Ignition System - Buell 2002 X1 Handbook

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IGNITION SYSTEM

GENERAL
The vehicle uses a breakerless inductive-discharge ignition
system. The system has both a primary and secondary cir-
cuit. The primary circuit consists of the battery, 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
1.
The scan tool can access the information received by and
stored in the electronic control module.
The electronic control module (ECM) attaches to the vehicle
frame next to the fuse block. 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 six different sensors to monitor rider demands
and changing engine conditions. These sensors are:
Throttle Position (TP) Sensor
G
Cam Position (CMP) Sensor
G
Intake Air Temperature (IAT) Sensor
G
Engine Temperature (ET) Sensor
G
Oxygen (O2) Sensor
G
Bank Angle Sensor (BAS)
G
The ECM uses the information provided by the TP and CMP
sensors to calculate how much air is entering the engine.The
TP 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 mea-
sures the temperature of the air entering the engine, provid-
ing the rest of the information necessary to determine the
density of the air entering the engine. The ECM also monitors
the CMP sensor to determine the exact position of both cylin-
ders in the combustion cycle and the engine speed.
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 mix-
ture will lean and the spark advance will decrease.
2002 Buell X1: Electrical
The information provided by the O2 sensor allows the ECM to
ensure a proper air/fuel mixture by monitoring the final com-
bustion efficiency in the exhaust system. This ensures opti-
mum engine performance at any altitude or barometric
pressure. The O2 sensor input to the ECM is required to
ensure a stoichiometric (14.6:1) air/fuel ratio during closed
loop operation.
The Bank Angle Sensor (BAS) provides input to the ECM on
Figure 7-
whether the vehicle lean is greater than 55 degrees. As long
as lean angle does not exceed 55 degrees fuel supply and
ignition operation are unaffected. If the vehicle exceeds a 55
degree lean angle, the BAS will interrupt the operation of the
ignition system and fuel supply.
The ECM-controlled ignition coil fires each spark plug inde-
pendently 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 rotor and cam position sensor are located in the gear-
case cover on the right side of the motorcycle. The Cam posi-
tion sensor consists of a Hall-effect device, magnet and plate.
The plate is mounted over a rotating cup ("rotor cup"). The
rotor cup is mounted on the camshaft and operates at one-
half crankshaft speed. As the rotor cup turns inside the gear-
case, six asymmetrical teeth on the rotor cup sequentially
break the magnetic field between the magnet and the Hall-
effect device. The edges of these teeth are cut to correspond
to specific positions of the camshaft during the engine cycle
such as TDC for the front cylinder. The output of the CMP
sensor is used by the ECM to not only determine engine posi-
tion, but also to calculate engine speed. This method of mea-
suring camshaft position provides accurate information on
engine position down to zero engine speed.
For more information on the sensors used in conjunction with
the ECM see Section 4 Fuel System.
See the wiring diagrams at the end of this section for addi-
tional information on ignition system circuits.
TROUBLESHOOTING
See Section 4 Fuel System for troubleshooting information.
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