Improving the performance of two-stroke spark ignition engine by direct injection

Two Stroke Spark Ignition Engines have high exhaust emissions and low brake thermal efficiency due to the short-circuiting losses and incomplete combustion, which occur during idling and at part-load operating conditions. In the present work an attempt was made to eliminate the short-circuiting losses by direct injection. A low-pressure direct fuel injection system was developed with the Bosch electric fuel pump and solenoid injector. The necessary electronic control unit hardware and software were developed in the institute for research purpose. The present work was conducted in three phases. In the first phase the carburetor was replaced by the manifold injection system and the performance of the system was optimized for minimum emissions. In the second phase the extra reed valve concept reference (10) was implemented on the manifold injection system to improve scavenging. In the final phase the direct injection system was developed which eliminates short-circuiting losses completely. The performance, emissions and combustion characteristics of the above three systems at 2500,3000, 3500 and 4000 rpm were analyzed on a 150-cc single cylinder engine. The operation of the three systems and their benefits are described in detail in the following sections. Copyright © 2001 ATA, SAE International and SAE of Japan.