It looks like the Hemi engine, an icon for the Chrysler Corporation, won't be included in forthcoming applications due to changing fuel economy standards. Rising gas prices have already hurt sales of vehicles featuring these engines, causing Chrysler to cut back production. Now co-president Jim Press has declared, "The Hemi is not the powertrain of the future." Similar to the direction taken by GM, Chrysler is banking on newly developed V6 powerplants to take the reigns from current V8 options. These Phoenix engines are scheduled to hit production in 2009.
The Hemi engine's downfall is its inability to adapt to features proven to increase efficiency. The large combustion chamber design and dual valve structure leads to blow-by of unburned fuel, thus producing large levels of undesired emissions. The use of dual spark plugs has improved burn in the hemispherical combustion chamber, however, it's a solution that increased cost and complexity. More modern and efficient chamber structures, unlike the Hemi, can fit four valves and utilize dual overhead camshafts. Chrysler plans to implement these features into their future V6 engines, along with cylinder deactivation and variable valve timing.
[Source: Automotive News - Sub. Req.]