Having immersed myself in nineteen fifties-tech frames, I need a breath of fresh air: Like the new 2013 Prius C. OK, not exactly a CC (only half-way there), but the problem is, I’ve yet to read something that puts it fully in its proper context. Way too many articles and comments bitching about why its EPA numbers 53/46/50 (city/highway/combined) end up with the same combined rating as the larger, more powerful and heavier regular Prius (51/50/50), and not enough explanation.
First of all, the Prius C wasn’t designed specifically to beat the Prius III in fuel economy. It’s part of Toyota’s oft-stated goal to offer hybrids in every class of vehicle they sell. The HSD system in this Prius C is also going into the European Yaris hybrid. The design goals for this system were to most of all be cheaper to build, and weigh less. All the key components have been slimmed down, including the electric motor/generators (MG 1 & MG2). And the battery has been substantially reduced in size, weight, and voltage (144 V vs. 273.6 V). That alone may account for the single biggest part of the equation.
The battery plays a critical role in the Prius, because it both stores converted kinetic energy from braking as well as buffering the small 74hp 1.5 L Atkinson cycle gas engine. Toyota has only revealed the voltage, not the actual capacity. But given Toyota’s tendency to use certain size cells in their NiMh batteries, this downscaled battery may possibly only have as little as half the capacity of the Prius III battery.
A smaller battery means more frequent use of the gas engine, and possibly in rpm/load ranges that make it less efficient. This is Prius Lite, or HSD Lite. Undoubtedly, the Prius C’s almost 500 lb weight advantage is what gives it the slightly higher city EPA number (53) than the Prius III (51).
The Prius C’s lower highway mileage is undoubtedly a combination of aerodynamics, as well as the reduced battery buffering (to a smaller extent). The C’s Cd is 0.28; the Prius II’s is 0.25. We don’t know yet what the frontal area of the C is, which will somewhat mitigate that higher Cd number (total aerodynamic drag is the Cd x FA (frontal area)).
The Prius C is almost twenty inches shorter than the the Prius III, and as we know from these two stubby Falcons trying to turn themselves into one long Foord (which added 500 rpm to their top speed), a longer body almost invariably has better aerodynamics.
The Prius C’s role is to expand the Prius brand downward, given its sub $19k price, just like the Prius V extends it into the realm of a station wagon/MPV. And the plug-in Prius will be the banner-wearer for ultimate mileage numbers.
Toyota’s greatest achievement with the Prius C is in its continued cost reduction of its HSD components, not in shoehorning in the battery under the seat. A decently equipped 50 mpg Prius starting at $19k is the breakthrough.
Anyway, when one gets in the questioning a couple of mpgs one way or another at around the 50 mpg point, it really becomes largely irrelevant. It’s really an artifact of our system of using miles per gallon, which makes it seem that every additional mpg is the same degree of improvement as the one before it. Not so. The European convention of Liters per 100km much more accurately shows the actual degree of improvement in fuel use. Improving mileage from 40 mpg (5.88L) to 50 mpg (4.70L) results in a saving of 1.15 liters; going from 50 to 60 mpg (3.92 L) results in savings of .82 liters. Especially with American fuel prices, these differences are mostly useful for forum debating points. But that’s ok too.
Did engineers forget about the carbureted cars of the 1980s that were able to acheive similar EPA ratings. This Prius III is aerodymamic, but its also heavy and expensive. Cut out the weight and the hybrid system and install a small, mildly tuned engine and a manual transmission with tall overdrive and I’ll bet that the EPA numbers could be matched. The non-hybrid would be cheap too, Toyota!
This comes up a lot. The 1991 Geo Metro XFI had (adjusted) EPA ratings of 43 (city) 52 (highway) and 47 (combined). But actually comparing the two is a classic case of apples and oranges. The Prius C will undoubtedly be a faster, safer, roomier, more comfortable and pleasant car, by a huge margin.
The hybrid system in the Prius C is now so small, light and low-cost, that it really wouldn’t be possible, IMHO, to top it with what you’re describing. Which is, of course, why it exists. Especially getting high city EPA numbers without a hybrid is essentially impossible.
If it could be done, it would, right? It would be a selling point.
Dont forget the strange size of a US gallon at only 3.7 litres against 4.5 for imperial it makes 50mpg achieveable elsewhere I used to get 48 imp out of my 2.1 TDI 406 Peugeot wagon
Especially getting high city EPA numbers without a hybrid is essentially impossible.
What about using stop-start engine technology, such as Mazda i-stop?
Helps, but not as much as a hybrid, because it converts braking into electricity to be re-used for propulsion. That is the single biggest advantage of the hybrid system.
It doesn’t help much because the EPA city cycle doesn’t take spent time idling into consideration.
Evan Boberg addresses this in his book, Common Sense Not Required. Boberg was an OJT engineer with AMC and later Chrysler…it’s probably good for him he didn’t try to eke out a living as a writer. But…poor writing notwithstanding, he discussed, intelligently, the pros and cons of hybrid drive…and concluded that for most users, it was a loser and a dead technological end.
His point was exactly what was made: The nominal advantages hybrid drive gives, are outweighed by the weight and complexity of the drive train. The winning plan, he proposes, is to use the lightweight chassis, aerodynamic body, and low-resistance tires on a small-engine direct-drive chassis…with almost the same result in highway driving.
In city driving, he concurs, hybridization offers advantages in economy. But someone truly interested in economy may take the bus and save MORE. And even using his private car, he “saves” by not paying for the complexity of the hybrid and paying somewhat more in fuel.
In the city. On the highway, hybrids are no advantage.
A true cheapskate in my old age, I had considered a Prius…but truly, the advantages and savings will never make up the cost. Instead, I chose the Yaris…tremendous purchase savings, and more savings at the pump. And acceptable even on the highway.
The long Falcon is actually 2 engines versus ! frontal area giving more speed a trick used by convoying truckies once upon a time in Aussie (now illegal). For highway mileage that Prius isnt great the owners manual gives my Citroen 5.4 L/`100kms and on a run can actually do 5 in traffic and 2 lane roads it runs neatly at max torque right on the 100kph speed limit ok its diesel which helps but I had thought Toyota with all its research facilities could have done better.
Diesels certainly do well on the highway in particular. Keep in mind that diesel fuel in the US runs 10-20% higher than gasoline. With the Prius’ superb city mileage, and roughly comparable highway mileage (to a diesel), the Prius still comes out well ahead, here anyway. Helps explain why they sell so well here. Plus, they’re so quiet too; a minor additional benefit.
Yes in my car you can just hear the engine at speed on smooth tar. Diesel here is 50c less than gas but we are taxed $50 per 1000kms road user charge for diesel so in that respect a hybrid wins hand down. The reason I went for a 1905cc PSA rig is its all mechanical no engine management system so I can unplug the speedo and use GPS for speedo cut down on the ruc costs. A Prius starts at $45k or so here
Any small diesel in the USDM 07+ is also going to have to deal with the strictest emissions standards in the world. All use some combination of a EGR, a Particulate Filter & Urea after treatment. Figure this adds ~$2k to the diesel premium and carriers a 10-20% fuel economy penalty over a pre-emissions model.
Diesel in the US also competes with home heating oil as they are very similar products. Increase diesel consumption and watch home fuel oil go through the roof.
If diesel took off in the US and home heating fuel oil prices went up and availability went down because of it, I’d be screaming to my state senator and rep to have the state put at least a $1.00 Tax on diesel at the fuel pump so I could afford to heat my home.
Sorry, but I see no justification for demanding that random total strangers should subsidize your heating bill. Put on a sweater or move to a smaller house.
In a more general way, I really don’t get how the idea of imposing taxes to force the other guy to behave the way you think he ought has gained so much traction. It’s a total abuse of the purpose of taxation.
Well I am impressed. Probably it could be argued I am easily impressed.
Have driven in a daughters prius and if it were not for all the bells and whistles you would not know it was a hybrid. It just does a decent job of moving a roomy car down the road.
If something like that can be delivered for $20k, that is the impressive part.
If I had the dough, I just might buy one.
That’s what I don’t get.
What you SAVE in fuel costs, isn’t made up until well over 150,000 miles. That’s assuming a catastrophic failure of the hybrid components doesn’t put you even deeper in the red.
K.I.S.S. It’s as valid for engineering as for military evolutions. And it’s something that pays in the long run, when shopping for an automobile with costs in mind.
That’s right, MPG is a really misleading measure of fuel economy. Passing the 30 mpg or 40 mpg barrier sounds significant, but only in the realm of bragging rights. Your annual cost of running a 29 MPG car vs. a 31 MPG will be almost the same. Until I did the numbers myself, I didn’t realize that you save the same amount of fuel by trading from 20 to 25 MPG as you would trading from a 33 MPG car to a 50 MPG car.
Fuel efficiency is a fine goal but it has diminishing returns, like any other form of tech-spec racing.
Really smart, Paul, I hadn’t seen the EPA numbers on the C yet. You’ve covered the explanations I would have, plus some I wouldn’t have thought of.
I think we all expected slightly higher than 53/46/50, the highway number in particular, but we were (unconsciously) assuming the same level of hybrid. You put your finger on it, this is a smaller and cost-reduced hybrid system.
Toyota certainly hit their target price point and economy with the C. Compare with the very disappointing 2nd-gen Honda Insight, 42/41/44 at $19K. Honda has a simpler and less effective hybrid technology. Only Toyota, Ford and their licensees have the full hybrid.
Plus the difference in length and shape. The Prius V dropped more mileage than I expected too, for similar reasons. Comparing the airflows of all three would be most interesting.
Highway mileage on a hybrid is challenging, since there’s much less starting and stopping. Ultimately it’s the efficiency of the engine and how much power it takes to push the car through the air. I was surprised to see my 2010 Prius show 48 mpg on a Portland – Salt Lake City trip last May, cruising at 65-75 mph. Since the electric motor can provide low speed torque in the city, the engine can run Atkinson cycle and be optimized for highway power efficiency.
For the record, I paid $21.5K for the Prius in April 2010, and got 0% financing, since they were recovering from the “sudden acceleration” nonsense.
All very interesting, nicely done!
Interesting they call it Prius C though this seems a Yaris subcompact class car.
So to reinforce Paul’s example, Prius gets 50mpg highway meaning 4.7 l/100km and Prius C gets 46mpg meaning 5.1 l/100km.
So let’s say with 10000 highway miles a year, the savings are about 64 litres meaning 17 gallons i.e. $68 with $4 per gallon. Hardly substantial savings but somehow it still gets lot of marketing and internet forums coverage.
Prius C is simply a cheaper Prius for people who want to spend less and don’t need the extra space. Ideal commuter car. Much nicer inside and higher status than the Yaris.
And it comes in ORANGE!
“The Prius c’s available exterior colors include vibrant hues that are unique and expressive. The available colors for Prius c include three new colors –Habanero, Moonglow, and Summer Rain Metallic – along with Blue Streak Metallic, Absolutely Red, Black Sand Pearl, Magnetic Gray Metallic, Classic Silver Metallic, and Super White.”
What the hell color is Habanero? Don’t you just love car color names? There’s a good topic.
I’d assume it’s an orangeish red. That’s the color of most varieties of the pepper.
Personally, I’m more impressed with a little factoid about a 68 Chrysler Imperial I was looking at. Measures in around 19 feet long, weighing the better part of 5,000lbs. Pondering the idea of electronic ignition and throttle-body fuel injection to the 440. Horrifying? Yes. Inefficient? Grossly. Off-topic, but cool? Oh yeah.
Prius is the ultimate empty gesture. Sure, it’s bigoted, but I’d put people in Prii right up there with the folks who walk through life with an iPhone stuck to their face, just crying out for Darwin to select them out of the gene pool in some downtown crosswalk.
Sure, it’s your blog to do with as you like, but whattaya say we get back after the real classics, eh?
We love all interesting cars here. The ’68 Imperial is a rare and fabulous car, I’m glad for those who care for the classics we can all appreciate. Electronic ignition and TBI is a super good idea. Enjoy it.
Thanks for the information and insight, Paul.
When modern, fuel efficient cars are the subject, some crumbmugen always pipes up about how efficient some old car was, or how dangerous these tiny cars may be. The fact is that they are far cleaner and safer than anyones grandfather’s Buick, and just as comfortable to travel in. I don’t have one of these, but if I had a long stop and go commute I would. They make sense.
I live on the Texas border with Mexico. I don’t cross the border. Much these days, what with the armed revolution they have cooking, but I do get to see plenty of Mexican manufactured vehicles on this side. They remind me of 60’s era European cars like my Saab 96 in that they are tall, narrow, and short, yet they have plenty of room for four adults and have a useable trunk and some have a real, useful top carrier for extended trips. They also have small, skinny tires. The newer ones have front and passenger airbags.
Drivers tell me they can reach 60mpg, (converted from kilometers per liter) , even running the AC. Manufacturers include Nissan, Renault, VW, and even one labeled as a Pontiac. All of the ones I have checked out have 5 or 6 speed manual transmissions. Like in Europe, autos never have been popular in Mexico.
I doubt any of these could be federalized, but they do mKe uninteresting study of how efficient a motor vehicle can be if the consumer swilling.
Meaning no offense…but I suspect what you’re being told isn’t the gospel.
Once you get above 40mpg, gains are painful. There aren’t many Euro-cars that can beat it…only a handful of MOTORCYCLES can. Even 250cc scooters, with wind-cheating fairings and fuel injection, only get in the high fifties and lower sixties.
To believe an enclosed auto with air conditioning, can get upward of 60mpg…passes belief.
This is exactly what Toyota needed to with their hybrids. This technology seems to work better if not applied to a hulking 5,000 pound monster. I like the fact that the Prius C is traditional hatchback rather than the wedge shaped nerd mobile that is also on offer.
One question though. Why doesnt Toyota include a rolling resistance generator to recharge the batteries instead of using regenerative braking? Couldn’t a turbine
Ike generator be attached to the drivetrain to send power back to the battery?
They already do, they use the electric motor as a generator under braking to send power back to the battery, the traditional brakes are used to apply more braking force than what that system can supply.
In a hybrid a rolling resistance generator takes power to work. For that reason it is like robbing peter to pay paul. As mentioned in your other reply, that is how regenerative braking works.
It is tempting to think of shorcuts but, right now, there is no free lunch. The closest is probably wome sort of wind generator that would work well in a slight breeze. Solar panels do work but they are not yet efficient to the degree that is needed. Both also have some drawbacks. They would rob from aerodynamics and it would cost sales for it’s looks. There is a lot of background info on the subject that can be found in Mother Earth Magazine from the 70s. You can find them cited on the CC article from last month on Classroom EV.
One thing that is in the works that may turn into free energy is the solar paint. Right now it is in the baby steps of development.