on direct injection in-line six diesel engines around 12 litres displacement but with entirely different fuel and valve systems when compared with previous Volvo engines. Built at the purpose-built facility at Skövde on a fully automated line where the bulk of the engine assembly is done by robots and the final engine dressing is carried out manually. The D12A was designed as a "world engine" to be able to meet the latest demands in high power output, low fuel consumption and lower emissions with its single OHC (overhead camshaft) design, four valves per cylinder, and one centrally located electronic unit injector, integrated engine compression brake and two-piece, steel and aluminium pistons. The engine design left the door open for future upgrades in both power output and emission technologies. VEB VEB The Volvo Engine Brake is a compression type engine brake first introduced on D12A and since used on later designed OHC engines from 9 to 16 litre displacement. The brake operates on a principle where exhaust valve cam followers act on a secondary cam profile when engine brake is activated. Engine oil pressure is used to eliminate extra valve clearance thus this action forces the follower against secondary lobes and unseating exhaust valves temporarily to achieve so-called compression bleeding as employed by similar systems from Jacobs, Cummins and Mack however Volvo system has an extra cam lobe thus giving two openings of the exhaust valves and is designed to work in conjunction with an exhaust brake so two of the engine's four strokes are used to raise engine braking effect - Exhaust and Compression strokes. Operation Description The exhaust stroke is used when exhaust brake shutter closes exhaust manifold after turbocharger opening as a result exhaust back pressure is raised creating the braking effect. The compression stroke is used next to utilise the backpressure in exhaust where at the piston's Bottom Dead Centre the exhaust valve is opened briefly and high pressure in the exhaust manifold is then let in acting against the piston moving upwards on its compression stroke thus slowing it even more [further explanation needed, exhaust braking functions in relation to cylinder pressure, not piston speed] and increasing the engine braking effect. At the end of the compression stroke just before piston's Top Dead Centre exhaust valves are open briefly again to release "bleed" compression thus again slowing the piston on its subsequent downwards movement and consequently