I am not a tuner by all means but what would be the difference if your running in open or closed loop, Say if fuel ratio had to be set to where your running in open loop?

 

open loop is when the ECM relies on preset ( canned) maps to alter fuel and ignition timing

closed loop, the ECM takes in data from sensors- esp. the o2 sensors and alters the fuel and ignition timing reacting to the incoming data.

data is often provided as to air temp/ air density, road speed, rpms, gear, motor temperature etc as well by other sensors..incl throttle position


on most vehicles open loop is used when the motor is first turned on, many sensors do not provide reliable data until operating temps are reached.

open loop may also be used for certain conditions such as wide open throttle- or as noted by some riders the motor appears to "cut out" when decelerating past 1800 rpms- the "map" for that condition turns off the fuel for a moment


some of the tuners on the market keep the ecm in open loop or only use some of the sensors and may not use data such as from the o2 sensor.

the o2 sensor tells the ecm if the mixture is lean or rich in real time


mike

 

Open loop simply means there is no feedback to the ECM which 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 means there is feedback to the ECM. This sensing is mostly done by the O2 sensors in the exhaust pipes which generate a voltage based on the gas around it.

 

It helps to understand the difference in wide-band and narrow-band sensors for this discussion. The HD sensors that come on the bikes are only paying attention and reporting on the low rpm and upper rpm, nothing in the middle.

To really take advantage of a closed loop system you need to add wide-band sensors to fully monitor and then feedback that information across the entire powerband to the ECM.

 

Closed loop is intended to minimize emissions. That's all it was intended to do. So it tries to run as close as it can to stoichiometric. That's when it has a perfect air to fuel ratio to burn all the fuel.

 

As Bingee states, it is for maintaining the engine at a optimum fuel air ratio to use up all the fuel, so any add of a fixed map tuner actually drops the self adjustment characteristics and allows the open loop operation so one can feed more gas whether it does much good or not.

With the basis in mind, why does one have to retune a engine that will self adjust for mods to air filtration or exhaust flows? Seems a unnecessary waste of time and effort. I can see the add of wide band sensors to help speed the process and add more, faster adjustments but not a retune as that would possibly/probably be over written in the ECM over the course of riding.

 

For HD closed loop, max adjustment to afr is +/-0.5 if I'm not mistaken.

 

Thanks Guy's well explained, I think after I have it tuned with dyno I will purchase the wide band sensors and mabee even autotune module to go with my power vision..

 

Then skip the dyno and save your money.

 

You may want to review both statements as I think someone has given you some false information.

(A) Sensors, either wide or narrow, are capable of "paying attention" to cells in the upper, lower, and MIDDLE.

(B) Readily available sensors (wide or narrow band) will NOT sample across the "entire powerband" - both have upper and lower limits.