Description

Engine

Description

General
The KV6 is of all aluminum construction, with a 90° V configuration. The KV6 uses long cylinder head bolts engaging in threads 70 mm below the mating face of the cylinder block to attach the cylinder head to the cylinder block. This ensures sufficient structural stiffness to take advantage of the compressive strength of aluminum alloy and minimize tensile loadings. There are 8 cylinder head bolts for each cylinder head, located below the camshafts.

The engine features 24 valves, sequential fuel injection, liquid cooling and is transverse mounted. It is controlled by a Siemens engine management system utilizing a range of sensors to constantly monitor and optimize engine performance.

Cylinder Block Components
The cylinder block components are described below

Cylinder Block and Main Bearing Ladder
The cylinder block is constructed of an aluminum alloy and is cast in three sections,
^ Cylinder block.
^ Main bearing ladder.
^ Lower crankcase extension.

For strength and rigidity, the main bearing ladder is manufactured from special alloy A357TF as used in manufacturing components in the aerospace industry. The main bearing ladder is secured to the cylinder block with 16 bolts, thus creating a very rigid crankcase 'box'. A separate outer crankcase extension adds further strength to the lower end of the cylinder block. The lower crankcase extension is sealed to the underside of the cylinder block, using jointing compound, and secured with 10 bolts. Fitted to the lower crankcase is an aluminum alloy sump.

Pistons and Cylinder Liners
The aluminum alloy, thermal expansion, lightweight pistons, with semi-floating gudgeon pins, are offset to the thrust side and are carried on forged steel connecting rods. Pistons and cylinder liners are supplied in two grades, 'A' and 'B' and are also color coded to assist identification, The pistons are marked to ensure they are correctly oriented in the cylinder liner, the 'FRONT' mark should be toward the front of the engine.

The cylinder block is fitted with 'damp' cylinder liners, the bottom stepped half of the cylinder liner being a sliding fit into the lower part of the cylinder block. The liners are sealed in the block with a bead of sealant applied around the stepped portion of the cylinder liner. The top of the cylinder liner is sealed by a multi-layer steel cylinder head gasket when the cylinder head is fitted.

The cylinder liner diameters are smaller than the big-end forging of the connecting rods and need to be removed complete with pistons and connecting rods from the cylinder block.

Connecting Rods
The KV6 engine utilizes forged steel H-sectioned connecting rods, with the gudgeon pin being an interference fit in the small end of the connecting rod. The big-ends are horizontally split.

Big-end bearing diametric clearance is controlled by selective bearing shells with three grades of thickness. The big-end upper and lower bearing shells are plain with locating tags.

Piston Rings
Each piston is fitted with two compression rings and an oil control ring. The top compression rings are chromeplated steel. The 2nd compression rings are chrome-plated cast iron. The oil control rings have stainless steel top and bottom rails and integral expander rings.

Crankshaft, Sump and Oil Pump Components
The crankshaft and sump components are described below:

Crankshaft
The short, stiff crankshaft is supported on four main bearings, with each pair of crankpins mutually offset by 30' to give equal firing intervals. Cast in Spheroidal Graphite (SG) iron, the crankshaft has cold rolled fillets on all journals, except the outer mains, for toughness and failure resistance. End-float is controlled by thrust washer halves at the top and bottom of the rear main bearing.

Main Bearings
Oil grooves are provided in the upper halves of all the main bearing shells to supply oil, via drillings in the crankshaft, to the connecting rod big-end bearings. The lower halves of the bearing shells in the bearing ladder are plain.

Sump
The cast aluminum sump is a wet-type, sealed to the lower crankcase extension using sealant applied to the sump flange. The sump is fixed to the lower crankcase extension using 10 bolts. A baffle plate is fitted in the lower crankcase extension to minimize the effects of oil slosh.

An oil pick-up with integral strainer is located in the center of the sump oil well, as a source for the supply of engine lubrication oil to the oil pump. Oil is sucked up though the end of the pick-up and strained to prevent solid matter from entering the oil pump.

Oil Pump
The oil pump is directly driven from the crankshaft. The oil pump housing includes the oil pressure relief valve, oil filter, oil pressure switch and return/supply outlets for the engine oil cooler.

Oil Filter
A full-flow, disposable canister-type oil filter is attached to the oil pump housing at the front of the engine.

Oil Cooler
A liquid cooled oil cooler keeps the engine lubrication oil cool, under heavy loads and high ambient temperatures.

The oil cooler is cooled by the engine cooling system and attached to a bracket secured to the front of the sump by three bolts. Oil is delivered to and from the oil cooler through hoses connected to the oil pump housing. Hoses from the engine cooling system are connected to two pipes on the oil cooler for the supply and return of coolant.

Oil Pressure Switch
The oil pressure switch is located in a port at the outlet side of the oil filter. It detects when a safe operating pressure has been reached during engine starting and initiates the illumination of a warning light in the instrument pack if the oil pressure drops below a given value.

Cylinder Head Components
The cylinder head components are described below

Cylinder Head
The cross-flow cylinder heads are based on a four valve, central spark plug combustion chamber, with the inlet ports designed to induce swirl and control the speed of the induction charge. This serves to improve combustion and hence fuel economy, performance and exhaust emissions.

LH and RH cylinder heads are identical castings.

Camshafts
Twin camshafts on each cylinder bank are retained by a camshaft carrier, line bored with the cylinder head. The camshafts are located by a flange which also controls end-float. A crossover drive for the exhaust camshaft, from the rear of the inlet camshaft is by a short toothed belt, which allows for a much shorter and simpler run for the main camshaft drive belt at the front of the engine.

The exhaust camshaft drive gears have dampers integral with the gear to minimize torsional vibration. The inlet camshaft for the LH cylinder head incorporates a reluctor which is used in conjunction with the Camshaft Position (CMP) sensor to measure engine position. The CMP sensor is bolted to the LH camshaft cover.

Cylinder Head Gasket
The KV6 utilizes a multi-layer stainless steel cylinder head gasket. The gasket comprises four stainless steel functional layers, and a stainless steel distance layer to maintain fitted thickness. A full embossment profile is employed to seal the combustion gases and half embossments are used to provide a durable fluid seal. Sealing characteristics are further enhanced by the application of a fluro-elastomer surface coating to all layers of the gasket.

Hydraulic Tappets
Self-adjusting, lightweight, hydraulic tappets are fitted on top of each valve and are operated directly by the camshaft. The valve stem oil seals are molded onto a metal base which also acts as the valve spring seat on the cylinder head.

Valves
The exhaust valves are of the carbon break type. A machined profile on the valve stem removes any build up of carbon in the combustion chamber end of the valve guide. All valve seats are machined in three planes, improving valve to seat sealing.

Camshaft Cover and Engine Cover Components
The camshaft cover and engine cover components are described below

Acoustic Cover
A molded plastic acoustic cover is fitted over the engine to absorb engine generated noise. Foam is bonded on the inside surface of the acoustic cover and a rubber seal is fitted around the oil filler cap.

The acoustic cover is located on the engine by two rubber studs on the underside of the acoustic cover. A rubber strap, at the rear of the engine, and two quick release fasteners, at the front of the acoustic cover, secure the acoustic cover in position.

Resonators and part of the engine intake duct are integrated into the acoustic cover, and the engine air filter is installed in a compartment below a lid secured with two Torx bolts.

In NAS markets, a metal foil heatshield is installed on the underside of the acoustic cover.

A rubber duct connects the engine intake duct in the acoustic cover to the RH inner wing. In all except NAS markets, engine air is drawn from the space between the inner and outer wings. In NAS markets, a further duct is installed between the inner and outer wings to draw engine air from the base of the A post.

Throttle Body Assembly
All markets except NAS

The throttle body is attached to the inlet manifold chamber and comes in one of two variants, with and without cruise control. The housing of the throttle body incorporates ports for crankcase ventilation and the idle air control valve.

NAS markets
The throttle body is an electrically actuated unit controlled by the Engine Control Module (ECM). The position of the throttle plate is controlled by a DC motor and a return spring integrated into the throttle body. Two feedback potentiometers supply throttle plate position signals to the ECM for closed loop control.

Four Torx bolts secure the throttle body to the inlet manifold chamber. A rubber seal, keyed to a groove in the inlet manifold chamber, ensures the joint is air tight.

Inlet Manifold Chamber
The inlet manifold chamber is a sealed plastic assembly. The inlet manifold chamber combines plenum resonance for good low speed torque, with variable length primary tracts for optimum mid and high speed torque.

The throttle body assembly feeds into a 'Y' piece which separates into two secondary inlet pipes. The secondary pipes feed into two main plenums, one for each bank of three cylinders. At the closed end of the plenums is a balance valve, controlled by an electric actuator, that connects the two plenums together.

The variable intake system uses valves and actuators to vary the overall tract length of the inlet manifold chamber. The aluminum alloy inlet manifolds are sealed to each cylinder head with gaskets and to the inlet manifold chamber with 'O' rings and seals.