Auto mechanics Paper 2 WASSCE (PC 2ND), 2018

Question 1

 

(1)        The sketch below shows a type of engine

(a)        What is the name of the working cycle of the engine?
(b)        Name the parts labelled W, X,  Y and Z.
(c)        Explain the function of each of the parts labelled W, X, and Z.

 

Observation

 

This question attracted most of the candidates.  This may be due to primacy effect as it was the first question. However their performance was not encouraging as they could not provide the required responses to the various parts of the questions. The required responses the candidates were expected to give are:
 (a) Two stroke cycle, two stroke engine, valveless engine or three-port engine 
                                                                                                           
 (b) W        -           Transfer port
    X         -           Deflector, deflector crown or deflector hump
    Y         -           Exhaust port or outlet port
    Z         -           Inlet port or intake port                        
                                                   
        (c)  W  -   Transfer port is the passage through which the mixture or charge is  
transferred from the crankcase to the top of the cylinder or combustion chamber.           
                                                                                                           

 

                                               
X  -  This is the deflector. Its purpose is to:

  • direct the incoming mixture upwards;
  •  reduce mixture loss through the exhaust port.

OR

  •  prevent the new charge from passing out;
  •  assist the expulsion of burnt gases.

                                            

Z -  Inlet port is the passage through which fresh mixture or charge flows
into the crankcase.