Emission Control of In-Use Vehicles

Anil Chhikara, Head - Car Fleet Operations for Commonwealth Games 2010

Indian automotive industry has made rapid strides in switching over to Bharat Stage-IV Emission Standards and is catching up fast with European and other developed countries in controlling emissions from motor vehicles. However, in-use (old) vehicle emission check regime in India has hardly made any contribution to protect the environment. It does not mean that we are not sincere; the fact is that we have not targeted the gross pollution from vehicles plying on roads. We are targeting only a small proportion of new vehicles, while highly polluting and smoke belching in-use vehicles, which constitute a major chunk of the vehicle population virtually go scot-free. The objective of prevailing emission control practice and vast majority of vehicle users is just to meet the legal requirements. No sincere effort or spirit is visible in either containing pollution or conserving fuel.

The vehicle engine has broadly two stages of fuel supply - at no-load and at load-mode. The fuel supply at no load or during idling is very low compared with a driving condition when a vehicle is negotiating a gradient and/or is fully loaded. The emission measurement of in-use vehicles, at present, is done only at no-load, while no tests are done at full-load or loaded mode. Normally, while we drive our vehicle, the vehicle remains idle or without accelerator being pressed only for 10-15% of the whole travel. At idling, the fuel supply is minimum adjusted; so, it may not provide the profile of the emission behaviour of normal driving pattern during commutation or journey. Since 2004, fast idle test has also been introduced for BS-II compliant vehicles and above. But, this test also has a limited scope and does not capture the true results or the health of engine. Similar situation is for Diesel Vehicles checked at fast idle no-load mode. The vehicles passed at no-load test should not lead one to conclude that it is not polluting at high speed, hilly terrain or overloaded condition. Conversely, it also does not mean that a vehicle passed at load mode will meet the other parameters of tests at no load. It is important to note that the existing test for inline fuel injection pump is very difficult and complex. This test is hardly carried out properly anywhere in India with defined procedure except at few places.

It is also important to know what is emission - it is broadly un-burnt fuel and harmful gases arising out of fuel burning, which need to be minimised for controlling emissions. For new vehicles, the initial adjustments are able to control pollution but after prolonged usage, the emission level increases manifold. A mal-adjusted vehicle can still pass the emission tests at no-load and such settings may have very little effect in minimizing the crude smoke i.e. un-brunt fuel. Few of such adjustments are broadly summarised as under:

S No.	Item	Gasoline/ petrol engine	Diesel engine
1	Air cleaner chocking restricting fresh air to come in
2	Nozzles of fuel clogged or tip damaged
3	Valve timing overlapping releasing unbrunt fuel
4	RPM setting
5	Spark plug, induction coil, timing, distributor system		X
6	Carburetor, diesel/petrol fuel management system
7	After-burn system e.g. cat convertor, PM filters

 
It is now clear that we had the strategy to control the input substances i.e. fuel and air at no-load but did not do anything to check the performance with regard to emissions, which is also equally important parameter of good engine performance. When we see overloaded trucks/three-wheelers running on roads, highways or hilly terrains, one can see excessive smoke coming out of the exhaust pipe with a burst when the accelerator is pressed, particularly while negotiating a gradient. At no-load, these vehicles behave smart but while climbing up a hilly terrain they emit smoke.

 
The above profile illustrates the fuel supplies to engines in case of diesel and petrol engines and how the fuel intake increases with increased RPM and load. The unburnt fuel increases, if full combustion does not take place or compression of engine decreases. Needless to mention, a loaded truck needs more power. The engine needs more fuel for more power and the vehicle needs to be driven at a lower gear, particularly at gradients, with full accelerator pressed. As a result, a large amount of fuel (up to 60% in some cases) is wasted as un-burnt fuel. The decreased compression capacity of the engine with prolonged use of vehicle results in excessive smoke. Therefore, the no-load test does not truly reflect the engine or emission performance. The other fallacy of the idle tests is that they are not able to check the NOx increases in case of high temperature / high pressure, lean burn or incomplete combustion. This NOx creates smog or haze making white translucent cover over cities particularly when air is not blowing fast.

Solution

To mitigate these problems, the loaded mode test, which will check the emission constituents in actual driving conditions or simulated conditions, should be introduced. This test will provide the authentic emission profile of the vehicle during varied conditions at which the engine operates. The only difference the test in load-mode will make is that a dynamometer with power absorption will have to be attached to the smoke meter / gas analysers .The results available from such test will also indicate the behaviour of engine like stalling, missing, vibrations, if any, which does not come out during no-load conditions. The results will show if engine is weak or an incomplete combustion is taking place resulting in high fuel consumption, lack of power and visible smoke.

This test further brings out information about clutch and power transmission deficiencies. In addition, the test also informs about the level of NOx, which varies depending upon the temperature or pressure.

Catalytic converter performance test is also possible through the test using dynamometer. This test is sometimes also called the smog test, because only such test can quantify various emission contents. This test is similar to treadmill test of heart patient. The test, in nutshell, gives the entire profile of engine and power transmission for which no other test that measurers various parameters of emission and engine performance so meticulously, is available at present.

Such an emission control program, widely called as I&M 240 or ASM (Accelerated Simulation Mode) is obtaining in various states of US, Europe and leading countries of Asia, who count emission as a major concern. In India, till now, the emission testing is almost a perfunctory activity and the system of Inspection and Maintenance (I&M) needs to be promoted proactively by all stakeholders. This system holds good both for Petrol and Diesel vehicles. The time taken for an individual test may be around 10-15 minutes and the cost of equipment would be around 30-40 lacs (indicative). However, the benefits would be enormous. It is estimated that savings in fuel consumption would be around 1.2 % of India's GDP. An effective I&C/I&M regime will help not only fuel conservation but also lower vehicle emissions leading to clean environment.

 
Conclusion:

1.	Visible emission and smoke from a vehicle may be the best way to identify a polluting vehicle from a distance.
2.	The loaded mode test needs to be incorporated as one of the annual mandatory tests for non-transport vehicles (PVs & Two-Wheelers) and transport vehicles (trucks/buses) in addition to the existing practice of no-load tests.

 
Disclaimer: The author's observations are purely personal and are shared with a view to generating discussion among all stakeholders on the need for an effective I&C/I&M regime in India.