Precision assembly is key to novel fuel injection system

Kistler's electromechanical NCFT servo press module is being used to provide the essential assemble precision and repeatability for a new type of fuel injection system. The new system is both low cost and simple enough to be viable on small engines from 50 to 250cc, a range that covers everything from lawnmowers and small marine outboard motors to motorcycles and scooters.

The rig used by Scion Sprays to hold the components in place during laser-welding uses a Kistler NCFT servo press module. These modules are simple to install, requiring only a 3-phase electrical supply, and have integral piezoelectric force and absolute encoder displacement monitoring capabilities that simplify the precise programming of home position, return stroke, joining stroke and an intermediate position. Of special importance to Scion Sprays is the 0.005mm repeatability of the NCFT units under real-world production conditions, ensuring that the injector pulse volume of 1ul (one micro litre) is maintained during quantity production.

Designed and manufactured by Scion Sprays, the new system avoids the need for expensive high-pressure fuel pumps and complex electronics by using Pulse Count Injection (PCI), which injects a small, geometrically fixed volume of fuel repeatedly into the engine intake manifold rather than the Pulse Width Modulation used by conventional systems. The amount of fuel injected is determined by the number of pulses injected during the intake phase of the cycle. Typically, the pulse volume is 1ul and the pulse frequency greater than 1kHz. In this way, the injector acts as both pump and flow meter.

In addition to reliability, simplicity and low cost, the Scion Sprays PCI injectors make a valuable contribution to environmental protection by reducing emissions of HC+NOx by 35 per cent and CO by over 88 per cent compared with a standard carburettor-fitted engine, and minimise the amount of unburned oil in the exhaust of 2-stroke engines.

For more information about the electromechanical NCFT servo press module from Kistler, visit the website at www.kistler.com.