Modern Hemi
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The current-production "HEMI" engine heads are flatter and more complex than the 1950s–'70s Hemi V8 chamber. The chambers are no longer truly hemispherical. It uses a coil-on-plug distributorless ignition system and two spark plugs per cylinder to shorten flame travel leading to more consistent combustion which helps reduce emissions. Like most of Chrysler's past-model Hemi-head engines, the 5.7 version is rated at approximately one horsepower per cubic inch (But the current engines are SAE net, whereas the old Hemi engines were rated SAE gross.). In 2009, updates to the 5.7 motor increased its output to approximately 375-390 hp, depending on application.
A new variable displacement technology called Multi-Displacement System (MDS) is used in some versions which can shut off two cylinders on each bank under light load to improve fuel economy. For the 2009 model year power has been bumped up to 357-390 horsepower (266-291 kW) and 389-410 lb·ft (527-556 N·m) depending on application. It also gets 4% better fuel economy. Variable valve timing (VVT) was also introduced.
Read more about this topic: Chrysler Hemi Engine
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