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Discussion Starter · #1 · (Edited)
Hey, back in time, i bought a k9 1000 with full
akrapovic racing line system on it. There was red
"Fl' light on, because of 02 sensor unpluged.

To turn off that ugly "Fl" light, i followed some
manual (i think from yoshimura full system) and
do the trick with wires from the ECU and finally
that red light goes off forever.

So my question is: Can someone explain me the
sitoation here, in more details. I know that o2
sensor is there to regulate the air/fuel ratio. But
what happens if the sensor is removed and
bypassed? (Like in most cases with full exhaust systems on) Does in this situation, ecu is using the standard A/F ratio all the time?(14.7:1 is the standard ratio for k9 1000) What is the positive and what is the negative effects? What is better… With plugged or unplugged o2 sensor?

here is mine,

-o2 sensor unpluged
-Also o2 connector unpluged (up there) so, the whole sensor is unplugged.
-Wire from ecu unpluged (to fix Fl light on dash)

Edit: after posting this thread, i found that i have o2 eliminator on my bike, and that Fl light that i solved with removing the 5th black/white wire from the ecu was from the removed servo exhaust valve instead of unplugged o2 sensor, as i thought before. (Because with o2 eliminator, there would not be Fl light)
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GSX-R 1000 2014 L4 in the Netherlands
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That looks like an O2 eliminator plug (with resistor, resistance is 326 Ohm ) ?
So it should be possible to connect like it was?

My gsx650f had one and that one is now in my 1000 L4 (2014)
no lights on both.

I think O2 eliminator gives best resistance (the 14 something for the ecu, better than no resistor (emergency program?)

For the valve thing in exhaust and cat I dont really know if it is bad or good (real data, not people thinking or assuming)
For the other bike the brake effect when releasing throttle was almost dangerous and O2 eliminator cured that very well, also have X-tre.
 

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L1 750
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The resistor (o2 eliminator) is to trick the ECU into thinking the sensor is still plugged in by replicating the resistance across the heater on the sensor. So the FI light stays off.

But the ecu is looking for a voltage on the other 2 wires. It's looking for a voltage between 0.1v & 0.9v but because its not connected, it receives 0 volts which is out of range so the ecu just uses the map as-is (rather than adjusting the fueling according to the voltage it receives from the sensor).

I elimated my o2 sensor when I got my bike but due to gas prices, I've plugged mine back in and I havnt noticed any negatives.
 

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This is the best explanation of what's going on that I know of. I'm pleased to not have one to worry about.

For years I thought that HO2 referred to the hydroperoxyl radical and that it was present in hot exhaust gas. I later discovered that it's just an acronym for Heated O2. Sigh!
 

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Discussion Starter · #5 ·
That looks like an O2 eliminator plug (with resistor, resistance is 326 Ohm ) ?
So it should be possible to connect like it was?

My gsx650f had one and that one is now in my 1000 L4 (2014)
no lights on both.

I think O2 eliminator gives best resistance (the 14 something for the ecu, better than no resistor (emergency program?)

For the valve thing in exhaust and cat I dont really know if it is bad or good (real data, not people thinking or assuming)
For the other bike the brake effect when releasing throttle was almost dangerous and O2 eliminator cured that very well, also have X-tre.
Yes, looks like the previous owner puts the O2 eliminator. I think it should be possible to connect like it was... just plug in o2 sensor back in the exhaust, remove the eliminator white resistor from ecu and plug the oem o2 connector there and that's it..

And about the Fl light, just discovered (from yoshimura manual) that the light comes from the exhaust servo valve not the o2 sensor as i thought
 

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AFAIK both the servo valve and the HO2 sensor can turn the red fault light on, as can several other faults.
 

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Discussion Starter · #7 ·
The resistor (o2 eliminator) is to trick the ECU into thinking the sensor is still plugged in by replicating the resistance across the heater on the sensor. So the FI light stays off.

But the ecu is looking for a voltage on the other 2 wires. It's looking for a voltage between 0.1v & 0.9v but because its not connected, it receives 0 volts which is out of range so the ecu just uses the map as-is (rather than adjusting the fueling according to the voltage it receives from the sensor).

I elimated my o2 sensor when I got my bike but due to gas prices, I've plugged mine back in and I havnt noticed any negatives.
Thanks bro!
This helped me a lot to understand the process! Now i get it almost all…

things that is still unclear to me:

1. If i plug back o2 sensor, would the sensor only tells the ecu to remove some fuel from default A/F Ratio Or there would be situations where the o2 sensor would tell the ecu to put more fuel from default A/F Ratio? (Not to add more fuel after several times of fuel subtraction)

because i read somewhere that o2 sensor is only suggesting the ecu to make a/f r more lean to pass emmission tests, exhoust sound etc… to lose performance in other words. And not to make the bike riding rich -it makes sense because everyone who wants performance uses those o2 eliminators…

2. with o2 sensor plugged. When would o2 sensor works? In which gears? At what temperature? All the time?

3.Now im riding with o2 eliminator.
-Is my bike supposed to run constant, better (more fuel/rich) air fuel ratio map now? Than With o2 sensor plugged?

(Exhaust flames are extremely rare, so it seems like AF ratio is lean…)it makes no senso to me…

also want to plugg back the sensor like you, just to see would be any difference(performance loss)

i am not worried about the fuel economy, i want better performance
 

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From what I read, the o2 sensor is possibly only active at idle & cruise in 4th, 5th & 6th.
& only when the engines hot.

The ecu will read the voltage from the sensor & then go slightly lean or rich to try to make the voltage stay around 0.45v.

Which indicates that the sensor is reading that the most complete combustion has occurred for emissions & fuel economy.

If you're not interested in economy, take the sensor off and have a dyno tune. Your tuner can tune the bike to run perfect without the sensor trying to fuck around with the fueling.
 

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Discussion Starter · #10 ·
From what I read, the o2 sensor is possibly only active at idle & cruise in 4th, 5th & 6th.
& only when the engines hot.

The ecu will read the voltage from the sensor & then go slightly lean or rich to try to make the voltage stay around 0.45v.

Which indicates that the sensor is reading that the most complete combustion has occurred for emissions & fuel economy.

If you're not interested in economy, take the sensor off and have a dyno tune. Your tuner can tune the bike to run perfect without the sensor trying to fuck around with the fueling.
Yes i know that, with Dyno tune the bike would be perfectly tuned to get maximum out of the bike, but i dont have a PC jet. I only compare performance with or without 02 sens

With that being said, with 02 eliminator the ecu would runs overall-more richer air fuel ratio map. (More fuel)

And default air fuel ratio map which would be used all the time, with 02 eliminator, would be higher than that 0,45v. Voltage all the time. Maybe like 0,70v? Am i getting this right?
 

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No. Your o2 eliminator is simply tricking the ecu into thinking the o2 sensor is plugged in.
It is not returning any voltage to the ecu.
Zero Volts. Open Circuit.
 

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Discussion Starter · #12 · (Edited)
No. Your o2 eliminator is simply tricking the ecu into thinking the o2 sensor is plugged in.
It is not returning any voltage to the ecu.
Zero Volts. Open Circuit.
Yes yes i get that all, but i wanted to ask: would that default ecu map which would be using after o2 eliminating, would be overall more richer than the map with o2 sensor plugged? (Thats why i said, more richer like in case if the plugged sensor and ecu is trying to achieve complete combustion of i.e. 0,70v for economy and emissions) (LIKE IF) i hope you get me, my english is not so good…
 

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I think I get you but realistically, without running it on a wideband O2 sensor (on a dyno or Autotune), you're not gonna know if you're rich or lean.

Usually if you add mods, full system, air filter, etc. Then the bike will run lean at the bottom but still a little rich at the top.

I should think if the bike is stock, it will run slightly richer without the sensor. As a margin of safety.
But if the bike is modified then you're not gonna know for sure without a dyno.

Are you thinking that if your bike is running lean, then you can plug the sensor in to richen things up?

If your bike is lean when the ecu starts reading from the sensor (closed loop), then it can add fuel to try to reach stoich (14.7:1) but it will only add a certain amount & only in certain situations.
But its definitely no substitute for a custom tune or Autotune using a Wideband sensor.
 

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Discussion Starter · #14 · (Edited)
I think I get you but realistically, without running it on a wideband O2 sensor (on a dyno or Autotune), you're not gonna know if you're rich or lean.

Usually if you add mods, full system, air filter, etc. Then the bike will run lean at the bottom but still a little rich at the top.

I should think if the bike is stock, it will run slightly richer without the sensor. As a margin of safety.
But if the bike is modified then you're not gonna know for sure without a dyno.

Are you thinking that if your bike is running lean, then you can plug the sensor in to richen things up?

If your bike is lean when the ecu starts reading from the sensor (closed loop), then it can add fuel to try to reach stoich (14.7:1) but it will only add a certain amount & only in certain situations.
But its definitely no substitute for a custom tune or Autotune using a Wideband sensor.
Yep, makes sense…

I think that the bike is maybe lean because there is almost never “popps or exhaust flames” when reving or when relasing the throttle like on another bikes here and there… yesterday i rode friend’s z750 with arrow slip on and some aftermarket air filter and the bike was popps almost every time after relasing the throttle…

I have full akrapovic racing line system and k/n race filter fitted on my k9 1000 (previous owner tells me that he had bazzaz but sells it before i bought the bike from him)

interested to see if i found any difference by plugging back o2 sensor… i would do that soon!
 

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Do you have the PAIR valve removed/plugged?
The PAIR valve injects air into the exhaust which makes pops.
Mines tuned on a wideband with PAIR removed & doesn't pop at all.
 
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