An A.F.R postulation

[RoadKingKohn]

a question.

What is the stock cruising AFR of a 2005 Twin Cam verses a 2007 Twin Cam?

Just being curious.

[route66paul]

Originally Posted by HDMD 88

The Harley ECM doesn't read the wide band sensor nor oxygen....it takes a reading from the sensor by a chemical reaction sending voltage to the ECM between 1 and 0 volts. Stoich has a voltage of .45 , the more voltage the ecm sees the more fuel it provides. ie, .50 is more voltage so the ecm richens the mixture in the area that the sensors are being used. You can alter this voltage in the Closed Loop Bias Voltage Table in the SERT. The max voltage you can program is .798 which is 14.1 to 14.2:1 afr everywhere in the AFR table that has a value of 14.6 showing. The 14.6 is not the AFR value...it is a switch, the ECM sees 14.6 and it opens up the communication to the 02 sensor. If you change the 14.6 AFR value in the AFR Table you are shutting down the sensors. Many dealers are doing just that when they install pipes. The stock sensor can only operate in a .5 parameter to where a wide band will operate from 10:1 to 18:1 ie the stock 02 can go from, say 14.0:1 to 14.5:1. There is a lot more to all this butr it's all I can type for now.

Is there a modified sensor or sending unit that will richen up those values? If all the closed system can do is make it "too lean" to "even leaner", it will only be bypassed. If someone has designed a piggyback unit (like PCIII), or a sensor or sending unit that would change the range, we could have a great ECM already on the bike.