Multec 3.5 Fuel Injector Application Manual
Product Description
Delphi Energy and Chassis Systems
Revision:
11/05-1
3-15
3. Engine’s Brake Specific Fuel Consumption (BSFC) ratio
•
BSFC is the ratio of measured engine fuel flow to engine
horsepower output (Lb
m
/HP*Hour)
.
It is determined on a
dynamometer and is a function of RPM. If data is available, the
engineer should use the BSFC value at peak horsepower RPM. If
data is not available, 0.55 Lb
m
/HP*Hour can be used for initial
estimates. The BSFC used should comprehend the alternate fuel
requirements for the application. Higher concentrations of
alcohols will have higher BSFC requirements.
4. Number of cylinders
•
The number of engine cylinders information will be required to
convert required engine fuel flow to required injector fuel flow.
(Assuming a one injector/cylinder design.)
5. Minimum fuel flow rate
See Section 3.10.1
•
The ratio of the minimum flow rate and the maximum flow rate
determined from this procedure will determine the required linear
flow range for the injector. The linear flow range calculation will
help determine which injector design would meet the vehicle
requirements. To determine the minimum fuel flow rate, four
conditions should be considered.
−
Idle
(The minimum fuel rate required by the engine is based
on a no load idle of a warm fully broken in engine at altitude.
No load implies a charged battery, no air conditioning, no
steering wheel motion and vehicle in neutral. Testing at
altitude decreases the pumping work. If the minimum
required flow rate is not measured at altitude, then an
additional safety factor of 10% to 15% should be used to
account for the effects of altitude.
−
If the vehicle calibration requires
make-up pulses
. Make-up
pulse requirements could be one tenth of the idle flow
requirement. (A make-up pulse is a fuel injection pulse
delivered after the normal injection pulse, but before the
intake valve opens. The make-up pulse is calculated in
response to increased engine power requirements occurring
after the normal pulse was calculated and delivered.)
−
Any
deceleration fueling requirements
. The fuel flow rate
required during steady state decel is a function of the engine
speed and manifold pressure during decel.
−
Any idle
purge requirements
. The amount, if any, of
evaporative canister fuel vapor recirculation must be
determined as a percentage of the fuel supplied to the engine,
reducing the fuel flow rate requirements of the injector.
