IC EnginesShort Questions and Answers

Prepared by: MJK / AAA

1. What is the firing sequence of a four cylinder engine?1-3-4-2 is the standard firing order followed in four cylinder engines

2. What is operating cycle of a patrol engine?Otto cycle

3. What is operating cycle of a diesel engine?Diesel cycle

4. What is the mechanism of a reciprocating IC engine as per theory of machines? Also sketch it Common to most reciprocating engines is a linkage known as a crank-slider mechanism.

5. How do you define a stroke in a reciprocating engine?Distance form TDC (top dead centre) to BDC (bottom dead centre) is called a stroke.

6. Draw PV diagram of an Otto cycle

7. What is piston displacement?The piston displacement is the product of the piston cross-sectional area and the stroke

8. What is the relation between Piston displacement and engine displacement? The volume swept by the piston as it passes from TDC to BDC is called the piston displacement, “d”. Engine displacement, “D”, is then the product of the piston displacement and the number of cylinders “n” i.e.; D = {(n) (d)}

9. What is bore?The cylinder inside diameter (and, approximately, also the piston diameter) is called its bore

10. What is compression ration in an IC engine cycle? (Keeping in view clearance volume V2 and initial volume V1 )Compression ration (CR) is ~ CR = [V2 + (V1 - V2)]/ V2

11. In which part of patrol engine fuel air mixture is produced?It is produced in carburetor

12. What is lean and rich mixture of patrol fuel? A mixture with excess air is called a lean mixture and a mixture with excess fuel is called a rich mixture

13. What kind of mixture is produced in carburetor when driving uphill?The automotive carburetor produces a rich mixture during acceleration by supplying extra fuel to the air entering the intake manifold.

14. What is equivalence ratio? And what is correlation with lean and rich fuel mixtures?The equivalence ratio, Ø is defined as the ratio of the actual fuel-air ratio to the stoichiometric fuel-air ratio. Thus Ø > 1 represents a rich mixture and Ø < 1 represents a lean mixture. In terms of air-fuel ratio, Ø = (A/F) stoich. / (A/F)

15. What is octane number?The octane number is a measure of a gasoline’s ability to avoid knocking in combustion chamber

16. What is engine breathing? Then intake of fresh air and exhaust of flue gases through its poppet valves is called engine breathing

17. Where dynamometer and water brakes are used?They are used on engine test beds for measuring an engine’s performance.

18. What are principal cycles for IC Engines?a. Otto Cycleb. Diesel Cyclec. Dual Cycled. Brayton Cycle (IC gas turbine cycle)e. Wankel Cycle (Recent of all, first introduced for Mazda RX-7 in 1990)

19. Sketch PV diagram of Diesel Cycle

20. Are spark plug used in diesel engines? No

21. In which cycle the compression ratio is greater Diesel cycle

22. Out of Otto and diesel cycles which one has greater efficiency? Diesel cycle is more efficient because of greater calorific value of fuel used.

23. What is turbocharger? It increases the overall engine efficiency of an engine, by utilizing the draft of flue gases.

24. What is scavenging?To effectively discharge the all of burnt gases from the cylinder

25. What is VTI ENGINE?An engine having ability of VARIABLE TIMING OF IGNITION

26. What is MPFI? MULTIPORT FUEL INJECTION (a new technology in gasoline engines to enhance efficiency)

27. What is EFI? ELECTRONIC FUEL INJECTION (it is substitute of carburetor)

28. Why gasoline doesn’t become efficient by use supercharger?Supercharger basically increases air fuel ratio, which is kept under limit in gasoline engines under certain limit to avoid self ignition.

29. How do you convert a diesel engine into CNG engine?It requires ample modifications in the engine design, like

a. Installing a carburetorb. Spark plug c. Reducing air fuel ratio by modifying cylinder design

30. What are usual compression ratios for patrol and diesel engines?Patrol engine 11-13%Diesel engine 20-22%

31. What are different methods of super charging?a. Turbocharger (Exhaust gases driven turbine drives the blower to increase the intake air mass)b. Shaft driven Blowerc. Motor driven blower

32. What is the basic difference between two stroke and four stroke engine? In two stroke engine, power stroke is received in each crank shaft revolution, whereas in four stroke engine powers stroke is received in every two crank shaft revolution.

33. What is gudgeon pin?It is the pin used for connecting small end of connecting rod to piston

34. Is connecting rod forged or casting? Forged

35. What kind of rings are used on a piston and why?a. Compression rings for sealing the leakage of gases above piston b. Oil rings for lubricating piston along its travel to avoid friction against liner walls c. Oil scrapper ring for scrapping oil in back stroke of piston

36. How is fuel injected in diesel engine cylinder for combustion?Through a specially designed atomizing fuel injector

37. What are V-type engines? What is its main advantage? The arrangement of cylinder on the crankshaft forms the shape of letter-V. Its main advantage is that it consumes less space then an in-line or straight arrangement of cylinders.

38. What is the use of CAM-shaft?The inlet and discharge valves are opened and closed by means of a CAM-shaft.

39. What are different strokes in a four stroke engine?a. Inlet b. Compressionc. Powerd. Exhaust

40. Why lubrication and cooling systems are required in an IC engine?Lubrication system is required for avoiding excessive wear tear between the metallic parts, whereas cooling system removes the excessive heat generated during the power strokes.

41. Out of patrol and diesel which one has greater flash point Diesel