WORK 1 : MEMORANDUM PHASE 3: COMPRESSION TEST ANSWERS QUESTION ANSWER MARK What is engine It is the pressure that is up in the cylinder, √ compression and during compression stroke. During compression 4 √ how does it work? stroke, both valves are closed; The ascending piston forces the air in the cylinder into a smaller space, thereby compressing it. √√ What might the If the compression pressure is too low or high this effect be of low and will lead to a loss of power, pre-ignition, √, √ high compression in misfiring√ or even non-starting of the engine. 4 √ an engine? When should the Only once the engine has reached normal operating compression be temperature. To allow for expansion of the parts, √ √ checked in an otherwise we get a lower reading. 4 √√ engine and why? State the TWO Dry compression test and a √ compression tests Wet compression test √ carried out on petrol 2 engines. What is the purpose To help seal compression rings on the pistons 2 √ of squirting oil in the in the cylinders √ cylinders? (If the pressure remains the same it means that pressure is either escaping pass the valves or head gasket, if it increases it means that pressure is being lost pass the piston rings.) TOTAL: Compression test questions 16 WORK SHEET 2 : MEMORANDUM 3: COMPRESSION TEST PROCEDURE ANSWERS PROCEDURE REASON MARK
WORK 1 : MEMORANDUM PHASE 3: COMPRESSION TEST ANSWERS QUESTION ANSWER MARK What is engine compression and how does it work? It is the pressure that is up in the cylinder, √ during compression stroke. √ During compression stroke, both valves are closed; The ascending piston forces the air in the cylinder into a smaller space, thereby compressing it. √√ 4 What might the effect be of low and high compression in an engine? If the compression pressure is too low or high this will lead to a loss of power, √, pre-ignition, √ misfiring√ or even non-starting of the engine. √ 4 When should the compression be checked in an engine and why? Only once the engine has reached normal operating temperature. √ √ To allow for expansion of the parts, otherwise we get a lower reading. √√ 4 State the TWO compression tests carried out on petrol engines. Dry compression test √ and a Wet compression test √ 2 What is the purpose of squirting oil in the cylinders? To help seal √ compression rings on the pistons in the cylinders √ (If the pressure remains the same it means that pressure is either escaping pass the valves or head gasket, if it increases it means that pressure is being lost pass the piston rings.) 2 TOTAL: Compression test questions 16 WORK SHEET 2 : MEMORANDUM 3: COMPRESSION TEST PROCEDURE ANSWERS PROCEDURE REASON MARK
PAT%20Phase%203%20MEMORANDUM%202015.docx