Is That a HEMI?
“HEMI”. It’s a well-known term. Some consumers may know about the HEMI engine because of the old commercials where two guys would pull up in a truck and then look to the side to see well-known actor Tom Virtue in a vehicle powered by a HEMI engine. Every vehicle had ended the same way – with the two guys in the other car getting smoked by Virtue’s car with a HEMI engine. The other chunk of the consumer base knows about HEMI engines because of muscle car automaker Dodge, and the vehicles that made HEMI engines famous.
“HEMI” is short for hemispherical combustion chamber and is used as an acronym for referring to a line of Chrysler engines. It all started with the FirePower engines of the 1950s but became much more popular in the early 2000s with the 392-cubic-inch HEMI engine developed by Chrysler in 2005. Able to generate a conservative output of 525-horsepower and 510 lb-ft of torque. With a little tweaking, the engine was eventually placed in small vehicles, namely the SRT8 Dodge Charger, Chrysler 300C, and Jeep Grand Cherokee. For such small vehicles, the horsepower was brought down to 470-hp. Today, the HEMI is well-known as two incarnations: (1) the 329-cubic-inch 6.4-liter V8 SRT HEMI engine that produces 485 horsepower and 475 lb-ft of torque, found in the Dodge Challenger SRT 392, and (2) the Supercharged 6.2-liter HEMI SRT Hellcat V8 engine, able to generate 707-horsepower and 650 lb-ft of torque and found in the 2018 Dodge Challenger SRT Hellcat. The 2019 and 2020 model year vehicles have some upgrades bringing it to 717 horsepower for the Dodge Challenger SRT Hellcat and 797 horsepower for the Dodge Challenger SRT Hellcat Redeye.
The Chrysler HEMI engine has changed a lot since its very incarnation, but it wasn’t just a Chrysler engine, clearly used by Dodge, although the manufacturer sits comfortably under the Fiat Chrysler Automobiles (FCA) umbrella. Several other manufacturers have used HEMI engines in their designs, though not as well known, not making full use of the potential a HEMI engine offers. Earlier HEMI engines were costly and complex with “double rocker arm” arrangement required by the angled valves of the hemispherical chambers, and although often regarded as a good design for a two-valve engine, many modern engines today tend to feature four or five valves per cylinder, making HEMI engines almost obsolete for mass-produced vehicles.
For anyone looking at a HEMI today, the modern HEMI engine is more like a tribute to the original than the original itself. Like a tribute to the greatest song in the world, auto manufacturers today won’t replicate the original design of the HEMI, lacking features like the distinctive hemispherical dome shape that gave the original HEMI its namesake, the HEMI engine has changed with the times to ensure performance with greater combustion while still improving emissions control and fuel efficiency. How much longer high-performance vehicles will last, let alone the HEMI engine, is unknown with electric vehicles slowly claiming the auto market. Even Dodge intends to get a plug-in hybrid or electric lineup one day.