Development of Electronic Carburetor for 4-Stroke Two-Wheeler Vehicles 2003-26-0025
Automotive emission regulations in India are becoming stringent day-by-day. With the deterioration of air quality, the new techniques suitable under Indian condition to reduce the emissions from automotive vehicles are becoming extremely important. In India large percentage of the vehicle population is 2-wheeler vehicles using a mechanical control for the air/fuel ratio. A project was undertaken to develop the simple Electronic Control System (ECS) for 4-stroke 2-wheeler vehicles.
With the unleaded petrol available in the India, catalytic converters are becoming popular and are used on almost all passenger car vehicles as well as 2-stroke 2-wheeler vehicles. Efficiency of the 3-way catalytic converters is optimum for all the three pollutants provided the Air Fuel (A/F) ratio is maintained at the stoichiometry. It is very difficult to maintain A/F ratio at stoichiometry with the mechanical controls presently used. If the 3-way catalytic converter is used with present system, the efficiency will not be optimum, but it will be possible to meet the Bharat Stage II norms. The effort was made to optimize the system to achieve best possible results for the futuristic norms.
An innovative way of controlling the fuel in the carburetor by controlling the air in the air bleed circuit using a solenoid valve was tried out on a 4-stroke 2-wheeler vehicle. An Electronic Control Unit (ECU) was developed to control the solenoid operation depending on the feedback from the lambda sensor in the exhaust. The A/F ratio was maintained at the stoichiometric value.
Optimisation was carried out to optimize various system parameters both under steady state and transient condition.
It was possible to achieve the CO and HC+NOx emissions at the level of around 0.3 g/km on Indian Driving Cycle (IDC) as against the present limits of 2 g/km.
The paper also gives the results of the improvement possible in the catalytic converter efficiency with and without electronic controls.