An Alternative to Alternative Fuels and Vehicles 322
markmcb writes "While the world is working to solve energy and environmental issues with today's petroleum fuels, some vehicles simply don't have good alternatives, namely off-road platforms. For those not willing to give up their gas-guzzling habits, Matt Vea offers an innovative alternative. Using the OBDII interface in his Jeep, a laptop, and the infinite power of Excel, Matt conducts some performance tests and uses the results to tweak both his vehicle's engine and his personal driving habits for optimal fuel consumption both on and off road." Rigorous testing and good use of available technology; nice work.
Best way to conserve energy: (Score:4, Informative)
An alternative to alternative Fuels (Score:2, Informative)
And where does the electricity come from? (Score:3, Informative)
Peak Oil and Grasping at Straws (Score:0, Informative)
Ethanol - Not going to happen. Best case EROEI of just 34% compared to 3000% for light sweet crude???!! Ethanol is not going to happen
Hydrogen - Another non-starter. No way to store it for long periods. Negative EROEI.
Biodiesel - EROEI of 95%, still not nearly good enough to keep the interstate highway going.
Nuclear Fission - Too many enviroweenies, too specialized, too long to build a plant.
Wind - Fine for powering a small town, but no where near the power needed to run modern society.
Solar Photovoltaics - Another non starter. Not enough raw materials to make the necessary panels.
Solar Thermal - Useless above 30 degree+ lat
Nuclear Fusion - 50 years away
Re:Works for a limited audience (Score:3, Informative)
I've occasionally rented SUVs when going out to the desert for recreational purposes, but when I do, we're pretty well stuck in one spot. If you want to do something like follow the Mojave Trail, or general four-by fun, a rental just isn't going to cut it.
Excellent article... (Score:2, Informative)
A good model of auto fuel consumption (Score:3, Informative)
The fundamental assumption is that just about all gas-engined cars run the same thermodynamic cycle and about the same compression ratio these days, so the non-ideal Otto cycle runs about 38 percent efficiency. Ross then presents an empirical model of both the manifold vacuum pumping loss and the mechanical friction losses in an engine as a function of speed and load; he also assumes that the transmission is 90 percent efficient, and there is a fixed power loss from engine accessories. Throw in the rolling resistance of a car, the aerodynamic drag, and voila, you get the steady-state highway cruise no-wind fuel economy.
Crunching the numbers on my 97 Camry 2.2 litre, using gas with 115,000 BTU/gal, 80 deg F air temp, no wind, I should get 41.7 MPG at 55 MPH, 40.1 at 60 MPH, and 37.5 MPG at 65 MPH. By comparison, I did a road test both ways on a short section of freeway at 55 MPH and averaged 41.1 MPG on a fuel mileage meter connected to the OBD-II, and I get about 36 MPG on trips where I travel 65.
You would think that the dominant loss at highway speed is the air drag, and going from 55 to 65 you are increasing in speed by 20 percent so your gas mileage should take a 40 percent hit. Well it does not, in large measure because the friction in your engine along with part-load manifold vacuum "pumping loss" in large measure tend to dominate. One way to manufacture vehicles with better highway mileage would be to use smaller engines turning over at slower speeds, and the formulas show that if I put a 0.8 litre engine in the Camry, I would get 47 MPG at 65 MPH but I would not have any reserve to climb a hill without downshifting.
The EPA has their Test Car List Data web page which gives car weight, engine displacement and final drive ratio, and drag coefficient values from which one can try out this model and make predictions of the steady-speed mileage of various cars. They give a coast down time from 55 to 45 MPG in seconds and they also give a dyno drag model of the form F = A + B V + C V^2 where A, B, C are numbers in their table and V is speed in MPH.
The funny thing about their A B C numbers is that some cars have anomolously low C numbers (the V^2 air drag) but suspiciously high B numbers (viscous drag of the transmission in neutral in a coastdown test?) and similar cars (like the Ford Taurus with two different 3 litre engines) have widely different ABC numbers and even noticably different coastdowns. I suspect the whole EPA testing procedures would not hold up to rigorous error analysis -- I wonder if anyone has done any sensitivity/numerical conditioning analysis on their procedure determining the ABC numbers used to program the dyno -- but like legislation and sausage making, you probably don't want to know what is going on.
Re:It's approaching immorality at this point... (Score:5, Informative)
I always get a charge when it snows here, and the SUV drivers in the no-season tires think that all you need is the latest Ford behemoth. I drive a '92 Mazda Miata. Yes, a tiny little roadster, but with snow tires. Until the snow is higher than the undercarriage, a Miata with good snow tires can't be stopped. Driving past SUVs in the snow is a blast, but I do feel bad when I see them flipped over.
Re:Works for a limited audience (Score:3, Informative)
F-350 versus Camry in a crash, there's no question that you win. F-350 versus Camry in a high speed emergency maneuver, and there's a good chance you'll flip a few times. The Camry almost certainly will not flip. If you both run into a concrete wall at the same speed, the occupants of the Camry are likely to fare better. It has superior crumple zones to absorb the impact, while the average truck has a more rigid structure that passes more of the impact forces to the occupants.
Ideally, you want a very large vehicle that has excellent crumple zones but is also quite low to the ground with an equally low center of gravity. Then you have the advantage of mass but also a low rollover risk and better crumple zones. The Maybach 62 sedan is 20 feet long and 6300 pounds - just a few hundred pounds lighter than your truck. That's a spectacular choice. If only I had a spare $400,000.
Re:Works for a limited audience (Score:4, Informative)
Rental companies aren't interesting in helping out recreational types, they put too much wear on a vehicle to be worth it for them.
Re:Wagons... (Score:3, Informative)
My wife and I have a Jetta Wagon TDI (because you can't get a passat with a manual transmission) and *love* it. 40+ mpg and we burn biodiesel whenever we can. Luckily we live near Piedmont Biofuels [biofuels.coop]. We get an average of ~44 mpg but hit about 50-51 on road trips.
I'm also on the tall side, 6'2". Driving and riding in the driver's passenger is fine, but the back seats are a bit cramped for tall people. The wagon is best suited for two adults, 2-3 kids, and lots of cargo space; or two adults and lots and lots of cargo space.