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Why US Gas Mileage Advances Don't Help Consumers a

greenrainbow (1724788) writes | more than 2 years ago

Idle 2

greenrainbow writes "The average, fuel efficiency for US vehicles actually increased by 60 percent between 1980 and 2006 but at the same time cars in the US got bigger (by 26% on average) and their horsepower increased (by 107 hp on average), which, when factored in, means that the average fuel efficiency of American cars only increased by a mere 15%. Almost all of the new technology went into making cars more efficient per pound of weight so that the cars could get bigger and still fit within average mile per gallon expectations."
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What about hybrids? (1)

Lucas123 (935744) | more than 2 years ago | (#38612168)

The Toyota Camry LE (gas-only) costs $25,900 with a fuel efficiency of 8.0 l/100km (35 mpg) and average annual fuel cost of $1,600. The Toyota Camry Hybrid costs $32,000 with a fuel efficiency of 5.7 l/100km (50 mpg) and annual fuel cost of $1,140. According to the above numbers, it would take 10 years of driving (200,000 km) to recoup the initial price difference between a Camry Hybrid and Camry LE. On the other hand, a Toyota Prius costs $29,500 with a fuel efficiency of 4.1 /100km (57 mpg) and annual fuel cost of $820. (The fuel costs are based on 20,000 km (12,427.42 miles) per year at $1 per litre/ $2.18 per gallon.). So it would only take two years (40,000km) to recoup the price difference between a Toyota Prius and a Camry LE (excluding increased interest charges). If gas prices continue to rise, the payback time decreases. Likewise, the higher gas prices climb, the higher the resale value of a hybrid is already considerably more than that of a gas-only vehicle. The upshot? If you're in the market for a new car anyway, a hybrid might well make economic sense.

The issue is heavier bigger cars, not bigger engin (1)

macpacheco (1764378) | more than 2 years ago | (#38613312)

A bigger engine doesn't use more power necessarily. As long as new engines are running LEAN OF PEAK mixtures, they can use the same fuel flow for more power output.
But a full time lean of peak engine limits power output, however it results in an extremely clean combustion output, with no carbon, no carbon monoxide and even some oxygen going through unburned.
I know this from studying aircraft gas engines, which are similar to car engines, and in many respects, less advanced, but same principle.
As long as you limit yourself to using 50-60% power, current electronic injection/ignition systems should result in that anyways.
We have lots of 1000cc engine cars in Brazil, and they end up using the same fuel than a 2000cc (2 liter) engine if you step on it, even moderating acceleration doesn't save that much fuel.
Even a monster 3 liter engine can be fuel efficient, all it takes is the driver moderating acceleration and the fuel control systems of the engine making maximum use of LEAN OF PEAK mixtures (that means cooling the combustion with excess air instead of cooling the combustion with excess fuel).
Its also very important that all cylinders get a uniform supply of AIR and FUEL. Imbalances between cylinders limit power output, increase fuel consumption and makes the job of the fuel control system a lot harder.

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