The O2 sensor reading -26%

not knowing the operation of the pcv i will assume that u r right. i was just making a statement to see what would happen. the more opinions i get the more i learn. i was hopping that someone would post directions.

The Powercommander instructions say plug in the white O2 sensor eliminator and go about your life. They have the instructions this way, because, they can't assume you can access the ECU, so they cant tell you "get TuneECU and disable the O2 sensor", which, would also bring EPA legalities for them potentially.

So, knowing how the O2 simulator works, heat sinks the heater circuit and simulates a 14.x AFR at all times to the ECU to avoid stock ECU fueling corrections, the clear and obvious route to avoid any issues is just uncheck the box in TuneECU. Now your tune isn't relying on a $0.05 cost resistor to provide feedback to the ECU.

Why is that better? Because if the resistor starts to wear or go bad or is just off when new (not rare for bulk produced resistors), and it will over time, your ECU will start getting out of stoich feedback, so it'll start trying to make fueling adjustments (trims). Your PC-V has no idea it's doing this and will compensate by adjusting the tune from the changed AFR seen at the Wideband. The stock ECU will never get a signal that the long term trim fixed the lean/rich condition, so it will eventually end up at max enrichment/enleanment, or, +/- 26%. The result is the same, your bike will now be able to be tuned and hold it perfectly because the ECU has reached max adjustment.

The reason that's bad, is now you've had to compensate for the long term trims of the ECU with the PC-V. The larger the +/- number in the PC-V table, the less accurate the numbers represent a percentage and just become an adjustment value, there is a difference when trying to dial in the last 0.1 AFR adjustment.

You can skip all that ECU adjustment by just disabling the sensor, it also saves you on electrical load and battery drain while flashing the ECU.

Either method can work, just tuner preference really.

In other words, Power Commanders were designed to trim the fuel without using any O2 signal other than the wide band signal the dyno tuner measured in your exhaust. This was before auto tune. So their little plug disables the ECU from changing the fuel based on the stock O2 sensor as this would interfere with your dyno tune.

TURBO200R4 said:

well this is getting good. what does the directions say? to leave the O2 box checked
i guess it depends on what is hooked up to the o2 connector.
i don't know $hit about those aftermarket boxes that why i am giving my opinion
if it uses a wide band o2 then i think it would take that info and program it to a voltage that the ecu can use and put it back into the o2 connector and u would have to have the o2 checked for the ecu to get the wide band o2 info.
if u have the bypass i would assume that gives a fixed signal and u would have to have the o2 box checked other wise if unchecked the ecu would set its own voltage. Correct
i guess i have thought enough for one morning.

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dougl said:

The wide band O2 sensor that is used by auto tune with the PCV is, as far as I know, completely independent of the ECU. The PCV intercepts fuel pulses from the ECU and uses the auto tuning function to modify those pulses. For a stock setup, the ECU uses the stock narrow band sensor to determine the fuel below about 20% throttle and below about 4400 rpm. You can prevent it from doing this by unchecking the O2 box, as virtually all custom tunes do. I found after a while they would cause low thrttle hesitations resulting in having to reset the adaptives a repeating this every so often grows tiresome

The PCV should be getting a constant pulse from the ECU for every TP and RPM. When the ECU is in closed loop, using the narrow band sensor, it isn't clear how consistent the pulses are for a given TP-RPM pair. So, the auto tune may or may not be able to adapt in a reproducible way.

Better to get rid of closed loop operation altogether and either plug the narrow band sensor connection with the Dynojet part or uncheck the O2 box in TuneECU or do both.[/QUOTE]

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The AT =Auto Tune can not function if it is not connected to the Wide Band O2 sensor therefore the PCV could only work of values it has in the "Fuel Table" and if you uncheck the O2 box the ECU will default to trying to lower the Fuel it sends at low throttle load which will effect the PCV +AT as the AT only works above 2% throttle

Oh and the uncheck/check O2 box issue was verified by a Dyno Jet Tech as when I was fitting mine some of my instruction were missing so I rang them up in the States to verify that and some other fitting Questions I had

am thinking, i am thinking, i just hate it when i have to understand how something works and my brain wont let it go.
just finished reading dyno jet comander /auto tune. i am learning

i well tell u what i have learned. i have learned enough to stay out of this thread.
however hanso is the man and he knows a $hit load more than i know.

Really, it doesn't matter, checked or unchecked, they accomplish the same thing in the end.

**** I've just recieved my PCV and AT with the eliminater or the optimizer missing and after reading this thread I think I'll sell it and just get a dyno tune...

RocketMan3 said:

**** I've just recieved my PCV and AT with the eliminater or the optimizer missing and after reading this thread I think I'll sell it and just get a dyno tune...

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You don't need to use the AT. Just uncheck the O2 box, install the PCV with a zero map in it, and get it dyno tuned. Also, make sure the secondaries table values in the tune in your ECU are all 100% before you get it tuned.