Thursday, November 10, 2005

Engine tricks attempt to pump up SUV gas mileage

KATU has a great article about diplacement on demand. Dodge is using Demand on Displacement in their hemi engines. There is a lot to like about the much-maligned Sport Utility Vehicle, or SUV. You sit up higher in traffic, the crash protection is better than a small car and it can haul a ton of people and gear- literally. And when you push down the gas pedal, the power just flows. But there is one thing most SUV owners hate: the terrible fuel economy. With high gas prices apparently here to stay, the pain at the pump is real and immediate for SUV and most large truck owners. Most of the big rigs get less, sometimes much less, than 20 miles per gallon, and usually premium fuel is required.

Confronted with slumping SUV sales and a rising outcry about poor fuel mileage, carmakers are turning to a readily available technology called 'displacement on demand' to preserve the power of an SUV while significantly increasing the fuel mileage. 'Displacement on demand' is not very new, Cadillac was using it in the 1990s to improve the mileage in their big cars.

But the concept is catching on again at other carmakers, since it is relatively easy to design into current engine designs, and does not increase the cost of a vehicle like a hybrid design.
The concept is fairly simple: when cruising down the highway, the engine management computers restrict gas delivery and spark to some of the engine cylinders, saving fuel when only a small fraction of full power is needed to keep the car moving at highway speeds.
Step on the gas to pass or accelerate, and all the cylinders come back into play, supplying the full power of the engine. The changes are transparent to the driver.

Displacement on demand does not boost the gas mileage of an SUV up to that of the miserly hybrids, but it can lift a gas guzzler into the 20-plus m.p.g. level, or even higher.

So for those that must have the power, carrying capacity and other benefits of an SUV but are tired of the wallet-emptying gas bills, help is one way.

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