The generation three Chrysler Hemi differs in many ways from its earlier counterparts in that the engine now had a coil-on-plug, distributorless ignition system. This system uses two spark plugs per cylinder for shorter flame travel, which increased combustion in the cylinder as well as reduced emissions in the process. The cylinders themselves were no longer totally hemispherical in their shape. The 5.7-liter still rated at one horsepower per cubic inch displacement, but now the more accurate SAE net system provided the rating process, rather than the older Gen 2 SAE gross hp method.
Chrysler boosted the 2009 Hemi 5.7 slightly, so it put out from 357 to 390hp (266-291 kw) and offered around 389 to 410 lbs.-ft. (527-556 Nm) of torque, depending on the application. The car uses variable valve timing, and as a further bonus, the engine now gets around 4 percent better fuel mileage. There were more fuel savings on some versions when two cylinders shut down to give the engine a lighter load. This variable displacement technology is called the Multi-Displacement System or MDS.
A 5.9-liter Hemi on the 1500, 2500, and the 3500 model, gasoline-powered Dodge Ram pickup replaced the Magnum 5.9-liter engine in 2003. In ’04 MDS was not available in the Durango and the uptown sedans or the high-performance Charger and Challenger models with the six-speed transmissions.
The 5.7 (345-cubic-inch) Hemi for the Ram delivered 345hp (257 kW) putting out 540 N-m (398 lbs.-ft.) of torque, but the same engine in the Magnum R/T Chryco 300C offered the lesser-rated hp at 340 or 253.5 kW and up to 390 lbs.-ft.(529 kW) of torque. The sedans got precisely 100 more horses than their larger 5.9-liter predecessors did. As with the predisposed MB engines, the 90-degree V8 5.7-liter sported two valves per cylinder in a bore of 3.917 inches with a 3.578 stroke. For the ’03 to ’07 model years and then again in 2009, Ward chose this engine as one of the top 10 manufactured power plants.
The biggest change for the 5.7 Hemi from the 2008 to 2010 model years was actually variable valve timing, but Chrysler called it VCT or variable crankshaft timing, which controlled oil flow with an unusual phasing mechanism for the camshaft sprocket that would either retard or advance the timing of the camshaft. The 5.7 had five unique camshaft configurations available with VCT starting in ’09. Chrysler revised the cylinder head shape for increased flow along with an intake manifold that was model specific.
The hybrids excluded the Durango and Aspen, which had an active intake manifold using a short runner valve to maximize the horsepower and the torque produced. The valve closes at low RPM, directing the air intake to the manifold’s center and opens as acceleration increases, upping the hp in the process. The HEV models lack the short runner valve in the manifold with their passive design. All heavy-duty trucks as well as all models with the six-speed transmission do not have the MDS system.
The Hemi engine also had as an offering a 6.0-liter (369.7-cubic-inch) version having a bore of 4.06 inches that allowed this engine to develop 425hp (317 kW) and produce 420 lbs.-ft. (569Nm) of torque at 4800 RPM. The block had different cooling channels than the lesser 5.7 and uses oil jets for piston cooling and lubrication. The 6.0 also had a forged crank with heavy-duty con rods and lighter pistons, which made a stronger package. Chrysler developed the aluminum cast intake for the 6.1 to work at high RPM and didn’t integrate the multi-displacement system or the variable length technology.
A 6.4-liter (392-cubic-inch) Hemi engine showed up in 2005 and was available as a crate option from 2007 as a 392 Hemi. This engine produced up to 525hp (391 kW) with 510 lbs.-ft. (691 N-m) of torque, and the design is in the same manner as the old 6.1 with aluminum alloy pistons. The engine was available in the 2011 SRT8 and in the automatic, and MDS autos had the variable crank timing. The latest 392 had the moniker of the “Apache,” based on the 3G 5.7-liter Hemi, but that latest version had very few components of the earlier crate 392. The power plant was a choice for the SRT8, 300C, and Grand Cherokee as well as special edition Chargers complete with all the badging to denote the status. The block on this engine is completely different from the earlier crated version and now put out 470hp (350 kW) and developed 470 lbs.-ft. (637 N-m) of torque. In 2012, a 590hp (440 kW) 426-cubic-inch Hemi V8 displayed in Detroit under the hood of the Dodge Charger Redline.