gas tuners and O2 sensors

[tabbedout79]

I don't know if I have this right but here goes; on my 2007 fxst the O2 sensors "sniff" the exhaust and tell the ECM when the AFR is not at optimum ratio 14.7:1. The ECM then sends a signal that restricts the gas flow to achieve a ratio as close to this as possible. If a gas tuner is used but the O2's are still in play the ECM will continuously try to lean out the AFR. If a sensor eliminator is used this makes the ECM think the O2's are still in play and the system is responsive to fuel adjustments without trying to lean out the AFR. Is this correct. Carb guy trying to understand "closed loop" EFI.

Also, if wideband sensors are what is needed then why did HD put in Narrow band and will the DElphi ECM work with widebamd without the aftermarket interface stuff. I called Delphi and the "motorcycle guy" gave me the song and dance about Stoichemetric and after all was said and done couldn't say whether the ECM was compatible with wide band.

On nightrider.com they say they aren't sure if it is and they say one wideband on the front cylinder may be enough because theECM prioritizes the front cy;inder O2. They sell the wide band for $200/unit. they are made by Innovate Motorsports.

[Mike]

Your close. The O2's use a reference table called "Closed loop Bias" to target AFR's related to the voltage value in that table. The AFR table tells the ECM when to use the Bias values vs. offset values (offsets assume real tailpipe AFR's match base settings, which they will so long as air flow through the motor has not changed from stock). A value of 14.6 in the AFR table tells the ECM to compare O2 voltage readings to the bias voltage values and change fuel (VE) values until they match. The bias values can target anything from 14.1-14.8, this is the range of the narrow band O2's. The target AFR's are not neccesarily 14.7 (or 14.6, as the AFR table would imply). Narrow bands are used because of cost in both the sensors and ECM programming/processing power and they are sufficient for stock/near stock applications. The stock ECM would not be compatible with wide bands since the programming and lookup tables are not in place to use their greater range. It may be coming but I'm pretty bad at outguessing H-D. The H-D system does not prioritize the front, though some emmisions testing is done on the front cylinder, it fully optimizes each cylinder independantely. This is another reason Race Tuner is our favourite tuning device because it use's the same stratigies and allows access to many of these tables (some tables are still hidden and not open for change but this will even more true of other devices). The sensor eliminator basically sends a constant signal to the O2 but I'm not sure what value they are using since the bias table uses a variety depending on load and rpm and the O2's are not switched off via the AFR table (any value less than 14.6). This stratigy takes off line one of the main selling features of the 07 and later models and we would like to see this feature active and utulized as a further level of fine tuning to whatever mapping we may develope using Race Tuner. When we tune with Race Tuner we switch off the closed loop mode, mathc tail pipe measured AFR to our base table AFR and then switch back on the closed loop. Now the open and closed loop offsets and targets are adjusting/correcting known real world values. If our mapping is accurate, those adjustments will be minor (mostly due to invironmental changes).

Last, I'm not sure how the wide band would be wired since they use anywhere from 5 to 7 wires where the narrows use 1-3. It's the function of those extra wires that the stock ECM has no capacity to deal with.
Mike