Wednesday, May 13, 2009

Diesel vs. hybrid

Focusing on automotive technology, the green trend AOL Autos identified at the recent 2009 Detroit Auto Show seems to be pushing buyers into two camps: diesel or hybrid.

Today, the celebrities of the green movement are diesel- and hybrid-powered vehicles.
The defining characteristic of the diesel engine is its compression ignition cycle; this means that the engine uses ultra-high compression ratios in the combustion chamber to ignite the fuel-air charge (gasoline-burning internal combustion engines use spark plugs to fire up).

The defining characteristic of a hybrid is that these vehicles use a combination of electric motors and internal combustion engines (working in tandem) to propel the vehicle.

Clean diesel technology

With the advent of high-pressure direct fuel injection and special exhaust emissions systems, modern automotive diesel engines bare little resemblance to their stinky, smoke-belching forefathers.

And unlike the truly dreadful diesel engines perpetrated on trusting American drivers by Oldsmobile from 1978-85, today's diesels are reliable.

Ford Motor Company, General Motors, and Chrysler are adding clean diesel engines to their light trucks in 2010, but there are several cars and crossovers available this year that prove that diesel engines are viable for today's American driver.

Past award winners have been hybrids, but the Jetta's clean exhaust and exceptional real-world fuel economy (30 mpg city, 41 highway) won over the judges.

Powerful torque is a characteristic of diesel engines. Even though the Jetta's turbo diesel displaces only 2.0-liters (about 128 cubic inches), with 236 lb-ft of torque, the Jetta accelerates as if it's powered by a large gasoline V-6 engine.

Torque is the overriding trait that defines the diesel driving experience. The Q7, just like the smaller Jetta TDI, demonstrated another diesel hallmark: efficiency (mpg) at highway speeds.

The downside of diesel

Unfortunately, diesel engines are more costly to produce than most gasoline engines, so there is a higher up-front cost when you buy or lease. Worldwide demand for diesel fuel is also up, putting further upward pressure on pricing compared to gasoline (Europe ships diesel to the U.S. at bargain prices).

Taxes add to the price differential between gasoline and diesel, and Larson estimates the difference is another six cents to diesel's cost-per-gallon disadvantage. Unfortunately, diesel fuel's higher cost typically erases most cost saving from its better fuel economy.

Say hi to more hybrids

Recently, automakers have rolled out hybrids in great supply. Honda introduced their 2010 Insight hybrid. BMW also has new production hybrids, including a new mild-hybrid powertrain for their full-size 7-Series.

Obviously, hybrids are hot. Why? Because there are several different categories of hybrid powertrains, we'll generalize the group's benefit: hybrids use battery-powered electric motors to reduce the energy required from their vehicle's internal combustion engine. This saves fuel.

Most hybrids can operate on only electric power for short distances at city-driving speeds. For example, the 2010 Prius is rated at 50 mpg city, 48 mpg highway. Likewise, the 2009 Ford Escape Hybrid SUV racks up 34 mpg city, but only 31 mpg on the highway.

The lows of hybrids

Unlike diesel-powered vehicles, the highest-mileage hybrids tend to be a bit lackadaisical in regards to acceleration. Some also exhibit odd driving behaviors.
Hybrids also use electrically-driven power steering. Compared to otherwise comparable non-hybrid models, hybrids cost anywhere from $1750-$15,000 more.

What engine technology will drive us in 2014?

Diesel engines and hybrid powertrains will continue to offer high-mileage solutions for those willing to pay the required premium. Many manufacturers, such as Volkswagen, Audi, and Mercedes-Benz see potential for diesel-powered vehicles. Until the cost of diesel fuel drops to be closer to gasoline, company representatives told AOL that they are content to focus on hybrids and maximizing the efficiency of their traditional engines.

What about a normal engine?

This may come as a surprise, but traditional internal combustion engines represent a solid green choice based on their improving fuel economy and comparatively low cost.
According to Volkswagen's Group Powertrain Engineer Wolfgang Hatz, internal combustion engines will continue to improve. Hatz estimates that the fuel economy of gasoline engines will improve 15-perent in the coming years. Both Ford Motor Company and General Motors are already introducing gasoline engines with a new type of fuel injection that enhances fuel economy. Their engines utilize direct injection that helps boost mpg up to 20 percent.

Evidence points to a technology battle that's broader than diesel versus hybrid. Doing the math, this means that 80-percent of cars and light-duty trucks will remain powered by traditional gasoline engines in 2014.

At most, diesel and hybrid technologies help focus the driving public's attention on efficiency, and that's a good thing regardless of which engine technology is under the hood of your next vehicle.

Right now you can go out and buy a diesel-, hybrid- or traditional internal combustion-powered vehicle.


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