Can anyone help me to understand the main differences between the open and closed loop EFI's ???
I have a 2005 FXDX , so I have the open loop.
I am wondering why HD switched to the closed loop design.
Was there a problem with the open loop???

 

Closed loop lets the ECM see what the bike is doing and make adjustments as needed.

 

In closed loop you have 02sensors in the exhaust that constantly sends signals to the ECM in regards to fuel delivery. All cars manufactured today are closed loop. All motorcycles will be closed loop in the next few years. I think Harley is just testing the waters with the 06 Dynas.............BG

 

The term open and closed loop are terms from the automotive industry. The terms apply to the condition of the car. When you start the car and it's cold that information is sent to the ECM and until the car warms up (70C) the O2 sensors will be ignored for adjusting the fuel delivery.(Open Loop) Once the car warms up to "the" temperature, the O2 sensor information will be used along with the information from the throttle Position sensor and the Mass Air Flow meter to determine how long the injectors should stay open.(Close Loop)

So to say a bike is Open loop if it doesn't have O2 sensors is not "technically" correct, however I think everyone gets the idea. On the Bikes that have O2 sensors they will run Open loop until warmed up then switch over to closed loop.

If a bike doesn't have an O2 sensor set up they run fuel maps that are set in the ECM to match the different conditions the bike could be in.

If the bike has O2 Senosrs, it has fuel maps for the open loop operation and then uses the variable information from the sensors to determine injector duration when in closed loop.

 

Closed Loop is a term from Process Controls that has to do with Feedback control. It measures a variable (Oxygen Level) and makes an adjustment based on the measured variable. Just like a room thermostat that adjusts heating/cooling to room temperature.
Open Loop refers controlling the variable by a fixed set of values representing the measured variable. Leaving the thermostat in manual but turning it on when needed is an example of Open Loop control or Feedforward control.
Advantages to FF control is you do not need an error in measuring variables for it to work.

 

Wow, you really dug in to the archives on this one, this post is alomost 4 years old. hehe