Small Diesels Compete With Hybrid Fuel Champs
The combined influences of high fuel prices and tighter emission standards are forcing automobile manufacturers to new technological heights, with several of them vying for builder of the most fuel efficient car or truck sold in America. The new Audi A4 Dle sedan tops the Toyota Prius in Europe with a combined city/highway driving economy of 51 MPG but it may not be available stateside for some time.
The Audi uses stop/start technology, which is now ubiquitous among fuel sippers and even larger hybrid guzzlers. The engine management computer shuts off the engine at stops and immediately restarts it (if the battery is in the ‘charge’ mode) when the gas is pushed. I have only driven the Prius and Honda Civics with this feature but it is almost spooky to be sitting at a light in complete silence, only to have the engine fire up on its’ own as you pull away. The A4 also uses regenerative braking to charge the cars battery. This feature has been exclusive to hybrids in the past, but apparently the engineers thought that the small fuel economy gain derived from using the car’s weight as you brake to charge the battery was worth the additional cost.
Here in the States a close cousin of the Audi, the new Volkswagen Jetta TDI direct injection turbo diesel, is EPA rated at 29MPG city and 40 MPG highway. Unlike most cars, which usually get worse fuel economy than the ratings in real world driving, owner reports suggest that real world economy will be more like 44MPG average with up to 54 MPG on the highway. The Prius still beats up the Volkswagen around town, but on the highway they are neck and neck. We have one Prius customer at Morin Brothers that regularly commutes to San Diego and back; he reports that his typical trip average is up to 55MPG. Pretty phenomenal considering he is driving on the freeways in Los Angeles!
Fuel economy is only one of the considerations when looking at buying a car. Another, of course, is style. Do you like the way the car looks and drives? Yet, another consideration is the difference in cost between regular unleaded gasoline and diesel. The diesel is always more expensive and often not as available. And then there is power. The Jetta not only accelerates like a car with a small V8, but it handles like a sports car, neither of which can be said of the Prius.
Other manufacturers are hard at work trying to increase fuel economy and decrease carbon dioxide emissions. Volvo has a diesel/electric hybrid in the works that can be charged overnight from conventional household current, allowing the car to travel up to 31 miles on its lithium-ion battery pack alone. This technology in a midsize car will allow Volvo to leapfrog over its competitors in a single bound, with dramatic improvements in fuel economy and reductions in carbon emissions. Fiat/Chrysler (well, actually, Fiat) is working on a “Multi Air Valve Control” gasoline engine that can open and close intake and exhaust valves with precise control. Current valve control technology can advance and retard cam timing; even, in the case of Honda’s Vtech, increase valve lift, but none can vary the valve timing and lift to suit the conflicting demands of economy, power, and low emissions simultaneously. Fiat claims that this technology, since it is confined to the cylinder head and computer software, is readily adaptable to a variety of engine and drive train configurations, so it may appear on some of the smaller Chryslers in the not-too-distant future.
For more information:
Prius vs. VW Jetta: http://www.popularmechanics.com/automotive/new_cars/4284188.html
Fuel economy comparisons: www.fueleconomy.gov/
Google “Volvo diesel/electric” or “Fiat multi air valve control” for more info.