Carburettors with options to adjust air / fuel mixture are now a thing from past. Electronic Fuel Injection or the EFI is the norm now on modern engines as the world moves towards stringent emission norms to fight global warming.
EFI’s is basically a device with a computer program doing the air fuel mixture and pumping into the engine cylinder at an exact volume to make sure optimum power is created. This ensures less wastage of fuel and optimum combustion.
However, there are two types of EFI’s that we see on motorcycles, one the “Closed Loop” and the other “Open Loop” EFI’s.
Let us quickly understand the difference between them.
Closed loop EFI’s : In a closed loop EFI there is a feedback mechanism that constantly sends real time data from the O2 sensor on the header pipes to the ECU to adjust the volume of air/fuel to be sprayed into the cylinder.
The O2 sensor is also referred as Lambda Sensor by few and the job of this sensor is to identify how much Oxygen is still left when the gases leave the cylinder after the exhaust stroke. The volume of oxygen is monitored and based on that the fuel volume is either increased or decreased by the EFI. This is a continuous process.
In case of switching to a new exhaust or air filter, some recommend to let the engine start and idle for 15 - 20 mins with the new exhaust and air filter so that the EFI’s receives the feedback from the sensor and auto tunes it. Only then the bike engine can be revved or taken for a spin.
Open Look EFI’s: In this case, there is no feedback from O2 Sensor and the EFI keeps spraying a pre programmed volume of air and fuel irrespective of being rich or lean. The O2 sensor is absent in the system and no feedback is provided to auto adjust the mixture. In case of exhaust or air filter change in a motorcycle with open loop EFI, there will be erratic firing and excessive heat in engine and header pipes.
The best solution is to get the EFI remapped with the new exhaust system and air filter so the software programs the EFI’s based on the new free flow filter and muffler. This step needs to be done every time there is a change in either the air filter or exhaust. You may also need to constantly keep checking and cleaning the air filter to keep optimum air supply to the efi.
EFI is a massive topic that has so many finer details that can be shared. For now the scope was to share a general overview to a layman biker to understand the difference between the open and the closed loop EFI’s. Also the steps to take when they switch to a well engineered and designed aftermarket exhaust such as BARREL EXHAUST.