Experimental Results of New Fuelling Strategies for High Frequency Low Cost Injection Systems for Small Engines

With increasing pressures to reduce engine emissions in the small engines market there is a need to precisely meter the fuel flow into the engine under all running conditions. Therefore this cost competitive market requires a well engineered injection system that combines good control of fuel metering at all speed / load conditions, and meets the markets competitive pricing requirements. It must also offer the potential to allow these engines to meet stringent future legislation, leading to the addition of closed loop control with 3 way catalysts.

This paper presents an experimental investigation into the effect of wall wetting and fuel injection strategy on a small engine. The engine was fitted with a novel form of port fuel injection, Pulse Count Injection (PCI) [1.] This novel high frequency digital fuelling system allows rapid oscillation of the fuel quantity from one engine cycle to the next.

The result of the investigation is a novel fuelling strategy that enables good fuelling control under no load idle conditions where very fine fuelling control is most desired.