:58 AM) [snapback]254625[/snapback]</div>

Speeds for one hour so the battery is not assisting? I don't think that's possible unless the car is broken.

Remember, the way the PSD is arranged, the Battery can be charged at any time by the Engine by just diverting a little excess energy to the generator.

Even at highway speeds, the HSD system is still charging the battery and using the battery for assist. The transition from charge to assist can happen several times a second in actuality.

But, think of it this way.

The Atkinson Engine is a lot like a Diesel Engine in that it is happiest at a specific relatively narrow performance band, where it is very efficient.

The HSD works to keep the Atkinson Engine working at peak efficiency.

It does that by siphoning off a little energy when there is spare, then providing it back when it's needed so the ICE doesn't have to rev up and down or even throttle up and down. Changing throttle settings is one of the most wasteful things you can do on an internal combustion engine

Gust of wind? - little push from the battery.

Tailwind? - divert a little energy back to the battery.

In other vehicles, the ICE is constantly forced away from optimal. In the Prius the HSD makes sure it spends as much time as possible at optimal.

A CVT can help do that in a regular vehicle. It keeps the ICE RPM constant and in the most efficient band, but it does nothing to prevent the need for throttling up and down.

The HSD goes a step further and allows the ICE to remain absolutely constant while taking care of the 'little stuff'.

 

<div class='quotetop'>QUOTE(Tempus @ May 13 2006, 09:32 AM) [snapback]254698[/snapback]</div>

Excellant post, great way to look at it!

I always tell people who are way impressed with the Prius (well, that's me as I'm an HSD snob) that is still burns gas...just in the most efficient/clean way, that requires no changes to your driving habits. Then, I'll also say that the tools are on-board for you to "go that extra MPG" mile and really make HSD efficient.

Cheers,

Curt.

 

<div class='quotetop'>QUOTE(finman @ May 13 2006, 11:06 AM) [snapback]254723[/snapback]</div>

Patrick Bedard figured it out a couple of years ago, and explained it better than I ever could.


"Here's the real story about hybrids. It's taken us the better part of that 100 years to figure out how to do what we already knew ages ago would be beneficial. When I went to engineering school in the '60s, it was everyday knowledge that IC engines are most efficient at full throttle. You're wasting a share of your gas money at light loads—running the air conditioning, for example—and when idling.

But there was little you could do with this info to boost miles per gallon. You could have a small engine, which needs full throttle often just to keep up with traffic. Or you could have overdrive, or a long axle ratio, to lug the engine and thereby cause wide throttle openings at normal cruising speeds. But these methods create torpid performers that most folks shun.

The customers want flexibility and zip. Even though most of their miles may be in the urban slog, they still want effortless reserves for passing and merging. The IC engine is the only choice that can do it all, but it's not operating at its best in the everyday way we actually use our cars.

...

The Prius separates the engine (ICE) from the everyday task of propulsion, turning it instead into an independent power unit that runs only when there's an efficient load.

... the Big Idea depends on the genius-gizmo planetary at the heart of the drive system. ... it seamlessly blends the following conditions to find efficiency as you drive: The engine can be on or off; the car can be rolling or stopped; and the motor/generators, each independent of the other, can be motors or generators.

On the road, you get the same slipping-clutch feeling as with continuously variable transmissions now available on some cars. Your right foot tells the computer how much speed you want. It decides the best source. If it chooses to run the engine, it does so "largely unthrottled," Hermance says, just enough manifold vacuum to keep emissions canisters purged. Remember, unrestricted throttle openings give greatest efficiency.

Instead of controlling engine speed with the throttle as normal cars do, the genius gizmo adjusts the final-drive ratio to lug the engine, thereby adjusting the burden as necessary to hold revs at the right place on the power-output curve."

...

At 70-mph cruise, the powerful Camry part-throttles along at 27-percent efficiency while the just-right-sized "independent power unit" of the Prius runs essentially at full throttle for 37-percent efficiency.

The Toyota Prius will change the way we think about cars and engines."



Ain't it the truth.