The Obama administration has cut its 2025 fuel economy target for automakers from 56.2 miles per gallon to 54.5 mpg. Shaving 1.7 mpg from the goal is apparently garnering early positive response from Ford, GM, Chrysler, Honda, and Hyundai.
Nevertheless, tough technical impediments remain towards meeting such a high Corporate Average Fuel Economy (CAFE) bar.
This post isn't going to focus on the proposal. Rather, I'm posing the salient engineering question: How do we get there? We're pretty much already capable of building 40 mpg vehicles, by paring weight through use of lighter materials and using advanced hybrid power plants. I'm not going to get into the issue of the poorer crashworthiness attendant to lighter bodies. Nor do I want to debate the still-moving target of how one defines "fuel" economy for plug-in electrics. Both are important issues, but subjects for separate posts.
My point is, while 40 mpg is mostly achievable, the 50-plus mpg benchmark is, to force an analogy, a gas station too far. Still, if we attack the challenge on multiple fronts, we can get close. Listed below are the areas we'll have to attack.
The Honda CR-Z, rated 37 mpg highway, is the EPA’s highest-mileage gas-engine car.
Materials: This is probably the single most important component in making 54.5 mpg CAFE. Of course, while fiber-reinforced components could significant cut the weight of cars, they'd also send costs soaring to prohibitive levels. I'm oversimplifying, but beyond advanced plastics, many lighter materials pose the same problem. It's possible that some useful advances will come out of the Department of Energy's Vehicle Technologies Program.
Form Factor: Smart car or highway cruiser? On the design side, the question of which provides greater economy answers itself. In terms of what consumers will buy, not so much. This dichotomy is the root cause of automakers' history of fiddling around with their fleets -- e.g., some high-mileage Fiestas alongside numerous F150s -- to conform to CAFE standards.
Powertrains: What's the balance between the size of the gas engine and the electric motor? Are train-like cars (the engine drives a generator, à la the Chevy Volt) really viable, or just a way to allow manufacturers to send paperwork to the government that they're building 93 mpg(e) equivalents?
Tires: Low rolling resistance like we've never seen before, and nitrogen-fill mandatory. What else do we need to do here?
Fuel: Wikipedia has an interesting table showing gasoline gallon equivalents (GGEs). Diesel and biodiesel are roughly equivalent to gas in terms of BTU/gallon. Liquid and compressed natural gas possess far less stored energy per unit. I'd be interested to compare the BTU/unit weights of CNG versus gas. All this relates to the weight issue, which in turn effects achievable mileage.
IVHS: We're been talking about Intelligent Vehicle Highway Systems for over 20 years now. (More correctly, we talked about it, then stopped.) Granted, two decades ago, IVHS was blue-sky and implementation was impossible. We're much further along the path to achievability now. Truth be told, the main impediments will soon be political and financial, not technological. It's my personal belief that IVHS is the surest route to better driver and passenger safety as well as "higher mileage." I put that in quotes because by the time IVHS is full baked, fleets are likely to be electric, which offloads the issue of input-energy production to power plants. One would hope they'd be nuclear, but they'll more likely be coal-fired.
So what do you think are the keys to higher CAFE? Please discuss below.
One thing you kind of neglect to mention is the fact that our on ramps in many places around western PA are less than 500ft, so 0-x speed before getting rammed by traffic or causing a major pile up can be a lot of fun.
Your roads out there have honestly had a lot more forethought to their design than most of what's located here, and that even goes for our new rebuilt goat paths.You guys weren't afraid to move some dirt, which is good, here it's either into a river or stream or into the side of a hill. True, ours may not be miles long, but there are so many undulations that setting cruise is bad joke at best. You're never on one long enough to get to a steady state before you're back to closed throttle and on the brakes.
One thing about arguing with liberals I always forget, they are never wrong. Sooner or later, I'll learn to just let you go on in your utopia world, and I'll go about my business happily elsewhere. Sorry for the inconvenience.
Half of Arizona is above 5,000 ft elevation.. Flagstaff is at ~8,000ft. Prescott ~5300ft. Arizona's highest mountain.. over 12,000 ft.
Some of the biggest (steepest/longest) road inclines in the entire US are in Arizona.
Western PA highest point- Mount Davis less than 3500ft.. nice hill, not real mountain.
If you have been to AZ.. it was apparently only in the southern part of the state (Phoenix less than 1500 ft, Tuscon at less than 2500 ft)
Hope you spend a bit more time researching your other "observations"...
I have friends with cars that get 40mpg @ 80mph while going up 5 percent inclines. It is done on regular basis... yea , the same "hills" that slow SEMIs to 25mph.
I'm sure that 2 liter VW engine in the car did great for merging on highways, moving more than 4 adults, assuming they fit in the car, and climbing hills. I suppose if you live in Arizona where there are no hills, but in western PA, and other locations, that car would be passed by an overweight amateur cyclist on nearly every hill.
There's a reason those cars were rejected by consumers: they SUCK.
They still do, but when you have an energy policy who's stated goal is to have gas at 8-9 bucks a gallon to force people into this crap, the peon masses (read everyone but the liberal elites) have no choice but to buy the SUCKY car...
Wow... kinda reminds me of communist Russia. Bottoms up, comrade!
Gasoline does not have the same BTU value as gasoline... not even close. If that were the case, you could use it in a diesel assuming you could get the detonation issue under control. Diesels will run on almost anything that burn... even molasses... ask Alis Chalmers (or was it Case back in the early 20's-30's)... they had an ad campaign that capitalized on that. Except for the one farmer that literally ran molasses in it, their reps changed filters nearly weekly, but it did in fact work and did the job.
We do NOT need another tax on the consumer for anything. One has to ask the question again, what is the point of these ridiculous numbers for MPG? Is it to save the environment, consume less oil, or control the masses? I would wager my life on choice #3.
I can't wait to see the tractor trailer that gets 56MPG, and can haul more than just the operator. Why aren't those big truck manufactures being harassed about their numbers too? All the new emissions standards have cut the MPGs of those trucks in half or worse, and reliability is a thing of the past.
So I ask you again, what exactly IS the purpose of this anyway?
Back in the 60's, Austin did a promotional tour of the USA, with the original Mini, and averaged 50 MPG. You know the one, 10 foot long box with no thought to areodynamics, 850cc, bathtub shaped combustion chamber, drooling SU carb. Lucas, the prince of darkness made the ignition, charging system, and the fuel pump, I don't know which was less reliable, all three required frequent attention. Voted second most important car of all time, after the Ford Model T.
Talk about your conspiracy theories, try Googling " 1973 opel 376.59 mpg". I am wondering how come I never heard of that back in the day?
I have gotten 64.6 MPG from my '81 VW Rabbit Diesel, and hope to get it to 75 MPG. VW has substantially improved the engine by going to TDI, and the Aerodynamics Design, and used the improvements to allow a much larger car, like the beloved VW Jetta Diesel Sportwagon to be far more comfortable, safer, and get 50 MPG, even though it is much bigger and heavier. VW's two seat tandem prototype from a couple of years age was doing 240 MPG.
I am not worried about the auto makers hitting the CAFE targets, but I agree with the previous suggestion, that it should be a fuel tax, and the free market, that gets us there.
I have been interested in obtaining the best milage possible from every car I have owned. Most of the burden for optimizing milage has been placed on the automakers. This is just not right. I am all for the automakers using every drop of fuel efficiently but there are other 800 pound gorillas in the room.
Drivers. I always get a kick out of the guys that blow past me in town only to catch up with them at the next light and perhaps even pass them because I didn't have to stop, just slow down for the light to change. It's the same on the open highway. I frequently observe others who fly past me several times on a trip.
One of my biggest bugaboos with drivers is the lack of attention at lights. While many people seem reticent to stop at red lights these days, it is even worse when people wait an inordinate amount of time at a green light to even begin moving. This increases the number of cars idling at a light.
Drivers also can control the amount of fuel they use by simply planning trips to minimize the use of fuel. They can also plan the use of vehicles so the compact car and not the pickup/SUV is used for commuting.
Highways: You can talk about intelligent highways, but in truth much could be done with current technology by requiring cities to time lights and create variable speed limits so cars don't have to stop down. Round abouts also prevent idling and unnecessary stop/start cycles. Cities should have to show some kind of optimization of fuel milage in their road planning including drastic plans to prevent freeway traffic speed from dropping below 30mph.
One technology you didn't mention for vehicles is maintaining constant drive train temperatures. Automatic transmissions do this now. Extend this to final drives and perhaps even wheel bearings and less viscous lubricants can be used meaning big improvements in milage for the 2 mile trip to the grocery store in colder climates.
VW Rabbit Diesel 1985 48mpg (It was never as good as my brother's car; 55mpg)
Honda Insight 2005 60/65mpg 63.4mpg over 34,000 miles when I got rid of it.This car was so highly optimized that a passenger, rain or open windows would drop the milage 2-3mpg. Low temperatures <60F killed the milage (45mpg) due to loss of auto engine shutdown and thicker oil in bearings and gearbox. Because of the low rolling resistance tires it was lousy on gravel roads or any slippery surface. Ground clearance was extremely low so it was unusable in winter. But it was quite roomy for my 6ft frame. The perfect commuter car.
Beetle 1958 28mpg/35mpg
Mercedes Turbo Diesel Wagon 1985 26/30mpg
Subaru Forester 2010 24/30mpg 26mpg over 34,000 miles in a northern climate. This is a full time 4wd car with the Cd of a brick. The CVT version does even better.
When European cars get imported here, we always get the biggest engine. Is always the V6 or turbo 4. We never get the 1 or 1.4 liter. That is an easy low hanging fruit. So you don't win at the drag race, but is fine 99% of the time sitting in traffic.
The basic engineering of ICE's has improved tremendiously, right up to the point of ignition. The reason that some high-mileage vehicle models haven't seemed to vastly improve in the last twenty years is due to the triple effect of the following....
stringent emission requirements (a good thing for overall air quality), probably the biggest factor in offsetting mpg potential.
crashworthiness requirements (another good thing that requires more materials and thus more weight to achieve),
consumer demand for more of everything....electric everything from seats, media, lighting, which means more parasitic drag and more electronic weight due to motors and copper.
There is no way I would trade my 2011 Jetta Sportwagen Diesel that gets 45 mpg and a wonderful driving experience for a car like the old VW Rabbit diesel just to get and additional 5-8 mpg, and neither would the vast majority of buyers.
as to the fuel comment in the article. diesel has the same btu's as gasoline, BUT the conversion to power/work is more efficient for diesel. europe has taken a different approach to the overall efficiency issue and gets a lot larger/faster car for a similar fuel economy car here. yes, small diesel/diesel hybrid production cars already acheive the 50+ mpg targets.
the calculation that is needed is btu unit cost for each fuel vs the distance per unit mass. i.e CSX advertises 1 gal of diesel will move one ton of freight 100 miles.
note: i really wish the govt would stay away from dictating MPG in favor of adding a tax to the fuel or adding a tax to the engine sizes. this seems to work well in other countries by helping to finance public transportation options AND allowing the auto market to work with supply and demand priciples.
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