Open Loop vs Closed Loop: Understanding Fuel Injection and Tuning

[sam2019]

If you have no knowledge about these issues and want to use the Red Box ECU - or in general understand why sometimes engines behave in a certain way - on this pages a great explanation is given - just a few minutes read and fully worth it!

Open Loop vs Closed Loop: Understanding Fuel Injection

Understanding how open loop vs closed loop modes work in fuel injection — problems they can cause, how to identify them, and how to tune them out.

motofomo.com

 

[Sbinf74]

and this explains why if you install a powertronic V4 you also need fuelx

 

[sam2019]

But only in the V4 Version. The V3 took care of the Ox sensor afaik.
In any case, red box users need not worry about fuelx