DETROIT -- The Chrysler group will add the more economical version of its Hemi V-8 engine to more vehicles in the 2006 model year, says Chrysler COO Tom LaSorda.
The Hemi engine's cylinder deactivation system, which Chrysler calls a multidisplacement system, or MDS, will be added to the Dodge Durango and Ram and the Jeep Commander.
The engine alternates between four and eight cylinders. Four of the cylinders shut down when less power is needed.
The average gain in fuel economy is 10 percent, the company says.
In some driving conditions the increase is as high as 20 percent, Chrysler says.
Chrysler now offers a 5.7-liter Hemi V-8 in seven models. The Hemi MDS is available in four vehicles: the Jeep Grand Cherokee, Dodge Magnum and Charger, and the Chrysler 300.
In the 2006 model year, all seven models equipped with the 5.7-liter Hemi will use the cylinder deactivation system.
"We think this is going to be big for the marketplace," LaSorda says. "You do not know when it goes from eight cylinders to four cylinders."
The additional MDS applications were in the company's product plan and were not triggered by rising gasoline prices, LaSorda says.
Changes in the engine mounts, exhaust system and engine calibration were required to meet the towing and cargo capacities of the Durango, Ram and Commander, says Cole Quinnell, Chrysler group spokesman.
"The tricky part was deciding when to let it go into four-cylinder mode so you don't feel it when you have extra weight in the vehicle or are towing," Quinnell says.
"The customer should never feel it go from one mode to the other," he says.
The fuel-economy gains in the three trucks will be announced in June after EPA certification, he says.
The system deactivates the valve lifters. This keeps the valves in four cylinders closed, and there is no combustion. Also, energy is not lost when air is pumped through the cylinders, Chrysler says.
The system makes its transition in 40 milliseconds, the company says.
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