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GM tosses the turbocharged three cylinder engine out in favor of a naturally-aspirated four cylinder

Ever since the Chevrolet Volt was first announced in early 2007, it has garnered a lot of attention due to its radical design and unorthodox approach to vehicle propulsion. The Volt's main source of power comes from a lithium-ion battery pack which can provide enough juice to power the vehicle for 40 miles. When the battery pack's charge dips below 35%, a 1.0-liter, turbocharged three cylinder engine was commissioned to charge the batteries back to 100%. Alternatively, the Volt can be recharged using a household electrical outlet.

According to GM's Executive Director of Hybrid Powertrain Engineering, Larry Nitz, the Volt will be ditching the complex turbocharged three-cylinder engine in favor of a more conventional naturally-aspirated 1.4 liter four cylinder engine. For its given application in the Volt, Nitz says that the four cylinder engine provides better fuel economy which is key in a eco-friendly vehicle like the Volt.

Another advantage to going with the four cylinder engine is in refinement. While four cylinder engines aren't always known for smoothness or utmost refinement, they are much better in these respects than three cylinder engines. "The objective is to keep the engine off and when the engine comes on, you don't want to know it's on," said Nitz. "You want it really smooth and four cylinder is smoother than a three."

When it comes to packaging, the naturally-aspirated four cylinder engine doesn't have to accommodate the turbocharging or its requisite plumbing; thus it's lighter than original three cylinder engine envisioned for the Volt. The four cylinder engine, however, is still slightly longer than the three cylinder engine with its attachments, so changes to the vehicle packaging had to be made.

Nitz went on to say that the Volt's 16 kWh battery will provide the best range of performance for the vehicle when operating at a 35% to 85% charge. Once the four cylinder gasoline kicks in at below 35% charge, it will provide 50 kW to power the vehicle instead of the usual 100 kW provided by the lithium-ion battery pack.

Even when operating in this reduced capacity, the Volt will still be able to respond on command when a surge of power is needed. "Zero to sixty, passing maneuvers, you'll be fine, the ability to actually use more than about 50kW doesn't exist very frequently," explained Nitz.

The Chevrolet Volt has made the news quite frequently over the past month. Most recently, GM announced that it would work with utility companies to provide the infrastructure necessary to support electric charging facilities for electric vehicles like the Volt.

Earlier this month, it was reported that GM reduced the capacity of the fuel tank from 12 gallons to 7.2 gallons -- this cut the estimated driving range from 600 miles to 360 miles. Finally, GM Vice Chairman "Maximum" Bob Lutz in mid-June expressed his confidence that the Volt will arrive in showrooms in 2010.





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