INSTRUCTION: This section consists of SIX (6) essay questions. Answer FOUR (4) questions only.

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1 INSTRUCTION: This section consists of SIX (6) essay questions. Answer FOUR (4) questions only. ARAHAN: Bahagian ini mengandungi ENAM (6) soalan esei. Jawab EMPAT (4) soalan sahaja. QUESTION 1 SOALAN 1 CLO1 (a) Distinguish between internal and external combustion engines. Bezakan antara enjin pembakaran dalam dan enjin pembakaran luar. CLO1 (b) Describe THREE (3) adavantages and TWO (2) disadvantages of internal combustion engines compare a to the external combustion engines. Huraikan TIGA (3) kelebihan dan DUA (2) kekurangan enjin pembakaran dalam berbanding enjin pembakaran luar. [5 marks] [5 markah] CLO1 (c) Draw FOUR (4) diagram processes of the four-stroke compression ignition engine. Lukiskan EMPAT (4) gambarajah proses bagi enjin nyalaan mampatan empat lejang. [8 marks] [8 markah] CLO1 (d) Describe the working principle as sketched in Question 1(c). Terangkan prinsip kerja seperti yang telah dilakarkan di Soalan 1(c). [8 marks] [8 markah] 2

2 QUESTION 2 SOALAN 2 (a) Differentiate between the clearance volume and the displacement volume of reciprocating engines. Bezakan antara isipadu kelegaan dengan isipadu anjakan bagi enjin salingan. (b) Define the compression ratio for reciprocating engine. Berikan maksud nisbah mampatan bagi enjin salingan. C4 (c) The compression ratio of an air-standard Otto cycle is 9.5. Prior to the isentropic compression process, the air is at 100 kpa, and 35 C. The temperature at the end of the isentropic expansion process T 4 is 800 K. Using constant specific heat values at room temperature, determine: Nisbah mampatan bagi udara kitaran Otto adalah 9.5. Semasa proses mampatan isentropic berlaku, udara berada pada 100kPa dan 35 C. Suhu di akhir proses pengembangan isentropic T 4 adalah 800K. Menggunakan nilai haba tentu malar pada suhu bilik, tentukan: i. The highest temperature and pressure in the cycle; Suhu dan tekanan maksimum di dalam kitaran; ii. The amount of heat added; Jumlah haba yang dibekalkan; 3

3 iii. The thermal efficiency Kecekapan haba Take c p = kj/kg.k and c v = kj/kg.k [17 marks] [17 markah] QUESTION 3 SOALAN 3 (a) Describe the terms below: Huraikan terma-terma dibawah: i. Stoichiometric ratio Nisbah stoichiometric ii. Pre-ignition Pra-penyalaan iii. Ignition delay Perlambatan penyalaan [6 marks] [6 markah] C4 (b) Sketch and analyse the graph combustion (pressure vs. crank angle degree) with: Lukis dan analisis graf pembakaran (tekanan melawan darjah aci engkol) dengan: i. Normal Combustion with no knocking Pembakaran normal tanpa ketukan ii. Combustion with light knocking Pembakaran dengan ketukan ringan 4

4 iii. Combustion with heavy knocking Pembakaran dengan ketukan kuat [9 marks] [9 markah] C3 (c) Sketch and label the graph of pressure vs. crank angle position for every stage involves in a compression ignition engine. Lakarkan graf dan labelkan tekanan melawan kedudukan sudut aci engkol untuk setiap dalam palam pencucuh. peringkat di enjin yang menggunakan [5 marks] [5 markah] (d) Identify FIVE (5) factors that influence the period of ignition lag. Kenal pasti LIMA (5) faktor yang mempengaruhi jangka masa perlambatan penyalaan. [5 marks] [5 markah] QUESTION 4 SOALAN 4 (a) Define the following terms: Berikan maksud terma-terma berikut: i. Indicated power, ip Kuasa tertunjuk ii. Brake power, bp Kuasa Brek [2 marks] [2 markah] 5 [2 marks] [2 markah]

5 iii. Frictional power, fp Kuasa geseran [2 marks] [2 markah] C4 (b) A six cylinder four stroke petrol engine having a bore of 90 mm and stroke of 100 mm has a compression ratio of 7. The indicated thermal efficiency is 23.46% when indicated mean specific fuel consumption is 0.3 kg/kwh. Estimate the specific fuel consumption in kg/hr and the calorific value of the fuel. Given that indicated mean effective pressure is 8.5 bar and speed is 2500 rpm. Sebuah enjin petrol enam silinder empat lejang mempunyai diameter 90 mm dan panjang lejang 100 mm mempunyai nisbah tekanan 7. Kecekapan haba tertunjuk adalah 23.46% apabila min penggunaan bahan api tentu tertunjuk adalah 0.3 kg/kwh. Anggarkan penggunaan bahan api tentu didalam kg/jam dan nilai kalori bahan api. Di beri min tekanan efektif adalah 8.5 bar dan kelajuan enjin 2500 rpm. [10 marks] [10 markah] (c) List FIVE (5) factors that influence volumetric efficiency. Senaraikan LIMA (5) faktor yang mempengaruhi kecekapan isipadu. [5 marks] [5 markah] 6

6 C3 (d) Sketch the engine performance curve for each parameter below against engine speed based on Figure 4(d). Lakar graf prestasi enjin untuk parameter dibawah melawan kelajuan enjin berdasarkan Gambarajah 4(d). Figure 4(d) : Graph Power vs Speed Gambarajah 4(d) : Graf Kuasa melawan Kelajuan i. Torque Kilasan ii. Power Kuasa iii. Specific fuel consumption Penggunaan bahan api tentu iv. Brake mean effective pressure (Bmep) Tekanan berkesan min brek 7

7 QUESTION 5 SOALAN 5 (a) Cylinder block is the main component of an engine. It has different types of shapes and materials according to its applications. Blok silinder merupakan komponen utama bagi sesebuah enjin. Ianya mempunyai perbezaan rekabentuk dan bahan binaan yang bergantung kepada aplikasinya. i. List TWO (2) cylinder block s functions. Senaraikan DUA (2) kegunaan blok silinder. ii. List TWO (2) processes involved in making cylinder block. Senaraikan DUA (2) proses yang terlibat didalam pembuatan silinder blok. [2 marks] [2 markah] (b) Explain how the aluminium cylinder block is manufactured. Terangkan bagaimana silinder blok aluminium di hasilkan. C3 (c) Sketch and label TWO (2) types of spark ignition combustion chamber design. Lakar dan labelkan DUA (2) jenis kebuk pembakaran yang digunakan di dalam enjin penyalaan percikan. i. Hemispherical combustion chamber Kebuk pembakaran hemispherical 8

8 ii. Wedge combustion chamber Kebuk pembakaran wedge [8 marks] [8 markah] C3 (d) Figure 5(d) shows a direct injection high swirl chamber. With the aid from the figure, demonstrate the combustion process in this combustion chamber design. Gambarajah 5(d) menunjukkan kebuk pembakaran pusingan tinggi secara pancitan langsung. Dengan bantuan gambarajah dibawah, demonstrasikan proses pembakaran yang berlaku di dalam rekabentuk kebuk pembakaran ini. Figure 5(d) Gambarajah 5(d) [7 marks] [7 markah] 9

9 QUESTION 6 SOALAN 6 (a) State FOUR (4) effects to engine if clearance between piston and cylinder wall is too small. Nyatakan EMPAT (4) kesan terhadap enjin jika kelegaan diantara omboh dan dinding silinder terlalu kecil. (b) Explain piston slap condition in an engine. Terangkan maksud keadaan tamparan omboh di dalam sesebuah enjin. [2 marks] [2 markah] (c) Explain briefly FOUR (4) methods on how to control piston skirt expansion. Terangkan secara ringkas EMPAT (4) cara untuk mengawal pengembangan piston skirt. [8 marks] [8 markah] (d) Define the purpose of compression ring and oil control ring at the piston. Nyatakan tujuan menggunakan gelang mampatan dan gelang kawalan minyak pada omboh. [6 marks] [6 markah] C3 (e) Draw and label the diagram of valve part. Lukis dan label gambarajah bahagian injap. 10 [5 marks] [5 markah]

10 ... SOALAN TAMAT 11

INSTRUCTION: This paper consists of SIX (6) structure questions. Answer any FOUR (4) questions.

INSTRUCTION: This paper consists of SIX (6) structure questions. Answer any FOUR (4) questions. ARAHAN: Kertas ini mengandungi ENAM (6) soalan struktur. Jawab mana mana EMPAT (4) soalan. QUESTION 1 SOALAN