Mopar Dodge And Chrysler 5.7 Liter Hemi Engine - Inside The 5.7 Hemi

We have all heard the hype and seen the cool commercials with the beat-up Duster, the new Hemi-powered truck, and even a front engine dragster sporting a first-generation Hemi, but does the new Hemi engine live up to our expectations? While we really doubt the 5.7 Hemi-powered full-size Dodge truck would smoke a front engine digger (even with the chute deployed), the 380hp rating did pique our interest. We know modern fuel injection and electronics can make a relatively small displacement V-8 far more efficient than a carbureted version, but we felt the power and economy this engine produces had to be attributed to more than computers.

When it comes to engines, we know the best way to see what makes them tick is to go inside and take a look. I must say, we were impressed by what we found in the latest version of the most powerful production V-8 in the world.

Any die-hard Mopar fanatic knows the prowess of the Hemi engine. The Chrysler engineers really did their homework when they designed cylinder heads utilizing hemispherical combustion chambers. As it turns out, the design created the most powerful internal combustion engines ever. The next time you see an NHRA drag racing event, take a look at the top two classes of Top Fuel Dragster and Fuel Funny Car. Regardless of the sponsor of the car or the body on the car, the powerplant is a Hemi. That's right, John Force's Mustang Funny Car is powered by a Hemi with the same design as the 426 version introduced by Chrysler in 1964, albeit with a few enhancements. Why the Hemi? It's the only engine that makes enough power to be competitive in drag racing's top classes. Does Chrysler's newest version of this engine live up to its name? If judged by horsepower and torque ratings alone, the answer is yes.

Let's look at a horsepower-per-cubic-inch comparison of the engines. The 5.7 Hemi is 345 ci and the '09 version makes 380 hp (as rated in the Ram 1500), or exactly one horsepower-per-cubic-inch. In comparison, the 425hp, 426ci Hemi makes .997 hp-per-cubic-inch-making the two engines nearly equal in power output per-cubic-inch. The 6.1L (372ci) Hemi available in SRT models is not as tame as its little brother, making an amazing 425 hp [soon to be 450HP], a whopping 1.14 hp-per-cubic-inch. The 6.1 Hemi is the hands-down winner. When drivability is considered, the new Hemi is also a winner. The 426 Hemi, while known for high-end horsepower, was notoriously low on bottom end torque, not so with the new version. The new 5.7 Hemi not only makes 390 lb-ft of peak torque, it also makes over 300 lb-ft from 1,200-rpm up-giving it the best of both worlds. Driving a 5.7 Hemi-powered car or truck is like launching a powerful 440 torque-monster (well, almost) with a smooth transition to the top-end Hemi power. The net result is a vehicle that marries great power with excellent drivability. We know what you're thinking, the new Hemi engine sounds powerful, but can I afford to feed it? Thanks to some pretty incredible engineering, the answer is yes.

We had a chance to drive an '06 Charger R/T with the 5.7 Hemi recently and were somewhat surprised by the economy advertised by DaimlerChrysler. How could a 340hp V-8 in a 4,300-pound car get 25 mpg? The answer is technology that Chrysler calls a Multi-Displacement System or MDS. The theory behind MDS is when the on-board computer senses that all the engine's power is not needed to sustain vehicle speed, four of the cylinders are dropped, and the engine runs on the remaining four, netting a 20-percent increase in economy. While this sounds good in theory, we had visions of a rough-running V-8 with four plug wires off-not a nice ride. We were amazed the MDS works so well-the transition is seamless. Not only does the engine continue to run smoothly on four cylinders, it responds well and picks the other four back up as soon as the throttle is depressed. The driver is unaware the system is working; other than noting improved economy.

The Multi-Displacement System works by electronically dropping the coil pack and the injector from the selected cylinders and utilizes special oil restricting valves in the lifter galley to force oil to the exhaust lifter of each dropped cylinder, pumping the lifter up to keep the valve off its seat so that cylinder pressure is bled off with no vibration as the dropped cylinders cycle through their compression stroke. The remaining four cylinders now work a little harder as they are both propelling the vehicle and spinning four extra pistons and connecting rods, and the net result is a 20-percent gain in economy, giving the new Hemi-equipped vehicle V-6 or even four-cylinder economy, while retaining its horsepower and torque numbers. Does it work? While we didn't see 25 mpg as the window sticker on our Charger advertised, we did find it easy to average 20 mpg during a combination of highway and city driving. We're sure that 25 mpg is attainable, just not with our lead feet. Adding to the overall economy of the package is the fact that as a function of the detonation-resistant Hemi head, the engine runs great on the recommended mid-grade fuel and does not require premium. We'll use the 20 or so extra pennies per gallon to save up for a cold-air kit and maybe an exhaust upgrade.

Enough about theory, we needed to look inside the new Hemi engine to see what really makes it work. It turns out, our friends over at Crane Cams in Daytona, Florida, had just what we needed-a 5.7 Hemi they were using for some research and development. They were nice enough to let us come over and dissect the Hemi for a first-hand look inside. We think you'll be pleased at what we found.

Whether you like the styling of Chrysler's new product line or not, the Hemi engine is a powerplant to contend with. The combination of the hemispherical cylinder head design with an advanced oiling system, and modern ignition and fuel-injection technology makes this engine a real winner. It's no wonder so many people are transplanting this motor into their show and race cars. Mopar Performance is already committed to the 5.7 Hemi as its latest crate motor, available in both injected and carbureted versions. We look for the aftermarket to support this engine as well, and look forward to seeing how much power can be extracted from this potent little motor. Plus, dude, it's a Hemi. Sweeeet!

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