100 MPG Cars

I think those super carburators have been pretty well debunked. But the Prius hyper-milers are well-documented, though they use an extreme driving style. (And I had not previously heard of a 2001 doing it.) Make a car small enough, and light enough, and you can get remarkable mileage. You have less car, but many people drive more car than they need. On the other hand, do you want to drive a tiny, super-light car on the same road with monstrous SUVs, often driven by people with a cell phone in one hand and a hamburger in the other?

I had occasion to drive a Pontiac Grand Prix (rental car) and I think it burned about twice as much gas as my Prius, but I think it weighed twice as much also. It certainly was easier to handle at the freeway speed limit in windy weather.

Diesels are inherently more efficient than gas engines, but they have high particulate emissions. I suspect that some kinds of external-combustion engines may be more efficient than diesels, and cleaner than gas ICEs, and may be practical with hybrid technology. But you still have the physics that accelerating X amount of mass requires Y amount of energy.

Best of all, of course, are electric vehicles using renewable sources of energy. And with world demand for energy growing exponentially, fossil fuels are going to become so expensive that fuel-burning cars will become moot, super carburator or no. And I'm not talking science fiction, as Darell can attest! He's doing it now!!!

 

Straight gas cars (and light trucks) use about 20% of the energy potentially available in the fuel, and get an average (US) of about 20 MPG. If this miracle device could extract 100% of the energy, you'd get 120 mpg - for the average US vehicle. (Clearly, more than that for a Prius, which is both ligher and more aerodynamic than the typical US vehicle.) A 200 mpg carburetor, for the average US vehicle, would break the laws of physics. A 100% efficient conversion is impossible, and nothign more than a tiny improvement is even remotely plausible, given that the rest of the combustion process would be unchanged (you'd still be blowing the same hot gasses out the tailpipe, still incur the frictional and pumping losses of the engine, etc.) A 200 mpg carburetor is fiction. It's quaint fiction - last car I owned that actually had a carburetor was ... hmm ... must have been an early 1980s AMC. I don't think they've manufactured a car with a carburetor for a couple of decades or so. Fuel injection killed the caburetor because it's superior. I think anyone who has ever disassembled a carburetor to blow the varnish out of the jets would agree. Beautiful pieces of engineering and machining, but total Rube Goldberg devices. But you can't run a hoax off a 70-year-old plans for a fuel injection system, I guess, so it has to be a carburetor.

On diesel, much of the presumed better mileage of diesels is a mirage. You can't compare a gallon of gasoline to a gallon of diesel fuel any more than you could compare a gallon of gasoline to a gallon of (say) compressed natural gas. To make the comparison right, you have to account for the differences in the fuels.

Some sites suggest a rule-of-thumb that diesel mpg should be multiplied by 0.80 to make it equivalent with gasoline mpg. That's from the perspective of units of crude oil require per mile of transportation, as it takes about 25% more crude to make a gallon of diesel than of gas. For example, you can see that here:

http://www.ucsusa.org/clean_vehicles/fuel_...el-dilemma.html
http://www.grinningplanet.com/2005/04-12/d...ine-article.htm

If those diesels "edge close to" 80 MPG, then call it 75 MPG (assuming that's US gallons). Using the rule of thumb above, those cars use as much crude oil as a 60 mpg gasoline car. That's modestly better than the Prius, for a much smaller vehicle.

Systematic analyses of the issue show that diesel vehicles are only slightly more efficient that straight-gas cars in terms of overall "wheel-to-well" efficiency, and are substantially less efficient than gas hybrids. For example, here's a study by US Department of Transportation:
http://www.transportation.anl.gov/pdfs/HV/300.pdf

And another study done in a European context:
http://ies.jrc.cec.eu.int/media/scripts/ge...port_030506.pdf

In terms of what you can buy, commercially manufactured, right now, for a given car, nothing beats a gas hybrid in terms of overall efficiency. An EV or PHEV would, but those aren't commercially available products. The CalCars PHEV Prius conversion gets the equivalent of a 75 MPG gas car (in terms of total C02 emissions). An EV would presumably do modestly better. A diesel hybrid would also be slightly better then a gas hybid (though not as good as PHEV). But straight diesel is not as efficient as hybrid gas, for a given car. It will only look that way, sometimes, if the comparision is between dissimilar vehicles and/or the comparison fails to account for the differences in the fuels.

 

My answer is we are on the edge of 100mpg vehicles. I could do it in my 5-speed Insight on a summer day on an extended 40mph cruise - Prius hypermilers could do the same in similar conditions. A expermental VW 2-seater diesel got 250mpg, but it takes at least 20 seconds to reach 60mph and is essentially a motorized recumbant motorized bike.

No stock cars exist that can get 100mpg cruising at 60-65mph now, though it could happen in a decade. Remember how excited people were when a car could get 50mpg in the 1980's?

The Prius III may not get 75mpg by the new EPA estimates, but I'd guess it could easily do it at 60-65mph with mild hypermiling.

I love this Popular Science article that states a 100mpg sedan is possible now - if you are willing to pay 60-70K for composite materials, a turbo-diesel-hybrid and maybe live 0-60mph in 15 seconds. ( see http://www.popularmechanics.com/automotive...to/3374271.html long but nice article )

The other possibility of 100mpg vehicles is aftermarket plug-ins, there are still speed limitations and putting down at least 8K for the upgrade (corrections if necessary). Hope that will change.

 

<div class='quotetop'>QUOTE(Delta Flyer @ Feb 21 2007, 06:38 AM) [snapback]393884[/snapback]</div>

The much-promised but so-far undelivered EDrive Systems Prius PHEV conversion would get some (half?) its motive energy from electricity even at highway speeds. The speed limitations of Prius EV mean that the ICE runs, but the conversion simultaneously injects electric power while there is charge available in the battery. So within its distance range, it would benefit greatly from electricity even at higher speeds.

Last time I checked, their web site was still promising expansion of installers nation-wide in 2006. As far as I know, even the promised L.A. start-up installation facility has not opened. I think the price was supposed to be $15,000. A year ago I'd have given serious thought to it. Now I want an EV, and keep the stock '04 Prius for road trips.

Vaporware, I guess.