Engine Management System Information

(derived from Speed Triple 955i manual model 2002 - 2004, other models may vary)

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System Description (Speed Triple 955i model 2002 - 2004)

Goto Speed Triple T509 (885 cc) & 955cc   Goto Speed Triple 1050    Goto  Daytona 675     Goto  Rocket III


Each model is fitted with an electronic engine management system which encompasses control of both ignition
and fuel delivery. The electronic control module (ECM) draws information from sensors positioned around the engine, cooling and air intake systems and precisely calculates ignition advance and fuelling requirements for all engine
speeds and loads. In addition, the system has hardware diagnostic functions | similar to the US state of California requirements for ! on-board diagnostics (OBDII).This function ensures I that, should a malfunction occur in the system, the malfunction type and engine data at the time the malfunction occurred are stored in the ECM memory. This stored data can then be recovered by a Triumph dealer using a special service tool which is mandatory for all Triumph dealers. In this way, precise diagnosis of a fault can be made and the fault quickly rectified.

System Sensors (varies by year and model)

Intake air temperature sensor situated in the top of the airbox towards the rear. Because the density of the air (and therefore the amount of oxygen available to ignite the fuel) changes with temperature, an intake air temperature sensor is fitted. Changes in air temperature (and therefore air density) are compensated for by adjusting the amount of fuel injected to a level consistent with clean combustion and low emissions.

Barometric pressure sensor the barometric pressure sensor is incorporated in the ECM itself and is connected to the airbox via a hose The barometric pressure sensor measures the air pressure in the airbox. From this measurement the air density is calculated, and when added to other inputs to the ECM, the engine load is calculated.

With this information, the amount of fuel per injection of fuel is adjusted to suit the prevailing conditions.


Crankshaft position sensorsituated behind the alternator on the left side of the engine. The crankshaft position sensor detects movement of a toothed wheel attached to the left hand end of the crankshaft. The wheel has 21 teeth which are evenly spaced, and one triple length tooth next to a triple length gap. The triple length tooth/gap gives a reference point from which the actual crankshaft position is calculated. The crankshaft position sensor information is used by the ECM to determine engine speed and crankshaft position in relation to the point where fuel is injected and ignition of the fuel occurs.


Oxygen (Lambda) Sensorsituated in the exhaust system. At idle and other specified engine speeds, the oxygen sensor continuously senses the content of the exhaust gases and signals this information to the ECM. According to the signal received, the ECM adjusts the air/fuel ratio to within specific parameters thus controlling idle CO and eliminating the need for manual adjustment.

Engine coolant temperature sensor situated in the left side of the cylinder head. Coolant temperature information, received by the ECM, is used to optimise fuelling at all engine temperatures and to calculate hot and cold start fuelling requirements.


Throttle position sensorsituated at the left hand end of the throttle spindle. The throttle position sensor gives
a reading in the fully closed position and all other throttle opening angles are calculated using the fully closed position as a base. Throttle angle is used by the ECM to determine fuelling requirements for all throttle positions.


Neutral switchsituated in the gearbox. The neutral switch indicates when the transmission is in neutral.
In addition, the neutral switch provides an interlock facility preventing the rider from riding off with sidestand down.
If a gear is selected with the sidestand down, the supply to the ECM is removed causing the engine to cut out.

Side stand switch situated at the top of the sidestand leg. If the sidestand is in the down position, the engine will not run unless the transmission is in neutral or the clutch lever, which also has a switch, is pulled in to the handlebar.

Clutch Switch
Situated on the clutch lever. The engine will not start unless the clutch lever is pulled to the handlebar.

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System Actuators  (varies by year and model)

In response to signals received from the sensors, the ECM directs messages to a series of electronic and electro-mechanical actuators. The function and location of the actuators is given below.


Idle Air Control System located inside the airbox. The system comprises an air control valve fitted with a stepper motor. The system has a controlling influence over the following:


Induction air supply during engine overrun.

Air/fuel ratio correction when operating at idle at altitudes above sea level.

• Cold and hot start air/fuel ratio correction. When in operation, the stepper motor opens the air control valve by
a variable distance, allowing a controlled supply of air to flow along a series of pipes, into the induction system.
The air is fed to a point between the throttle plates and the inlet valves.


Secondary Air Injection Control Valve (not all markets)situated in the airbox. At certain specific

engine speeds above idle (determined by the factory programming of the engine management system), the secondary air injection control valve is opened by the ECM and allows an air feed into the secondary air system where, each time a pair of exhaust valves open, the exhaust gases in the exhaust port create a depression which causes reed valves in the secondary air injection system to open. When open, the depression in the exhaust port draws air from the control valve, through the open reed valves, into the exhaust port. This air promotes secondary combustion of the exhaust gases in the ports and header system. Once the exhaust valves close, the depression is reduced and the reed valves close.


At other engine speeds, the system is disabled by closing the control valve mounted in the airbox.

This allows an oxygen sensor to control air to fuel ratios. If air was fed to the exhaust system when the oxygen sensor was operational, the incoming air would cause inaccuracies in the readings sensed by the oxygen sensor (which requires access to 'raw' combustion gases) which would lead to rough running.


Canister purge valve (California models only)situated in the vapour return line between the carbon canister and the throttle. The purge valve controls the return of vapour which has been stored in the carbon canister during the period when the engine is switched off. The valve is 'pulsed' by the ECM to give control over the rate at which the canister is purged. If the valve was not pulsed, all the stored vapour would immediately be drawn into the engine briefly causing
a rich mixture and very high emissions.


Injectors located in the cylinder head. The engine is fitted with 3 quadruple-jet injectors which are targeted as close as possible to the back face of the inlet valves. The spray pattern of the injectors is fixed but the length of time each injector remains open is variable. The duration of each injection is calculated by the ECM using data received from the various sensors in the system.


Plug top ignition coilsmounted directly onto the top of each spark plug. The ECM controls the point at which the coils are switched on and off. In calculating the switch-on time, the ECM allows sufficient time for the coils to charge to a level where a spark can be produced. The coils are switched off at the point of ignition, the timing of which is optimised for good engine performance.


Main power relay situated adjacent to the ECM, beneath the motorcycle seat. When the ignition is switched on, the main power relay is powered up to provide a stable voltage supply for the ECM.

When the ignition is switched off, the ECM holds the main power relay on so that it can carry out the power down procedure which includes:

writing data to the ECM memory,

referencing the position of the idle air control valve stepper motor,

running the cooling fan until the engine is sufficiently cool.

Once all the power down procedures have been carried out, the main power relay is turned off.


Fuel pump – located inside the fuel tank on the right hand side of the motorcycle. The electric pump delivers fuel into the fuel system, via a pressure regulator, at a constant 3 bar pressure. The pump is run continuously when the engine is running and is also run briefly when the ignition is first switched on to ensure that 3 bar is available to the system as soon as the engine is cranked.


Cooling fan – located in front of the radiator. The ECM controls switching on and off of the cooling fan in response to a signal received from the coolant temperature sensor. When the coolant temperature rises to a level where the cooling effect of natural airflow is insufficient, the cooling fan is turned on by the ECM. When the coolant temperature falls sufficiently, the ECM turns the cooling fan off. 

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