The crankshaft gear drives the camshaft gears through idlers. Both camshafts must be timed to the crankshaft in order to get the correct relation between the piston and the valve movement.
The camshafts have three lobes for each cylinder. Two lobes operate the valves and one operates the fuel injector.
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| Illustration 1 | g00281786 |
Valve system components (1) Rocker arm (2) Bridge (3) Rotocoil (4) Valve spring (5) Pushrod (6) Lifter | |
As each camshaft turns, the lobes on the camshaft cause the lifters (6) to move up and down. This movement causes the pushrods (5) to move the rocker arms (1). The movement of each rocker arm will cause each bridge (2) to move downward on the dowels in the cylinder head. One bridge (2) will open two valves simultaneously. The valves can be either inlet valves or exhaust valves. There are two inlet valves and two exhaust valves for each cylinder.
The valve springs (4) cause the valves to close when the lifters move downward.
Rotocoils (3) are actuated by the movement of the rocker arm. This will cause the valves to turn while the engine is running. The rotation of the valves keeps the carbon deposits on the valves to a minimum which gives the valves a longer service life.