300+ TOP Internal-Combustion engine Interview Questions [LATEST]

  1. 1. What Is I.c Engine?

    The internal combustion engine converts chemical energy into useful mechanical energy by burning fuel.

    Chemical energy is released when the fuel-air mixture is ignited by the spark in the combustion chamber. The gas produced in this reaction rapidly expands forcing the piston down the cylinder on the power stroke.

  2. 2. What Is 2-stroke Engine?

    A Two-stroke engine is an internal combustion engine in which the piston’s two strokes are required to complete single thermodynamic cycle.

    2-STROKE engine is designed by DUGLAD CLERK in 1880, the expansion and exhaust takes place during 2-Stroke of piston.

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  4. 3. What Is 4-stroke Engine?

    A four-stroke engine is an internal combustion engine in which the piston’s four separate strokes are required to complete single thermodynamic cycle.

    A 4-stroke engine is an internal combustion engine in which the piston completes four separate strokes— intake, compression, power, and exhaust— during two separate revolutions of the engine’s crankshaft, and one single thermodynamic cycle.

  5. 4. Definition Of Octane Number And Cetane Number?

    Octane No
    . – Octane number is defined as the percentage, by volume, of iso-octane in the mixture of iso-octane and h-heptane. It is the measure of rating of SI engine.

    Cetane No
    . – Cetane number is defined as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthalene. It is the measure of rating of CI engine.

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  7. 5. Name The Main Steps Involve In 4-stroke I.c Engine?

    The steps involved here are:

    • Intake stroke:
      The mixture of Air and Fuel. are drawn in.
    • Compression stroke:
      Fuel vapor and air are compressed and ignition takes place.
    • Combustion stroke:
      Fuel combustion takes place and piston is pushed downwards.
    • Exhaust stroke:
      Exhaust is driven out.
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  9. 6. Among Two-stroke Engine And Four-stroke Engine Which Is Generally Preferred And Why?

    Two stroke engine is generally preferred. Because it has smaller size for the same output.

  10. 7. During Idling Process, A Petrol Engine Requires Lean Or Rich Mixture?

    Lean mixture.

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  12. 8. What Are The Advantages Of Lubrication In Ic Engine?

    • It reduces the wear and tear of the moving parts.
    • It damps down the vibration of the engine.
    • It cleans the moving parts.
    • It makes the piston gas tight.
  13. 9. Name The Fuel Used By I.c Engines?

    Petroleum spirit, Petroleum diesel, liquefied petroleum gas(LPG), Compressed natural gas, Jet fuel ,Residual fuel.

    Methanol, Gasoline, Diesel fuel.

    Biofuels and Veg Oils:
    Peanut oiL and other veg oils, Biobutano, biodiesel, Dimethyl. Ether, biogas, hydrogen.

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  15. 10. What Are The Advantages Of Lubrication In I.c Engine?

    following are the advantages of Lubrication in IC Engine:

    • it reduces the wear and tear of the moving parts.
    • it damps down the vibration of the engine.
    • it cleans the moving parts.
    • it makes the piston gas tight.
  16. 11. Why Have Eight Cylinders In An Engine? Why Not Have One Big Cylinder Of The Same Displacement Of The Eight Cylinders Instead?

    There are a couple of reasons why a big 4.0-Liter engine has eight half-Liter cylinders rather than one big 4-Liter cylinder. The main reason is smoothness. A V-8 engine is much smoother because it has eight evenly spaced explosions instead of one big explosion. Another reason is starting torque. When you start a V-8 engine, you are only driving two cylinders (1 Liter) through their compression strokes, but with one big cylinder you would have to compress 4 titers instead.

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  18. 12. What Causes White Smoke In Two Stroke Locomotive Engines?

    That is because of engine running too Lean mixture (lack of fuel). This condition wilt lead to overheating and failure of the engine.

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  20. 13. Why Efficiency Of Gas Turbines Is Lower Compared To Lc. Engines?

    In gas turbines, 70% of the output of gas turbine is consumed by compressor. I.C. engines have much Lower auxiliary consumption. Further combustion temperature of l.C. engines is much higher compared to gas turbine.

  21. 14. What Do You Understand By Timed Cylinder Lubrication?

    For effective lubrication, lubrication oil, needs to be injected between two piston rings when piston is at bottom of stroke so that piston rides in oil during upward movement. This way tot of lubrication oil can be saved and used properly.

  22. 15. In Some Engines Glycerin Is Used In Place Of Water For Cooling Of Engine. Why?

    Glycerin has boiling point of 90°C which increases its heat carrying capacity. Thus weight of coolant gets reduced and smaller radiator can be used.

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  24. 16. Why We Do Not Use Same Technology To Start Both Si/cl Engine ?

    The S.I. or spark ignition engine uses petrol. as a fuel and the Ci. or compression ignition engine uses diesel as a fuel. Both the fuels has different compression ratio.

    • In SI engine the compression ratio is 8-12:1.
    • In CI engine the compression ratio is 16-22:1.

    So in case of SI engine, the compression ratio is not sufficient for fuel to burn so a spark plug is used, whereas in ci engine, the compression ratio is so high that due to its internal heat the fuel is combusted so there is no need for a spark plug. So the technology used in SI engine is different from CI engine.

  25. 17. Which Has More Efficiency: Diesel Engine Or Petrol Engines?

    Diesel. engine has the better efficiency out of two.

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  27. 18. What Is The Position Of Piston Ring?

    In 180 degree angle the Top ring, Second ring and Oil ring are fixed. Position the ring approximately 1 inch gap below the neck.

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  29. 19. What Are The Advantages And Disadvantages Of Using Lpg In Car?


    1. Complete combustion
    2. FueL saving
    3. Homogenous combustion.


    1. As complete combustion is occurring, more heat Liberated, not advised for Long journey, engine will be over heated
    2. Installation is difficult
    3. Reduce engine Life efficiency.
  30. 20. What Is Scavenging?

    Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends.

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  32. 21. What Is Meant By Supercharging?

    Supercharging is a method of increasing an engine’s power output, by forcing air into the engine under greater than atmospheric pressures. Supercharging usually refers to belt driven compressor (I.E. roots/screw or centrifugal), some early uses superchargers were driven directly off the crank shaft.

  33. 22. Why Diesel Engine Don’t Have Spark Plug?

    The compression ratio is high enough to combust the diesel without the aid of sparkplugs Answer Most diesel engines will have a glow plug, this gives of enough heat to help get the engine started, the heat generated from the first few revolutions together with the compression from the piston is enough to ensure the engine keeps running. Some modern diesel engines no Longer require a glow plug.

  34. 23. Which Are The Reference Fuels For Knock Rating Of 5.1. Engines?

    n-heptane and ISO-octane.

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  36. 24. Which Pollutant Is Major Greenhouse Gas And What Is Its Effect?

    CO is major greenhouse gas and it traps the radiation of heat from the sun within earth’s atmosphere.

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  38. 25. What Are The Important Operational Performance Parameters In Design Of Fuel Firing Equipment?

    Fuel. flexibility, electrical Load following capability, reliability, availability, and maintenance ease.

  39. 26. How The Analyses And Calorific Values Of Fuels Can Be Reported?

    It may be reported as

    1. As received or fired (wet) basis
    2. Dry or moisture free basis.
    3. Combustible or ash and moisture free basis.
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  41. 27. What Is Atft Technology Used In Honda Hunk?

    ATFT means Advance Tumble Flow Induction Technology, Tumble flow means swirling. In this technology fuel air mixture from the carburetor into the engine cylinder with a swirl action. The advantage being one gets a more efficient burning of fuel hence more power and better fuel. economy with lesser emissions.

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