me 2602 motor vehicle technology

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U N I V E R S I T Y O F M O R A T U W AFACULTY OF ENGINEERING

DEPARTMENT OF MECHANICAL ENGINEERINGB.SC. ENGINEERING

S EM E S T E R 3 E XAM I N A T I O N 2011(09 B A T C H )M E 2602:MOT O R V E H I C L E T E C H N O L O G Y

Time Allowed: 2 hours March 2011A D D I T I O N A L M A T E R I A L : No additional material is required.

I N S T R U C T I O N S TO C A N D I D A T E : This paper contains 6 questions and 5 pages including this sheet. Answer any F I V E Q U E S T I O N S . A l l questions carry equal marks. Use neat sketches wherever necessary to clarify your answers. This is a closed book examination. This examination accounts for 70% of module assessment. The total maximum mark

attainable is 100. W R I T E Y O U R I N D E X N U M B E R , T H E M O D U L E C O D E AND T H E T I T L E of

the paper in the answer book. Also write your index number on each additional sheet orbook attached.

Assume reasonable values for any data not given in or wi th the examination paper.Clearly state such assumptions made in the script. I f you have any doubt as to the interpretation of the wording of a question, make your

own decision, but clearly state it in the script. Read al l questions first before attempting to answer.

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Question 1

Sketch a standard conventional igni t ion system of a spark igni t ion engine, and brief ly explainthe function o f ;(a) The capacitor that is connected across the contact breaker points [6 marks](b) The centrifugal/flyweight governor in the distributor system [7 marks](c) The inlet manifold vacuum operated diaphragm, that is connected to the plate on

which the contact breaker points are mounted. [7 marks]

Question 2(a) Write short technical notes on how the design o f the combustion chamber in a spark

igni t ion engine influences;( i ) The thermal efficiency of the engine( i i ) The pollutant hydrocarbon emissions through the exhaust manifold( i i i ) The intensity of "detonation" i f it does occur.

[10 marks]

(b) Derive an expression which w i l l enable the compression curve of a spark igni t ionengine to be determined in terms of known and measurable quantities, without the useo f combustion charts.

[10 marks]

Question 3(a) Write a brief technical note on "direct and indirect injection" in compression igni t ion

engines, highlighting the reasons why engine designers take pride in advertising thattheir engine is of direct injection type. Br ie f ly comment on the designs they adopt tomaintain direct injection. [10 marks]

(b) A direct injection, four stroke compression igni t ion engine whose design speed is4000 rpm has a compression ratio of 18:1. The combustion chamber is in the form of acylindrical recess in the piston. The bore and stroke are 150 mm and 180 mmrespectively. At TDC the clearance between the piston crown and the f lat cylinderhead is 1 mm. The diameter of the cylindrical recess in the piston is 75 mm. Theinjector is centrally placed and has 5 equispaced orifices. Injection commences 25degrees before TDC and continues for a period o f 30 crankshaft degrees. Determinethe swi r l rpm that should be induced during suction stroke for proper combustion totake place. [10 marks]

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Question 4(a) A typical Ackermann steering linkage is shown in the figure Q4(a). In order to satisfy

conditions for true ro l l i ng , Show that

Rof , 2aba + +tan a I sin a

b ^ + ( c -a )

Where, Rof is path of outer front wheel wi t h respect to point O.[10 marks]

(b) Explain the operation of the cam and lever steering system shown in the figure Q4(b).[10 marks]

HELICAL GROOVE

BEARINGDROP-ARM SP1LEVER

SPUMED JOINT

PIN PROJECTED IN GROOVESTEERINGSHAFT

^-COLUMNEAWM6

WtSHfR FOR PLAY

ASIKfc0R0P ARM

Figure Q4(b)

ME 2602 Page 4 of 5


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Question 5

(a) Explain what is meant by;( i) spring rate( i i ) sprung weight( i i i ) unsprung weightassociated with automobile suspension systems. [6 marks]

(b) Describe three types of springs used for suspension of an automobile. [6 marks](c) What are the advantages o f having front independent suspension? Wi t h the aid of a

neat sketch of a typical independent front suspension explain the functions performed

(a) Explain wi th the aid of a sketch the working principle of the master cylinder of ahydraulic brake system. What w i l l happen i f there is a leak in one o f the brake lines?

[6 marks](b) Draw a graph illustrating the variation of the deceleration o f a motor vehicle wi th time

starting from the moment the driver reacts unt i l the vehicle comes to a complete stop.Indicate on the graph main instances and the relevant time periods/distances.

[6 marks](c) Explain br ief ly the functions of;

( i ) speed sensors( i i ) valves( i i i ) pump( i v ) electronic controllerin an anti-lock braking system. [8 marks]

by;(0( i i )( i i i )

control armsstrut rodsbushings .

[8 marks]

Question 6

** E N D O F P A P E R * *

ME 2602 Page 5 of 5

me 2602 motor vehicle technology

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