Hybrids get all the attention these days, says a story in the Chicago Tribune, but automakers have other engine technology that consumers should consider.
Toyota engineer Dave Hermance said variable valve timing and direct injection improve mileage and manage emissions better. GM's Dave Lancaster pointed to cylinder deactivation in Vortec V8 engines and direct injection (shown in photo) in the Ecotec 4-cylinder engines. DaimlerChrysler's Mark Chernoby added the benefits of diesel.
The engineers also touted other fuel-saving measures that need to be applied to vehicles, such as improved transmissions, weight reduction and better aerodynamics. But Chernoby said the long-term goal is to move away from oil-based engines toward hydrogen.
"That's when you'll see significant jumps in fuel efficiency," he said.
My only point of contention was with an episode that Lancaster recalled. The story said he found the fuel economy display on a new Suburban showing 23mpg while going 70 to 75mph in the V4 mode. I recently drove a new Avalanche, which is based on the Suburban, and found it difficult to keep the engine in V4 in any condition other than downhill or coasting. I've heard many complaints voiced that the cylinder deactivation, formerly called Displacement on Demand and now trademarked as Active Fuel Management, is too timid and won't stay on long enough to achieve significant savings. If memory serves, the V4 mode didn't even come on during idle. When I see 23mpg on the display for an extended length of time while not going downhill or coasting in a Suburban, I'll be impressed.
[Source: Chicago Tribune]
Reader Comments (Page 1 of 1)
Jim 1:33PM (9/25/2006)
Honda calls it VCM, or Variable Cylinder Management. They use it on both the Odyssey, for a small incremental improvement, and the Accord Hybrid, for more significant savings. Both are V6 engines. The Accord is able to stay in VCM mode longer because it uses the electric motor to subsidize 3 cylinder mode.
Reply
MikeW 11:42AM (9/26/2006)
No one idles of half their cylinders.
Maybe GM is referencing fuel economy numbers from a rear drive suburban, with really tall gearing.
MotorTrend's long term honda odyssey touring reporting getting 25mpg@75mph with the ac running.
Reply