Delphi Multec 3.5, Руководство по применению

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Fundamentals Multec 3.5 Fuel Injector Application Manual
2-8 Delphi Energy and Chassis Systems
Revision: 11/05-1
2.2.3 Fuel Spray Characteristics and Injection Timing
For maximum vaporization, fuel is typically targeted at the intake valve,
as it is typically the hottest surface in the combustion chamber induction
path. Fuel is typically injected before the intake valve opens and is
allowed some residence time to allow the fuel to vaporize. Fuel
vaporization also occurs as the air/fuel mixture passes the valve on its way
toward the combustion chamber. As the time between valve events
decreases (as engine rpm increases), the time for vaporization is also
reduced.
PZEV (partial zero emission vehicle) exhaust emission regulations have
placed additional emphasis on fuel delivery (atomization and timing.) The
majority of the tailpipe emissions measured during a Federal Emissions
Test Procedure (FTP) are generated during the time period between engine
start and catalytic converter warm-up (reference section 2.2.7.3.)
Alternate fuel delivery schemes may be employed during this time period
to minimize emissions. Consult with your Delphi Applications Engineer
for more information.
Note Reference Worldwide Emissions Standards booklet available from Delphi
for emissions regulations and test profiles.
Spray not targeted at the intake valve can be stored as liquid on the intake
port walls. The conditions when this collected fuel enters the combustion
chamber may be difficult to predict, affecting engine emissions and
driveability.
See Section 5 for
calibrating optimum
injection timing Typically, open intake valve fuel injection timing is not recommended for
conventional fuel injection systems with Multec 3.5 injectors because the
fuel bypasses the heating effects of the intake valve. If injection takes
place as the intake valve first opens, the reversion pulse at the end of the
exhaust stroke can divert the spray, greatly affecting both the targeting of
the spray and the particle size. If injection occurs just as the intake valve
closes, the fuel spray may be affected by a back flow of air caused by the
pressure wave generated by the valve’s closure.
Direct injection schemes that utilize open valve injection require specific
hardware. Please consult a Delphi representative for more information on
Delphi direct injection (DI) fuel systems.
Note This manual covers only the basics of spray particle size, targeting and
injector timing. Consult a Delphi Applications Engineer for more
information.