How good mileage could the Prius get

<div class='quotetop'>QUOTE(Per @ Jun 10 2007, 04:32 PM) [snapback]459306[/snapback]</div>

Lots of people ask for improvements. But many people on PC do not think that increasing smog-producing emissions is an improvement. Nobody is faulting you for asking for improvements. We are disagreeing with you about what constitutes an "improvement."

And I personally doubt that a significant amount of gas could be saved by allowing the Prius to pollute more.

As for the gas tank, the bladder prevents gas fumes from evaporating into the air. If you ask for a bigger tank, I'll agree with you. If you ask for a tank without the obnoxious bladder, I'll reply that it serves a useful purpose, and I don't feel that eliminating it (and thereby allowing more pollution) would be an "improvement."

 

<div class='quotetop'>QUOTE(Per @ Jun 10 2007, 05:31 PM) [snapback]459333[/snapback]</div>

Because some of us want a better, cleaner car than "regular" cars. I bought my Prius because I didn't want a "regular" car. But if you do want a "regular" car, there are plenty to choose from. Those of us who want the cleanest car that still burns gas have only one choice: the Prius. It makes no sense to deprive the environmentally-consciencious driver of his only choice, when folks who do not care about the environment have a thousand cars to choose from.

Most of us are willing to put up with the obnoxious gas bladder, because it makes the car that much cleaner. I want the cleanest car I can get. You correctly point out that the European and Japanese Prius is not as clean, because it does not have the bladder. I am glad that Toyota decided to allow me to buy a car that's even cleaner than the version they sell outside of North America.

Maybe they'll solve the "guess gauge" issues and give us a one-gallon-bigger tank for the 2009 model year. That would be nice.

 

<div class='quotetop'>QUOTE(Per @ Jun 8 2007, 09:35 PM) [snapback]458415[/snapback]</div>

Right ... . . . unless you remember the fact that that the car holds twice as much and even w/o passengers, weighs well over 1/2 ton more

I guess you could always strip the Prius down ... no spare ... sit on the floor w/ no seats ... remove all the electronics ... to make the 2 cars more similar ... or? maybe some other great / practical ideas?

And since when do cars only drive on flat ground ... to measure basis of comparison?

 

<div class='quotetop'>QUOTE(Per @ Jun 10 2007, 06:32 PM) [snapback]459306[/snapback]</div>

I guess we're more puzzled by statements like "I would like the Prius optimized for mileage". It gets double the mileage of a similar-sized sedan, and is better than any other car in the American market today. If you were a former Insight owner, I could see some valid nostalgia. The Prius has a lot of optimizations for mileage, like the Atkinson engine, aluminum for the hood and hatchback, streamlined Kammback shape, the engine coolant thermos, even the hubcap style, to the dismay of several. You'll be hardpressed to find another car with any of these optimizations, let alone all of them.

Regarding diesel, remember that a gallon of diesel contains something like 25% more hydrocarbons, so going 25% more on a gallon is a wash, as far as pollutants and CO2 goes. That's just because it's more energy dense.

There are plenty of people here who want the PHEV option (and we've been pretty vocal about it), so they can charge up the batteries (by solar or wind or even residential hydro power preferably) and drive without any gas at all, at least for around town. An electric car is really the best long-term option for situations where public transportation and bicycles don't work.

Modifications like you're talking about (dropping the bladder or engine auto-warm-up cycle) might add 5-10% mpg under normal conditions. To a hypermiler that might be big, but for most of us, the car is already 50%-80% better than similar sized vehicle, so another 8% is not a big deal. You can do that by driving a little slower or smarter.

But if that doesn't satisfy you, wait a year or two and a smaller version of the Prius should be available. They're making three variations on the Prius, adding on a smaller and bigger version, and they're improving the hybrid system, so I would imagine the smaller version (closer in size to the Honda CRX-HF?) would do quite well.

 

<div class='quotetop'>QUOTE(Per @ Jun 10 2007, 06:32 PM) [snapback]459306[/snapback]</div>

I have a MKIV Jetta TDI and my friends have a MKV Jetta TDI. They both smoke on acceleration and and start-up. Not the dark clouds of black soot you see from semi's and F350's that have been chipped but a small puff of grey smoke.

If the TDI is question had been chipped then clouds of black smoke on acceleration is a definite possibility. With TDI's you can chip them and get more power, torquer, and mileage but at the cost of emissions.

 

Per,

You are the typical engineer arguer, and I mean that in a good way. Kind of. You do have a problem with changing the point of the argument mid stream.

I bought a Prius because it has a collection of features that I wanted in a car. Most are good, but there are of course bad features too. Dismissing a Prius because it has a bladder in the fuel tank is silly, but it is your choice.

Back to the mileage argument.

I looked up on the EPA web site when they began reducing the mpg numbers and it was in 1986. So, the CRX is using the "reduced" number. They actually measured approximately 70mpg in the EPA tests of the CRX. OTOH, you need to look at the whole picture if you want to compare the two cars. I am not sure what your point is either?!?! Are you trying to prove that the CRX engine was more efficient than the Prius? Or are you just trying to proove that the Prius sucks?

Anyway, lets look at some more data. I KNOW that you love data.

Curb Wt. Frontal Area Cd Drag*Area Factor Hwy MPG
Prius 2950 2.57m2 .26 0.668 51
CRX 2125 2.13m2 .29 0.617 56

I got the frontal area from your numbers. (I dont have that data) What do you see when you see that data? Well the weight is SIGNIFICANTLY lower for the CRX. The EPA test involves a series of accelleration and decelleration manuevers. As you know, the weight of the car will affect the rolling resistance of the tires, as well as the mechanical rolling resistance from the bearings. The weight also affects the amount of energy required to bring the car up to speed. The overall drag and cross sectional area for the Prius is 8% lower. The weight difference is 38%!

You previously stated that the weight of a car does not significantly affect highway mileage. That is irrelevant, since we are comparing EPA numbers, and the weight of the car will affect EPA numbers.

When you factor in the weight and drag numbers, it is clear that a Prius would not get 51mpg if you put the CRX HF engine in it. I bet the the mpg would be more like 45mpg(A SWAG). It would also be a much slower car. The CRX had only 62hp. The Prius (combined elec and engine) has 110hp. HP to weight ratio for the Prius is 26.8lb/hp for the CRX it is 34.2lb/hp. So, clearly the Prius is a faster car than the CRX HF.

Prius puts out less emissions than the CRX.

Looks like the Prius beats the CRX HF in every measurement.

Again, what is your point?

 

<div class='quotetop'>QUOTE(jhinton @ Jun 11 2007, 04:01 PM) [snapback]459713[/snapback]</div>

The VW's in the rally were converted to Biodiesel by teams of High School kids. The entire weekend was devoted to the kids. There was a shorter rally for the pure electrics and autocross competitions to determine who built the "best" car (or pickup). After our rally one of the biodiesels, hobbit's Prius, and an organizer's gas car also ran the autocross. Where available, the biodiesel is significantly cheaper (maybe half?). The kit car smoked through the autocross so I think it is either normal or intentionally designed.

If HIGH SCHOOL kids can get electric cars on the road (and all of them were registered) NOW I'm not buying one word of GM's whiny excuses about batteries. Maybe GM needs to can their engineers and hire a few dozen high school graduates to get the Volt on the road.

 

<div class='quotetop'>QUOTE(Per @ Jun 12 2007, 11:52 AM) [snapback]459917[/snapback]</div>

OK, please tell us what mpg number do you expect, for example at 70 mph?
And, what is your idea to improve the highway mileage?

Ken@Japan

 

first of all why are we comparing a small compact with a midsize??? The 88 crx if I remember correctly was a very small 2 door hatchback that was half the size of the current prius model.

If we were to compare the prius to anything I think it should be classed in with the other midsize cars of its class.. All of these cars in the non-hybrid version are getting high 20's low 30's in COMBINED real world driving. If you were to compare these cars that are in the same weight class to the prius, hands down the prius wins in several factors including mpg

BTW the camry/accord/altima are classified as midsize cars also but get significantly less milage even with todays technology.If you compare apples to apples then the prius doubling the milage of a standard camry is a feat all in its self. I believe that if you add in your options that you can order (smart key, JBL, factory nav, leather, bluetooth, hid lighting ) it is prudent to compare the prius to the camry/accord/altima class.

weight has a factor in accleration. The lighter the car the faster it will acclerate. We as americans would rather have a 2900lb car with a 5.0 liter V8 but those days are comming shortly to an end. In terms of gas milage it does have a factor if the weight is largly different.in this case however not enough to be concerned about. The camry weighs 3209lbs and the prius weighs 2834. That is only a difference of 375 lbs!!!! I know these weight figures because I own both cars.

With that said I am currently getting around 26mpg with my 2007 camry LE . The prius I always average around 53 which is more then double what I get with the camry. If I drive at 60mph, no ac or heat I can achieve closer to 56mpg. That is a 30 mile commute mixed highway speeds and city speeds through the suburbs of NYC.

By no means am I saying that the prius is the best car ever.. or is for everyone. Clearly it is not . If you want a good clean car with alot of features that are actually useful and good mpg then by all means consider the prius. If you want snappy accleration, good sqishy ride, all baby cow interior, and fake wood grain, go with a caddy.

 

We're comparing unlike vehicles because doing so gives the OP the opportunity to raise abstract issues rather than real ones. The point being that with the technologies available in the 80s capable of delivering good fuel economy in any car, modern technologies ought to have enabled rather more significant gains in the meantime than they actually have.

It is a valid point in itself, though of course in the US marketplace, the notion of fuel-efficiency is a relatively new thing and not yet at mass-market proportions, while in many other markets where fuel has been substantially more expensive for a long period of time, there are plenty of examples of fuel-efficient vehicles that have become established products. By their nature, these have tended to be of the small variety, simply because despite the OP's earlier insistence that weight doesn't have any impact of fuel economy in 'straight and level' driving, the real world does not include much of that ideal. Given that most vehicles spend more time in traffic than on the open road, small, light, cars will have better fuel efficiency than large, heavy ones, all else being equal.

Mind you, weight does have an impact in more ways than purely acceleration. Weight acts as a downward force, meaning that more energy is required to propel a heavier vehicle in a straight line on a level surface than is required for a lighter one. On the other hand, heavier vehicles gain more momentum on a down slope than a lighter one, and thus 'generates' more energy. It's easy to see therefore that in reality, the supposition that all the energy used to propel a car (not just a Prius) comes from the gas tank is actually not the case. Some energy comes from the effect of gravity pulling the car down hill. One also has to take into consideration relative efficiency of the method by which the energy is used, because if gas flows from the tank to the engine and propels the vehicle that way, efficiency is actually pretty low because internal combustion engines are not efficient power plants under load. However, if energy generated from regenerative braking or a lightly loaded ICE is then fed via the electric motor, efficiency is much higher, meaning more of the energy gets applied to the wheels.

The OP's original supposition that modern emission controls create less fuel-efficient vehicles is of course very true, and there's no doubt that without those controls built in, almost any car would travel further per gallon of fuel. However, part of the science of vehicle development is to find not just ways to improve fuel economy, but also produce fewer by-products which harm the environment, and thus allow lawmakers to impose viable emission controls to help short-term pollution and long term environmental impact.

We are at the early stages of the development of these technologies, first started in the 60s, 70s and 80s where the onus was almost purely on fuel-efficiency, to the point where we can now buy and operate vehicles such as the Prius which give a good set of compromises between fuel economy, size and utility, power, and ecological impact. One could trade off any of those compromises for better fuel efficiency, to the detriment of utility/comfort/features or higher emissions, but ultimately the car manufacturer has to make product decisions based on economic viability, not least bearing in mind the need to ensure that sales of one product do not cannibalize sales of another.

The Prius represents Toyotas best set of compromises given today's technologies and their economies of scale and production. Tomorrow's mileage may vary substantially.

 

<div class='quotetop'>QUOTE(Per @ Jun 12 2007, 10:49 AM) [snapback]460113[/snapback]</div>

But then a bigger battery would mean more weight, which would require more energy to accelerate it from standstill, maintain it in motion and to bring it to a standstill, resulting in reduced fuel efficiency. Also it would require more energy to charge it, meaning that unless one could increase the energy gained from braking, more ICE, thus fuel, required.

As for the potential for diesel power, perhaps so, though it may be that it would be harder to engineer a diesel engine that can deliver on the variable demands of the present ICE with the same efficiency. I find it hard to believe that Toyota would not have considered that - though it is of course possible they did not, or found that it would not have been economically viable to produce the Prius in that configuration.

 

<div class='quotetop'>QUOTE(ZA_Andy @ Jun 12 2007, 10:17 AM) [snapback]460135[/snapback]</div>

Diesel might also have been ruled out due to emissions issues. And auto emissions are not simply a global-warming issue for many of us. It's a daily air quality-of-life issue. When I get the increased health benefit of riding my bike to work, I get the decreased benefit of sucking in all that exhaust. Lower emission vehicles can have a broad-based health benefit for society. I enjoy the fact that when driving our Prius, we not spewing as many fumes. Asthma rates have been steadily increasing in the U.S. "Asthma rates in children under the age of five have increased more than 160% from 1980-1994." I mean, when I lookup our air quality in Chicago (Cook county), we get an F from the American Lung Association.

I'm happy to sacrifice a little mileage for reduced emissions.

 

I am not that sensitive Per. Thanks for the reasoned response. However, let me point out a couple things.

1. Rolling resistance increases proportional to the weight of the vehicle.
2. You keep trying to dismiss the weight as a mpg factor. However, it is very important in every measurement of mpg. You cant just say it is insignificant in a highway mileage number.
3. Ken is not out to get you. He is just trying to define the argument.
4. A bigger battery would not help the Prius very much, unless it was a plug in. There are only a few situations where more battery capacity would help, and highway mileage is not one of them.

The best way to help the Prius get better highway mileage would be to ensure that the engine is operating at a load that is the most efficient for the engine. That could be done by pulsing the engine, and then pulseing the elec motor while idling the engine. However, the charging system for the NiMh batteries is only about 65% efficient (so I have heard). Thus, that would not work. Although the Lithium Ion batteries are supposed to be much more efficient.

As far as engine technology within the last 20 years. I think engines are more efficient than they used to be. Especially, high hp engines are able to be more efficient at lower loads. Unfortunately, there is not much more efficiency that one can get out of the Otto cycle engine. I would bet the Prius engine alone is probably 10% more efficient than that CRX Honda engine. There isnt much more efficiency to be had.

I think there are two main reasons why diesels are not used in hybrid vehicles.

1. They weigh more than gas engines
2. They have more internal friction. In the hybrid system the engine is often spinning without providing any power.

 

<div class='quotetop'>QUOTE(MegansPrius @ Jun 12 2007, 12:19 PM) [snapback]460185[/snapback]</div>

Indeed so! One can talk about such things as the vehicle's carbon footprint and the impact on global warming and long-term environmental issues, but that doesn't begin to cover some of the pollutants which have the most immediate impact on human physiology. Many diesels, for example, produce high levels of particulates which are very damaging to respiratory systems and have been linked to a number of long-term health problems. Unlike the pollutants from cigarette smoking where the 'innocent' at least have some option to avoid polluted locations, the same is not true where diesel exhaust is the cause.

http://ntp.niehs.nih.gov/ntp/roc/eleventh/...es/s069dies.pdf http://en.wikipedia.org/wiki/Diesel_particulate_matter and http://www.epa.gov/region1/eco/airtox/diesel.html are but three quick links to the subject.

It's also worth noting that regulation of diesel exhaust pollutant varies greatly from country to country, so it may be that Toyota was unable to find a viable engine to meet the most stringent requirements of any of the Prius target markets.