Engine - L Series (Description): Description and operation

DESCRIPTION

The ’ L’ Series 2.0 litre engine is a 4 cylinder, in-line, direct diesel engine having 2 valves per cylinder operated by a single overhead camshaft. A cast iron cylinder block incorporates direct bored cylinders, each pair of cylinders being strategicly positioned in the cylinder block to reduce engine length and give good structural rigidity.

An alloy camshaft carrier is bolted directly to the alloy cylinder head, the camshaft bearing journals are line bored between the two components. The camshaft operates the valves via hydraulic tappets, the camshaft gear, which incorporates a tortional damper, is driven by an internally toothed drive belt by a gear on the front of the crankshaft. Belt tension is achieved by means of a semi-automatic tensioner and an idler pulley is also fitted. A gear on the rear end of the camshaft drives the fuel injection pump belt.

A single spring is fitted to each valve, the valve stem oil seals are moulded onto a metal base which also forms the valve spring seat on the cylinder head. The valve stems run in guides pressed into the cylinder head.

The aluminium alloy, graphite coated pistons are fitted with two compression and an oil control ring, the top ring is located in a steel insert which helps to provide a minimal reaction to compression forces. The piston crowns are domed in the centre, the combustion chamber being formed in a bowl around the dome. Fully floating gudgeon pins retain the pistons to the connecting rods, the pins are offset towards the thrust side of the pistons and are secured in the pistons by circlips.

Oil squirt jets, located in the cylinder block provide additional piston cooling and gudgeon pin lubrication. Plain big-end bearing shells without location tags are fitted, with the connecting rod bearing caps being retained by flange headed bolts to the connecting rods. The big-end has a ’Fracture Split’ joint between the connecting rod and bearing cap. The connecting rod to bearing cap has no identification marks, therefore, to prevent incorrect fitment of the bearing cap to connecting rod, the bolts are off-set by 1mm.

The crankshaft runs in 5 main bearings, grooved bearing shells are fitted in the cylinder block with plain bearing shells in each main bearing cap. Positive location of each main bearing cap is by means of hollow dowels. Crankshaft end-float is controlled by single size thrust washers, located each side of the centre - (Number 3) main bearing in the cylinder block. The crankshaft front oil seal is located in the oil pump body whilst the rear oil seal is integral with a housing bolted to the rear of the cylinder block. Additional oil sealing is provided by RTV sealant injected into grooves and along the joint lines of the front main - (Number 1) bearing cap and the crankshaft rear oil seal.

A rotor type oil pump is driven from the front of the crankshaft, the pump is sealed to the cylinder block with a gasket.

The cast alloy sump is bolted to the cylinder block and rear main bearing cap and is sealed to the block with a rubber gasket which incorporates location lugs for the block and sump. Compression limiters in the bolt holes prevent distortion of the gasket.