2008-01-24

[ Chrysler LLC blog ]

Next-Gen 5.7-L HEMI: Improving on a Legend
Joe Guertin

Joe Guertin is Director of 90-Degree V Engine Design

The 5.7-liter HEMI engine has been very successful. The HEMI has held a position on the coveted Ward's 10 Best Engines list for five years running and has enjoyed success in the marketplace, as well. In fact, for Chrysler, HEMI is not merely an engine; it's a brand. But we never want to rest on our laurels, so we set out to upgrade the HEMI engine's fuel economy, refinement and performance -- and boy did we ever.

So what makes the 5.7-liter HEMI special? The engine features Chrysler's Multi-displacement System (MDS), which shuts down four of the eight cylinders when not needed to save on fuel. MDS is part of the reason the 5.7-liter HEMI is our most efficient V-8, but with rising fuel prices, we needed to get better, and we did. The new 5.7-liter HEMI, available in the all-new 2009 Dodge Ram, has four percent improved fuel economy compared with the previous engine.

While we were improving fuel economy, we also wanted to improve overall refinement (such as idle quality, noise and vibration). Many of our customers love the sound of the HEMI, so we were careful to maintain the nice smooth rumble note.

So how did we save fuel and boost performance at the same time? By increasing the compression ratio and adding variable valve timing, we gave ourselves the flexibility to finely tune when the valves open and close. An active intake manifold design was also added for the Ram truck application to optimize low end torque without compromising peak power. Improved cylinder head port flow was accomplished through major cylinder head design changes which included increased valve size and lift. The result is even more torque at lower engine speed (rpm), which gets you off the mark quicker, improves drivability and is important for towing.

What does it all mean? Customers get a more refined HEMI engine with better fuel economy and improved performance. Horsepower is increased from 345 hp to 380 hp, and torque is improved from 375 lb.-ft. to 404 lb.-ft., a substantial increase.

The new 5.7-liter HEMI engine really raises the bar on performance, refinement and fuel economy. But reading about it isn't nearly as fun as experiencing the engine for yourself; get out and drive it.