Durability Improvement for 2-Stroke Forced Air Cooled SI Engine 2014-32-0113
In recent past, the two stroke vehicle manufacturers are continuously motivated to develop extreme low emission vehicle for meeting the requirements of emissions regulations. To achieve this emission compliance, manufacturers have developed engines with better induction system, improved ignition timings, increased compression ratio (C.R) and larger after-treatment devices. As an effect of above changes, engine operating temperatures are quite high which reduces the block-piston life. Even though, typical two stroke engines are forced cooled engines, there is a lot of potential for optimizing block cooling to reduce maximum liner temperature and block gradient for enhancing block-piston durability. This paper presents an experimental study of various measures to reduce liner temperature for a two stroke, single cylinder 70 c.c. engine used for two wheeler application. By studying the cooling air flow around the block and block to interface parts heat transfer, the following parts were redesigned to reduce maximum liner temperature - exhaust gasket, base gasket, cooling fan profile and cooling cowl. The new design showcased a maximum liner temperature reduction of 25°C and 35% reduction in block temperature gradient while testing on road at wide open throttle condition. Whereas under city drive condition, the maximum liner temperature reduced by 29°C while block gradient reduced by 33%. The new design also improved the block piston durability by 2.4 times under seizure simulation test cycle. Also, the hardness of engine tested piston with new cooling configuration was 28% higher compared to base engine.