Software
Multec 3.5 Fuel Injector Application Manual
5-2
Delphi Energy and Chassis Systems
Revision: 11/05-1
•
The mass airflow system
directly measures the airflow into the
cylinders using a mass airflow sensor normally placed at the at the
throttle body inlet.
5.2
Control Algorithms
The following closed-loop and open-loop software sections briefly
describe engine and engine management system components that typically
influence air/fuel control and thereby impact control of the fuel injector.
The system software has control algorithms to make corrections to injector
pulse-width. Corrections are determined using closed-loop and open-loop
feedback. Each correction has its own algorithm within the performance
characteristics of the application specific software.
Note
The complexity and size of control system software and algorithms are
driven by emissions and diagnostic requirements. The use of the following
algorithms is dependent on government and customer requirements (some
systems do not require closed-loop correction to meet performance and
emissions goals).
5.2.1 Injection
Methods
Refer to Section 5.2.5
There are four fuel injection timing methods. (See Figure 5-1.) Cost and
emissions output play key roles in determining which of the four methods
is used.
5.2.1.1 Simultaneous Single Fire (SSF)
Injectors are pulsed simultaneously once per engine cycle (i.e. once every
two crankshaft revolutions). SSF is used during transitions to and from
Deceleration Fuel Cut Off to avoid going below the minimum injector
pulse-width. It is not recommended for use during idle or driving modes
because it can cause problems with engine combustion stability.
5.2.1.2 Simultaneous Double Fire (SDF)
SDF pulses the injectors twice every engine cycle, or once per crankshaft
revolution. But rather than alternately pulsing injector groups like ASDF,
SDF pulses all the injectors at once. Each pulse-width is shortened,
dispensing half the required fuel per engine event. SDF results in even
more variation in fuel vaporization entering the cylinder, but is less costly
than ASDF because there is only one injector driver.