Jeffrey Allen

A Novel Low Cost High Frequency Fuel Injection System for Small Engines

Small engines (<19kW) are used in many offroad applications, in both the domestic and industrial markets. The dominant driving force in these markets is cost; therefore the vast majority of these engines still use low cost carburettors to meter the fuel into the intake port. However all these engines are now facing increasingly strict emission targets and hence require new technologies to meet these new regulations, but any new technology must be extremely cost effective to be applicable. The conventional fuel injection solutions used for many years in the automotive market require complex systems including a fuel pump, pressure regulator, and fuel injector coupled to a sophisticated control module and a multitude of sensors. This type of solution is far too complex and expensive for the vast majority of engines in the small engines market, and would cost significantly more than the engine itself. A novel solution to this problem is high-frequency Pulse Count Injection (PCI). This design of fuel injection system has a single injector, shown in figure 1, which works as a simple positive displacement pump with a fixed geometric volume (typically 0.5μL). Each time the injector is energized it will deliver this known quantity of fuel to the engine (Fig. 2,) without the need for a separate fuel pump or regulator. The total amount of fuel required by the engine can therefore be delivered as a number of high frequency pulses each engine cycle. With the pulse injector working at a fixed frequency (over 1kHz) and a fixed pulse width, the fuel requirement for the complete speed/load range of a small displacement engine can be accomplished. Load and speed inputs can be processed very simply, and as a result the electronics and the power required to run such a system can be kept to a minimum. Figure 1. A PCI next to a UK penny (20mm diameter). Figure 2. Spray pattern generated by a prototype PCI

Low Cost Hybrid Motorcycle Optimisation Model

Contained within this paper is a discussion into the modelling and control of the electrical architecture for a HEV. Two configurations of electrical architecture are discussed; a system in which the bus voltage is allowed to vary during vehicle acceleration and regenerative braking and secondly, a fixed bus voltage system in which the voltage is held constant by the inclusion of a bi-directional DC-DC converter. The relative merits of each nsolution are discussed. Consideration is given to the component sizing of the energy storage device, the associated control system complexity and finally the performance of the HEV.

Fuel Injection for Low Emission 50cc 2-Stroke Scooter

The ideal attributes of light weight, low cost and high power density have made the 2-stroke engine unrivalled in the scooter and moped market for many years. However, the challenges of meeting new emissions regulations, especially the latest Euro III emission test cycle have reduced the 2-strokes dominance and it is now often considered to be too dirty and inefficient to have a future. As a result its product placement is on the decline. This paper introduces and discusses the latest application of a low-cost high-frequency injection system (Pulse Count Injection [1,2]) to both the fuel flow and lubrication oil flow of a 2-stroke scooter; allowing both fluids to be individually mapped and optimised for the complete engine operating range. This in turn enables the 2-stroke engine to pass the latest Euro III test whilst improving the fuel economy by a considerable margin, without changing the architecture of the engine. Examples of the latest developments of a highly integrated engine management system, including fuel and oil injector technology are shown. The paper draws conclusions from the test results showing the clear benefits of electronic fuel injection both for emissions and fuel consumption, and demonstrates that these benefits are achievable from a compact well integrated throttle body unit suitable for the small 2-stroke engine market. INTRODUCTION: 2-STROKE MOTOR APPLICATIONS, CONCERNS AND FUTURE POSSIBILITIES Although the 4-stroke engine has replaced 2-stroke engines in markets where emission legislation has been brought in force, there are still many applications where the light weight and low cost benefits of the 2-stroke engines are so significant as to make them irreplaceable. The lower powered, heavier and more costly 4-stroke engine replacement would severely compromise the function and/or performance of the end product. Examples Page 2 of 14 of these applications are the chainsaw, small outboard motor and limited capacity moped or scooter, where maximum power from a very small, lightweight and low cost engine is paramount. Examples are shown in Figure 1. Figure 1 Examples of applications requiring the lightweight power of a 2-stroke engine However, even in these specialised areas there is a necessity to meet new clean emission standards and reduce fuel consumption (CO2 emissions) in line with environmental trends. It is therefore essential that full electronic control of the 2-stroke engine is applied in order to fully optimise the combustion and performance of these small engines and ensure compliance with future standards. Table 1 shows the historic emissions regulation limits for 2-stroke mopeds and the proposed new limits coming into force in 2012. Table 1 Emission limit trend for 50cc mopeds. Stages Emission limits for type approval and conformity of production for Mopeds Test cycle CO (g/km) HC + NOx (g/km) 1999 (EURO 1) 6.0 3.0 UN-ECE Reg.47 2002 (EURO 2) 1.0 1.2 UN-ECE Reg.47 2012 (EURO 3) 1.0 1.2 UN-ECE Reg.47 Hot and Cold Cycles Previous work has been done showing the dramatic reduction in emissions that can be achieved with 2-stroke engines using Direct Injection of the fuel into the combustion chamber [3,4,5] and this technology is often applied to high end expensive 2-stroke engines such as high performance outboard motors and jet skis. However, this solution while technically applicable to the smaller engines carries with it a high on-cost and complexity which has prevented it from large scale application in the low cost markets.

Low cost electronic fuel injection for 2 and 3 wheeled motorcycles

As a result of environmental pressures and end-user demands many companies are working on low cost fuel injection and engine management systems for 2 and 3 wheeled vehicles. This market sector accounts for up to 80% of new vehicles in many Asian countries, with over 9 million new 2 wheeled vehicles registered in India alone annually, the vast majority of these still being fuelled with carburettors. A common approach to fitting EFI to these applications is to take an existing engine management system derived from automotive or high end motorcycle applications and re-design it to try and reduce its size and cost for the 2 and 3 wheeled market.