| Sorry, humour is sometimes hard to convey in a forum.
Ducati Engine Management System
Ducati’s engine management is provided by an open-loop fuel injection system that uses a computer to control the opening duration of its injectors based upon voltage levels presented to it from several sensors. The longer the injector is opened, the more fuel is supplied to the engine.
The computer contains a Eprom chip that stores a look-up table of injector durations for 16 throttle positions and 16 engine speeds. This chip can be removed from some computers and replaced with one re-programmed with different durations (fuel map) needed for fuel mixture changes necessitated by engine modifications. The fuel map supplied by Ducati is programmed to provide good fuel economy and to meet exhaust emission standards, so does not really provide optimum performance.
The chip also contains a look-up table of degrees of ignition advance (spark map) for the same 16 throttle positions and 16 engine speeds that are used for the fuel map.
The computer determines throttle position from the voltage level sent from the throttle position sensor (TPS) and determines engine speed from pulses sent from a pick-up coil on the engine that indicates crankshaft RPM.
Unlike a closed-loop system that also samples its exhaust gases to make corrections to fueling, the Ducati system only makes corrections (trim factors) to the base map based upon engine coolant temperature, ambient air pressure (altitude) and temperature.
The coolant temperature sensor (thermocouple) monitors the engine coolant temperature so the computer can supply additional fuel while the engine is warming-up and retard ignition timing if the engine gets too hot.
Engines need more fuel when for a cold start as there is no heat in the ports and chambers to keep the fuel atomized as vapor, so it condenses. Fuel as a liquid burns very badly in the combustion chamber, so throwing more at it ensures enough stays as vapor for some sort of combustion. Injected engines get a very nice fuel spray from the injectors and this is why injected engines behave well when cold.
The atmospheric pressure sensor monitors the air pressure so that the computer can supply additional fuel when you ride at lower elevations where the air is more dense. Conversely, if you ride in the mountains where the air is thinner, the voltage output of the sensor drops, which tells the computer to make a pre-programmed reduction to the fuel map injector durations.
The atmospheric temperature sensor voltage level tells the computer how much to modify the fuel map injector durations for a given air temperature. When you take a ride on a hot day, the air is thinner and consequently will cause an engine that has its air/fuel mixture set correctly for a nominal 68°F day, to run too rich. The sensor's resistance increases with air temperature.
Intake Air Temperature Sensor
When you take a ride on a hot day, the air is thinner and consequently will cause an engine that has its air/fuel mixture set correctly for a normal 68°F day, to run rich.
To avoid this mixture variation, Ducati fuel injection systems have been provided with air temperature sensors that tells the ECU how much fuel to deliver for a given air temperature. The atmospheric temperature sensor voltage level tells the computer how much to modify the fuel map.
For a given ECU fuel map, there is a range of enviromental trims. So, when the air is colder than what the map says is "ambient" - 70°F or so - the ECU adds fuel. If it's hotter than 70°, it reduces fuel. The sensor's resistance increases with air temperature, 30 K-ohms at -20°C, rising to 370 K-ohms at 80°C.
When this sensor fails to an open circuit (infinite resistance), the resistance goes outside this range. So, to avoid letting the computer think that the day is very hot and producing an overly-lean fuel mixture at normal operating temperatures that could damage an engine, the computer defaults to the preset ambient setting.
So, with a properly set-up engine with a given maximum capacity for volumetric air flow, tell me, how will modifing the resistance of the air temperature circuit with one of these devices result in a more favorable air/fuel ratio and more power? In my opinion, it can't and won't.  | 
07-May-2005, 22:03 
Shazaam!
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