Product Description Multec 3.5 Fuel Injector Application Manual
3-18 Delphi Energy and Chassis Systems
Revision: 11/05-1
Additional assumptions for the following calculation
− One injector per cylinder
− Sequential injector firing
Engine repetition rate = [1/ RPM] * [(60 sec/min)* (2 rev/inject)*
(1000msec/sec)
Example @ 600 RPM:
Engine rep rate = [1/600 RPM]*120,000 msec/inject
= 200 msec
Injector test stand repetition rate is normally 10 msec.
Required fuel flows at test repetition rates:
Minimum fuel flow = 0.023 gm/sec * [200 msec/10 msec]
= 0.46 gm/sec (on test stand at 10 ms
period)
Maximum fuel flow = 3.68 gm/sec
Required Flow Range = Max flow / Min flow
= 3.68 / 0.46
Required Injector Linear and/or Working Flow Range = 8
Sections 3.10.1 and 3.10.2 describe the differences between linear and
working flow range. The engine control algorithms available for a
particular application will determine whether the system flow range
requirement calculated above will impact the linear or working flow range
requirements for the injector. The different calibration control algorithms
are described in section 5.2.
Note: These calculations assume constant injector pressure drop. For non-
vacuum biased fuel systems, the flow rate calculations will need to be
adjusted to compensate for the non-constant pressure drop between idle
and maximum power operating conditions due to varying manifold
vacuum.
In other words, the minimum engine fuel flow rate calculated above will
occur at a higher injector pressure drop than the maximum fuel flow rate
for a vacuum biased fuel system. The max and min flow rates should be
normalized to the same injector pressure drop before making the flow
range calculation.
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