IC engine Notes

–Internal Combustion Engines–

Ø The working cycle in case of four stroke engine is completed in 2 number of revolution of crankshaft.

Ø In a diesel engine, the fuel is ignited by heat resulting from compressing air that is supplied for combustion.

Ø Scavengine air in diesel engine means air used for forcing burnt gases out of engine’s cylinder during the exhaust period.

Ø Supercharging is the process of supplying the intake of an engine with air at a density rgreater than the density of the surrounding atmosphere.

Ø Does the heat supply of scavengine air at a density greater than then that of atmosphere mean engine is supercharged? : No

Ø The ratio of indicated thermal efficiency to the coresponding air standard cycle efficiency is called relative efficiency.

Ø Compression ratio of  I.C. engines is the ratio of volumes of air in cylinder before compression stroke and after compression stroke.

Ø The air standard efficiency of an otto cycle compared to diesel cycle for the given compression ratio is more or less depending on power ratng.

Ø The calorific value of gaseous fuels is expresssed in terms of Kcal/M3

Ø Indicated power of a 4 stroke engine is equal to pLAN/2

Ø If the intake air temperature of I.C. engine increases, it efficiency will decrease.

Ø All heat engines utilise low heat value of oil.

Ø An engine indicator is used determine the m.e.p. and I.H.P.

Ø Fuel oil sonsumption guarantees for I.C. engine are usually based on high heat value of oil.

Ø In case of gas turbine, the gaseous fuel consumption guarantees are based on low heat value.

Ø In a typical medium speed 4 stroke cycle diesel engine the inlet value opes at 20 degree befroe top dead centre and closes at 35 degree after the bottom dead centre.

Ø The maximum temperature in the I.C. engine cylinder is of the order o 2000-2500 degree celcius.

Ø The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will decrease.

Ø 2 stroke engine can run in any direction. 

Ø In 4 stroke engine, a powee strroke is obtained in 4 strokes.

Ø Thermal efficiency of 4 stroke engine is more due to positive scavenging.

Ø Petrol engines work on otto cycle.

Ø Combustion in compression ignition engines is hetrerogeneous.

Ø The ful in diesel engine is normally injected at pressure of 90-130 kg/cm2

Ø The specific fuel consumption per BHP hour for diesel engine is approximately 0.2Kg.

Ø The temperature of interior surface of cylinder wall in normal operation is not allowed to exceed 180 degree celcius.

Ø Crankcase explosion in I.C. engines usually occurs as first a mild explosion followed by a big explosioin.

Ø Compression loss in I.C. engine occurs due to leaking piston rings, use of thick head gasket, clogged air-inlet slots and increase in clearance volume caused by bearing bushing wear.

Ø The air requirement of a petrol engine during starting compared to theoretical air required for complete cumbustion is loss.

Ø The inlet value of a four stroke cycle I.C. engine remains open for nearly 235 degree.

Ø Steam turbine is not an internal combustion engine.

Ø Thermal efficiency of diesel engine is about 34%.

Ø Theoretically correct mixture of air and petrol is approximately 15:1.

Ø If one cylinder of a diesel engine receives more fuel than the others, than for that cylinder the scavenging occurs.

Ø The output of a diesel dngine can be incrased without increasing the eingine revolution or size in flowing way superchargine.

Ø If the temperatuer of intake air in IC engines is lowered then its efficiency will increase.

Ø In a typical mudium speed 4 stroke cycle diesel engine compression starts at 35 degree after bottom dead centre and ends at top dead centre.

Ø For the same compression ratio otto cycle is more efficient than the Diesel.

Ø The process of breaking up or liquid into fine droplets by spraying is called atomization.

Ø As a result of detonation in an I.C. engine rate of rise of pressure attains very high value.

Ø All reversible engines working between same temperature limits have same efficiency.

Ø Most high speed compression engines operate on Special type of air cycle.

Ø If one cylinder of a diesel engine receive more fuel than the others, it is a serious condition for that cylinder and can be checked by checking cylinder exhaust temperature with a pyrometer.

Ø The accumulation of carbon in a cylinder results in increase of effective compression ratio.

Ø Air alone is compressed in a Diesel engine cylinder.

Ø The air-fuel ratio of the petrol engine is controlled by carburettor.

Ø In a typical medium speed 4 stroke cycle diesel engine fuel injection starts at 10 degree before top dead centre and ends at 20 after top dead centre.

Ø Diese fuel compared to petrol is more difficult to ignite.

Ø In diese engine the diesel fuel injected into cylinder would burn instantly at about compressed air temperature of 1000 degree celcius.

Ø When crude oil is heated, then natueal gas hydrocarbon is given off first.

Ø The rating of diesel engine, with increase in air-inlet temperature will decrease linearly.

Ø A heat engine utilises the high heat value of oil.

Ø A 75cc engine has swept volume parameter as 75cc.

Ø Gaseous fuel guarantees are based on low heat value of oil.

Ø Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads the small difference in cooling water temperature or internal friction has a disproportionate effect.

Ø Polymarization is a chemical process in which molecules of compound become larger.

Ø The term scavengine is generally associated with high efficiency engines.

Ø In desel engine, the compression ratio comparison to expansion ratio is more.

Ø The cam shaft of four stroke I.C. engine running at 1500 rpm will run at 750rpm.

Ø Engine pistons are usually made of aluminium alloy because is is lighter.

Ø Most high speed compression engines operate on Dual cycle.

Ø The specific fuel consumption of a petrol engine compared to diesel engine of same H.P. is more.

Ø A diesel engine as compared to petrol engine is more efficient.

Ø The size of inlet valve of an engine in comparision to exhause valve is less.

Ø In a typical medium speed 4 stroke cycle diesel engine expansion starts 20 degree after top dead centre and ends at 35 degree befroe bottom dead centre.

Ø In a cycle the spark lasts roughly for 0.001 sec.

Ø Excess quantities of sulphur in diesel fuel are bojectionable because it may cause piston rings and cylinder wear, formation of hard coating on piston skirts and oil sludge in the engine crank case.

Ø The fuel air ratio in a petrol fitted with suction carburettor, operating with dirty air filter as compared to clean filter will be higher.

Ø Super charging reduces knocking in diesel engines.

Ø There can be limited supercharging in petrol engines because of detonation.

Ø Supercharging at high altitudes is essential.

Ø Supercharging is essential in aircraft engines.

Ø The actual volume of fresh charge admitted in 4 stroke petrol engine is less than stroke volume.

Ø The magneto in an automobile is basically d.c. generator.

Ø The reason for superchargine in any engine is to reduce weight and bulk for a given output.

Ø The opearation of forcing additional air under pressure in the engine cylinder is known as superchargine.   

Ø Supercharging is essential for air crafts.

Ø The minimum cranking speed in case of petrol engine is about 60-80rpm.

Ø In atypical medium speed 4 stroke cycle diesel engine exhaust valve opens 35 degree before bottom dead centre and closes at 20 degree after top dead centre.

Ø Flash point of fuel oil is minimum tempreture to which oil is heated in otder to give off inflammable vapour in sufficient quantity to ignite memontarily when brought in contact with a flame.

Ø The mean effective pressure obtained from engine indicator indicates the average pressure.

Ø For the same power developed in I.C. engines, the cheaper system is supercharged than turbocharge.

Ø Installation of supercharger on a four-cycle diesel engine can result in upto 100% increase in power.

Ø Scavenging is usually done to increase power output.

Ø Gasoline is most lightest and volatile liquid fuel.

Ø Air fuel ratio for idling speed of a petrol engine is approximately 10:1.

Ø For maximum power generation, the air fuel ratio for a petrol engine for vehicles, is of the order of 12:1.

Ø 9-10 m3 air is required for consuming 1 litre of fuel by a four stroke engine.

Ø Pour point of fuel oil is the temperature at which solidifies or congeals.

Ø Diesel engine can work on very lean air fuel ratio of the order of 30:1. A petrol engine can also work on such a lean ratio provided: can not work as it is impossible.

Ø A diesel engine has 3 valves.

Ø A high flame speed is obtained in diesel engine when air fuel ratio is about 10% rich mixture.

Ø The knock in diesel engine occurs due to instantaneous and rapid burnging of the first part of the charge.

Ø The ari fuel ratio in petrol engines is controlled by carburettion.

Ø Volatility of diesel fuel oil is indicated by 30% dosto;;atopm temperature i.e. when 90% of sample oil has distilled off.

Ø In the opposed piston diesel engine, the combustion chamber is locatred between the pistons.

Ø A stoichimetric air fuel ratio is chemically correct mixture.

Ø In anaturally aspirated diesel engine, the air is supplied by a caccum chamber.

Ø In loop scavenging, the top of the piston is contoured.

Ø In the crankcase method of scavengine the air pressure is produced by movement of engine piston.

Ø In order to prevent fromation of carbon on the injector, the temperature of nozzle tip should be between 250-300 degree celcius.

Ø The thermal efficiency of a petrol engines of two stroke with crank case scavengine as compared to four stroke petrol engine with same compression ratio will be lower.

Ø Ignition quality of petrol is expressed by octane number.

Ø Petrol is distilled at tempreature in range of 65-220 degree celcius.

Ø Kerosene is distilled at 220-350 degree celcius.

Ø Iso-octane has octane number of 100.

Ø Octance number is determined by comparing the performance of the petrol with the mixture of normal heptance and iso-octance.

Ø Cenane is a straight chain paraffin.

Ø Ethyl fluid is used to increase the octane rating of the fuel.

Ø The self ignition tempreature of diesel oil comprared to petrol is higher.

Ø Normal heptance accelerates auto-ignition.

Ø Cetane number is determined by compating the performance of diesel oil with the mixture of cetance and alphamethyl nepthalene.

Ø Lean mixture has high reaction time.

Ø Rich mixture has high reaction time.

Ø Chemically correct mixture has minimum reaction time.

Ø Violent sound pulsations within the cylinder of an I.C. engine are caused due to detonation.

Ø Auto-ignition temperature is that which it catches fire without external aid.

Ø Ignition lag is the time taken by fuel after injection (before top dead centre) to reach upto auto ignition temperature.

Ø The spark plug gap is normally maintained at 0.45 to 0.6mm

Ø The function of a fuel pump in a petrol pump is to, pump fuel so that it reaches carburettor.

Ø The delay period in petrol engine is of the order of 0.002 second.

Ø Detonation is caused by peroxides, aldehydes and ketones.

Ø If oerhead clearance is less, then the Horizontal type of engine should be selected.

Ø V-type engine has compact design requiring lesser space, improved distribution of air to cylinder, casting has liable to distortion and reduced torsional vibration because of shorter crankshaft.

Ø The piston are usually given a coating such a tinplating in order to reduce possibility of scoring.

Ø Piston rings are usually made of cast iron.

Ø Piston rings are plated with chromium, cadmium or phosphate in order to reduce wear and eliminate scuffing.

Ø The top piston ring hearer to the piston crown is known as compression ring.

Ø In order to prevent knock in the S.I. engine the charge away from the spark plug should have low temperature, low density, long ignition delay and rich mixture.

Ø Diesel engines have low specific fuel consumption compared to petrol engine.

Ø To reduce the possibility of knock in the C.I. engines the first elements of fuel and air should have high temperature, high density, short delay and reavtive mixture.

Ø The detonation tendency in petrol engines for specific conditon of fuel rating, compression ratio, speed etc. can be controlled by having smaller cylinder bore.

Ø According to Recardo’s theroy, detonation occurs due to instantaneous auto ignition of last part of charge to be burnt.

Ø A fuel will detonate less if is has higher self ignition temperature.

Ø The knocking in diesel engines for given fuel will be enhanced by decrreasing compression ratio.

Ø The ignition of charge by some hot surface in the engine cylinder fecore operation of spark plug is known as pre-ignition.

Ø Injection lag is time before fuel injectionand the pump pluger starts to pump fuel.

Ø Ignition quality of diesel fuel oil is expressed by an index called cetane number.

Ø For best results of efficient combustion, high speed diesel engines need an approximate cetane number of 50.

Ø Calorific value of diesel oil is of the order of 15000 Kcal/Kg.

Ø Carbon residue in diesel oil should not be more than 0.1%.

Ø The most popular firing order in case of four cylinder in-line I.C. engine is 1-3-4-2.

Ø The compression ratio of motor cars is 7.

Ø The specific gravity of diesel is 0.85.

Ø Freezing temperature of petrol is usualy less than -30 degree celcius.

Ø The specific gravity of petrol is 0.75.

Ø Detonation can be controlled by retarding the spark timing.

Ø The efficiency of I.C. engine normally is of the orde of 30-35%.

Ø The firing order in a six cy I.C. engine is 1-5-3-4-2-6.

Ø Sulphur content in diesel oil should not be more than 1%.

Ø The m.e.p. of a diesel cycle having fixed compression ratio with increase in cut off will increase.

Ø The ash content in diesel oil should not be more than 0.01%.

Ø The pour point of diesel oil must be lower than the coldest atmospheric temperature at which oil is to be pumped.

Ø High cabon content in diesel oil used for diesel engine leads to deposition on engine parts.

Ø Exhaust pipes of engines are covered with insulating material in order to reduce heat transfer to the engine room.

Ø Ignitiontiming of a multi cylinder petrol engine can be adjusted by rotating the distributor.

Ø Fuel consumption with increase in back pressure will increase.

Ø Leakage past the piston rings and valve seats in I.C. engines with increae in speed decrease.

Ø The heat wasted in diesel engine is of the order of 65%.

Ø With increase in speed of vehicle, the back pressure will increase.

Ø The function of a distrubutor in an automobile is to time the spark.

Ø The ratio of useful power, engine friction, exhaust gas losses, cooling water, air and oil losses for a diesel engine is of the orer of 25:5:35:35.

Ø For same power and same speed, the flywheel of a four stroke engine as compared to two-stroke I.C. engine will be bigger.

Ø Air injection in I.C. engine refers to injection of liquid fuel and air.

Ø Solid injection in I.C. engines refers to injection of liquid fuel only.

Ø The system of lubrication used for motor cycles and scooter is by mixing about 5% lubricating oil with petrol.

Ø The m.e.p. of a petrol engine first increases as the fuel air ratio  is increased and then decreaes on further increae in fuel air ratio. The m.e.p. is maximum in the zone of rich mixture.

Ø The specific fuel consumption for a petrol engine first decrease with increase in fuel air ratio and then increae with further increase in fuel air ratio. Minimum value occurs in the range of lean mixture.

Ø The thermal efficiency of a two cycle engine as compred to four cycle engine is less.

Ø Diesel engines as compared to petrol engines require bigger flywheel.

Ø Auto ignition reaction time for petrol engine first decrease with increasei in fuel air ratio, reaches a minimum value and then increases with subsquent increase in fuel air ratio. The minimum value occurs in the region of chemically correct fuel air ratio.

Ø The tendency of a diesel engine to knock increases, if compression ratio is increased.

Ø The tendency of a petrol engine to knock increases by supercharging.

Ø Free acids in diesel oil for diesel engine lead to demaging of both the storage tank and the engine.

Ø Thermal efficiency of high speed diesel engine at design load may be of the order of 35%.

Ø The thermostat in I.C. engines permitting hot water to go to radiator is set around 80-85%.

Ø The brake mean effective pressure of an I.C. engine with increase in speed will ramain unaffected.

Ø High ash and sediment in diesel oil used in diesel engine lead to excessive engine wear.

Ø Mixing of fuel and air in case of diesel engine occurs in engine cylinder.

Ø The advantage of reversing the flow of air in an air cleaner is throw out a large percentage of foreign matter.

Ø The most effective air cleaner in case of diesel engine is oil bath type.

Ø Fins are provided over engine cylinder in scooters for better cooling.

Ø The elements of most concrn in regard to pollution caused by engine are CO and hydrocarbons.

Ø The preferred laoction of an oil cooler is after the filters.

Ø The petrol from tank to the automotive engine is fed by pump run by engine.

Ø In petrol engine increase of cooling water temperature will increse th eknocking tendency.

Ø With increase in engine speed, the ignition of spark in petrol engine has to be increased.

Ø In petrol engines, the maimum power is developed corresponding to relative fuel air ratio of 1.1 to 1.3.

Ø In petrol engines using a fuxed octrane rating fuel , increase of engine speed will decrease the knocking tendency.

Ø In petrol engine using fuel having fixed octange rating increase in compression ratio will increase the knocking tendency.

Ø In a petrol engine Nitrogen as gets exhausted out without burning and without transformation.

Ø The level of fuel in the float chamber of a carburator as compared to the lvel of the jet in the venturi is lowe.

Ø In carburator the top of the fuel jet with reference to the level of the float chamber is kept at slightly higher level.

Ø Carburettor is done to break up the mix the petrol with air.

Ø Powerimpusles from an I.C. engine are smoothed out by flywheel.

Ø For low speed operation or for idling in petrol engines, the engine requirements are for rich mixture.

Ø In petrol engines, advancing the spark timing will increase the knocking tendency.

Ø In case of passenger cars, downward draught type of carburettor is preferred.

Ø The essential equipment for producing high voltage for sparking in petrol engines with bettery is ignition coil, contact breaker and ocndenser.

Ø The ignition coil in diesel engines produces volrage of the order of 20000 volts.

Ø If the door of a diesel enine crackcase is opened just after shutdown before cooling of engine then there is a risk of explosion taking place.

Ø The thermal efficiency of a diesel engine is of the order of 35%.

Ø The thermal efficiency of a petrol engine is of the order of 25%.

Ø Theoretically 4 stroke C.I. engine has maximum efficiency.

Ø The part load efficiency of a carburettor is poor.

Ø In petrol engine using a fixed octane rating fuel and fixed compression ratio, supercharging will increase the knocking tendency.

Ø High sulphur content in diesel oil used for diesel engines lead to production of highly corrosive gases corroding the cylinder walls and exhaust system.

Ø In open combustion chamber in diesel engines the shape of layout of the piston crown, the inlet port, and the valve produce the turbulent effect on the fuel mixture.

Ø The basic requirement of a good combustion chamber is high power output and high thermal efficiency.

Ø Deposition of cabon in petrol engine ylinder would result in increase of compression ratio.

Ø C.I. engine can work in very lean mixture.

Ø If petrol is used in a diesel engine then higher knocking will occur.

Ø Hor air standard diesel cycle efficiency with increas in value of Ca decrease.

Ø In turbulence chamber in diesel engine fuel is injected into an auxiliary chamber that is separated from the cylinder by an orifice or throat.

Ø For low load operation, more suitable engine is I.C. engine.

Ø A two stroke crank compressed engine has suction port, exhaust port and transfer port in the cylinder.

Ø For the same size and weight a two stroke engine as compared to four stroke engine will genetate power about 1.7 times.

Ø A two stroke engine is usually identified by absence of valves.

Ø If diesel is fed by mixtake in the oil tank of a petrol engine then engine will not run.

Ø The thermal efficiency of a semi-diesel cycle having fixed compression ratio and fixed quantity of heat, with increase in pressure ratio will increase.

Ø Scavengine air is supplied to a two stroke engine at a density greater than that of atmosphere. This means the engine is supercharged.

Ø Piston speed is equal to 2*stroke*rpm.

Ø In precombustion chamber in diesel engine only a part of air charge is ocntained in an auxiliary chamber in which the ful starts to burn with insufficient air which due to explosion tendency mixes thoroughly into main cylinder charge.

Ø In a diesel engine, injection pressure developed yb injector is of the order of  1400Kg/cm2.

Ø All the four operaitons in the two stroke engin are performed in one revolution of crank shaft.

Ø In the case of compression ignition engine, th e% of CO in exhaust gases is zero.

Ø As the number of cylinders in multicylinder engine increases, the power to weight ratio decreases.

Ø In isochronous governing speed droop is 30%.

Ø Method of governing use din petrol engine is quantity governing.

Ø For petrol and large gas engine, quantity governing is preferred.

Ø In quantity governing, air fuel rati is almost constant and quantity of charge is changed depending on load.

Ø In hit and miss governing fuel supply is completely cut off during one or more number of cycles.

Ø For close regulation of speed, combination of both quality and quantity governing is used.

Ø Method of governing used in diesel engine is quality governing.

Ø The bi-fuel engine uses liquid fuel diring start up and gas as the basic fuel.

Ø Morse test is used to determine mechanical efficiency of multicylinder engines.

Ø During idling stage, gasoline does not flow through the carburettor tube because of venturi vaccum.

Ø Thermal efficiency of I.C. engine on weak mixture is higher.

Ø In petrol engine the actual pressure developed compared to the predicted maximum pressure is 50%.

Ø Octance number of petrol normally used in petrol engines is of the order of 80-90.

Ø A fuel of octane rating 85 matches the anti knock qualities of a mixture consisting of 85% and 15% respectively of iso-octance and normal heptane.

Ø Octane number of petrol available from Indian refineries of the order of 13.

Ø Octane number of iso-octane is 100.

Ø n-heptane fuel detonates readily.

Ø Iso-octance has little tendency towards detonation.

Ø In spark ignition engines, the knocking tendency can be decreased by adding dopes like tetraethyl lead and ethylene dibromide.

Ø For spark ignition engines fuel in order of decreaseing knock tendency are paraffins, nepthenes, aromatics.

Ø Tendency of detonation in S.I. engines increases with increase of compression ratio.

Ø Anticlock for compresstion ignition engines is tetra ethyl lead.

Ø Detonation in petrol engines can be suppressed or reduced by the addition of small quantity of lead ethide.

Ø Performance number are indicative of the fuels having anti knock qualities superior to iso-octane.

Ø It is possible to obtain a number of blends of the fuel by mixing/blending cetane with alpha methyl napthalene.

Ø Compression for spark ignition engines usually varies between 6-13.

Ø Four stroke petrol engines as compred to two stroke petrol engines having same output rating and same compression ratio have higher thermal efficiency.

Ø Compression ratio for compression ignition engines usually varies between 14-25.

Ø The air requirement of a petrol engine during acceleration period in compression theoretically correct air required for complete combustion is less.

Ø Centane number of petrol is around 15-20.

Ø The Cetane number of diesel oil, generally available is of the order of 55-70.

Ø Morse test in multicylinder engines is used to determine mechanical efficiency.

Ø High speed diesel engines need a cetane number ot 50.

Ø The volatility of a diesel fuel oil is indicated by the 20% distillation temperature.

Ø Speed droop is the decrease in engine speed from no load to full load.

Ø Hunting occurs due to over control by the governor.

Ø Rocker arms are used in overhead valve engine type of I.C. engines.

Ø Cetane number is the measure of ignition quality.

Ø The detonation tendency in petrol engines increases with increase of compression ratio.

Ø The antifreeze solution commonly used in automobile biles is glycol.

Ø The power to weight ratio in a two stroke engines as compared to four stroke engines is more.

Ø Freezing temperature of petrol is of the order of 50 to -30 degree celcius.

Ø Injection lag in diesel engines is caused by expansion of fuel oil discharge lines under high pressure, compressibility of fuel and leakage past the fuel oil plunger.

Ø Pistons of diesel engines are usually cooled by lubricating oil.

Ø In order to reduce wear and eliminate scuffing, the piston rings are libricated.

Ø The back pressure of petrol engine is usually of the order of 1.2ata.

Ø The cause of smoky exhaust in a diesel engine could be fuel is not distributed equally to all the cylinder, exhaust valve receives too much lubricating oil, fuel injection is late or injector is not adjusted right and water in the fuel.

Ø The device used to reduce exhaust noise is called muffler.

Ø An engine will generate maximum torque when it runs at lowest speed.\

Ø The specific fuel consumption is expressed as the fuel consumed per hour per unit brake horse power.

Ø While two wheeler drives are started by kicking, four wheel drives are not because it requires less force to start two wheeler by kicking, it is not practicable to provdie kicking in a car and provision of battery ignition system in two wheel drives would occupy lot of space.

Ø Hgiher calorific value of a fuel is based on the assumption that the water is present in vapour form.

Ø When an engine is idling, it requires rich fuel air mixture.

Ø An ignition coil in the spark engine performs the function of supplying high voltage to the spark plug.

Ø In the case of compound engine, equal power is developed by each cylinder with a view of obtain uniform turning moment.

Ø The power to weight ratio of multicylinder engines with increase in number of cylinders for the same power will decrease.

Ø The compression ratio is kept low in petrol engine compared to a diesel because higher compression ratio in petrol engine would lead preignition of fuel.

Ø A distributor in spark ignition engine performs the function of providing the correct firing order in the engine.

Ø A temperature indicator is usually provided for automobiles. It indicates temperature of jacket cooling water.

Ø Lead-acid type of battery is commonly used in automobile applications.

Ø The gear ratio in the differential unit of a passenger car is of the order of 3:1.

Ø The differential in automobiles performs the function of permitting two rear wheels to have flexibility of relative speed, whenever it is required.

Ø Four wheel drive implies all the four wheels have power.

Ø Automobile engines are usually designed as multicylinder engines because of better balance uniform torque output.

Ø Commonly used accelerators are acetone peroxide, ethyl nitrate, isoamyl nitrate.

Ø Igniton acccelerators are substances which increase the rate o perflame reaction and reduce the ignition lag.

Ø Normal heptane accelerates auto ignition and iso-octane helps to resist it.

Ø Petrol engines are not suitable for part load operation because, mechanical efficiency is poor due to increasing internal losses at increased throttlin.

Ø Higher octane number means lower volatility.