Buell 2004 XB9S Service Manual Download

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2004 Buell Lightning: Fuel System

4-3

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DYNAMIC DIGITAL FUEL INJECTION (DDFI)

4.2

INTRODUCTION

The Buell Dynamic Digital Fuel Injection (DDFI) System pro-
vides microprocessor-based electronic engine management
for the 984cc and 1200cc high performance engines. The
DDFI system has the following features:

●

Independently mapped spark and fuel control.

●

Engine and air temperature compensated fuel delivery.

●

Engine load measurement through throttle position.

●

Single point spark delivery (no waste spark).

●

Sequential port indirect (manifold) fuel injection.

●

Open/Closed-loop air/fuel control.

●

Automatic enrichment at start-up.

●

Electric cooling fan for improved thermal management.

●

Engine speed and position determined using a single
sensor (Cam Position Sensor).

●

Full diagnostic capability compatible with the DIGITAL
TECHNICIAN (Par t No. HD-44750-P28/Panasonic
Toughbook or Part No. HD-44750-D150/Dell Desktop).

●

Returnless fuel system (excess pressure relieved in tank
by Fuel Pressure Regulator Valve).

●

Interactive muffler control with muffler valve position
feedback for 1203cc engines only.

The DDFI system uses six sensors to monitor the operating
conditions of the engine and make decisions as to spark and
fuel delivery. These sensors are:

●

Throttle position (TP) sensor.

●

Cam position (CMP) sensor.

●

Engine temperature (ET) sensor.

●

Intake air temperature (IAT) sensor.

●

Oxygen (O2) sensor.

●

Bank Angle Sensor (BAS).

The DDFI system also analyzes how the engine performs
during a ride. It then stores this information internally so it will
be available for the next ride.

The XB12S utilizes an interactive exhaust system which has
an electronically controlled actuator that activates a butterfly
valve that controls exhaust flow in the dual-chamber muffler.
The engine ECM monitors engine speed and throttle position
while activating the valve. See

7.6 INTERACTIVE EXHAUST

SYSTEM (XB12S)

GENERAL

The Buell DDFI operates both as an open and closed loop
system which allows it to adjust for all possible operating con-
ditions. During open loop operation, the system utilizes pro-
grammed fuel and spark maps in the ECM which provide
ease of cold starting and maximum power at wide open throt-
tle (WOT). The adaptive fuel value which is “learned” during
closed loop operation is applied during open loop operation to
adjust fuel and spark maps for optimum performance.

During closed loop operation, the system relies on input from
the O2 sensor to provide for the most efficient, stoichiometric
air fuel mixture (14.7:1) which results in reduced emissions,
good fuel economy and power. In order for the system to
enter closed loop operation, the following conditions must be
met:

●

O2 Sensor at operating temperature (Engine at normal
operating temperature).

●

Operation below 5000 RPM with engine under normal,
steady load conditions.

By using both open and closed loop systems, engine perfor-
mance is continuously tuned to compensate for changing
conditions and provide maximum performance.

Buell 2004 XB9S, Service Manual

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