ME-501 I C Engine - Dec 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aCompare Homogeneous Charge Compression Ignition Engine, Lean Burn Engine & Stratified Charge Engines with respect to combustion process, efficiency, emissions and practical usages.
   How to answer

   • Define HCCI, lean-burn and stratified-charge concepts
   • Compare combustion process and mixture preparation
   • Compare thermal efficiency and fuel economy
   • Compare NOx, HC, CO and particulate emissions
   • Compare practical applications and control challenges
2. 7 Marks
   bExpress the factors affecting delay period in CI Engine, in detail. Justify it with suitable reason.
   How to answer

   • Define delay period in CI engine - physical and chemical delay
   • List engine design, operating and fuel factors
   • Explain effect of compression ratio, pressure, temperature
   • Explain effect of fuel properties and injection parameters
   • Justify each factor with combustion reasoning
3. 7 Marks
   aDifferentiate Otto Cycle and Diesel Cycle. Find the expression of Thermal Efficiency, Work done and mean effective pressure of Diesel Cycle.
   How to answer

   • Differentiate Otto vs Diesel on heat addition and p-V diagram
   • State assumptions and Diesel cycle processes
   • Derive $\eta_{th}=1-\frac{1}{r^{\gamma-1}}\frac{\rho^{\gamma}-1}{\gamma(\rho-1)}$
   • Derive work done and mean effective pressure expression
   • Compare efficiency trends with compression ratio and cut-off ratio
4. 7 Marks
   bWhat do you understand by Theory of Carburetion? Explain in detail.
   How to answer

   • Define carburetion and air-fuel mixture requirement
   • Explain venturi action and fuel discharge theory
   • Explain simple carburettor equation for air-fuel ratio
   • Discuss factors affecting carburetion
5. 7 Marks
   aDescribe working principle of fuel pump and fuel injectors.
   How to answer

   • Define function of fuel pump and injector in CI engine
   • Explain working principle of fuel pump
   • Explain working principle of fuel injector
   • Mention pressure, timing and atomization role
6. 7 Marks
   bWhat do you understand by Nozzle? Define its type.
   How to answer

   • Define nozzle and its function
   • Explain atomization and spray requirements
   • Classify types - single hole, multi-hole, pintle, pintaux
   • Compare applications
7. 7 Marks
   aExplain alternative fuels for SI and CI Engine. Explain the fuel characteristics of LPG, CNG and hydrogen.
   How to answer

   • Define need for alternative fuels in SI and CI engines
   • List LPG, CNG, hydrogen, alcohols, biodiesel options
   • Explain properties - calorific value, octane/cetane, storage
   • Compare fuel characteristics of LPG, CNG and hydrogen
8. 7 Marks
   bA four-stroke, eight-cylinder engine is tested running at $3600$ r.p.m. The inlet air temperature is $5^{\circ}C$ and the pressure is $760$ mm of Hg. The total piston displacement volume is $4066$ cm$^{3}$. The air fuel ratio of the engine is $14$:$1$ and b.s.f.c is $0.38$ kg/kwh. The power output is $86$ kw. Find the volumetric efficiency of the engine.
   How to answer

   • Calculate fuel consumption from $bsfc$ and power
   • Calculate air mass flow using air-fuel ratio
   • Calculate theoretical swept volume flow at $3600$ r.p.m.
   • Compute $\eta_v$ = actual air volume / swept volume
   • Use $p=760$ mm Hg and $T=5^{\circ}C$ for air density
9. 7 Marks
   aExplain the methods of supercharging in IC engines. Also explain the engine modifications required for supercharging.
   How to answer

   • Define supercharging and its objectives
   • Explain mechanical, turbo, and other drive methods
   • Explain effects on power, efficiency and emissions
   • List engine modifications - compression, cooling, materials
10. 7 Marks
    bExplain how electronic control improves boost pressure regulation, engine safety and fuel efficiency?
    How to answer

    • Define boost pressure regulation need
    • Explain electronic waste-gate / VGT control
    • Explain engine safety via sensors and limits
    • Explain fuel efficiency gain by optimized boost
11. 7 Marks
    aDiscuss the lubrication system of SI engine. Highlight the importance of lubrication and its components.
    How to answer

    • Define purpose of lubrication - friction, cooling, sealing
    • Describe mist, wet-sump, dry-sump systems for SI engine
    • Highlight main components - pump, filter, oil
    • State importance for wear and life
12. 7 Marks
    bAn IC engine working on Diesel Cycle has bore $200$mm, stroke $300$ mm. If the clearance volume is $420$ cc and fuel injection takes place at the constant pressure for $5$% of the stroke. Find out thermal efficiency of the engine. If the cut off is delayed from $5$ to $8$%. What will be the percentage loss in efficiency in both cases? The compression ratio is same.
    How to answer

    • Compute swept volume from bore and stroke and compression ratio
    • Determine cut-off ratio for 5% and 8% of stroke
    • Apply Diesel efficiency formula with $\gamma=1.4$
    • Calculate percentage loss in efficiency
    • Comment on effect of delayed cut-off
13. 7 Marks
    aDiscuss the term knock in SI engine. What are the effects of knock. Also discuss the methods to reduce detonation.
    How to answer

    • Define knock/detonation in SI engine
    • Explain auto-ignition and pressure waves
    • List effects - power loss, damage, noise, overheating
    • Discuss methods to reduce - fuel, design, operating parameters
14. 7 Marks
    bExplain in detail the construction, working and disadvantage of TBL.
    How to answer

    • Define TBI - throttle body injection concept
    • Explain construction and working with single injector
    • Compare with MPFI / carburettor
    • List disadvantages - distribution, response, emissions
15. 7 Marks
    aDescribe the term carburetor. Explain the working of Solex carburetor.
    How to answer

    • Define carburettor function and requirements
    • Explain Solex carburettor circuits and devices
    • Explain starting, idling, normal and acceleration operation
    • Mention advantages for SI engine
16. 7 Marks
    bDiscuss the importance of firing order with respect to engine balancing, vibration reduction, and crankshaft design.
    How to answer

    • Define firing order and typical orders
    • Explain role in balancing and uniform torque
    • Explain vibration reduction and crankshaft design
    • Give examples for 4, 6, 8 cylinder engines