1.)CRITICAL COMPRESSION RATIO – Lowest compression ratio at which any particular fuel will ignite by compression under prescribed test procedure. The lower the critical compression ratio the better ignition qualities the fuel has.
2.)DEGREE OF ATOMIZATION– is indicated by the smallness of the size of the particles in the spray and also by the smallness of the variation in the size of the particles.
3.)DELAY PERIOD – Time interval between the start of injection and begining of combustion as indicated by a rise in the pressure crank angle curve, from the curve which represents compression and expansion of air while motoring. Also called IGNITION DELAY.
4.)DIRECT INJECTION ENGINES– have a single open combustion chamber into which the entire quantity of fuel is injected directly.
5.)OPTIMUM INJECTION ADVANCE – Fuel injection timing before TDC which will result in minimum ignition delay.
6.)RESIDUAL PRESSURE – The pressure at which the fuel is retained in the fuel line when the injector needle valve and the pump delivery valve are in the closed position.
7.)SAC VOLUME– is the dead volume between the nozzle seat and the end of the spray holes, in a multi hole injector.
8.)SOLID INJECTION SYSTEM – The system which injects only the metered quantity of fuel by means of a pumping device. Also called AIRLESS INJECTION SYSTEM.
9.)UNIT INJECTOR – A combined fuel injection pump and fuel nozzle.
10.)VALVE CLOSING PRESSURE– is the fuel pressure at which the fuel injector needle valve snaps back on its seat. For the differential valve stem, this is less than the nozzle opening pressure.
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