Chrysler's Hemi

The importance of Chrysler's new 5.7L Hemi V-8 can't be overstated. But DaimlerChrysler is unwilling to officially announce any application beyond the '03 Ram Heavy Duty. Dodge hopes to sell about 140,000 HD Rams in the first year, 75 percent of which will be powered by 5.9L Cummins turbodiesels. That leaves a bit fewer than 35,000 Hemi HDs, with the rest powered by the 8.0L V-10. Chrysler has capacity for 440,000 Hemi V-8s per year, says DaimlerChrysler Executive Vice President for Product Planning and General Manager of Car Operations Richard Schaum. That would more than cover total sales for the 1500 series Ram. The possibilities seem endless.

The Hemi always has been "strictly a truck engine," Schaum adds, declining to explain whether a 6.0L-plus version might be considered a separate engine. Cylinder cutoff for the truck Hemi is in the works, but Schaum can't say how soon.

The Heavy Duty Ram's Hemi is a modern take on traditional (read old) technology. A "hemi head" is a hemispherical combustion chamber, or one shaped like half a sphere, for greater airflow. It creates high volumetric efficiency by allowing larger, less-shrouded valves and straighter intake and exhaust ports. A Hemi's small surface-to-volume ratio minimizes heat loss and charge cooling that can lead to high hydrocarbon emissions, and the layout's centrally located spark plug also enhances fuel-mixture combustion.

Built with an iron block, aluminum head, and a cast crankshaft, the new Hemi pushrod V-8 has the kind of low-end grunt most expect from load-hauling/trailer-towing pickups. But Schaum allows that a retuned Hemi is capable of more than 400 hp, which seems perfect for a performance car. Still, Chrysler plans no aluminum version--at least that they'll admit to.

"Its primary use is as a truck engine," Schaum explains. "If I were to spend the money on an aluminum block, I'd get slight weight savings." And it best fits the Ram's need for a strong, durable engine. "The aluminum head helps the octane refinement and allows us to retain specific output.

"You'll find that each of our engines--the 4.7 replaces the 4.9, and the 5.7 replaces the 5.9--exceeds the output of the engine it replaces, but reduces throttle losses and improves fuel efficiency." Chrysler believes the Hemi engine is good for about 1 mpg better fuel economy on both city and highway EPA loops, versus the 5.9L V-8. The '03 Ram 1500 4x2 with the old 5.9 V-8 gets 12/18 mpg and the 4x4 gets 11/16, according to the EPA.

With an iron block and pushrods, the Hemi seems the antithesis of what DaimlerChrysler's "better half" is all about. Multivalves and variable timing, needless to say, are out. Still, the Hemi proved an elegant solution. "The heritage was very inspiring as we were planning this engine," Schaum continues. "I wanted to have the highest output and the best fuel economy at the lowest cost."