aydy
New Member
Fellow riders and grease monkeys, Please read this helpful info on how Fuel Injected bikes work before venturing into modification.
I know that a lot of people are mostly used to Carbureted bikes and are confused with the Fi system.
Hope this guide helps you
FI/ EFI: (Electronic) Fuel Injection, a computer controlled fuel delivery system.
ECU / ECM: Engine Control Unit/Module.
Piggyback: Intercepts the ECU's sensor signals making the ECU think it's running lean, causing the ECU to compensate by enriching the air-fuel mixture.
MAF sensor: Mass Air Flow sensor, measures the mass flow rate of air entering the engine.
MAP sensor: Manifold Absolute Pressure sensor, measures the barometric pressure in the engine intake manifold. (Not installed on a stock Grom/MSX)
IAT sensor: Intake Air Temperature sensor, measures the temperature entering the manifold. (Not installed on a stock Grom/MSX)
TPS: Throttle Position Sensor, monitors the throttle position.
WOT: Wide Open Throttle, when your bike goes BRAAAAAAP.
AFR: Air-to-Fuel Ratio, maximum power is frequently reached at AFRs ranging from 12.5 to 13.3:1.
Stoic (hiometric): A/F ratio of 14.7:1, produces a “chemically complete combustion event”. The ECU tries to aim for this ratio fora optimal balance of performance, fuel economy and emissions.
Lean: When you have more air relative to fuel than ideal (ratios greater 14.7:1)
Rich: When you have less air relative to fuel than ideal (ratios less than 14.7:1)
O2 / Lambda sensor: Measures the A/F ratio.
EFI / ECU Basics
In its simplest terms, an EFI system is a computer controlled fuel delivery system. The ECU reads various sensors located on the bike and makes the determination of how much fuel to allow the engine to have based on this information. The computer will open and close the injectors allowing gasoline into the engine based on the sensor inputs and the fuel map programmed into the computer.
(Harley-Davidson Motorcycle Fuel Injection Explained)
Functions of an ECU
1. Air/fuel mixture control: It determines the amount of air and fuel entering into the engine and accordingly plans the combustion process by varying the amount of fuel delivered through the fuel injectors.
2. Ignition timing control: There is a certain crank angle in the compression stroke which gives maximum torque output if the air/fuel mix is ignited at that point. The ECU decides this and accordingly fires the spark plugs.
3. Idle speed control: It controls the idle speed of the engine depending on the ambient temperature and engine oil temperature of an engine. This is the reason that when starting the engine for the first time in the morning, the RPM is more compared to normal idle RPM.
(Motorcycle Engine Control Unit (ECU) Explained » BikesIndia.org)
Open Loop
When the engine is first started the system goes into open loop operation. Open loop simply means there is no feedback of the result to the ECU. In our case, it means there is no sensing or measuring of the exhaust gas to see how the bike is running. The fuel injected is determined by the RPM and throttle position, derived from fuel injector pulse width numbers stored in the fuel maps, and is trimmed for environmental conditions due to air temperature, air pressure and engine temperature.
Closed Loop
Closed loop means there is feedback of the result to the ECU. In our case, it means there is sensing or measuring of the exhaust gas to see how the bike is running. This sensing is done by the O2 sensor.
(BikeBoy.org - Fuel Injection – Open Loop and Closed Loop)
narrowband O2 Sensor
A narrowband O2 sensor is an oxygen sensor that is only calibrated to know three things. Rich, stoic, and lean. What I mean by this is that it only has a narrow window that it see’s the air fuel mixture through. The sensor knows that the engine is running rich or lean, but not by how much.
wideband O2 Sensor
A wideband O2 sensor is much more sophisticated than a narrowband sensor, and can be relied upon to be used as a tuning tool. wideband sensors not only are a lot faster acting in the reading, but can tell you the exact a/f ratio that the motor is currently at. wideband sensors give the ECU the ability to tune exact A/F value’s to a tenth of a decimal instead of just enriching and leaning the mixture until a stoic value is seen.
(Air Fuel A/F Ratio Basics | Wideband vs Narrow O2 sensor)
Credits to brasz from hondagrom.net
I know that a lot of people are mostly used to Carbureted bikes and are confused with the Fi system.
Hope this guide helps you
FI/ EFI: (Electronic) Fuel Injection, a computer controlled fuel delivery system.
ECU / ECM: Engine Control Unit/Module.
Piggyback: Intercepts the ECU's sensor signals making the ECU think it's running lean, causing the ECU to compensate by enriching the air-fuel mixture.
MAF sensor: Mass Air Flow sensor, measures the mass flow rate of air entering the engine.
MAP sensor: Manifold Absolute Pressure sensor, measures the barometric pressure in the engine intake manifold. (Not installed on a stock Grom/MSX)
IAT sensor: Intake Air Temperature sensor, measures the temperature entering the manifold. (Not installed on a stock Grom/MSX)
TPS: Throttle Position Sensor, monitors the throttle position.
WOT: Wide Open Throttle, when your bike goes BRAAAAAAP.
AFR: Air-to-Fuel Ratio, maximum power is frequently reached at AFRs ranging from 12.5 to 13.3:1.
Stoic (hiometric): A/F ratio of 14.7:1, produces a “chemically complete combustion event”. The ECU tries to aim for this ratio fora optimal balance of performance, fuel economy and emissions.
Lean: When you have more air relative to fuel than ideal (ratios greater 14.7:1)
Rich: When you have less air relative to fuel than ideal (ratios less than 14.7:1)
O2 / Lambda sensor: Measures the A/F ratio.
EFI / ECU Basics
In its simplest terms, an EFI system is a computer controlled fuel delivery system. The ECU reads various sensors located on the bike and makes the determination of how much fuel to allow the engine to have based on this information. The computer will open and close the injectors allowing gasoline into the engine based on the sensor inputs and the fuel map programmed into the computer.
(Harley-Davidson Motorcycle Fuel Injection Explained)
Functions of an ECU
1. Air/fuel mixture control: It determines the amount of air and fuel entering into the engine and accordingly plans the combustion process by varying the amount of fuel delivered through the fuel injectors.
2. Ignition timing control: There is a certain crank angle in the compression stroke which gives maximum torque output if the air/fuel mix is ignited at that point. The ECU decides this and accordingly fires the spark plugs.
3. Idle speed control: It controls the idle speed of the engine depending on the ambient temperature and engine oil temperature of an engine. This is the reason that when starting the engine for the first time in the morning, the RPM is more compared to normal idle RPM.
(Motorcycle Engine Control Unit (ECU) Explained » BikesIndia.org)
Open Loop
When the engine is first started the system goes into open loop operation. Open loop simply means there is no feedback of the result to the ECU. In our case, it means there is no sensing or measuring of the exhaust gas to see how the bike is running. The fuel injected is determined by the RPM and throttle position, derived from fuel injector pulse width numbers stored in the fuel maps, and is trimmed for environmental conditions due to air temperature, air pressure and engine temperature.
Closed Loop
Closed loop means there is feedback of the result to the ECU. In our case, it means there is sensing or measuring of the exhaust gas to see how the bike is running. This sensing is done by the O2 sensor.
(BikeBoy.org - Fuel Injection – Open Loop and Closed Loop)
narrowband O2 Sensor
A narrowband O2 sensor is an oxygen sensor that is only calibrated to know three things. Rich, stoic, and lean. What I mean by this is that it only has a narrow window that it see’s the air fuel mixture through. The sensor knows that the engine is running rich or lean, but not by how much.
wideband O2 Sensor
A wideband O2 sensor is much more sophisticated than a narrowband sensor, and can be relied upon to be used as a tuning tool. wideband sensors not only are a lot faster acting in the reading, but can tell you the exact a/f ratio that the motor is currently at. wideband sensors give the ECU the ability to tune exact A/F value’s to a tenth of a decimal instead of just enriching and leaning the mixture until a stoic value is seen.
(Air Fuel A/F Ratio Basics | Wideband vs Narrow O2 sensor)
Credits to brasz from hondagrom.net
