Maintenance of a car-
The exhaust gases in a petrol engine contain carbon monoxide, some burnt hydrocarbon, and oxide besides other harmful substances in negligible quantities. It is, therefore, obvious that unless the engine is maintained in good condition always, the exhaust gases are likely to contain higher parts of pollutants.
To keep and maintain the engine in good condition, the following should be checked regularly at stipulated intervals.
Cylinder pressure-
The cylinder pressure or compression should be maintained at the prescribed level. Otherwise, the engine cannot run effectively and deliver the desired power. The pollutant level in exhaust gases can never be kept at prescribed levels. Compression in the cylinders can easily be checked with a compression gauge.
In a Premier car, depending on the compression ratio varying from 8.3: 1 to 8: 1, the compression pressure should normally be 100 to 110 N/cm2.
Should it fall below 65 to 75 N/cm2 depending on the compression ratio of the engine, it indicates the necessity for an overhaul of the engine. Between the cylinders, a difference of more than 7 N/cm also warrants an overhaul of the engine. However, while the compression pressure is at the lower levels as above, the level of pollutants in the exhaust gases will be higher due to incomplete combustion.
In an Ambassador Car, the compression pressure should normally be around 80 N/cm2 and should not fall below 70 N/cm2. Below the level indicated, the engine needs an overhaul.
Valve-
The inlet valves in the engine permit air petrol mixture inside the cylinders and the exhaust valves allow the burnt gases to go out of the cylinders. Proper valve clearance must be maintained. It is 0.25 mm for the inlet as well as exhaust valves at the operating temperature of the engine (80-85°C) for Premier and Hindustan Ambassador cars.
In Maruti cars, the valve clearance should be 0.13 to 0.18 mm when the engine is cold and 0.23 to 0.28 mm when the engine is hot.
Inlet manifold-
Crank case ventilattion-
All manufacturers provide engine crankcase ventilation as well as absorption of the oil fumes by the air cleaner to be drawn into the engine along with the air-fuel mixture. The pipes, passages, and filler caps provided with breather passages or holes should be kept clean.
Air cleaner-
The car may have a dry paper filter type of air cleaner or an oil bath air filter.
The Air cleaner cleans the air going to the engine, silences the noise while the air is drawn into the engine, and is also a flame arrester when the engine backfires through the carburetor.
A choked dry paper air cleaner or an oil bath air cleaner with insufficient oil or an unclean one will result in the engine running on a rich mixture resulting in higher Pollutants levels in exhaust gases.
So, it is necessary to have an air cleaner and maintain it in a good condition. Change the dry filter element every clean and refill oil every 1500 km.
Carburetor-
The carburetor plays an important role in the composition and levels of pollutants in exhaust gases.
The carburetor helps in vaporizing the petrol in a fine mist and supplies the correct strength of the mixture at different conditions, such as starting, idling, cruising, and accelerating to enable the engine to develop maximum possible power with a possible economy on fuel.
The choke is to be used only to give a rich mixture for starting in cold weather. Once the engine runs smoothly, the choke lever should be pushed back to the original position and you should also ensure that the choke valve is fully open. Otherwise, the engine will continue to run on a rich mixture with the level of pollutants high in the exhaust gases.
Standard and economy carburetor jets and venturies are available for Premier cars. Economy jets and venturies may be used to obtain safe levels of pollutants in exhaust gases.
Carburetors should be adjusted correctly to allow the engine to idle smoothly at 500 — 550 rpm
The pollution level of exhaust gases is checked at idling speed. If the engine is to be kept idling for more than
1 or minutes then it is advisable to switch off the engine to reduce pollution, particularly at traffic stops and hold-ups.
The engine will not idle smoothly for various reasons like advanced or retarded timing, an incorrect gap at contact breaker points or spark plugs, incorrect adjustment of volume control screw (Air screw) in the carburetor, choked exhaust silencer, flooding of the carburetor due to faulty flood level or valve or higher discharge pressure of fuel pump due to sagged diaphragm besides poor and uneven compression in cylinders, improper valve clearance, rich mixture, choked cleaner, burnt exhaust or inlet valves.
Fuel pump-
The fuel pump should be serviced at prescribed intervals, say once in 3 months. If the fuel pump discharge pressure is in excess then it might either flood the carburettor and increase the fuel consumption even without flooding and result in a rich mixture being fed to the engine which will increase the level of pollutants in the exhaust gases.
Petrol tank leakage-
Never fill the tank to the brim and always keep the level of fuel above half the capacity of the tank to reduce evaporation loss and thus pollution also.
(i) The ignition system in an engine also contributes liberally to the upkeep of the engine and its efficiency.
The contact breaker points should be clean and free from pitting or uneven surfaces and the gap should be maintained between 0.27-0.38 mm.