PC III and O2 Sensor Question

[Fred W]

There is no need for an ECU fooler on an FJR. The ECU will run just fine with the O2 sensor unplugged.

Also, the FJR's ECU isn't sophisticated enough to do adaptation. It is what it is and doesn't have the capability to "learn" like an OBD2 car ECU.

But you had a PC-V, which allows you to install their "Auto-tune kit" which includes a wide band O2 sensor in place of the stock one. Is that what you installed? With that setup the PC-V is what "learns".

But you aren't supposed to keep it in learning mode. You are just supposed to allow it to learn enough to generate a custom map, and then turn "auto-tune" off and just run off that map.

 

[Gitbox]

I just verified that the O2 sensor wire (Gray/Green) on sub harness E does in fact pass through the PC III. That means that with a PC III installed and the O2 sensor connected, any changes to injection duration made by the PC III would be corrected by the ECU in closed loop mode. In open loop mode the PC III will do it's job of customizing injector duration. As far as "fighting" each other, I'm not sure that is true. The PC III just adds or subtracts a set amount to the injection duration. It senses nothing other than throttle position and RPM to choose the cell where the offset is stored. If, in closed loop mode, a particular cell is offset rich, then the ECU would correct that to get back the 14.7 fuel/air ratio. The reverse would be true if the cell had lean offset.

If the lurchiness of the engine is due to closed loop mode being too lean, then the O2 sensor should be disconnected. If the lurchiness is caused by leanness when in open loop mode, then leaving the O2 sensor connected would be desirable for emissions and fuel economy. Kind of the best of both worlds.

Anyway, what think ye?

 

[Fred W]

Yes, that is what I meant by "fighting each other". The programmed offset of the PCIII would be nullified in the closed loop condition by the O2 sensor's feedback.

And I do think that the lean cruise surging that happens on a stock FJR is at least partly due to a too lean target of the closed loop mode. So it depends which reason you installed the Power Commander for, whether it was to mitigate the lean surging or to reduce the throttle snatchiness.

 

[Gitbox]

Excellent! I think we agree.

It would be nice if there was an easy way to tell when the ECU enters closed loop mode. I might try running the PC III connected to a laptop and screen record the whole thing.

 

[bigjohnsd]

There are many Dyno Tuners present at the Sturgis Pirate fest, so many that Dynojet sends their Factory Dyno truck and three experts to handle the troublesome bikes that the normal dynotuners can't get right.

The Dynojet Factory truck is set up right next to us.

I visited with the three techreps yesterday, they and we weren't too busy in the mid-afternoon, they told me that for the FJR the O2 Sensor should definitely be unplugged when the PC3 is installed, that the unplugged O2 sensor will not and should not set a check engine light, and that if left connected the O2 sensor will cause the ECU to try and correct t the changes the PC3 is trying to make.

If anyone has a specific question, PM it to me and I will ask the experts and either PM or Post the answer, if you include a email addressiI'll ask the experts to contact you directly if you'd rather.

They were telling me that the OEM stuff on the newest bikes is so good they hardly ever can make more power, they can sometimes solve some lean surge issues, but that improvements by the OEMs has severely cut into their business.

 

[Fred W]

Nice! Thanks John.

And I agree with them. The 3rd Gen FJR fueling feels pretty much like where my 1st Gen was after adding the PCIII and a custom map. In other words Yamaha got it right on the 3rd Gen. No need for an add on Power Commander type box at all.

You might ask the DynaTune guys why it was that they designed the PCIII to pass the O2 signal through the box since they intended for you to disconnect the signal anyway? They could have accomplished the disconnect automatically just by not passing the signal through.

Maybe it comes down to not violating EPA rules about disconnecting emissions circuits. Which might also be why it is not found in the instructions to disconnect it.

 

[Gitbox]

More great info! Thanks guys.

BigJohn: I got the PC III for the surging and lurching issues at low RPM. I didn't need any more power.

Fred: Agree with the EPA comment.

At the risk of beating this subject to death, here's a couple more thoughts: if the surging is caused by the ECU going into closed loop mode, then disconnecting the O2 sensor should have a positive effect, right? If it has no effect, then it means that the engine is just running too lean at those RPMs? (based on all the maps that show a pretty large increase in injector time at 3.5 k RPM and under)

Yes, I know what DynoJet recommends, but I think they are more into squeezing out more power than they are into smoothness.

And yes, I am still fiddling with this mostly as a learning experience. This FJR is my first EFI bike! (carbs suck... uh oh, shouldn't have wrote that.

)

 

[bigjohnsd]

Metric Specialist at Dynojet says that there is no pass through of the O2 signal on the PCIII. The harness the PCIII plugs into is a FI harness and no O2 signal is present according to him.

 

[Gitbox]

I beg to differ. The PC III plugs in series to two harness connectors. One carries the FI signals, the other carries the throttle position sensor, O2 sensor and something else I can't remember without looking at the schematic. The O2 sensor wire is a dead short from its connector right through the PC III to the other connector on its way to the ECU.

 

[bigjohnsd]

I'll ask again, but.....

 

[bigjohnsd]

I'll ask again, but.....schematic coming, they don't process signal, the signal passes from one connector to the other. They can't do anything with a narrow band signal anyways.

 

[Gitbox]

I ran all this by one of DynoJet's tech support guys and he said that FJRs did not have O2 sensors, so...

 

[Fred W]

John... one of the connector that the PC3 is placed in between (electrically) has the following 4 signals (5 wires) in it:

O2 sensor

Cylinder ID sensor

Throttle Position Sensor

Intake Air Pressure Sensor

A common reference from the ECU.

These signals need to have a pass thru in addition to any monitoring or use the PCIII has for them.

 

[bigjohnsd]

The head Metric guy is looking at schematics to double check. He has their Schematic and the Services Manual for Festar's bike. Plus he's going to Dyno Festar's stock bike to see what it puts out at the rear wheel this afternoon!

 

[carlson_mn]

I never had any surging on my '04 when I used a PC3 so I kept the O2 sensor connected. I benefited by the power commander fueling change at mid and WOT conditions and when at cruise it went back to closed loop mode and I the bike maintained the stoich AF ratio and my mpg was just like stock. Hell I zeroed out the PC tables in the low throttle positions anyways so it was not changing anything there anyways.

 

[Enn]

I have PC V on my 08 and in the beginning the Yamaha guys, who installed it, did not disconnect the O2 sensor. I was pretty disappointed to the bike's behavior as it did not cure the throttle snatchiness. Until I found out that the O2 sensor was still there. So after unplugging, bike became smooth as butter. So for me everything Fred says makes lots of sense