Please excuse my ignorance if this is a dumb question.

On my recently purchased 06 Super Glide, I noticed yesterday that the previous owner unplugged the Oxygen sensors... they're still in the exhaust, but are unplugged from the other end.

Why would they do this? The bike also has a Power Commander III if that matters...

Thanks,

 

The use of the PC-llldoesaway withthe need for the O2 sensors. When you purchase a PC-lll, it comes with a pair of plugs which insert into the bike's O2 sensor connectors to keep the ECM from throwing error codes. They are called O2 Sensor Eliminators.

 

It's supposed to be like that with the PCIII. I bought the O2 sensor bolts from JP Cycles just to clean it up, but they dont come with crush washers. had to get them ordered from the dealer , cost $.50 each

 

Not strictly true. It doesn't eliminate the need; the oxygen sensors would defeat what the PCIII so they have to be eliminated. It's not a benefit -- it's a work-around.

 

Is it just me, or is the PCIII a bit of a piece of spit? First I find out that it causes the slow starting issues, and now find out it has a work around the oxygen sensors. Did Dynojet just not modify their product to work with the oxygen sensors?

Are the oxygen sensors bad? I'm sure they're there for pollution control, but do they hinder performance?

Trevor

 

what pipes are you running?

 

Right now I have the older SEII slipons, which I find too loud so I'm going to have to get something quieter.

Trevor

 

That's an interesting perspective on the PCIII, always wondered myself.
Interectingly enough, my parts guy at the HD dealership tried to save me money by talking me into purchasing the PCIII, instesd of the SERT.............. Ddn't work, I bought the SERT

PCIII must work pretty well because a lot of tuners like them, but don't know for sure.

DougJ

 

You can go to NAPA and buy oil drain plugs to plug up the pipes and take off the old sensors. I forget what size they are but they are cheap and makes the pipes look so much better.

 

This can get lengthy ---

The PCIII is a "pulse stretcher." That is, it works by taking the signal from the ECU to the injectors and making it last longer, thus injecting extra fuel over and above what the ECU normally would. Since there's almost never a case where you'd want to cut back fuel from the stock map, they do what they're supposed to do.

The oxygen sensors on the 06 and up bikes are actually pretty cool. When the bike is running along at steady throttle or idling the oxygen sensors feed back to the ECU and tells it how complete a burn you're getting. So instead of giving you fuel based on an entry in a fuel map, the ECU adjusts the fuel so the burn is correct.

The problem that happens when you mix oxygen sensors with pulse stretchers is that the oxygen sensors just tell the ECU to cut back on the fuel until the effect of stretching the pulse is removed. So they can't co-exist.

Oxygen sensors come in two flavors -- wide band and narrow band. The ones on the bike are narrow band. They basically just tell the ECU "you're too lean," "you're OK" or "you're too rich." They are designed to keep the bike at a set (I think it's 14.7) air/fuel ratio. The ECU makes corrections until it gets the OK signal. It is an article of faith at the EPA that 14.7 is exactly right for all engines because it results in the theoretical perfect combustion and least emission. It is an article of faith among Harley riders that 14.7 is too lean and runs the engine too hot, which is why PCIII and such exist.Most such systems use oxygen sensor eliminators which are just simple resistors that fake an "OK" signal no matter what's going on.

The coolest oxygen sensors are wide band. They report back the actual air/fuel ratio, so you can set your ECU (not the stock one -- it doesn't know how to read wide band) to a particular AFR and the oxygen sensors will keep it there. The TMAX Autotune system does that -- you replace the whole ECU and the oxygen sensors and it keeps your bike at whatever AFR your faith believes in. I think there's at least one other system that does the same thing. There are also hybrid systems like the Innovate Motorsports LC-2 that let you hang wide-band sensors on a stock ECU and program them to impersonate narrow band sensors but have them report "OK" at the AFR of your choice.

Don't you wish you hadn't asked?