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Old 07-12-2010, 03:04 PM   #1 (permalink)
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Effecting Oxygen Sensor output

Just me thinking here, if the only A/F measurement these bikes are using is oxy sensors, can't the fuel mixture be adjusted by simply altering the oxy. sensor signal?

Something as simple as unplugging the o2 sensors and replace them with a resistor? Or a simple circuit with a pot to have an adjustable range?

Or, the ideal situation may be to place a resistor inline with the o2 sensor to simply reduce the output by a small margin, that way there would still be some tuning changes to account for temperature.

Provided this would work, any idea how I could figure out what resistor values to use, without having access to any way to measure A/F Ratio?
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Old 07-12-2010, 03:10 PM   #2 (permalink)
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Much debate over these though...
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Old 07-12-2010, 04:20 PM   #3 (permalink)
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claydbal is reading this now saying WTF is this?
check out the mustang and camaro sites. they were doing that 15-20 years ago for closed loop. they also altered fuel pump pressure, moved iat to cooler locations, etc tricked ets to keep in open loop------- that was for the guys that didnt tune.
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Old 07-13-2010, 08:21 PM   #4 (permalink)
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Quote:
Originally Posted by Comingapart View Post
Just me thinking here, if the only A/F measurement these bikes are using is oxy sensors, can't the fuel mixture be adjusted by simply altering the oxy. sensor signal?

Something as simple as unplugging the o2 sensors and replace them with a resistor? Or a simple circuit with a pot to have an adjustable range?

Or, the ideal situation may be to place a resistor inline with the o2 sensor to simply reduce the output by a small margin, that way there would still be some tuning changes to account for temperature.

Provided this would work, any idea how I could figure out what resistor values to use, without having access to any way to measure A/F Ratio?
O2 sensors are actually little "batteries" that produce rapidly fluctuating voltage depending on the amount of residual oxygen in the exhaust moving through their pumping chambers. You couldn't just replace them with resistors. A resistor could possibly be used in the signal line to limit the max amplitude of the "swing", which would tend to make the controller think it was leaner than it actually was. Trick, as you say, would be to figure out how much to trim.

The sensor controller expects the output of a narrow-band sensor, which is a more limited range of voltage fluctuations. If you trimmed below what the controller thought was the minimum voltage to be expected, it might get confused???

Don't know much about Mullens' (nightrider.com) XIED or whatever he ended up calling it, but I'd be interested to know how he got around that problem--if it ever was one. Or did he eliminate the O2 sensor altogether, as others do?

Trouble with all strategies like this is they only correct in one direction. These bikes are lean in some areas, but rich in others. Ideally, you need to be able to add and subtract fuel at various load points. Seems to me that all you're trying to do is the most basic of "add" fuel trimming operations. If that's true, you could just to buy a cheap add-on and get the results you're looking for. Actually, any of them will do that for you.

As far as I'm concerned anyway, there is no way to effectively tune an EFI bike without a dyno, or at least an on-the-road data logger. Anything else is just a guess. (Yes, some are better "guessers" than others, depending on their experience with a particular bike combination).
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Old 07-14-2010, 09:38 AM   #5 (permalink)
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Above I wrote "...A resistor could possibly be used in the signal line to limit the max amplitude of the "swing", which would tend to make the controller think it was leaner than it actually was...".

I knew after I sent my answer that there was something about it that bothered me, but it wasn't until last night that I realized what it was.

The O2 sensor output is a variable amplitude signal all right, but it is directly proportional to the amount of O2 (sorta) in the exhaust. In other words, higher amplitude with a lean (or unburned) mixture, and lower with a richer mixture. Adding the resistor would make it think it was rich, not lean.

Got my signals crossed (pun intended). Sorry.
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Old 08-07-2010, 08:16 PM   #6 (permalink)
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"Adding the resistor would make it think it was rich, not lean."

True but what about using a 12v source and using a resistor to bring it down to .9v for 12.0-1 AFR.

Also, doesn't removing the sensor automatically change the AFR to 12.0-1 as stated below?

"During engine warm up the HD engine runs in open loop mode at a 12.0:1AFR. No matter what the engine temperature, this is the AFR that occurs at starting. If you disconnect the O2 sensors on the engine, this is the default idle AFR for the HD engine."

Can anyone verify the accuracy of the statement above? I am using 02 eliminators and it doesn't seem to be the case on my bike. I can't imagine I'm at 12.0-1 and generating the heat mine does at idle.

Also, my bike, no matter how hot, has never done this.

"In high temp mode the engine RPMs drops to 950 and the ECU goes to open loop mode, richening the fuel mixture to 12:1 in an attempt to cool the engine. As soon as the engine RPMs hits 1200, the ECU goes back to closed loop mode at 14.7:1 which is too lean. This means that the smallest amount of throttle will lean the engine out as long as the ECU is operating in "high heat" mode."

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http://www.nightrider.com/biketech/hd2007HD_heat_00.htm
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Old 08-07-2010, 08:42 PM   #7 (permalink)
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Quote:
Originally Posted by bamofo666 View Post
...Also, doesn't removing the sensor automatically change the AFR to 12.0-1 as stated below?
I think a more accurate statement might be that the system only "looks" for O2 sensor data when in closed loop. Removing the sensors might cause a code to be thrown, however.

Quote:
Originally Posted by bamofo666 View Post
..."During engine warm up the HD engine runs in open loop mode at a 12.0:1AFR. No matter what the engine temperature, this is the AFR that occurs at starting. If you disconnect the O2 sensors on the engine, this is the default idle AFR for the HD engine."

Can anyone verify the accuracy of the statement above?
I don't think that's correct. The system does use other tables during startup.

Quote:
Originally Posted by bamofo666 View Post
...Also, my bike, no matter how hot, has never done this.

"In high temp mode the engine RPMs drops to 950 and the ECU goes to open loop mode, richening the fuel mixture to 12:1 in an attempt to cool the engine. As soon as the engine RPMs hits 1200, the ECU goes back to closed loop mode at 14.7:1 which is too lean. This means that the smallest amount of throttle will lean the engine out as long as the ECU is operating in "high heat" mode."
Does you bike have the EITMS? If so, is it "enabled" and is it turned on?

This is one of the reasons so many go to a tuner that's capable of allowing changes in the AFR as well as timing pretty much across the map which, in turn, helps with cooling and performance issues.
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Old 08-07-2010, 10:15 PM   #8 (permalink)
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your bike is in open loop any time its not in closed loop, and it doesnt live in closed loop like you think. but open loop is not 12:1, it is still a leaner mix, and remember--------thats on an unmolested bike! imagine opening the flow and you are lean in open loop probably moreso than closed loop. at least closed loop TRIES to compensate. resistors or other gizmos will/can keep the codes away so your light dont shine, and usually take the o2 out of the loop so it forces you to open loop-------where you hope its richer, but t the end of the day, your timing still sucks and your fuel still aint tuned.
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