Closed Loop Operation

Just about all ECUs fitted to cars operate as closed loop controllers whereas all controllers on bikes ( except some BMWs ) are open loop controllers. Open loop and closed loop are technical terms used to describe feedback control systems. If you're not familiar with these terms, here's some simple examples.

Open Loop Example

You are standing blindfolded in front of a shelf and you are trying to pick up an object on the shelf. With training you can be learn where the object is. However if you change the environment in some way, i.e. wear high heel shoes (no I don't), your accuracy in finding the object is affected.
This is analogous to tuning the bike on a dyno, then changing the exhaust pipes. The bike basically needs to be retuned for the new configuration.

Closed Loop Example

Same scenario as above, this time you can remove the blind fold. You now have feedback as to where your hand is in relationship to the object. Now you can make the necessary adjustments so that you always connect.
For the ECU, the oxygen sensor allows it to see what the mixture is and to adjust it to be the desired mixture. You can now change pipes, intake filters and the mixture will stay correct all the time.

My16M Closed loop operation

Closed loop operation is disabled by SW1 on the My16M. When the switch is on, My16M operates as an open loop controller just as the WM16M. An exhaust sensor is not required for this mode of operation. At any time closed loop operation can be enabled by fitting an oxygen sensor and turning the SW1 off.

It is possible to disable closed loop operation for individual cells of the map. Why would you want to do this you ask? Currently the closed loop software is simple and only one target voltage can be specified for the O2 sensor. Usually you run a richer mixture for wide open throttles (WOT) and you may want to run a leaner mixture for the throttle back off. With the closed loop software at the moment you couldn't just program richer values in the map for WOT as the closed loop software will lean it out. This leaning will then be applied temporarily to the other areas of the map as the throttle is eased until the closed loop software again adjusts.

To solve this problem you disable the closed loop software for high throttle settings and low throttle settings by setting a flag in those entries in the map.

Benefits of closed loop operation

The main benefit of closed loop operation is the mixture is always close to the optimal setting. Hence power and efficiency are always close to optimal. This does not mean that a map is no longer necessary though. Response times of the gas sensor and the controller mean that there will be a slight delay in getting the mixture right if the static map is not right. The good news is that the controller can be made to improve the original map as you ride using feedback from the gas sensor. Over time you will attain the perfect static map for the bike's current configuration.
For mixture optimisation of the map a dyno is no longer necessary unless you want to correct the entire map in a short period of time.
Note: Currently My16M does not do this, but this is feature is high on the list of future enhancements.

What Oxygen Sensors can be used with My16M

I was quite surprised at the number of variants of oxygen sensors that are available. I would expect My16M to work with all the common types, although I have only tested on one.

The main variations in sensors are whether they are wide band or narrow band, and how many wires come out of it.

All the common types produce a voltage between 0 and 1 volt. Lean gives a 0 volt reading and rich gives a 1 volt reading. The cheaper sensors are narrow band and the voltage quickly changes as the mixture changes for rich to lean or visa versa. This sensors are digital in nature. There's no middle ground and all the ECU can do here is to keep the mixture correct.

Wide band sensors have a more gradual change in output. There are degrees of richness and lean. With these it is possible to be a bit smarter. You can have an acceleration/power mode where you run the bike a bit richer than normal, cruise mode where you run it a bit leaner, etc.

Sensors can come with 1,2,3 or 4 wires. The difference between 1 and 2 wires is that the two wire is isolated electrically from the exhaust. It has a signal and a ground wire that are wired straight into the ECU. The single wire relies on the ground being returned through the exhaust and engine and frame. This has more potential for noise and we don't want more of the earth problems that the bikes already have so I recommend the two wire over a single.

The 3 and 4 wire are basically the same as the 1 and 2 wire respectively. The other two wires are for a heater element that is run off 12 V. For the same reason as above I recommend a 4 wire over a 3. The heater element is to speed up the warm up of the sensor as they don't work until they reach 400 degree Celsius. Without a heater it can take minutes to warm up, with the heater its about 10 seconds.

I'm using the Bosch 0258 104 002. It's a 4 wire wide band sensor. On my bike the heater gets its power from the relay that powers the fuel pump, injectors and coils.