According to the illustrated polar timing...

Question 1 of 270705eccefa1bacbc34ba4d473d8

According to the illustrated polar timing diagram for a four- stroke cycle diesel engine, the exhaust valve is open for a duration of how many degrees of crank travel? See illustration MO-0084.

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Question 1 of 27070

According to the illustrated polar timing diagram for a four- stroke cycle diesel engine, the exhaust valve is open for a duration of how many degrees of crank travel? See illustration MO-0084.

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🔍 Key Concepts

• Identify which colored/hatched band on the polar diagram represents the exhaust valve open period (from opening to closing). • Remember that on a four-stroke engine, the crankshaft turns 720° for one full cycle, and exhaust typically begins before BDC and ends after TDC. • Add together the crank angle before BDC and after TDC during which the exhaust valve remains open, plus the 180° between BDC and TDC, if it stays open all the way through.

💭 Think About

• From the diagram, at what crank angle (in degrees) does the exhaust valve first start to open relative to BDC or TDC? • At what crank angle does the exhaust valve finally close relative to BDC or TDC? • If the exhaust stays open across BDC–TDC–BDC, how many degrees lie between those positions, and how do the given small lead and lag angles change that total duration?

✅ Before You Answer

• Be certain which arc (inner vs outer ring, and which color) corresponds to exhaust, not intake or fuel injection. • Confirm the direction of rotation shown by the arrow so you don’t reverse opening and closing points. • Add all relevant crank angles: opening lead + 180° sweep + closing lag (if the valve stays open over the full stroke).