Tuners! Help me understand 02 sensor voltages

[joe_lyons]

What headpipe do you have?  If stock then the rear will always have issues because of the goofy y section that pulls in air

[rigidthumper]

Last time I saw unusually high VEs @ idle in one cylinder and low in the other cylinder  the 02 sensors were swapped. 

[07heri]

What headpipe do you have?  If stock then the rear will always have issues because of the goofy y section that pulls in air

Stock Softail headpipes.  The rear has always been a problem with leaks at the crossover.  I think that may be part of the high VE's, which is giving me high 02 voltages.  Once I get it sealed up I will give it another shot and see what the 02 does. 

[lonewolf]

Wouldn't the o2 voltages have to be low to cause the high ve's?

[joe_lyons]

Use some copper exhaust sealant at the crossover and at the exhaust port, that stuff does wonders.

[Karl H.]

Wouldn't the o2 voltages have to be low to cause the high ve's?

[joe_lyons]

It would have to go into closed loop for it to do anything first.  A simple test just for giggles would be to swap sensors and just double check that.  Some bikes and pipes just don't do a very good job at all of getting a good read at idle with the O2 sensors.  For this reason I put most bikes in open loop at idle.  If you rev it up and the sensor comes back to life and then just cools back down when you go back to idle then the signal that you are getting from it I would say is unreliable in that area.  In the basic tune settings you can set the min/max of areas that are altered.

[rbabos]

Wouldn't the o2 voltages have to be low to cause the high ve's?

That's been my experience also. First noticed with an MT8 cal with ci too high in the constants. 2400 O2 volts and it was driving the ve's down. Once leaned out they started switching and ve's went up.
Ron

[hrdtail78]

But it still uses the bias voltage as a check on the temp of the sensor.  Not that it can do anything about it.

So, it is normal to have delays greater than 40 to 60 seconds for the sensor to reach the switching threshold in a sensor with out heaters?

I wouldn't say that is out of the norm.  Set warm up enrichment table to 0 and time from a cold start.  That is just one thing that can delay sensors coming on line.

[07heri]

Wouldn't the o2 voltages have to be low to cause the high ve's?

What are you calling low?   

[07heri]

Bingo sir.  Thats exactly what the guy said in the video.  You could have a junk sensor.  Does it become active at any point in time?

100% not a junk sensor.  I sealed up the exhaust with the -10 seals instead of the catalogs -03 seals, at the interconnect pipe.  Sliced 4 cuts into the pipe that slides over the interconnect seal and put homemade clamps on the pipe.  Finally a good seal.  Manually dropped the rear VE's to equal the front plus 10% to experiment.  Fired up the bike and watched 02 voltage on PV.  Started at 5.1 volts and within 60 seconds or so (43 degrees F in the garage) started seeing the voltage come down.  As the sensors heated up the voltage came right down to where they should be.  Both sensors are reading up and down super fast, just like the video.  The rear never moved like they are now.  Both front and rear from like .18 to .9 up and down fast.    Even at idle the voltage changes are super fast.  I had the bias set at .450 and it was pretty close to the same increase and decrease in voltage.  All this grief over a stinking exhaust leak. 

Now that I finally have the 02 issue worked out I'm curious to see how it tunes up.  That exhaust leak raised hell with me for over a year.  After going through all this and finally getting it straightened out the first thing I would tell a beginner DIY'er is to look at the 02's before even beginning to tune.  If those 02's aren't clearly working right I can see someone chasing their tale forever with these DIY tuning gadgets.