4.7 Liter Next Generation/Corsair V8 Engines (Dodge - Jeep)
Chrysler's first truly new V-8 since the 1960s - though initial development was at AMC - the Next Generation 4.7 had better power, gas mileage, and emissions than the 318 V8 it replaced. The engine was reportedly designed as a replacement for the 4-liter AMC I-6, with the closely related 3.7 V6
to replace the AMC 2.5.
Initially dubbed "Corsair," the engine originally didn't have EGR or knock sensors; these were added in 2005. For model-year 2008, Chrysler adapted lessons from the 5.7-Hemi
to the 4.7, and power shot up from 230 hp to 290 hp; gas mileage went up, and vibration went down.
The 2008 redesign had two spark plugs per cylinder, a 9.8:1 compression ratio, better port flow, and new slant/squish heads. The induction system was reworked, reciprocating mass reduced via a lightweight piston/rod assembly, and the accessory drive speed cut back. A new, normally-open valve lash adjuster system smoothed idling; and electronic throttle control was added to help stability control. The engine was still made at Mack Avenue (Detroit).
|2008 Dakota||302 hp @ 5,650 rpm||329 lb-ft @ 3,950 rpm|
|2008 Aspen / Durango||303 hp @ 5,650 rpm||330 lb-ft @ 3,950 rpm|
|2008 Grand Cherokee / |
|305 hp @ 5,650 rpm|| 334 lb-ft @ 3,950 rpm|
|2008 Ram 1500||310 hp @ 5,650 rpm||329 lb-ft 3,950 rpm|
Production ended in July 2013, and the 3.7 V6 equipment moved to Trenton, Michigan; the 3.7 ended soon afterwards, and trucks gained the 3.6 liter Pentastar V6 instead.
Mopar's first all-new production V8 in 41 years
By RICK EHRENBERG. © 1999 by Rick Ehrenberg. Used by permission.
This article covers the 1999-2007 version.
The new 287 is just that, new, sharing almost nothing but a heritage with the ol'reliables. For starters, it's the first true production Mopar V8 mill to incorporate aluminum cylinder heads (okay, we know about the 1965 A-990 Hemi) a plastic intake manifold, and magnesium valve covers. Nothing is re-hashed here, and the combustion chambers are almost hemispherical !
This is a real milestone, so let's take a detailed tour of what's what, beginning at the lower extremities.
Bottom end of the Corsair 4.7
Virtually all dimensions of the cast-iron block are new. The bore spacing was reduced from the 1955-1998 small block's 4.46 to 4.09" - an indicator of how large the new engine eventually could (or could not) be enlarged to. Basic bore size is 3.66," larger yes, than a 273 (by a mere 0.030) but smaller than all the other A-engines - the 318, even going back to the 1950s, was always 3.9." Why ? Small bores are easier to clean up for emissions. Speaking of bores, the roundness is held to a maximum of 0.00015", and taper to 0.0006" - virtually race engine specs.
Deck height is 9.09", compared to 9.60 for the ol' LA mill. As a even more profound indicator of jest how new the new design really is, even the offset of the left hand cylinder bank was reduced.
Like the LA-based V10, the 287 doesn't use individual main-bearing caps. Instead, what Chrysler calls a 'bedplate' (girdle to us old hotrodders) clamps all five mains at once, adding rigidity while reducing noise and vibration. The bedplate is high-tech even to the material - compacted graphite iron. It is sealed to the block with the old standby: RTV silicone sealer. Incidentally, this bedplate is such a beefy piece that disassembly is almost like "splitting the cases" on a motorcycle engine.
The crankshaft is nodular cast iron, hardened and microfinished. A one piece rear main seal, similar to the 2.2L
design, seals to the outside of the 100 mm o.d. rear flange, which is an 8 bolt, one-offset pattern, in Chrysler performance tradition. Main journals are 2.5" diameter, identical to the 318/340 (the 360 is 2.81"), and are crossdrilled. Rod journals are 2.0", 1/8" smaller than the 318's 2.125. All journals have rolled fillets, a significant step taken, in the best racing engines, to prevent stress cracks from forming. Balance is better than 18 gm/cm, and torsional vibrations are looked after by a modern 3 spoke-style snout dampener, with most of the weight placed where it will do the most good - at the outer diameter.
The stroke is 3.405", a shade longer than the 273-340 was at 3.31, but shorter than the 360's 3.58. Still we'd call it a 'short stroke' engine. Looking briefly at the block, there is room for some stroke increase. Having the cam out of the way helps a lot.
Carrying on a performance small-block tradition begun with the 1968 340, all bearings are bi-metal Federal Mogul aluminum alloy. As in all production small blocks, only the upper half of the mains are grooved. Unlike the previous smallblock, however, thrust isn't taken by a lip on #3 main. Instead, two (front and rear) separate 180-degree thrust bearing/washers float on the top half of the usual (for Mopar) #3 main journal.
Connecting rods. Yes! The long-rod Mopar tradition continues. The 6.12" length, same as all LA engines have always been, puts rod/stroke ratio at a very favorable 1.80, better than the current 360, and only a shade worse than the 273-340.
But the traditional forged steel rod is gone. Now you'll find powder-forged metal cracked rods [until model year 2008, when they switched to 36MnVS4 forged steel - thanks, Chris]. In this process, first used by Chrysler in the 2.0L SOHC Neon engine, the rods are produced and machined in one piece. Then the caps are literally cracked off, guillotined if you will, resulting in an absolutely perfect mating surface that almost lock together, preventing cap walk. Fasteners are hardened M9 capscrews threaded directly into the rod, no nuts are used. Rod weight is 556 grams, compared to 726 to 758 grams for various production LA-engine rods. 0.945" wrist pins, weighing in at 143 grams, are press-fit in the rods.
Compression ratio is "blueprint" (and advertised) at 9.5:1, and typically measures 9.0:1 [starting in the 2006 model year, the advertised compression was 9.0:1; the 2005 figure may have been an error]. Regular (87) fuel is recommended. The design allows for high-compression domed pistons in the future [these were used on the high output version.]
Pistons are cast aluminum, have moly coated skirts for break-in scuff resistance, and weigh 366 grams. They are fitted at 0.0008-0.0020" skirt clearance - rather snug but nothing unusual for a street engine. The usual 3-groove ring pack is used (.062/.062/.120") but in addition to the common plasma-moly-filled top rings, the second ring is chrome. Oil rings are chrome as well, with a stainless expander. Bucking the current trend, the oil ring tension is rather high (12 lbs) allowing good oil control even in high-mileage engines. In fact, the spec for the 95th percentile customer is 150,000 mile useful life.
In the never ending quest to reduce emissions, the distance from the top ring groove to the top of the piston has been reduced to only 1/8th of an inch, making these areas susceptible to excess wear and heat. To combat this, the top ring land, and the area from the land to the head, are hard anodized.
No oversized pistons are available, and the replacement pistons/rods are supplied only as an assembly. Can you say aftermarket?
The oiling system isn't radical, using a clever design first seen on the AMC V8s: the georotor-type pump is mounted in the timing cover, and is driven off the crank snout. Direct drive, unlike the current LA engine, which, if you think about it, is a nightmare. The oil pump drive torque comes off the crank nose, through the chain, to the cam, back through the full length of the cam, through a bevel gearset to the intermediate shaft, and then through a hexagonal drive to the pump itself. Whew! Can you say, simplified?
The new, block mounted pump has a 75 psi relief valve, and a displacement of around one cubic inch per revolution. The oil pan is stamped steel, includes a windage tray (integral with the pan gasket) and has a capacity of 5 quarts plus one in the filter. Pump clearances are designed for the recommended 5W30 oil [this appears to have changed to 5W20, probably with the 2008 model year].
Topside - 4.7 liter "Next Generation" Heads
They are Chrysler's first real production light-alloy V8 cylinder heads. Semi-permanent mold aluminum castings, the heads break no new ground but are nonetheless state-of-the-art. Head bolts are 11mm, but the meat is there for a future upgrade to a performance version 12mm. The head bolt pattern is the same for each cylinder (and almost perfectly square at 4.00 x 4.10"), and retains the traditional LA 10 bolt per head arrangement. A super quality 3 layer laminated stainless steel gasket seals the deal. The heads are 'handed' - ie. not interchangeable side to side, mostly because the ports are in a different order left to right.
The intake valves are 1.89", and the exhausts are 1.46," in keeping with the latest Detroit theories regarding Intake:Exhaust valve diameter ratio. With the intake splayed at 13 degrees, the 64cc combustion chamber is approximately hemispherical in shape.
Typical Mopar 3-groove, flash-chromed stems, hardened tips, and a length of 4.45" gives you an idea of the valve package - nothing radical, but a generous intake size for the displacement. Guides are press-in, and the stem diameter is approximately 9/32" - even smaller than the 5/16" used on Hemis and Magnum V8s. This is obviously to improve flow and reduce friction.
Springs are moderate, but adequate, given the 6,000 RPM fuel shutoff point. But the valve actuation - that is something else again. Gone are the pushrods. A head mounted camshaft on each cylinder head operates the valves through a set of needle bearing roller rocker arms, with opposite-end hydraulic lash adjusters acting as the fulcrum, a system not unfamiliar to anyone who's ever played with an 1988 or newer Trenton I-4 (2.2 or 2.5L
). But looky here, the Intake and Exhaust rockers are opposite each other. Yup, it's almost a Hemi.
The cams are each driven by a separate chain, each of which are driven off an idler, in the approximate location of the ol' LA's cam sprocket. This idler sprocket, in turn, is driven from the crank in typical pushrod practice timing set fashion. The camshafts themselves are radical - although not in lift or duration. These are truck engines, after all: 0.443" lift on the intake, and 0.429" on the exhaust, duration is 244 degrees intake, 254 on the exhaust, partially compensating for the smallish exhaust valves. Overlap is only 18 degrees. This is an emissions and torque motor, remember.
What makes the cams radical isn't the timing, but the construction. They are hollow steel tubes with the individual lobes, of powdered metal, sinter-bonded in place. In fact, the cams, being hollow, are used to bring oil to the intake lobes, which have oiling holes. Cam (valve) covers are cast magnesium.
The ports are 1.86 square inches at the port face, and the injectors are mounted to the port in the head, not the intake manifold, which as we shall see, is made of polymer.
Speaking of intakes, this is another cool deal - literally. Following in the footsteps of 'little cousin 2.0 SOHC
,' the manifold is a one piece glass filled nylon thingie. With a lengthwise plenum and 8 cross-over ram-type ports, it's quite a shock, especially if you are used to LD-340s and M-1s. Runner length (in manifold only) is 20 inches, and there's quite a bit of port length in the heads, so the mill clearly isn't designed for 8,500 RPM passes. But the all-plastic construction should go a long way toward keeping charge-air temperatures down, aiding HP production.
Up top, a single bore, side draft throttle body measures 2.56" diameter. If that sounds small, remember that a medium sized Holley 4-barrel has typically bores of 1.625." Doing the math, that computes to 8.3 square inches for the carb, and 5.1 square inches for the EFI throttle body. But remember that the carb has to pass the air around not only the throttle blades, but through the much smaller - and more restrictive - venturis. We're willing to bet that this throttle assembly passes about as much air as a 600 CFM carburetor ! Not bad for a 287-inch powerplant, eh ?
Exhaust manifolds appear to be logs, especially in the initial Jeep version (We expect the Dodge truck ones to be better.) But they are, in reality, individually ported, and not nearly as bad as they look. Heat shield over them is super high-tech - aluminum core with stainless on each side.
There are two interesting electronics-related details worth noting. First, this engine has coil-on-plug ignition. No plug wires, a separate ignition coil mounts to each plug. This something all us guys with headers and toasted plug wires can really appreciate.
Even wilder is the absence of a throttle cable - it's fly by wire, dudes. All you're doing when you mash the 'gas' is sending a signal to the computer, which will, hopefully, respond faster than "All ahead full....aye, aye, captain."
This is roughly what Chrysler told us about the first generation
The 4.7 has slightly more power than the 318. It produces 30% less pollution, and makes less noise, with less vibration. Fuel economy is 7% better with the new four-speed automatic. The engine has more pulling power, faster initial acceleration, and three miles per gallon better economy than the 318 did.
The 4.7 has a cast iron block and two cast aluminum cylinder heads with a single overhead camshaft per bank and two valves per cylinder. The small bore helped reduce overall length of the engine.
Breathing features include a new tuned-length runner intake manifold, free-flowing intake and exhaust ports and fast-burn combustion chambers.
Aluminum cylinder heads, a hollow camshaft with sintered steel lobes, magnesium valve covers and a molded composite intake manifold contribute to an overall weight reduction of 54 pounds (24 kg) compared to the previous 5.2-liter engine.
Driveability is enhanced by variable fuel injection timing, sequential multi-port injection, a quick-sensing inlet-side positioned thermostat and coil-on-plug ignition, in which each individual spark plug has its own secondary ignition coil.
To improve fuel economy, the new engine features a patented hybrid cooling fan system that combines in-line electric and engine-driven fans. This system allows the engine fan to idle at a very low speed (250-300 rpm. vs. the typical 650-700 rpm.), decreasing noise and vibration at idle and low speeds. The cooling system reduces power consumption by 12 percent (6 bhp/4.5 kW).
The new coil-on-plug ignition system, two-stage chain cam drive with automatic tensioners, premium gaskets and cylinder head mounted fuel injectors are a few of the basic design features that provide for a greatly increased engine life. The engine is designed to operate 150,000 miles (240,000 km) under normal conditions with only normal maintenance. A new automatic serpentine belt tensioner increases the average accessory belt life to 100,000 miles (160,000 km).
Specifications: first and second generations 4.7 liter Chrysler V8 engine
Common to both generations:
- Displacement: 287 cu. in. (4701 cu. cm)
- Bore x Stroke: 3.66 x 3.40 (93.0 x 86.5)
- Valve System: Chain driven, SOHC, 16 valves, hydraulic end-pivot roller rockers
- Fuel Injection: Sequential, multi-port, electronic, returnless
- Construction: Compacted Graphite Iron bedplate, cast-iron block, aluminum alloy heads
- Fuel Requirement: E85 (Ethanol) or Unleaded regular, 87 octane (R+M)/2
- Oil Capacity: 6 qt. (5.7L)
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