The Mopar/Dodge 5.7 Hemi Magnum V8 Engines
The SRT Hemi engines started with the 6.1 Hemi, with 425 horsepower at 6,000 rpm (matching the 426 Hemi), and torque of 420 lb-ft at 4,800 rpm. That was replaced by the 6.4 Hemi, with cylinder shutoff and 470 horsepower and 470 lb-ft of torque. Coming up is the supercharged 6.2 Hemi, due to appear in 2014 with over 600 horsepower.
A 6.4 liter non-SRT Hemi V8 was launched in the 2014 heavy duty Rams; redesigned for durability, torque, and economy with heavy loads, it runs on midgrade gas.
Coming soon, according to various sources, are updates to the 5.7 “Eagle” Hemi and 6.4 “Apache” Hemi which should boost horsepower and torque. These might include direct injection, which is slated for the Pentastar V6 in 2016-17.
|G1 5.7||G1 5.7||G2 5.7||G2 5.7||G2.1 5.7||6.1 SRT8||6.4 (392)||6.2 SRT8|
|As used in...||Ram||Charger||Ram||Challenger||Chall.||Challenger||Charger||2015 Challenger|
|Horsepower||345 @ 5,600||340 @ 5,000||390||375 @ 5,800||379||425 @ 6,000||470||Over 600|
|Torque||375 @ 4,400||390 @ 4,000||407||398 @ 4,200||410||420 @ 4,800*||470||575?|
* Manual transmission was limited to 410 lb-ft torque.
Upcoming changes for the 2015 model year
Sources claim that tuning changes are being tested for the 2015 Hemi engines, some of which may appear through calendar-year 2014 as the Dodge Challenger, Dodge Charger, and Chrysler 300/300C are all revised and relaunched. Modifications made for special-edition Challengers and other “hotter” cars may be spread through the lineup, along with, perhaps, technologies developed for the Pentastar V6 and supercharged 6.2 Hemi.
General Hemi engine information
The Hemi was smaller, more powerful, and cheaper to build than the aged LA-series 360 V8 and relatively-new 4.7 liter V8 it replaced, but produced more power and torque. It has been hooked up to the Mercedes five-speed automatic, Chrysler’s five and six speed truck transmissions, and the ZF eight-speed.
Don Sherman, in Automobile, wrote that the cast iron block has a “meaty” deep-skirt design, with a crankshaft supported by four bolts per main bearing (two vertical, two horizontal). The heads are aluminum, the intake manifold plastic (for light weight and high flow).
Tom Hoover, one of the engineers responsible for the 426 Hemi, told Hot Rod that he had discussed the Elephant Engine’s design with new-Hemi engineers. Three of his major suggestions — raising the camshaft (to shorten the pushrods, reducing valve-train inertia and simplifying the rocker arms), using twin spark plugs, and adding squish area (to make light load/low speed efficiency better and reduce emissions) were immediately adopted.
The Hemi V8 has been immensely popular. In 2005, Hemi engine take rates was around 45% on cars and trucks where it was an option. Retired tuning chief Pete Hagenbuch commented that it was the most successful Hemi ever, because it could be built at a profit.
2009: Hemi 5.7 Liter V8 Engine Revisions
The 2009 Hemi was extensively modified to increase both power and gas mileage. Changes included a higher compression ratio, better-flowing heads, intake, and exhaust, and an active intake manifold. This is a new technology that takes advantage of Chrysler advances in the 1960s; it switches from long runners to short runners by moving a flapper door, to switch from better torque at low engine speeds to higher horsepower as rpms rise.
The new variable valve timing system used hydraulic cam phasing, relatively simple and inexpensive. The hydraulic roller camshaft had oil passages in front to drive the cam phaser sprocket, and increase valve lift. A new piston/rod assembly had thinner walls with a stronger-alloy pin.
All the ports were redesigned, with a raised exhaust floor; the new intake valves were 2mm larger. Other upgrades were a stronger crankshaft, dual-mass crankshaft damper, floating pin pistons, new valve springs, and higher oil pump capacity. The results were better reliability and gas mileage, with more horsepower and torque at every point in the engine’s speed range. oh2o had predicted variable cam timing in mid-2007. Redriderbob correctly predicted an updated MDS system in May 2007.
Dual spark plugs
Michael E. Gemmel wrote: “Each cylinder has an ignition coil pack over one spark plug, and a regular plug wire connected to the other spark plug. Further, the coil pack also has a plug wire attached to it that extends to the opposite cylinder bank. Each cylinder shares a coil pack with another cylinder. Each of the two plugs on a given cylinder is fired by a separate coil. One plug has a coil directly attached, and the other is fired via an ignition wire connected to a coil located on another cylinder on the opposite bank. The benefits would be one-half the number of coils (8 vs. 16) compared to each plug having its own coil, and of course less weight.”
“Cryptojoe” wrote: “The extra plug fires during the power stroke to more fully burn the hydrocarbons. ... the second ignition allows additional power in the down stroke while lowering the need for restrictive catalyst plates in the converter. ... [using] dual fired plugs on each cylinder allows the firing to take place closer to top dead center, and then again when the piston is on the back side of the power stroke.”
Patrick added: “The extra set of spark plugs on the HEMI and on previous engines are designed to reduce NOx and ozone emissions before a catalyst is needed. They add some horsepower, but not much.”
Displacement on demand: cylinder deactivation
The cylinder deactivation or “Multi Displacement System” (MDS) turns off the fuel in four cylinders when power is not needed. Chrysler said that the MDS system saved nearly 100 million gallons of gasoline between 2005 and 2009, and reduced carbon dioxide (CO₂) emissions by close to a million metric tons. Cylinder deactivation first appeared in cars, and was added to Ram Hemis later.
The 2005 Chrysler 300C and Dodge Magnum RT were the first high-volume, modern production vehicles in North America to use cylinder deactivation (though GM was the first to use such a system with the failed Cadillac “four-six-eight” system). Bob Lee, Powertrain Product Team vice president, said, “The MDS was part of the engine's original design. This resulted in a cylinder-deactivation system that is elegantly simple and completely integrated into the engine design. The benefits are fewer parts, maximum reliability and lower cost.”
The first-generation Hemi could transition from eight cylinders to four in 0.04 seconds by keeping the valves in four cylinders closed. While some energy is lost through compression, none is lost by pumping air through them. The system raised fuel economy by around 10% overall. Because (as with the slant six) oil comes through the pushrods, the engine was still fully lubricated.
Chrysler engineer Cole added: “The modern Hemi always shuts off the same four cylinders. In our durability test cycle (150,000 customer equivalent miles driven at the 95th percentile, meaning that only 5% of our owners are more abusive than our testing), we have not found any adverse wear patterns.”
Specific Hemi advantages (written about the first generation)
The hollow cam has oversized journals and lobes to reduce side loading on the lifters; roller-style lifters reduce friction and wear. The valve springs are beehive types, more effective than standard springs, so they can be lighter, with less lifter collapse. Rockers are light, and their flow is enough to compensate for their conservative .500 inches of lift.
The new Hemi is precision cast, which allows it to be lighter than a typical 5.7 liter engine, even with a taller deck height than GM’s equivalent V8; the slipper-style pistons are light (413g), using cast eutectic alloy. For longevity, the Hemi pistons are anodized on the top ring, which works as a combined heat barrier and anti-micro-weld mix, and allows the top ring to be only 3 mm from the top of the piston. As with the 426 Hemi, the rings are thin; a reservoir groove undeneath the top ring cuts the pressure between the top and second ring. The skirt is coated to increase the fit range for ring seals and reduce noise.
The crank has larger inner counterweights than similar (2007) GM engines, but their weight is offset by the lighter pistons and rods. A windage tray under the crank makes sure oil is always available, and the serpentine belt pulley acts as a torsional vibration damper. Connecting rods are strong and light enough to eliminate the need for a balance pad.
As usual, Chrysler used a speed density system instead of a mass airflow sensor (the 6.2 uses a MAF instead, though).
The two-inch ports flow 270 cfm at .600 inches of lift, with peak flow at .375 inches, and good flow even at .250 inches of lift. The exhaust port hits 161 cfm at .600 lift, with a 1.55 inch valve. Both have good velocity and distribution throughout their range, compared with a contemporary GM LS6 engine.
General hemi engine notes
Hemi production began in June 2002 at the Saltillo plant in Mexico; the first supercharged Hemi engine officially produced by Chrysler was shown to the public in January 2003, pumping out 430 horsepower and 480 lb-ft of torque, using the 5.7 Hemi engine and a Whipple supercharger (in the Dodge Magnum SRT-8 concept). The 300C version had “over 400 horsepower” and 350 lb-ft of torque.
The famed 426 Hemi had powered the first, second and third place winners at the 1964 Daytona 500 and became the de facto drag racing standard. The 426 and modern Hemis have dual rocker shafts, similarly sized valves, and two similarly-placed valves per cylinder. The Hemi was 56 pounds lighter than the 5.9 truck engine when it debuted.
John Veatch added: “The engine came in at 345 c.i.d. @ 345 hp, the same displacement as the 1957 DeSoto Adventurer 345/345 Hemi, the first standard engine to make the one horsepower per cubic inch mark (the 1956 300 optional HP engine had also done so). Both preceded the optional 1957 Corvette engine."
Guidance for Mopar Hemi engine owners
If you have an MDS engine (all current 5.7 engines!), only use 5W20 oil. You need the right oil. If the owner’s manual says something else, follow its advice - but don’t be convinced by a mechanic. Insist on the right grade and if they don’t use it...get a refund and go somewhere else. (See TSB 09-015-04 and 09-013-04: “Vehicles with the Multiple Displacement System must use SAE 5W-20 oil. Failure to do so may result in improper operation of the MDS.”) Engine problems have been reported as being due to the use of the wrong oil. Usually, these problems can be resolved with an oil change, but not always.
Other Hemi V8 engine notes
The Hemi V8 has pushrod-operated overhead valves, sequential multiple-port returnless fuel injection, and a compression ratio of 9.6:1. Valve gear is within the head walls.
Mike V. wrote:
... to supercharge a Hemi correctly, you should swap out the pistons. ... The [Edelbrock] eForce is an amazing kit. It is a bit chunky looking, but it will fit right. The advantage of the Edelbrock over other similar Eaton-based kits is the fact that it uses a seperate belt, pulley, and tensioner system, for greater reliability.
As for MultiAir, Bob Sheaves wrote, “Adding MultiAir would take a complete set of engine castings, requiring complete cooling system changes and a whole raft of other stuff. It would take at least three years from the start of program approval.”
2004 Hemi specifications (courtesy Cole Quinnell)
|Bore x Stroke||3.92 x 3.58 in, 99.5 x 90.9 mm|
|Valve System||pushrod, 16-valve, hydraulic roller lifters|
|Block Construction||cast iron, deep skirt, cross-bolted main caps|
|Centerline of crank to head deck face||9.3 inches|
|Centerline of crank to centerline of cam||7.4 inches|
|Centerline of crank to oil pan rail||2.6 inches|
|Block maximum deck width at deck face||18.3 inches|
|Block height, oil pan rail to top of water outlet||15.4 inches|
|Overall engine length||21.1 inches|
|Combustion chamber volume||84.9 cc|
|Intake valve angle||18°|
|Intake valve head diameter||50.8mm, 2.00 inches|
|Exhaust valve angle||16.5°|
|Exhaust valve head diameter||39.4mm, 1.55 inches|
|Oil Capacity||7 quarts (6.6 liters)|
|Weight (with induction, wiring, flexplate, |
and exhaust manifolds, but not accessories)
|Modern Hemis||5.7 Hemi • SRT 6.1 and 6.4 • 6.4 Truck Hemi • Supercharged “Hellcat”|
|Classic Hemis||426 Hemi • Old Hemi History • 392 Crate Hemi • Development • Plane Hemi|