[image: View Post]HispanicSlammer, on 07 February 2011 - 04:20 PM, said:
I will answer the first question, YES. The bike has an O2 sensor and it needs to be eliminated.
Actually, it doesn't need to be eliminated, but in most cases it's the better course of action.
The bike operates in a open loop, following a predetermined (and lean) map. If the engine temp is above 160, RPMS are between 3.5K-5.5K (ish), the throttle is held steady with openings greater than 5% and less than 40%, the bike will go close loop and try adjust the mixture. The map is set up to be rich in these areas so if there's a failure the bike will not be harmed by a over lean mixture. The signal from the oxygen sensor will to lean the mixture in order to achieve better fuel mileage and lower emissions. If the throttle is moved off of "steady", out of the 5%-%40 "window", the engine speed leaves the 3.5K-5.5K "cruise window", or temp goes below 160 (yah right), control will go back to the map. At times, the difference between closed-loop and open-loop can be fairly large and the "in and out" can be felt when you make small changes in the throttle. Variances in injectors, fuel pressure regulators, O2 sensors, and even the weather and altitude can make this vary from "not noticeable" to "I'm trading this POS in".
A O2 sensor compares the oxygen content in the exhaust to the oxygen content on the outside of the sensor, which is handy because, in theory, it should compensate for altitude. When the air/fuel mixture is rich and there is little O2 in the exhaust, the difference in oxygen levels across the sensing element generates a voltage through the sensor's platinum electrodes: typically 0.8 to 0.9 volts. When the air/fuel mixture is lean and there is more oxygen in the exhaust, the sensor's voltage drops to 0.1 to 0.3 volts. When the air/fuel mixture is perfectly balanced and combustion is cleanest, the sensor's output voltage is around 0.45 volts.
When you remove the sensor, the voltage output to the ECU is 0 volts. When the ECU sees zero volts, it believes that the mixture is already as lean as possible, so it takes no action to move it from its rich starting point as set by the map. Removing the sensor doesn't stop the closed loop from happening, it just convinces the ECU that the bike is already too lean and no changes are made.
The O2 sensor has 4 wires, 2 are the sensor output and the other 2 are for the heater. The O2 sensor doesn't operate correctly until it gets hot, so in order to speed things up, they have a heater. The ECU monitors the current going through the heater to make sure that it's operating properly. If the heater burns out or somehow becomes a open circuit (unplugged), the current will stop flowing and the ECU will trip the "FI" light. The 330ohm resistor is actually put in place of the 2 heater wires to make the ECU think the sensor is still connected and operating properly.
The Power Commander "alters" the stock map but once you get the in "close loop window" the ECU will use the O2 sensors to re-adjust your altered map. In most cases, this will not work very well, but it won't hurt anything. It some cases, especially on a stock bike, it might be handy. Using the sensors will get you the best fuel mileage with no real change in performance because they only come into play during "cruise". However, depending on your bike and tolerance for the "on-off" of closed loop, you might want sacrifice some fuel for smoother operation.