Ok, a couple of things:
1) Can you do the first mile at 25-30 mph?This will let you get the engine and systems up to operating temperature. Thereafter, you'll get much better fuel efficiency.
2) The oil level is OK? 3) About your speeds:We have some MPG vs MPH data:
You control the speed, the MPG follows.
I use pump recepts for my long term average. I find the MFD is best used for 'tests' or learning how to drive.
Bob Wilson
Thanks, Bob. I appreciate the effort.
Good point! I'm genuinely interested in hearing accurate data for a change.
Trip computers are notoriously inaccurate (erring on the economical side - which auto manufacturer wouldn't prefer that?).
But over several fillups (say a couple of thousand miles) the total amount of fuel put in will be valid, and (give or take some slack on the last fill) should give a fair basis for the math(s) if you record the start and finish odometer readings. Then do the math, and see whether you still get 51 mpg, but I'm guessing the computer will turn out to be significantly optimistic. As the OP says, it's the _only_ way to get a realistic mpg figure (for any car).
The Prius is a reasonably economical car, especially in the urban cycle, but it still ultimately gets _all_ its energy from a gasoline engine, rather than a diesel, which is what we Europeans have come to know and love.
Steve P
I didn't know there was a hybrid diesel on the market. If you are comparing the Prius to the conventional diesel then your statement regarding energy deserves some clarification. In both cases the energy comes from the engine HOWEVER the Prius is capable of recovering some of it's own energy whereas the conventional diesel is not. Climb a hill with both and an efficient diesel will use less fuel than an efficient gas engine. On the other side of the hill, on the way down, the Prius will recapture some of that energy and store it in it's battery bank to be used when needed. When a Prius is slowing to a stop, it is recovering some of the energy required to get it up to speed in the first place. The conventional diesel, unable to recapture energy, is less efficient overall.
Then, of course, there is the matter of hydrocarbon emissions.... What Europeans have learned that Americans don't understand is that smaller, lighter vehicles take less fuel to operate. The situation in Europe, and especially in Asia, is remarkably different in another aspect. Population density is such that many more people can be served per truck-mile. When I lived in what was then West Germany, the country was the size of Minnesota with a population 1/4 of the U.S. population. That same population density made mass transportation economically feasable and, in many cases, preferable to personal transportation.
Don't get me wrong here. I don't excuse my fellow Americans for wasting fuel and emitting hydrocarbons. It's a national disgrace, worse in the long run than the unnecessary invasion of Iraq.
The Prius doesn't use a trip computer; it measures the gas being injected into one cylinder, multiplies that by four, and divides it into the miles travelled.
So? Diesel is dirty; it pollutes. There are a number of states (California, and most New England states, and New York) in the US where the sale of diesel automobiles, SUVs, pickups, and mini-vans is prohibited because of that.
Ummm, using a computer to calculate and display all this?
I'm afraid you're out of date. "Euro IV" standard diesels are exceptionally clean-burning, have multiple catalysts, and many new cars have particulate traps. The lower CO2 emissions outweigh the slight (inevitable) increase in NOx.
And also impractical because there is no infrastructure for fuelling millions of passenger cars with diesel? Surely the real problem is that our American friends have only recently come to appreciate the true cost of hydrocarbon consumption (political as well as economic and environmental) and haven't woken up to diesel for cars yet. That's also the main reason why the Prius has a gasoline engine. Believe me, you will wake up, and diesel hybrids will come.
Something we can agree on!
SP
Yes and no. Extensive reporting yields a couple of percent difference between the computed mileage and the actual mileage. Tire diameter changes with tread wear contribute to errors in both computed and manual calculations. Fuel pump pressure variations contribute to errors in the computed mileage. Frankly, both methods are so close as to render further discussion pointless.
They are certainly welcome to sell these in the U.S. once they meet California's strict emission standards. Haven't reached that point yet.
I would estimate 95% of our service stations have diesel pumps. Our trucking industry is about 100% diesel. There are lots of diesel pickup trucks on the road and some diesel cars. Where I live, gas was $2.99 and diesel was $3.19 when I last filled my Prius.
But not a "trip computer".
The infrastructure is there; a service station less than three miles from my house sells diesel. There are diesel trucks that travel all over the country, even in states where diesel cars, SUVs, mini-vans, and pickups are lot allowed to be sold. There are service stations that sell diesel to them and to those cars, etc., from out of state traveling through the state.
Surely the real problem is that your American friends have /not/ /yet/ come to appreciate the true cost of hydrocarbon consumption, either political or environmental. A governing regime that is thoroughly corrupted by greed for oil profits is doing its best to keep people from thinking about that -- doctoring research, trying to gag scientists, announcing that more study is needed to determine whether global warming is real, in short, doing all that it can to sow doubt as to whether reducing fossil fuel consumption is a desirable thing. GM -- let us all bow our heads and pray that it goes bankrupt soon, taking Ford with it! -- is doing its part by offering to buy gasoline for those who buy its 9 MPG SUV's.
We will find out in November of 2006 -- and in November, 2008 -- the extent to which Americans understand anything that is going on around them.
Davoud
Presuming that enough people continue to think hybrids are the way forward (I'm not yet convinced), Europe will go for diesel every time. In many countries, diesel cars far outnumber gasoline already. Several manufacturers who area talking about doing hybrids in Europe are talking only diesel, rather than gasoline. However, there are also makers such as VW who are releasing super-economical (non-hybrid) diesels with very low emissions and exceptional fuel mileage (aiming for 3 litres per 100km). It's interesting that in several cases recently the most powerful model in a maker's range is a diesel - e.g. the VW Touareg, Skoda Fabia, etc.
Of course, that's what the batteries are for (though I have met people who say that the reason for the Prius's economy is that some of the power is ultimately "electric", without having thought much about where the electricity comes from).
Correct.
There are two caveats. The first is that in normal driving (not in stop-start traffic) how much time do you actually spend pressing the brake pedal? Not much, as a proportion of a journey, unless you are a driver with exceptionally poor anticipation. This is evidenced by the very low capacity of the Prius battery pack, only able to power the car for a few seconds at full output, which in turn explains why Toyota provided no facility to charge it from the mains. There's no point.
Second, lugging the additional mass of the battery pack, electric motor / generator set, power and temperature control units, etc around all the time has an impact on economy.
Indeed, dramatically less. Increased vehicle body mass / engine power increases secondary items such as transmission, brakes, suspension, and it's a vicious circle.
In and around London it's the only sensible option. Millions of people take the train every day.
..which will bite the US in the bum.
Don't get me started. Aas a Brit, I'm disgusted that our government has been going along with it.
Steve P
Point of clarification:
The Prius does not wait for the application of the brake to begin the regeneration cycle. I've seen the display indicate regeneration at 50 miles per hour when the conditions are adequate. This is why steady driving is a good thing. If the electronics detects a request for 50 steady mph and there is a down slope of as little 2%, the controller may turn off the engine, turn on the motor, and may even begin regeneration. If the down slope is even more severe, but does not require braking to control the speed of the Prius, the electronics will still take advantage of the situation.
Your second point is offset somewhat by the continual running of a non-hybrid to support the ancillary requirements. The Prius air-conditioning is run off the traction battery, thus allowing complete shutoff of the engine at any complete stop. Given that some of our intersections require minutes of stopped cross traffic, that can be a major savings.
Probably the reason we don't have hybrid diesels for the U.S. is the high sulfur content of the petroleum we receive from our sources as opposed to the lower concentration in the supplies sent to Europe. There is a new requirement to lower that content at the refinery that should lead us to diesel hybrids as the best of both technologies.
In fact, I hope someone takes a close look at a serial hybrid (the Prius is a parallel hybrid in that both sources directly drive the wheels). A constant rotation diesel can be more efficient than a variable speed diesel. It would seem a diesel that charges a battery or capacitor that runs the motor would be the ultimate combination. And then, if we plug it in for the first twenty or forty miles of power requirements, we may have the best energy balance compromise.
The prius recovers energy whether coasting to a stop or braking to a stop.
What is evidenced by the battery packs capacity? The battery pack stores recovered energy. It has the capacity to do precisely what Toyota intended.
Of course, so does lugging around a diesel engine.
Steve, this discussion would make more sense if you gave us the make and model of the particular diesel you are comparing to the Prius. Having that, we can compare the specifications of that vehicle with the specifications of the Prius. Let's face it, you have made a lot of claims in this discussion but you are the only one who possesses both sets of specifications.
What? If the Prius is charging its battery while the engine is running, but you're not applying the brakes, that's got to be generation, not regeneration.
Again, if the (electric) motor is turned on, it's hard to see where the regenerative energy is coming from! Either the car is slowing and converting some of the energy (which in a conventional car would be lost as heat from the brakes) into battery charge, or it's drawing power from the battery to run its electric motor. It can't be doing both at the same time.
I presume this refers to cruise control 'braking' the car?
But surely no _net_ saving at all, since all the charge taken from the battery during rest has to be replaced by energy from the gasoline engine at some point (unless you believe in perpetual motion)?
Plus of course the fact that until recently gasoline in the US has been so cheap and plentiful that there's been no incentive to look for alternatives.
Yes, though it will always be more efficient to use the internal combustion engine (gasoline or diesel) directly, rather than using it to drive a generator to charge a battery to drive an electric motor to drive the transmission, since you have significant conversion losses at every stage. As I understand, it the main advantage of the battery in the Prius is that it boosts short-term acceleration (especially in the urban cycle) without a corresponding increase in instantaneous power demand (and hence emissions) from the IC engine. Energy recovery from regenerative braking is a bonus, but only of secondary importance.
Good debate, thanks for your input. SP
The motor/generator used to propel the Prius is a motor when accelerating, a generator when decelerating. Applying the brakes with light-to-moderate pressure increases the charging rate which in turn increases the generator load. Sort of like this:
Take foot off accelerator pedal = 1/3 charge rate. Apply light pressure to brake = 2/3 charge rate. Apply moderate pressure to brake = full charge rate. Apply heavy pressure to brake = mechanical brakes engaged.
Yes it can. The "(electric) motor" is an (electric) motor/generator. Take your foot off the accelerator pedal and it reverts from motor to generator. The generator is driven by the front wheels, not by the gas motor.
With or without the cruise control engaged, the motor/generator reverts to generator whenever kinetic energy can be recovered.
Actually the energy taken from the batter during rest was kinetic energy recovered as the car coasted and/or braked to a stop. With a good tail wind, some of it is actually wind energy.
Steve, your last paragraph doesn't describe the Prius drive system. I believe Toyota calls it "hybrid synergy drive" because the gas engine, the electric motor/generator or both simultaneously propel the car. Remember, energy is recovered from both braking and coasting.
I understand 'coasting to a stop' as being what happens when you release the accelerator (gas) pedal - on a level road, the car slows gently owing to friction from the air, rotating surfaces and tyre hysteresis, and ultimately engine braking, depending on the gear selected (I know the Prius has CVT so that's not applicable in the same way as a normal gearbox). 'Braking' is deliberate slowing of a much greater magnitude. I'd be surprised if the Prius regenerated when 'coasting', since this would inevitably slow the car (like deliberate engine braking does) much more than just taking the foot off the pedal.
Quite, which is just enough to give a short acceleration boost or run some utilities with the IC engine off, but not enough to operate as a true electric car for any distance. This isn't a criticism, just a clarification. Believe it or not, there are people out there who think the battery somehow contributes a net positive energy to the car.
Not to the same extent, the weight premium for a modern diesel (even including its heavier starter, turbo, etc) over a comparable-output gasoline engine is much less than the Prius battery pack etc.
I'm not actually making a comparison with a specific diesel, just trying to find out (see my first article in this thread) whether the mpg figures claimed by Toyota and some (naturally) pro-Prius subscribers to this forum are truly based on real measurements of road mileage and of fuel consumed (measured by what you put in the tank), or whether they are just what the 'computer' (OK, not a trip computer) on the dash says. That's all.
Clearly, there will be people (especially those who have bought Prius cars) who are very anxious to claim an optimistic figure. All I'm pointing out is that if you want really good fuel efficiency, we've been doing it in Europe with diesel cars such as the '3 litre' VW Lupo, for years. That's three litres per 100km which equates to about 94 mpg (imperial) or, say, 75 mpg (US gallon), and this is readily achievable even on long-distance driving. VW are bringing out even more economical models. In contrast, quoting from Wikipedia, "By the European method, the combined fuel economy of the Prius is 4.3 L/100 km or 55mpg (US)".
Again it's not a matter of specifications but of principle. I'm just curious to know whether the claims of fuel economy are based on real numbers, or the say-so of a dial on the dash.
For the record, my own car is a Skoda Octavia with a 2-litre diesel. Keeping a log of every litre of fuel I've ever put in it, over 13,438 miles it's used 1,340 litres and so averaged 42.2 mpg (imperial). This is a good bit worse than a Prius, but it's a much bigger and more capable car, and at least I know that the figure is accurate (as accurate as the fuel pumps at the forecourt and the odometer, which I have checked against the motorway mileposts on a long run). By comparison, the trip computer reads about 7% optimistic on average.
SteveP
So what about Euro IV? Diesels are under a different emissions rating plan than petrol (gasoline) vehicles, mostly to diesel's benefit, under the Euro standards.
Euro 4, Gasoline CO 1.0 g/km = 1.609 g/mi HC 0.10 g/km = 0.161 g/mi HC+NOx (not rated) NOx 0.08 g/km = 0.129 g/mi PM (not rated)
remembering to convert from g/km to g/mile is helpful. 1 gram / kilometer = 1.609344 grams / mile
The US Tier2 regs do not separate the fuel type, but treat the fuel and the car as a whole system. Because of the higher NOx and PM of diesel fuel, they'll get classified in a lower Bin because of their emissions, right next to an unclean gasoline car.
You can also view the US Tier2 and Tier 1 Emission standards here:
CA SULEV II, Emission limits at 100,000-120,000 miles NOx = 0.02 g/mi NMOG = 0.010 g/mi CO = 1.0 g/mi PM = 0.01 g/mi HCHO = 0.004 g/mi
My reading is that the Euro standards are very strict on CO, but if you ignore that compound the Euro4 petrol standard is about a Tier2 Bin6, and the Euro4 diesel standard is about a Tier2 Bin9c. But I could be wrong on my matching of data...
Most filling stations have diesel pumps. The bigger problem is that we're only starting to phase in low-sulfur diesel (
I went from Pittsfield MA and then onto MA Pike, drove 62 mph, and got 63.9 mpg.
You should drive a Prius. Toyota did a great job. The "feel" of the charging that takes place while coasting to a stop is identical to the feel of engine braking in a conventional car. A "B" (engine braking) shift position is provided if actual engine braking is needed for long hills. Yes, I was surprised too.
No, it can drive as a true electric car for a significant distance. We Prius owners call this the "stealth mode". Frankly, you need to rent one for a few days. From what you write here it is clear you are describing how you *think* the Prius works, not how it does work.
The tiny, 3-door Lupo hardly compares to the mid-sized, 5-door Prius.
I tried. They aren't comparable, one being a mini, the other being a mid. Couldn't find the Lupo emission figures.
Let's face it, you have made a lot of
Yes, it is a matter of specifications. Not every family of five will fit on a mo-ped. Rent one. You are trying to compare apples to oranges but you've never eaten an orange.
I can't fault your logic - I am speaking from what I've read, not first hand experience. However, despite our interesting debate (for which I thank you) I still haven't seen the real-world figures requested by the OP.
Steve
Steve, "real world figures" are anecdotal and largely depend on individual driving skills and habits. Your real world differs from mine. The same Prius will produce much better mileage for the husband than for the wife or visa versa. Where I live many of the highways have a 55 mph speed limit. This is very close to the speed at which our Environmental Protection Agency tests cars to determine the figures they publish, the ones that are by law posted on the window of every new car. If you drive 55 you will, on average, achieve the published figures.
As a consequence, the only fair comparison is of the EPA figures for vehicles of the same size. Deviations from the published figures will affect both vehicles. In fact, a number of people have "tested" the Prius and concluded it does not achieve the EPA figures in their "real world" scenario. They tested the Prius because they were astounded by the published figures and you will note they don't compare their "real world" results with the "real world" results of some other car that underwent an identical "real world" test. The same driver's "real world" would have a proportional effect on whatever car they tested. Also, a number of people have made a hobby out of exceeding the EPA figures. It is important to remember that a 10% reduction from 50 mpg is 5 mpg while a 10% reduction from 20 mpg is 2 mpg. 10% is 10%, but some people can't comprehend that.
I've concluded that publishers who whine about this "real world" of theirs are people who live in a world that doesn't care about either pollution or conservation. People who do will meet or beat the published figures. After all, this is what "Environmental Protection" is all about.
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