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In the past we developed an injection-rate detector, however, it becomes no more applicable to modern high-pressure piezoelectric injection systems having functions of multi-stage injection due to the following problems: High-pressure injection generates shockwaves that induce pressure fluctuation, whose amplitudes of high-frequency components could be not effectively attenuated with a low-pass filter, in the detector. High-pressure injection also causes heterogeneous distribution of temperature in the detector, because the pattern of fuel flow from the injection nozzle to the discharge valve at fuel-discharging process is inappropriate. Accordingly, fuel temperature, which is necessary for identifying bulk modulus of fuel, in the detector could not be precisely obtained, thereby causing an unacceptable level of scattering for determining injection quantity. Hence, we developed a new detector in modifying its constructive design to solve the problems.

The injection rate meter based on W. Zeuch's method was improved to meet the recent requirement for precise measurement of the multiple injection rate and amount in CDI (Common rail Direct Injection) diesel engines. A pressure sensor with a high sensitivity was added to measure the small pressure increase due to the pilot injection and after injection. At the same time a flow meter having a high accuracy was installed in the discharge pipe line to obtain a correction factor to the modulus of elasticity of volume. As a result it became possible to measure the multiple injection amount at an accuracy of ±0.2mm3/stroke in a range up to 40mm3/stroke.