the mopar hemi magnum v8 engines
TRANSCRIPT
The Mopar Hemi Magnum V8 Engines - 5.7, 6.1, 6.4 (392)
426 Hemi | Full Hemi History
2010 6.4 liter production V8: 392 Hemi engines
The 6.4 Hemi (392 Hemi) is to be in the 2011 Dodge Challenger
SRT8 and other SRT V8 models. The engine is very different from
the one in the Challenger Drag Pack (the Mopar crate engine), not
just because it has multiple displacement (four cylinders
automatically shut off when not needed to dramatically increase
gas mileage). The engines have a different bore, stroke, cam,
heads, compression, and intake.
oh2o told Allpar readers about the engine in 2005, with horsepower
estimated between 450 and 500; in 2008 we firmed our estimate at
480, and in 2010 it was launched with 475 horsepower and 460 lb-
ft of torque (on Challenger; on the 2012 Charger SRT8, it was 465
hp and 465 lb-ft). To limit emissions, both spark plugs were used at
top dead center and one was used before top dead center to burn
off the hydrocarbons, allowing the use of less restrictive catalytic
converters. The engine reportedly (“carcharger”) cannot pass
durability testing at 525 horsepower, due to piston skirt issues
when tested near overheat conditions. (Durability testing
reportedly requires 200,000 miles MTBF and extensive testing
under extreme conditions.)
The 392 Hemi (6.4
liter) will not have MDS (four cylinder mode) when paired with a
manual transmission.
A new, expensive but sturdy eight-speed automatic transmission
will eventually go along with the 6.4 Hemi, along with the V6 and
standard Hemi.
An “Apache 392” has reportedly been under development, a
supercharged version pushing out over 600 hp. Rumor has it going
into the Challenger and Grand Cherokee. Allpar member
“autojunkie” wrote:
I can say that the 392 supercharging is a done deal. It was
spotted on some Chrysler engineering documentation and
slated for 2014. It specifically mentioned the Grand Cherokee
for production intent.
I've seen many engineering documents that had projects that
were eventually cancelled. The document detailing the
supercharged 392 did point to production-intent, but it does
not mean that it couldn't fizzle off the plan still.
Mike V. added:
... to supercharger a Hemi correctly, you really should swap
out the pistons for some with a little more meat between the
rings. I personally cannot see Chrysler producing a production
supercharged car direct from the factory because it would
require different engine internals to meet and exceed all the
OEM specifications. Mopar Performance is a whole different
animal. If it happens (and I seriously doubt it) it will be a
performance kit from Mopar Performance with the typical 12
month/12,000 mile warranty.
The [Edelbrock] eForce is an amazing kit. It won't make the
power that the Magnusson guys are making, but it will make
enough power to be a street car from Heck. It is a bit chunky
looking, but it is truly OEM quality and will fit right everytime.
The advantage of the Edelbrock over other similar Eaton
based kits is the fact that it uses a seperate belt, pulley, and
tensioner system. It doesn't simply rely on the stock tensioner
and a longer belt on the stock serpentine. This is big because
some of the LX guys are having trouble with the factory
tensioner failing when using it with a supercharger.
Modern Mopar Hemi Engines
Hemi: (HEM -e) adj. Mopar in type, V8, native to the United States,
carnivorous, eats primarily Mustangs, Camaros, and Corvettes.
Also enjoys smoking a good import now and then to relax. - David
Charles Gedraitis
The Hemi V8 has been immensely popular. In 2005, Hemi engine
take rates was around 45% on vehicles offering the engine. In some
cases, it appears to be the main reason why people buy the car or
truck around it. One engineer commented, somewhat tongue-in-
cheek, that it was the most successful Hemi ever, because it could
be built at a profit.
The first generation 5.7 liter Hemi (the third generation Hemi)
produced 345 horsepower at 5,600 rpm (the figure varied
somewhat by application) and 375 lb-ft of torque (4,400 rpm) from
5.7 liters (345 cid*) when used in the Dodge Ram - one horsepower
per cubic inch.
The second generation 5.7 Hemi produced 390 horsepower and
407 lb-ft of torque in the 2009 Dodge Ram 1500, using variable
cam timing; it shuts off four cylinders when possible to get good
mileage. The same engine produces 375 horsepower in the 2009
Dodge Challenger R/T with manual transmission.
G1 5.7 G1 5.7
G2
5.7 G2 5.7
G2.1
5.7
6.1
SRT8
6.4
(392)
As used
in...Ram Charger Ram
Challenge
rChall. SRT8 SRT8
Horsepow
er
345 @
5,600
340 @
5,000*390
375 @
5,800379
425 @
6,000475
Torque375 @
4,400
390 @
4,000407
398 @
4,200410
420 @
4,800*460
EPA mpg 13/17 15/2313/1
916/25 17/25 13/18
* Manual transmission is limited to 410 lb-ft torque.
The 6.4 liter version, at a historic 392 cubic inches and projected to
reach 475 hp, is due for 2011 SRT8 cars. The crate version builds
505 horsepower; because it’s for racing only, sacrifices were made
for longevity, gas mileage, and emissions reduction. The 392 used
in production cars has multiple displacement (automatic
transmissions only) and many other changes for a long, trouble free
life.
Hemi engine information
The Mopar Hemi was
used in the Ram, Durango/Aspen, Grand Cherokee, and LX large
cars, in front of a five-speed automatic. The Hemi was smaller,
faster, more economical, and cheaper to build than the 360 it
replaced.
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. 2009 and later
models have a "fuel saver" readout in the EVIC and more
aggressive tuning.
The Hemi V8 started in the 2500 and 3500 Ram; it moved next into
the Ram 1500 (calendar year 2002). Cylinder deactivation first
appeared in cars, and was added to Ram Hemis with a redesign.
Don Sherman, writing in Automobile, noted that the cast iron block
has a "meaty" deep-skirt design, with a crankshaft supported well
by four bolts per main bearing (two vertical, two horizontal). The
heads are aluminum, with the usual Chrysler plastic intake
manifold.
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. At least three of his suggestions - raising
the camshaft (to shorten pushrods, reducing valve train inertia and
allowing simpler exhaust rocker arms), using twin spark plugs, and
adding squish area (to make light load/low speed efficiency better
and reduce emissions) were immediately adopted.
MultiAir
J. White wrote, “If you look at the 5 year plan, no MultiAir Hemi
was listed.” Bob Sheaves added:
[The Hemi is] tightly packaged — with poor angularity of the
pushrods between the lifters and rockers on both sides of the
combustion chambers, and hot spots and poor
manufacturability of the cooling cores due to the positioning
of the components. This caused the problems passing
emissions on all of the hemi engines.
Adding MultiAir will take a complete set of engine castings,
necessitating complete cooling system reconfigure, emissions
predictions, flame optimization, combustion chamber
optimazation, and a whole raft of other stuff. It would take
three years minimum from the start of program approval, (6
months before that for a concept design that mightbe feasible)
to enter production.
Dual spark plugs
The 2009 Hemi brought variable cam timing; a higher compression ratio; higher-
flowing heads, intake, and exhaust; and an active intake manifold that switches from
long runners to short runners, to optimize the engine for either better high-end
horsepower or better low-end torque. Other upgrades are crankshaft structural
upgrades, a dual-mass crankshaft damper, floating pin piston design, valve spring
design, and oil pump capacity increase.
The results of all this work are higher power, reliability, and gas mileage.
oh2o had predicted that the Hemi would get variable cam timing, in mid-2007.
Redriderbob correctly predicted an updated MDS system in May 2007.
oh20 also predicted a 6.4 liter Hemi expected to get nearly 500 hp (we have heard a
range from 470-490); and that the 6.1 Hemi might get MDS in 2009 or 2010.
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.
“In the 1980s Japanese manufacturers reduced unburned
hydrocarbons by placing spark plugs either in the exhaust pipe
(which fired with every piston ignition) or in the exhaust manifold
(which fired each time their corresponding cylinder fired). Chrysler
morphed this idea to include dual fired plugs on each cylinder,
which 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: “This [also reduces] NOx and ozone. Full
combustion results in heat, water, and carbon dioxide. NOx
emissions are only significant during incomplete or partial
combustion, due to the lack of available oxygen, high temperatures,
and various chemical reactions. That's why catalytic converters
have been standard on cars for the past 3 decades. The extra set of
spark plugs on the HEMI and on previous engines are designed to
reduce emissions before a catalyst is needed. They add some
horsepower, but not very much.”
Displacement on demand
The 2005 Chrysler 300C and Dodge Magnum RT were the first
high-volume, modern production vehicles in North America to
feature fully-functioning cylinder deactivation. The MDS (“multiple
displacement system”) seamlessly alternated between fuel economy
in four-cylinder mode, and power in V-8 mode. Owners receive the
powerful benefit of the Hemi engine with the fuel economy that
they would expect from a smaller engine.
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."
This system triumphs because of modern electronic controls and
electronic throttle control. The HEMI can transition from eight
cylinders to four in 0.04 seconds. The system works by cutting out
the valve lifters, keeping the valves in four cylinders closed; energy
is not lost by pumping air through them.
Fuel economy goes up by up to 20% percent under various driving
conditions, with a 10% aggregate improvement. Because (as with
the slant six) oil comes through the pushrods, lubrication is
maintained when cylinders are at rest.
Bob Sheaves discussed why the system is almost always used on
V8s and not V6s:
"An Otto cycle engine requires two full revolutions of the
crankshaft to fire all the cylinders. Two revolutions x 360 degrees
equals 720 degrees of rotation. Dividing that total rotation by the
number of cylinders to have an even firing engine (naturally
balanced) will give you 120 degrees, which means that you have a
cylinder firing every 120 degrees of rotation. When you take out 3
of the cylinders, you have increased the firing rotation to 240
degreees (720/3), still balanced between each firing of a cylinder.
The catch is that you have increased the harmonic vibrations as
the rpms increase. Deactivation of four cylinders in a V6 would
mean losing the multiple of six cylinders, which intrinsically
keeps the engine in primary balance. (The lack of natural balance
is why balance shafts are often used in 90 degree V6s and larger
inline 4 cylinder engines.)"
Ch rysler engineer Cole wrote: "The modern Hemi
always shuts off the same four cylinders. In our duarability test
cycle (150,000 customer equivelant miles driven at the 95th
percentile, meaning that only 5 percent of our owners are more
abusive than our testing), we have not found any adverse wear
patterns." Even in 2010, five years later, there have been no
reports of problematic uneven wear.
Jim Choate asked Bob Lee why the Hemi was not offered as an E85-
capable engine. Lee said that there is little demand for an E85
Hemi. Most of those who ran E85 fuel went back to gasoline. The
lack of E85 infrastructure in many markets makes engines tuned to
run better on E85 impractical.
Specific advantages
The source for most of this information is Popular Hot Rodding.
The cam was placed high up in the block to keep the pushroads as
short as possible. The hollow cam has oversized journals and lobes
to minimize side loading on the roller-style lifters. The valve springs
are beehive types, more effective than standard springs so they can
be lighter, with less lifter collapse. Rockers have much less inertial
mass than usual, with the form and size carefully designed for a
conservative .500 inches of lift; but the valves flow well enough to
make this more than enough.
The engine has been designed for lighter weight. 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 Chevy's; and, partly to
counter the inertia of its relatively long stroke, the pistons were
made light as well, using cast eutectic alloy. The slipper-style
piston has much in common with racing pistons, with a weight of
413 grams. For longevity, the Hemi pistons use a hard anodize on
the top ring land, to act as a heat barrier and anti-micro weld mix,
and to allow the top ring to be only 3 mm from the top of the piston,
cutting emissions while bringing more power. As with the old 426
Hemi, the rings are also relatively thin. Also in common with racing
engines is a reservoir groove undeneath the top ring, to reduce the
pressure between the top and second ring.
The skirt is coated to allow for variance in production piston sizes,
increase the fit for ring seal, and reduce piston noise. The
lightweight wrist pin is also high-set.
The crank has larger inner counterweights than equivalent Chevy
engines; but their weight is offset by the lighter pistons and rods. A
windage tray sits underneath the crank, while the serpentine belt
pulley also acts as a torsional vibration damper. The connecting
rods are also designed for strength and low weight, negating the
need for a balance pad. A cap bolt is used instead of a through bolt.
A speed density system is used for measuring air into the engine
rather than air mass.
The 2 inch ports flow 270 cfm at .600 inches of lift, with peak flow
at .375 inches. At .250, the stock head also had excellent flow. The
exhaust port hits 161 cfm at .600 lift, with a 1.55 inch valve. Both
have unusually good velocity and distribution throughout their
range - even compared with a Chevy LS6 engine. The engine
apparently takes well to simple porting.
General hemi engine notes
Hemi production began in June 2002 at the Saltillo plant in Mexico.
In January 2003, the public saw the first supercharged Hemi engine
officially produced by Chrysler. It pumped out 430 horsepower and
480 lb-ft of torque, using the 5.7 Hemi engine and a Whipple
supercharger, and was first shown in the Dodge Magnum SRT-8
concept. The 300C version had "over 400 horsepower" and 350 lb-ft
of torque.
The famous 426 Hemi powered the first, second and third place
winners at the 1964 Daytona 500 and became the de facto drag
racing standard. It re-entered production for racing in the late
1990s.
The original Hemis and the current one both have dual rocker
shafts, large (similarly sized) valves, and two valves per cylinder
arranged in a similar pattern for efficiency. The engine's unique
two-valve hemispherical combustion chamber provides impressive
air flow, torque, and power. Fifty-six pounds lighter than the 5.9-
liter V-8, the 5.7-liter Hemi produced 41% more power and 12%
more peak torque in its original form.
An electronic throttle control system compensates for changes in
the engine load needed by the air conditioning system, compressor,
alternator, power steering pump and automatic speed control.
The proportion
of regulated
pollutants is a
problem for
Chrysler. Bob
Sheaves noted:
The Hemi
design
combustion chamber is one of the poorest designs for
emissions - why do you think it took so long to get it into
production? It almost did not make emissions test
requirements even with the modifications.
John Veatch wrote:
"Seeing all the hoopla surrounding the new Hemi and the
previous speculation on whether its displacement was going to
be either the nostalgic 354 or 383, I am amazed no one has
made mention of what is probably the coolest link of all. The
actual production engine came in at 345 c.i.d. @ 345 hp, the
exact same specs as the 1957 DeSoto Adventurer 345/345
Hemi, the first standard engine to make the 1hp/ci mark (the
1956 300 optional HP engine had earlier accomplished the
feat). Both preceded the much ballyhooed optional 283/283 hp
1957 Corvette engine." [The 1950s engines were gross
horsepower while the current one is net.]
Guidance for Mopar Hemi engine owners
Will the Hemi survive? Yes, Sergio Marchionne said the Hemi “will continue to be
part of the DNA of this house.” (Jan. 2010, Toledo Blade .)
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. (You can quote 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.”) Watch the mechanic pour it in!
Hesitation when shifting (up to 2005). The engine computer
lowers torque when shifting to preserve transmission life, but a
service bulletin covers shift hesitation during wide-open throttle on
early (2005) SRT-8 cars. When the gas pedal is floored, the engine
RPM may go beyond the redline before the shift from first to
second is made, so there’s a “short hard bump” as the shift begins,
especially when the pedal is floored from about 15 mph. The
problem has been solved with new software, and only applied to
cars built before July 25, 2005. There is also reportedly a computer
upgrade that fixes intermittent engine RPM limiting and ineffectual
A/C in early (pre-2006?) Hemis.
According to Chrysler, owners can maximize the effectiveness of
the MDS (and increase gas mileage) by using the cruise control and
keeping a steady foot on the throttle.
What makes the SRT version different
The SRT engine includes numerous modifications from the standard
Hemi, such as:
Reinforced bulkheads.
Larger cylinder bores, by 3.5 millimeters, honed with torque plates to ensure a truer bore.
Oil squirters, aimed at the underside of each piston, aided by a special oil pump pressure relief valve.
Modified oil pan and windage tray.
Larger-diameter, flat-top pistons with high-load capability.
Revised connecting rods using higher-strength powder metal material. New floating piston pins.
Crankshaft forged from micro-alloy steel, in tri-metal main bearings, with retuned damper.
Head ports designed with larger cross-sectional area. This allows 11 percent higher flow in the intake ports, and 13 percent higher flow in the exhaust ports.
A billet steel, high-strength camshaft features more overlap and lift for better performance.
Intake valves feature hollow stems and 2 mm larger heads. The hollow exhaust valve stems are filled with sodium to dissipate heat. Premium valve springs with external dampers enable higher engine speed operation to 6,400 rpm and allow the peak output engine speed to increase to 6,000 rpm from 5,000 rpm.
Specially designed intake and exhaust manifolds.
Cast aluminum intake manifold with shorter, larger-diameter and tapered runners for high-speed tuning. Internal runners are core-dipped to smooth the runner finish and improve air flow.
14% higher fuel injector flow capacity; higher-flow air cleaner box with a tuned resonator delivering a deep performance sound character (and good for an extra eight horsepower).
Exhaust headers are individual tubes encased in a stainless steel shell. Exhaust runners allow increased gas flow while
maintaining fast catalyst light-off, while adding 12 horsepower over the 5.7-liter engine’s cast manifolds.
Dual knock sensors with premium fuel.
Other notes
The Hemi V8 has 16 pushrod-operated overhead valves, hydraulic
lifters with roller followers, sequential multiple-port returnless fuel
injection, and a compression ratio of 9.6:1. It uses a deep-skirt cast
iron block with cross-bolted main bearing caps, and aluminum alloy
heads with of course hemispherical combustion chambers. In this
regard, it is similar to the V10 (based on the venerable LA V8s),
which also has a deep skirt cast iron block, hydraulic lifters with
roller followers, and pushrod-operated overhead valves - two per
cylinder. (The V10 has iron heads when used in trucks.)
AI-Online noted that the Hemi has double rocker shafts in each
head, like its predecessors, but has valve gear within the head
walls.
The 5.7 has a cast iron cylinder block with a single in-block
camshaft and only two valves per cylinder, resulting in low
production costs — reportedly lower than the 4.7 and certainly
lower than the 318 and 360.
The two-valve-per-cylinder design means not only lower production
costs, but also better low-end torque.
2004 Hemi specifications (courtesy Cole Quinnell)
Bore x Stroke 3.92 x 3.58 in, 99.5 x 90.9 mm
Valve Systempushrod, 16-valve, hydraulic
roller lifters
Block Constructioncast iron, deep skirt, cross-
bolted main caps
Centerline of crank to head deck
face9.3 inches
Centerline of crank to centerline of
cam7.4 inches
Centerline of crank to oil pan rail 2.6 inches
Overall block maximum deck width
at deck face18.3 inches
Overall block height from
oil pan rail to top of water outlet15.4 inches
Overall engine length 21.1 inches
Compression Ratio 9.6:1
Combustion chamber volume 84.9cc
Intake valve angle 18 degrees
Intake valve head diameter 50.8mm, 2.00 inches
Exhaust valve angle 16y.5 degrees
Exhaust valve head diameter 39.4mm, 1.55 inches
Oil Capacity 7 qt., 6.6L
Weight (includes induction, wiring 485 lbs
harness,
auto-trans flexplate and exhaust
manifolds,
but not accessories)
Ignition Two spark plugs per cylinder
* The Hemi Engine Size Controversy
Different Dodge listings mentioned 345, 348, 353, and 354 cubic
inches as the engine size; possibly different people at Chrysler used
different formulas to get at the cubic inches. Gaymon Wright's
window sticker lists the Hemi as being 348 cid! Jack pointed out
that the bore and stroke times pi times the number of cylinders =
353 - perhaps someone at Chrysler incorrectly used that formula.
The 354 was probably a simple typo.
Derek wrote "the correct formula is pi x (bore/2) squared x stroke.
This is because bore is a circle and area of a circle is pi x r squared!
Try it and you will find 3.92/2 = 1.96; 1.962 (3.8416) x pi= 12.0687
x 3.58 stroke =43.20 x 8 cylinders = 345.6." (Mark Strode noted
that if you use millimeters to avoid rounding error, you get 345.06).