O2 Sensor failing... again

I got a rexer tune on my 16 939 which disables the 02 sensors, it’s a different bike, this should be the first mod anyone does. It’s not real cheap but worth every penny.

PaulT said:

I got a rexer tune on my 16 939 which disables the 02 sensors, it's a different bike, this should be the first mod anyone does. It's not real cheap but worth every penny.

Click to expand...

Agree, I put the full Termi on with a tune and the bike runs so much better. Smooth.

PaulT said:

I got a rexer tune on my 16 939 which disables the 02 sensors, it’s a different bike, this should be the first mod anyone does. It’s not real cheap but worth every penny.

Click to expand...

Paul,
from whom did you get a Rexxer file for the 939 without lambda ?
I am in permanent contact with Rexxer Germany (Daniele Moto, the Rexxer company itself) and they told me several times that unfortunatly they cannot disable lambda yet at EU4 model 939. Last time was 1 month ago.
Actually i have a file with O2 enabled, which is fine, but does not come near a disabled version.
I want a Rexxer without O2 since i have my 939, because such a file changed my former 821 completly.

I'm going to demonstrate my ignorance here and ask, why does disabling the O2 sensors improve things? Wouldn't the use of the O2 sensors allow for optimal fueling, or does the Rexxer tune just make some assumptions that generally work well for the engine? If it's not obvious I've never bothered to tune any of my previous bikes.

N4teTheGreat said:

I'm going to demonstrate my ignorance here and ask, why does disabling the O2 sensors improve things? Wouldn't the use of the O2 sensors allow for optimal fueling, or does the Rexxer tune just make some assumptions that generally work well for the engine? If it's not obvious I've never bothered to tune any of my previous bikes.

Click to expand...

because Ducati makes fine working maps which are stored in ECU, but then has to lean out in closed loop mode because of emission regulations to near Lambda1.
Disabling O2 sensors lets run engine in open loop, not only at full throttle but also in partial load, former closed loop.
this means that it only runs via internal map and not via O2 senors, so in partial load it runs not Lambda1 = 14.7 air:fuel ratio, but e.g. 13.5 , 13.2 or whatever Ducati means is optimal for engineperformance at this load.
Engine will run much better then but will not fullfill emission regulations anymore.

check the connectors for the O2 sensors and clean, I had slight corrosion in my front connector which would have caused high resistance and the sensor failed in the end.
I managed to get a sensor from ebay, £30 delivered and fixed the problem.
Mine has a rapid bike evo fitted, so when the sensor failed the bike still ran ok, but wasn't 100%, since o2 sensor fitted the engine is back to brilliant.