**AT6301 Automotive Engines Important Questions**

**Unit I**

**Compare two stroke engine and four stroke engine with regard to power output and thermal efficiency.****Briefly explain the working principle of four stroke SI engine (OR) two stroke CI engine.****a) Compare the SI engine and CI engine. b) Write the major difference between Otto cycle and Diesel cycle?****Compare the two stroke and four stoke engine.****In an SI engine working on the ideal Otto cycle the compression ratio is 6. The pressure and the temperature at the beginning of compression are 1.013 bar and 27°C respectively. The Peak pressure is 30 bar. Determine the pressure and temperature at the salient points, the air standard efficiency and the mean effective pressure. Assume γ = 1.4****An engine working with dual cycle has a compression ratio of 10 and 2/3 of heat of combustion is liberated at constant volume and the remainder at constant pressure. The pressure and temperature at the beginning are 1 bar and 27°C. and the maximum pressure is 40 bar. Find the temperature at the end of compression and expansion. And the air standard efficiency. Assume γ = 1.4**

**Unit II**

**Explain with neat sketch about common rail diesel injection system.****Explain the working principle of Jerk type pump & Unit injector.****A simple jet carburetor is required to supply 4.6 Kg of air per minute. The pressure and temperature of air are 1.013 bar and 25°C respectively. Assuming flow to be isentropic and compressible and velocity co-efficient as 0.8. Calculate the throat diameter of the choke for air flow velocity of 80 m/s.****A simple carburetor is designed to supply 6 kg of air per minute and 0.4 kg of fuel per minute. The density of the fuel is 770 kg/m3. The air is initially at 1 bar and 17 C. Calculate the venture throat diameter if the velocity of air at throat is 100 m/s. Assume Cda=0.84. Cdf=0.65 and γ=1.4. If the pressure drop across the fuel metering orifice is 0.85 of the pressure at the throat.****Explain the working principle of Constant vacuum type carburetor**

**Unit III**

**Briefly explain about the ignition timing with respect load and speed.****Briefly explain about various types combustion chamber designed for SI engines****Compare the Knock in SI Engine and CI Engine. Explain briefly the process of knocking combustion in a SI Engine****Explain briefly the Stages of combustion in CI Engine.**

**Unit IV**

**Briefly explain about the Eddy current Dynamometer & Hydraulic Dynamometer.****The following particulars were obtained in a trial on a four stroke gas engine: Duration of trial = 1 hour, Revolutions = 14000, Number of missed cycle = 500, Net brake load = 1470 N, Mean effective pressure = 7.5 bar, Gas consumption = 20000 liter, L.C.V. of gas at supply conditions = 21 KJ/Liter, Cylinder diameter = 250 mm, Stroke = 400 mm, Effective brake circumferences = 4 m, Compression ratio = 6.5:1 Calculate i) Indicated power ii) Brake power iii) Mechanical efficiency iv) Indicated thermal efficiency****Explain about the Supercharging & Turbocharging methods.****Explain : Turbo charging with waste gate & variable geometry**

**Unit V**

**Explain the requirements of lubrication system.****Briefly explain with neat sketch about the wet sump & Dry sump lubrication system.****Briefly explain with neat sketch about the Splash type lubrication system****Explain about properties of lubricant**

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