Modern Mopar / Chrysler / Dodge 5.7 Hemi Magnum V8 Engines
The first-generation 5.7 liter "new Hemi" produced up to 350 horsepower at 5,600 rpm and 375 lb-ft of torque (4,400 rpm) - one horsepower per cubic
The second generation rose to 390 horsepower and 407 lb-ft of torque in the Dodge Ram
- 375 horsepower in the 2009 Dodge Challenger
with manual transmission; power varied by car or truck.
SRT Hemi engines
started with the 6.1 Hemi
, with 425 horsepower at 6,000 rpm (matching the 426 Hemi
's number) and, in 2014, the supercharged 6.2 Hemi
went to 707 horsepower in 2014.
A 6.4 liter non-SRT Hemi V8
in the 2014 heavy duty Rams was designed for durability, torque, and economy with heavy loads.
Updates to the 5.7 "Eagle" Hemi and 6.4 "Apache" Hemi might
be coming; these were rumored to boost horsepower and torque, and to include direct injection, which is slated for the Pentastar V6 in 2017-18.
General Hemi engine information
|As used in...||Ram||Charger||2007 Ram||Challenger||Challenger|
|Horsepower||345 @ 5,600||340 @ 5,000||390||375 @ 5,800||379|
|Torque||375 @ 4,400||390 @ 4,000||407||398 @ 4,200||410|
| EPA mpg||13/17||15/23||13/19||16/25||17/25|
The Hemi was smaller, more powerful, and cheaper to build than the
LA-series 360 V8
and "Next Generation" 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
The cast iron
block has a "meaty" deep-skirt design, and the crankshaft is supported by four bolts per main bearing (two vertical, two horizontal). The
heads are aluminum and the intake manifold is plastic (for light weight and high flow).
Code names, based on planes:
5.7 = Eagle; 6.4 = Apache; 6.2 = HellCat
, "father of 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 (for more light load/low speed efficiency and reduced emissions) were 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; it included a higher compression ratio, better-flowing heads, intake, and exhaust, and an active intake manifold. The active intake, previously used on the 3.5 liter V6
, 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.
The ports were redesigned, with a raised exhaust floor; 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
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.
Bob Sheaves on why the system is usually used on V8 engines, not V6 engines:
An Otto cycle engine takes two revolutions [full turns] of the crankshaft
to fire all the cylinders. Two revolutions times 360 degrees [one complete circle] equals 720 degrees of rotation; dividing that by the number of cylinders gives you 120 degrees [on a V6], so you have a cylinder firing every 120 degrees of rotation.
On a V6, when you take out half of the cylinders, you have increased the firing
rotation to 240 degrees (720/3), balanced between each firing of
a cylinder but with increased harmonic
vibrations as the revolutions per minute increase. Deactivation of two or four cylinders in a V6
would mean losing the multiple of six cylinders, which is what keeps the
engine in primary balance. [Honda deactivates two
cylinders on its V6 engine, which improves the balance by making the firing rotation 180°, the same as in a V8 firing on half its cylinders. With all eight cylinders firing, V8 engines fire every 90 degrees.]
rysler 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 source for most of this information is Popular Hot Rodding.
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.
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 underneath 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
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 cubic inches of displacement and 345 hp, the same as the 1957 DeSoto Adventurer 345 Hemi
, the first standard
engine to make the one horsepower per cubic inch mark (the 1956
high performance engine had also done so). Both
preceded the optional
1957 Corvette engine [generally credited with one horsepower per cubic inch]."
Guidance for Mopar Hemi engine owners
you have an MDS engine (all current 5.7 engines!), only use 5W20 oil. You need the right oil.
the owner's manual says something else, follow its advice, but
don't be convinced by anyone else. 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 separate 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)
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