Ignition System - Buell 2009 XB Series Service Manual

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IGNITION SYSTEM

GENERAL
PART NUMBER
HD-48650 DIGITAL TECHNICIAN II
The vehicle uses a breakerless inductive-discharge ignition
system. The system has both a primary and secondary circuit.
The primary circuit consists of the battery, main fuse, ignition
switch, primary coil windings, computerized ignition timer and
associated wiring. The secondary circuit consists of the sec-
ondary coil, spark plugs and associated wiring. See
DIGITAL TECHNICIAN II (Part No. HD-48650) can access the
information received by and stored in the electronic control
module.
The electronic control module (ECM) is located in the fairing
(Firebolt models) or under the seat (Lightning and Ulysses
models). The module has three primary functions. First, it
computes the spark advance for proper ignition timing based
on sensor input. Second, it controls the independent, primary
windings of the spark coil and is thus able to provide sequential
and independent firing of the spark plugs (non waste spark).
Third, it calculates the correct air/fuel ratio based on input from
the sensors.
The electronic control module contains all the solid-state
components used in the ignition system. The dwell time for the
ignition coil is also calculated by the ECM microprocessor and
is dependent upon battery voltage. The programmed dwell is
an added feature to keep battery drain to a minimum and to
adequately charge the coil at all speeds. The ECM has added
protection against transient voltages, continuous reverse
voltage protection and damage due to jump starts. The ECM
is fully enclosed to protect it from vibration, dust, water and oil.
The module is not repairable. Replace the unit if it fails.
The ECM uses the following sensors to monitor rider demands
and engine conditions:
Throttle Position (TP) Sensor
Crank Position Sensor (CKP) Sensor
Intake Air Temperature (IAT) Sensor
Engine Temperature (ET) Sensor
Oxygen (O2) Sensor
Bank Angle Sensor (BAS)
Interactive Muffler Valve Position Sensor (XB12 models
only, except Ulysses) (Built-in to the actuator)
The ECM uses the information provided by the throttle position
sensor to calculate how much air is entering the engine. The
throttle position sensor monitors the amount of air entering the
engine by how far the throttle is open, whether it is opening or
closing and how fast it is opening or closing. The IAT sensor
measures the temperature of the air entering the engine,
providing the rest of the information necessary to determine
the density of the air entering the engine. The ECM also mon-
itors the crank position sensor to determine the exact position
of both cylinders in the combustion cycle and the engine speed.
6-6 2009 XB Service: Electrical
TOOL NAME
Figure 6-1.
The ET sensor provides the ECM the current engine temper-
ature. Proper fuel and spark delivery are dependent on the
temperature of the engine. The ECM will provide a richer fuel
mixture on start up and a higher degree of spark advance. As
the vehicle warms up to operating temperature the fuel mixture
will lean and the spark advance will decrease.
On XB12 models, an interactive exhaust system utilizes an
actuator valve in the muffler which is connected to a servo
motor via a cable. The valve position automatically adjusts to
enhance engine performance.
Cooling fan actuation is controlled by the ECM. For cooling fan
specifications refer to Table 6-10.
Table 6-10. Cooling Fan Specifications
KEY FAN ON
° F
ON 455
ON 437
(HDI models)
OFF 266
The information provided by the O2 sensor allows the ECM to
verify a proper air/fuel mixture by monitoring the final combus-
tion efficiency in the exhaust system. This verifies optimum
engine performance at any altitude or barometric pressure.
The O2 sensor input to the ECM is required to verify a stoi-
chiometric (14.7:1) air/fuel ratio during closed loop operation.
The Bank Angle Sensor (BAS) provides input to the ECM on
whether the vehicle lean is greater than the predetermined
bank angle limit. As long as lean angle does not exceed limit,
fuel supply and ignition operation are unaffected. If the vehicle
exceeds the predetermined bank angle limit, the BAS will
interrupt the operation of the ignition system and fuel supply.
To reset system, return vehicle to the upright position and
switch key OFF.
The ECM-controlled ignition coil fires each spark plug independ-
ently on the compression stroke of each cylinder (no waste
spark). The spark plug in the front cylinder fires at the end of
that cylinder's compression stroke, thereby igniting the air/fuel
mixture. The same sequence occurs at the end of the rear
cylinder's compression stroke (thereby igniting the air/fuel
mixture in the rear cylinder).
The crank position sensor is located in the left front side of the
crankcase. Readings are taken off the 30 teeth on the left side
of the flywheel (two teeth are missing to establish a reference
point). The CKP generates an AC signal which is sent to the
ECM where it is used to reference engine position (TDC) and
speed.
For more information on the sensors used in conjunction with
the ECM see the Electrical Diagnostic Manual.
See the wiring diagrams in the Appendix for additional inform-
ation on ignition system circuits.
6.3
FAN OFF
° C ° F ° C
235 383 195
225 383 195
130 230 110