6.4L HEMI V8 engine (ESG: 2011-on)

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Introduction

Chrysler’s ESG engine was a 6.4-litre V8 petrol engine that was produced from 2012 and powered vehicles such as the Chrysler LX2 300 SRT8and Jeep WK2 Grand Cherokee SRT8 (see table below). Manufactured at Chrysler’s Saltillo Engine plant in Ramos Arizpe, Mexico, key features of the 6.4L HEMI V8 engine included its:

• Deep-skirt, grey cast-iron block with a 90-degree ‘V’ and open-deck design;
• Forged micro-alloy steel crankshaft;
• Cast aluminium alloy pistons;
• Cast aluminium alloy cylinder head;
• 2 valves per cylinder actuated by pushrods;
• Variable cam timing;
• Multi-Displacement System (i.e. cylinder deactivation);
• Compression ratio of 10.9:1;
• Two spark plugs per cylinder; and,
• Electronically-limited maximum engine speed of 6400 rpm (for theChrysler 300 SRT8).

The ESG engine had a mass of 252 kg.

Compared to the 6.1L HEMI V8 engine (code: ESF) in which it was based, changes for the 6.4L HEMI V8 engine included its:

• Higher compression ratio (10.9:1 compared to 10.3:1);
• Larger intake and exhaust valves;
• Increased valve lift;
• Plastic intake manifold;
• Variable length intake manifold;
• Variable cam timing; and,
• Multi-Displacement System.

Key objectives in the development of the ESG engine included greater low-rev torque and enhanced volumetric efficiency.

For simplicity, this engine will refer to the ESG engine as the 6.4L HEMI V8 engine. However, it is also understood that the 6.4L HEMI V8 engine was also referred to by the code name ‘Apache’.
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Block

The 6.4L HEMI V8 engine had a deep-skirt, grey cast-iron block; while the iron was of a higher strength than that in the post-2009 5.7L EZD HEMI V8 engine, it is unclear if was the same 5037388AB casting as the 6.1L HEMI V8 engine which it effectively replaced. The open-deck block had large deck surface openings for easy sand removal after casting since the block did not have core plugs (to prevent coolant leaks). The 6.4L HEMI V8 engine had 103.9 mm bores (0.4 mm larger than the 6.1L HEMI V8 engine) that were spaced at 113.3 mm intervals and a 94.6 mm stroke (3.7 mm longer than the 6.1L HEMI V8 engine) for a capacity of 6416 cc. The cylinder banks formed a 90 degree ‘V’ angle and had a 22.4 mm offset.

It is understood that the front cover of the 6.4L HEMI V8 engine was made from die-cast A380 aluminium and sealed the front of the block and sump; the alternator, water pump, air-conditioning compressor, power steering pump and belt idler were all mounted on the cover.

Crankshaft

The crankshaft for the 6.4L HEMI V8 engine was forged from micro-alloy steel and fillet rolled with a 1950 kg rolling load. The crankshaft was supported by five tri-metal main bearings, each of which had four bolts (two vertical and two horizontal). Furthermore, the main bearing caps were made from powder metal and cross-bolted with a single M8 bolt each side.

For the 6.4L HEMI V8 engine, the crankshaft had four bolt holes in a circular pattern for the crank sensor that was located behind the last counterweight. However, Chrysler did not supply crank sensors separately because the crankshaft was balanced with the sensor on it and Chrysler claimed that balance would be adversely affected if the crank sensor was changed. Owners therefore had to purchase a new crankshaft (with sensor) if the original sensor failed.

The main crankshaft journals had a 65 mm diameter, while the small-end journals had a 54 mm diameter. Furthermore, a vibration damper was press-fitted on the nose of the crankshaft.

Fitted to the crankshaft were powdered metal forged connecting rods that were 157.5 mm long.

Connecting rods

The connecting rods were manufactured from powdered metal and had cracked big-ends. Each connecting rod was 157.5 mm long and attached to the piston by fully floating piston pin which had a diameter of 24 mm.

Pistons

The 6.4L HEMI V8 engine had cast aluminium pistons which had two compression rings and an oil control ring to reduce friction. Piston cooling jets were positioned in each cylinder to spray oil on the bottom of each piston to reduce surface temperatures and hot spots that could lead to pre-ignition. The pistons had a compression height of 30.75 mm (i.e. the distance between the centreline of the pin bore and the top of the piston).

Cylinder head

The high-flow cylinder heads for the 6.4L HEMI V8 engine were cast from A319F aluminium alloy, though modifications were made to the chemical composition of the alloy to improve high strength fatigue properties. During the casting process, special fine core sand (AFS 90) was used to provide the intake ports with the surface finish and air flow characteristics required for a performance engine.

The cylinder heads were mounted on a three-layer stainless steel gasket – which had a compressed thickness of 0.7 mm – and bolted to the block using M12 bolts around the bores and M8 bolts near the intake manifold.

Camshaft, pushrods and valves

For the 6.4L HEMI V8 engine, the high-strength, billet steel camshaft was positioned high in the cylinder block to minimise the length of the pushrods, though shorter pushrods were used for the intake valves relative to the exhaust valves. The pushrods actuated the rocker arms and the latter were fitted to a pair of shafts (one exhaust and the other intake) that were positioned in the cylinder head; each rocker shaft was supported by five pedestals.

The 6.4L HEMI V8 engine had two valves per cylinder with eight deactivating and eight conventional hydraulic lifters, all with roller followers. Specifications for the valves were as follows –

• Intake valve diameter: 54.3 mm (52.8 mm for the 6.1L HEMI V8 engine);
• Exhaust valve diameter: 42.0 mm (40.6 mm for the 6.1L HEMI V8 engine);
• Intake valve lift: 15.0 mm (13.3 mm for the 6.1L HEMI V8 engine);
• Exhaust valve lift: 14.0 mm (13.0 mm for the 6.1L HEMI V8 engine); and,
• Included valve angle: 34.5 degrees (18 degrees on the intake and 16.5 degrees on the exhaust side).

For the 6.4L HEMI V8 engine, the intake valve stems were hollow and the exhaust valve stems were filled with sodium. When the exhaust valve became hot, the sodium would liquefy to transfer heat from the valve head to the valve guides via the ‘cocktail shaker’ effect induced by valve motion. As a result, the sodium-filled exhaust valves helped prevent hot spots in the combustion chamber and valve head and reduced the possibility of pre-ignition. The valve seats and valve guides were made from powdered metal.

The lifters were oiled via the pushrods whereby oil circulated:

• From the pump to the cam bearings; then,
• Up through the cylinder heads to the rocker shafts; and then,
• Through the rockers and down the pushrods to the lifters.

As a result, the oil passages in the valley of the engine block could be used to deactivate the MDS lifters. Furthermore, the pushrods provided a reservoir of oil to prevent lifter noise at start up.

For theChrysler 300 SRT8, maximum engine speed for the 6.4L HEMI V8 engine was 6400 rpm.

Variable camshaft timing (VCT)

The 6.4L HEMI V8 engine introduced variable camshaft timing via an Oil Control Valve (OCV), an electro-hydraulic pulse width modulated solenoid that was attached to the cylinder block behind the timing cover. The OCV controlled oil pressure to a camshaft phaser which was contained in the camshaft sprocket. For the 6.4L HEMI V8 engine, the camshaft could be varied by up to 37 degrees to retard the inlet and exhaust simultaneously.

The camshaft phaser had internal vanes and the OCV regulated oil flow to either side of the vanes so that the phaser could rotate and change the position of the camshaft. Since valve timing was in advanced position by default, the OCV values operated as follows:

• If the OCV was 0%, valve timing was advanced (default position);
• If the OCV was at 100%, valve timing was retarded; and,
• If the OCV was at 50%, there was no oil flow and valve timing was held constant.

At full load, variable cam timing sought to maximise the volumetric efficiency of the engine by getting as much air into the engine as possible. However, variable camshaft timing could also improve fuel economy by:

• Reducing the engine’s pumping work by closing the intake valve later;
• Increasing the expansion process of the combustion event – this allowed more work to be transferred to the crankshaft instead of being removed from the exhaust port as heat; and,
• Expanding the operating range of the Multi-Displacement System.

Multi-Displacement System (MDS)

Unlike the 6.1L HEMI V8 engine, the 6.4L HEMI V8 engine had a ‘Multi-Displacement System’ (MDS) which enabled the engine to switch from eight to four cylinder operation. The MDS system used a separate oil gallery in the valley of the block and four solenoids to apply pressure to the pins in the sides of the deactivating valve lifters in cylinders 1, 4, 6 and 7. Furthermore, the fuel injectors were shut off.

When disabled, the lifter body continued to go up and down, but the plunger inside the lifter remained stationary so that the valves stayed closed. The exhaust gases trapped in each cylinder were compressed on the compression and exhaust strokes so that they helped push the pistons back down on the intake and power strokes. The ECU could activate and deactivate the MDS solenoids in 40 milliseconds.

Induction

Whereas the 6.1L HEMI V8 engine had a cast aluminium intake manifold, the 6.4L HEMI V8 engine had a thermoplastic intake manifold for cooler intake air due to the plastic’s lower thermal conductivity.

Unlike the 6.1L HEMI V8, the 6.4L HEMI V8 engine also had an active intake system which could vary the length of the intake runners via a switchable flap. At low engine speeds, a longer intake runner was used to harness pressure waves and increase torque. At higher engine speeds, however, a shorter intake runner was used to reduce intake resistance.

The intake manifold had an 80 mm diameter, electronically controlled throttle body.

Injection and ignition

The 6.4L HEMI V8 engine was so-called because of its hemispherical combustion chambers which Chrysler promoted for its large valves, high air flow and centrally positioned spark plugs. However, the chambers were not truly hemispherical since there were squish areas on both sides of the combustion chamber.

The 6.4L HEMI V8 engine had electronically-controlled, sequential multi-port fuel injection and a compression ratio of 10.9:1 (compared to 10.3:1 for the 6.1L HEMI V8 engine). The 6.4L HEMI V8 engine was designed for premium unleaded petrol and the engine management system used dual knock sensors.

The HEMI V8 engine had distributorless, coil-on- plug ignition via two spark plugs per cylinder – according to Chrysler, the two spark plug design shortened flame travel for more consistent combustion and reduced emissions. Both spark plugs ignited at top dead centre and one was used before top dead centre to burn off the hydrocarbons, allowing the use of less restrictive catalytic converters.

Lubrication

The 6.4L HEMI V8 engine had a gerotor oil pump that was driven from the crankshaft nose with a 1:1 drive ratio such that oil flow was directly proportional to engine speed. To limit oil temperature increases during track use, an oil cooler was fitted.

The 6.4L HEMI V8 engine had a cast aluminium oil pan that was designed to provide ‘superior oil management characteristics’ and additional structural rigidity to the engine. The pan was designed with special channels, baffles and scrapers to help funnel engine oil back into the bottom of the pan and away from the crankshaft for increased power. Externally, strengthening ribs were cast into the oil pan for support.

An integral gasket and windage tray was fitted between the oil pan and engine block to reduce the amount of oil that came into contact with the crankshaft – this mitigated the possibility of power loss from engine oil aeration or oil sloshing during high ‘g’ driving conditions.

Oil change intervals were recommended at 9600 km under normal driving conditions. If the ECM detected frequent start/stop operation or the engine was running at high ambient temperatures for sustained amounts of time, an alert would advise the driver to change the oil at 4800 km.

Oil capacity was 6.6 litres (7 quarts) and 0W-40 synthetic oil was specified for the Chrysler 300 SRT8.

Exhaust

Generally, the 6.4L HEMI V8 engine had stainless steel headers that were designed to minimise exhaust gas back pressure, though the Jeep Grand Cherokee SRT-8 had a cast iron exhaust manifold due to packaging constraints. To promote better light off at the catalysts, the free-flowing exhaust headers had an inner and outer shell.

The Jeep WK2 Grand Cherokee SRT8, Chrysler 300 SRT8 and Dodge Charger SRT8 were fitted with an active exhaust system that featured a pressure-activated valve and reduced noise levels during operation of the Multi-Displacement System.

For emissions control, the 6.4L HEMI V8 engine had dual close-coupled three-way catalytic converters and four heated oxygen sensors. Upon its release, the 6.4L HEMI V8 engine complied with Euro IV emissions standards.