🔍 Key Concepts
• Operation sequence of a four-stroke diesel engine (intake, compression, power, exhaust)
• Functions located in an air start cylinder head (starting air valve, fuel valve/injector, exhaust valve, possibly indicator cocks or reliefs)
• Difference between reversing the engine and normal running timing events (ahead vs astern)
💭 Think About
• List all the things on the cylinder head whose timing must be controlled by a cam (not just that they exist). How many different motions or events need correct timing?
• Think about which events must occur for BOTH ahead and astern rotation on a direct reversible engine. Does reversing change how many separate cam events you must manage?
• For each valve or device (fuel, exhaust, starting air, etc.), ask: is the timing the same in both directions, or does the camshaft need separate lobes/events for ahead and astern?
✅ Before You Answer
• Be clear which parts are actually cam-operated and which are not (e.g., fuel pump vs injector, starting air valve actuation).
• Count timing events, not just the number of physical valves. One valve can require more than one cam event on a reversible engine.
• Verify that you’ve accounted for both ahead and astern timing where separate cam lobes are required.