Engine Maintenance and Modification Bradley Artigue

FIAT 124 Spider
Engine Maintenance + Modification
Figure 41.1: Intake
Figure 41.2: Compression
Figure 41.3: Ignition
Figure 41.4: Exhaust
The diagrams above show the absolute end or beginning of each cycle. The duration of
time that the valves remain open and the timing of when each valve opens are
determined by the shape of lobes on the camshaft. On the FIAT DOHC there are two
camshafts, each with four lobes (one per valve, two banks (intake and exhaust)). The
camshaft lobes move through the four phases for each 90 degrees of rotation. In a
DOHC engine the opposite camshaft is in the same position and having the opposite
action; in other words, when the intake camshaft is in the intake position the exhaust
camshaft would be at the same angle, performing no action on the exhaust valve.
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