Is the city mileage rating bunk?

Except it aint. The truth how the Prius works, that is.

The Prius has its priorities, and efficient ICE use is #2. HV battery longevity is #1.

This leaves a window of opportunity for the driver to help out a bit, and drive with efficient ICE load when the battery is particularly high or low in SOC by modifying total power demands.

Two examples, each from my driving on city streets coming off a red light, without traffic behind me so that I can choose my acceleration:

1. HV > 6 bars: I decrease the gas pedal 2/3rds to 3/4rths
2. HV < 3 bars: I decrease the gas pedal 1/3 to 1/2

In both cases, I end up with ICE running 2000 - 3000 rpm, so that efficient fuel use results. I don't have a CAN; I just learned what that range rpm sounds like by listening to the engine while deadbanding at 4 bars SOC.

Placing an rpm gauge on the FCD screen would help new drivers learn to drive with load (DWL)

 

<div class='quotetop'>QUOTE(EricGo @ May 13 2006, 01:02 PM) [snapback]254769[/snapback]</div>

Yes, in fact it is exactly how the Prius Works.

<div class='quotetop'>QUOTE(EricGo @ May 13 2006, 01:02 PM) [snapback]254769[/snapback]</div>

Are you sure? So Emissions Priority is below both of those? What about Acceleration Speed Priority? What about Braking Time Priority?

In fact, I think the Priorities vary based on the situation.

OF COURSE some situations mean that the ICE cannot be kept at it's most efficient 100% of the time. That's bone-headedly obvious and no one has ever said that's the case. However, it does keep the ICE in it's prime range for a higher percentage of the time than any other system, by using exactly the methods that Patrick Bedard and I explained.

<div class='quotetop'>QUOTE(EricGo @ May 13 2006, 01:02 PM) [snapback]254769[/snapback]</div>

Nobody ever said that Driver Input isn't important in overall efficiency. "Modifying Total Power Demands" appropriately is exactly what driving for fuel efficiency means. It means exactly the same thing whether you're driving a Prius or a Diesel or a moped.

But, it has nothing to do with the way the HSD works.

The fact is, because the HSD can keep the ICE "closer" to ideal no matter what the "Total Power Demand", it will be more efficient in almost any circumstance than an ICE-only vehicle in the same circumstance.

That's the point. Your driving skill, or lack thereof is irrelevant in that portion of the equation.

What you can do is help keep the Prius in situations where it can be at it's most efficient just as you would driving for efficiency in any other vehicle. That's why YMMV. Some people do that better than others.

Thankfully though, the Prius improves the overall efficiency of even the worst driver compared to any other comparable car they choose to drive the same way.

 

Consider the situation where the driver demands 30 kW (common occurence).
Take the Prius as stocked, but with HV at > 6 bars. Compare to an ICE only car of similar size with an 80 kW engine (hard to find in the US, but easy in Europe). WHILE the SOC is > 6 bars in the Prius, which car will be more efficient ? The answer just may surprise you, and I'll point out that the Prius' result is as good as it is NOT because of the HSD, but because of the atkinson engine design.

 

<div class='quotetop'>QUOTE(EricGo @ May 13 2006, 03:33 PM) [snapback]254813[/snapback]</div>

And I think you're dead wrong on that

Anyone can make an Atkinson Cycle Engine.

Not anyone can make it drive like an Otto Cycle Engine.

HSD is what does that. Without HSD, the Atkinson Cycle Engine is useless for normal automotive propulsion regardless of it's efficiency (though Mazda has sort of tried with Miller Cycles and Turbos).

As far as your hypothetical situation, it's irrelevant to the point. Perhaps there is a moment in time in a certain alignment of the stars where another engine is more efficient than the Prius. Likely is for every other type of engine. It doesn't make any difference either in how the HSD operates or in why the HSD makes the Prius more efficient overall.

 

This is not a useful discussion. I average between 60 - 70 mpg in my city driving, in part because I recognize the limitations of the HSD system and adapt to them. How are you doing ? Feel free to have the last word.

 

<div class='quotetop'>QUOTE(EricGo @ May 13 2006, 04:41 PM) [snapback]254848[/snapback]</div>

I don't understand. Are you trying to substitute your mileage accomplishments for a technical discussion? Does the fact that you get decent mileage out of a Prius prove something about the Prius?

If it matters to you, my lifetime numbers in every respect are within about 1% of yours give or take on any given stat. At least according to your signature. That means total miles, and averages. It's not unusual for me to fill up, drive around for 30-40 miles, and arrive home with a MFD display over 70 MPG given favorable circumstances.

But that doesn't really prove anything about the car's technology.

And if mileage obtained is equivalent to understanding engine technology, then I guess it's also true that the driver who can go the fastest has the best technical understanding of applied chassis dynamics, shock and spring ratios, and tire stagger. Though I understand they often leave that to other folks.

There are folks out there who are far better than either of us at Hypermiling, but I don't think that says anything about their engineering skills.

Personally, I'd rather keep the egos out of it and stick to the engineering.

I figure someone who can drive for decent FE will get the most out of any car they drive.

And a car that gives good inherent FE will provide the best results for any driver.

 

<div class='quotetop'>QUOTE(windstrings @ May 11 2006, 02:37 AM) [snapback]253336[/snapback]</div>

To kind of tack on to what benighted has already said, the best speeds are in that range for city mileage. I find the best for me to between 35-40 mph. In general it is pretty easy for me to get 60+ in city driving (sustained 35-40 mph), even for most of the trips being 10-20 minutes. Although I realize the relative flatness, the timing of the stoplights and generally light traffic flow are in my favor and not representative of everyone. Right now, I am at 65.4 at around 120 miles, since I have been able to keep it from my wife's extremely short trips.


Actually, I think most cars get worse mileage at those speeds, at least our other car does (a Ford Taurus) gets only about 15-16 in this driving, 10-15% under it's rating.

 

<div class='quotetop'>QUOTE(itstwowords @ May 11 2006, 06:27 AM) [snapback]253378[/snapback]</div>

that was really helpful, ... BOT yep windsprings I feel your pain!

beryl

 

<div class='quotetop'>QUOTE(EricGo @ May 13 2006, 03:41 PM) [snapback]254848[/snapback]</div>

Actually I was rather enjoying the dialog. Tempus was giving technical explanations to the reason windstrings started this thread lousy city mileage.

For Ericgo to say I get 60-70, how are you doing isn't very helpful for us newbies to priuschat.com trying to make sense out of OUR lousy mileage.

I think sometimes on priuschat.com high mileage becomes a badge of honor such that hinders communication.

Again windstrings asked:

How many of these posts really answered those questions? How many for the lack of a better word 'bragged'?

I still can't believe 'itstwowords' said,

sheesh!

The best word I've read as a newbie yet is get a block heater. But I've checked out two past threads and still am not quite sure what a block heater is. Oh well, I'll try Yahoo!

Ahhh ... this is a good one, check this out windstrings,

http://priuschat.com/index.php?showtopic=1...40&#entry184740

 

Reposted just for you berylrb, since you missed it earlier in this thread:
Except it aint. The truth how the Prius works, that is.

The Prius has its priorities, and efficient ICE use is #2. HV battery longevity is #1.

This leaves a window of opportunity for the driver to help out a bit, and drive with efficient ICE load when the battery is particularly high or low in SOC by modifying total power demands.

Two examples, each from my driving on city streets coming off a red light, without traffic behind me so that I can choose my acceleration:

1. HV > 6 bars: I decrease the gas pedal 2/3rds to 3/4rths
2. HV < 3 bars: I decrease the gas pedal 1/3 to 1/2

In both cases, I end up with ICE running 2000 - 3000 rpm, so that efficient fuel use results. I don't have a CAN; I just learned what that range rpm sounds like by listening to the engine while deadbanding at 4 bars SOC.

Placing an rpm gauge on the FCD screen would help new drivers learn to drive with load (DWL)

----
I discontinued discussion with Tempus because of the poor quality of discourse. My mpg results were noted as empiric evidence that my understanding of HSD and its application to my driving yields improved results over what I had last year, and better than 99% of the members here. There are dozens of confounding variables, though, so my conclusions may be misplaced.

Prius Newbies seeking to improve their FE should read Evan Fusco's sticky on the subject for general driving techniques, and then take to heart Hobbit's advice: ICE off, or in the ~ 1800 - 3000 rpm range. My post above is an application of this truth in the 'Prius Way'.

 

Thanks Eric,

I actually did read Fusco's post I find the theories plausible for valley driving and even the other side of the bay but for the hills of SF proper, I've found very little practical advice for short commutes.

I get 6 bars in the city too, but they are far outweighed by the bars in the 20's, the one "flat" spot in my commute has 7 lights and several take two signals changes to get through, then BAM, I'm on another series of hills with trolley buses. It is not unusual to hit the gas a couple of times going up hill and most of the time because somebody is ducking into the gap created from trying to use Fusco's techniques.

Do you see the dilemma of our version of city driving, unpredictable and frequent stops in short commutes? I have never read a thread that adequately addresses this so that's why I was pointing out "you are apparently driving incorrectly" is just plain rude.

But don't get me wrong, I am quite satisfied with the Prius, because hitting the brakes on the same hill and waiting at those lights are every manner of other high mileage cars suffering too! And you betcha, I'm quite satisfied with out of the city mileage, oh yeah, I'd buy another Prius in a heart beat but using Muni we only need one car!

I'll try your listening RPM technique, that is a first for my reading priuschat.com, but I seldom have that luxury except for the races to beat the yellow lights, which are so dangerous! That is those are the only times where space in front of me opens up ...

Again, thanks there are a whole lot of in the city that are willing to learn but we need encouragement not ... well I'll shut up.

b

 

Driving in SF is a real challenge, no doubt about that ! In general, the more you are able to deplete the HV going uphill, and then recharge going downhill, the better your FE will be. Crazy traffic will conspire against you. If traffic allows, a heavy foot going uphill will pull energy from the HV. Another choice, if terrain allows, is to deplete the HV before the hill by gliding. Temper this with how much power is needed to go up the hill, since you do not want the ICE working much over 4000 rpm.

My mention of 'bars' was in regard to how full the HV battery is (1 - 8).

Good Luck ! I would not care to wager that I could best your results on your commute.

 

We could probably cut our oil imports a lot if more cities would just syncronize the traffic lights.

 

<div class='quotetop'>QUOTE(tomdeimos @ May 14 2006, 07:26 PM) [snapback]255474[/snapback]</div>

In Lacey Washington it is the opposite! Good old stop at every light Lacey!! No matter what you do except 110 mph you can't get through there with out stopping! I never buy gas in Lacey, I don't what them to get any revinue!

 

<div class='quotetop'>QUOTE(tomdeimos @ May 14 2006, 10:26 PM) [snapback]255474[/snapback]</div>

I may require correction here, but it seems to me that sync is a one-way advantage. I like one-way roads a lot, but it does complicate urban planning, some people don't, and having people drive in circles waste fuel.

 

<div class='quotetop'>QUOTE(berylrb @ May 14 2006, 04:47 PM) [snapback]255423[/snapback]</div>

Well there's your problem! You got hills! I know your pain I live in San Francisco too, and just about anywhere you go in the city you're likely to drive on hills of various grades (even in the relatively flat areas).

A few things I noticed, when starting your car at the ICE starts to warm the car up, try not to "be gentle" with the driving, use that engine! It's on anyways so you might as well get the most out of the fuel usage. This really sucks doubly for me because I live on a hill in the city, so instead of coasting all the way down hill to the freeway I have the engine trying to warm up the engine (ev switch, ev switch... ), and coming back up hill the batteries don't work at all unless I accelerate exxxxxxxtremely slowly (I usually end up about 10-15mph at the next block if I try to EV only it without a switch).

Use that engine up hills! Atleast initially, get up to speed do your penance then ease up and slighlty depress to get some battery power moving it. The battery alone won't get you up SF hills for anything, the best you can do is have crappy mpg initially and then ease up once you get to 15+ mph.

Do not use B mode down hill, from what I've seen B mode isn't as efficient at regaining power as braking.

Which leads me to the finale, yes you're MPG numbers are WAY lower than sticker for hilly city driving, it's a fact of driving life. When driving on flat land, you only have to overcome inertia and then wind drag, when driving hills (even slight grades) you are literally using that engine to lift the car up that distance as well as inertia & drag. EPA doesn't test for hilly cities. From what I understand you can at best get only about 40% of that energy back (now I'm unsure if this took into account EV only or not) so that's wasted energy lifting the car up and not all of it getting back from the car "falling" back down.

Only advise I can give (as a fellow SF prius owner) is learn the city, in many areas there are much steeper hills than others due to the geography, even though the destination isn't that high, find less hilly ways to get there if possible (I know it's not always possible). There are many times when you'd go up a hill just to go down it on the other side, and if you take another slightly non-direct route you can get there without going up that hill. It requires a bit more planning, and knowledge of the city and side streets, but it's like driving down Van Ness around 4pm, you'll be stuck in hell, but if you drive a few blocks over you can go on a side street and coast all the way to whereever you need to go.

 

<div class='quotetop'>QUOTE(EricGo @ May 14 2006, 08:57 PM) [snapback]255509[/snapback]</div>

I like one-ways a lot too. If only for the fact Its much easier to make left turns.

 

thanks MikeSF,

I was at SF Toyota yesterday and talking to a service rep and she said they should write a pamphlet for all the folks trying to get valley numbers in SF.

Yep, I'll try to live without the "B" gear, at least experiment. I've tried to do the accelerate up the hill thing and I've thought about alternate routes just haven't been consistent. My problem this year so far has been the sewer replacement stuff seems like everywhere in sunset and South of GG Park is a mess.

sure was good hearing from a SF'er, and you hit it, living on a hill and working on another hill really sucks, MPG, but we love living in the city wouldn't trade it for anything.

Another thread talked about cruise control for the freeway flats and increase decrease speed for freeway downhill uphill consecutively, sounds interesting, eh?

b

 

<div class='quotetop'>QUOTE(berylrb @ May 14 2006, 03:32 PM) [snapback]255387[/snapback]</div>

"I would prefer not to."