Oxygen sensor - How does it affect how the bike runs?

NSrider · May 27, 2009

I have a PC III installed on my bike but I have been getting really bad mileage with it. I installed a switch in line with the O2 sensor so I could switch the sensor in and out without having to lift the tank each time. I did this so I could try the zero map and see if the mileage improved any. (It was actually much worse with the zero map) Anyway back to the original question, how does the sensor affect how the bike runsI have read reports of the bike running badly with the PCIII and the sensor connected, however I could not notice any difference in mine with the switch on or off.

I installed the switch in the blue/red wire which traced back to the ECU, this wire showed 12V with the ignition on so I assume that was the correct wire to add the switch to.

wfooshee · May 27, 2009

O2 sensor must be disconnected for the PCIII to do what it does. The PCIII does not pursue a specific mixture, it merely modifies the mixture specified by the ECU. The PCIII actually has no idea what the mixture is.

Suppose you're cruising along at 4000 RPM and 5% throttle, and the map in your PCIII says +4 at that cell. If the O2 is connected, the ECU will see the engine running rich and reduce the fuel flow. The PCIII will simply add +4 to whatever the ECU sends it, and if the ECU has reduced the fuel, then the enrichment the PCIII is supposed to provide isn't happening.

With the O2 sensor disconnected the ECU goes to a default set, and the PCIII modifies mixture as expected. The ECU does not chase its own mixture map because it has no feedback.

Give it that feedback and it will override the PCIII.

Most maps work by enrichening the mixture, which will reduce your mileage. The factory settings are very lean a lot of the range for emissions, but at low or closed throttle, that lean mixture equates to poor response and sudden pickups.

Silent · May 27, 2009

Coudn't have said it better.

You did set your throttle position in the PC III... Right?

NSrider · May 28, 2009

wfooshee said:
O2 sensor must be disconnected for the PCIII to do what it does. The PCIII does not pursue a specific mixture, it merely modifies the mixture specified by the ECU. The PCIII actually has no idea what the mixture is.

So the O2 sensor should be disconnected while running the zero map as well? I had it disconnected for all maps except the zero map but thought that it had to be connected for the zero map.

I was prepared for a little drop in fuel mileage with the PCIII but I am getting nearly 100km less per tank which is more than I care for just before a coast to coast trip in June.

DailyCommuter · May 28, 2009

Silent said:
Coudn't have said it better.
You did set your throttle position in the PC III... Right?

how do you do that?

NSrider · May 28, 2009

DailyCommuter said:
Silent said:

Coudn't have said it better.
You did set your throttle position in the PC III... Right?

Click to expand...

how do you do that?

This is copied from the PCIII manual.

SET THROTTLE POSITION

Select Power Commander Tools 􀀡Set Throttle Position

The Set Throttle Position window allows you to re-calibrate your throttle position if

needed.

To reset both the closed and open throttle positions, ensure that the PCIII USB is

powered up and connected to the computer via the USB cable, then do the following.

1 Click Reset.

2 Twist the throttle wide open and release.

3 Click OK.

4 To reset only the Closed or Open position do the following.

5 Click the arrow next to the Closed box or the Open box

6 Click OK.

This is done while it is installed on the bike. Do it quickly, you don't want the motor revving too long without a load.

wfooshee · May 28, 2009

NSrider said:
So the O2 sensor should be disconnected while running the zero map as well?

Map doesn't matter. If the PCIII is installed the O2 sensor must be disconnected. The feedback the O2 sensor gives to the ECU will negate anything the PCIII tries to do. The PCIII does not have access to the O2 information, or any other sensors.

Oxygen sensor - How does it affect how the bike runs?

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Oxygen sensor - How does it affect how the bike runs?

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