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Trace

Make Your Own O2 Sensor Eliminators

107 posts in this topic

gallery_4428_747_79599.jpg

Close-up of connectors

You can make your own Oxygen sensor eliminators by installing 330 ohm resisters across the leads to the OEM sensors. Locate the natural and the black colored 4p connectors near the alternator cover (left side) and dissconnect them both.

gallery_4428_747_558427.jpg

Location under left fairing

PARTS

330 ohm resisters at Radio Shack $0.99 a pack of 5

Model: 271-1315

Catalog #: 271-1315

INSTALL

gallery_4428_747_79599.jpg

Install the Resisters across the leads

The 4p connectos have 4 leads. Use the two leads opposite the locking tab on each of the black and natural connectors, obviously on the side connected to the bike and not to the O2 sensors. You can remove the sensors and their wire harnesses if you want. Plugs that fit where the sensors screw into the exhaust pipes are easily found at most any auto parts store.

You can wrap with electrical tape or find large shrink wrap to protect the wireing job, zip tie them secure.

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Thanks for the 'how' to eliminate the O2 sensors...

What does it do for me? with a stock Vtec, no pipe or PCIII.

My guess is, it will prevent the bike from leaning itself out because it doesn't detect the rich mixture anymore.

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Thanks for the 'how' to eliminate the O2 sensors...

What does it do for me?? with a stock Vtec, no pipe or PCIII.

My guess is, it will prevent the bike from leaning itself out because it doesn't detect the rich mixture anymore.

I asked a similar question on another recent thread and am impatiently waiting for a response smile.gif

Here it is again to add to Dave's question:

If the 99 headers have no cat and the resistors are plugged into the O2s, what does that do to the FI without a PCIII? Does the bike run richer overall, but without the Cat produces more hp? If one were to simply run eliminators on a bike with a Cat and no PCIII, what would happen, assuming no aftermarket pipes? More hp / hurt performance / nothing? Inquiring minds want to know! I really know very little about the intricacies of the FI system and have learned a lot from some of our more technical folks at VFRD. As always, I appreciate the info!! Thanks.

Edited by VFRquig

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It is thought that eliminating the o2 sensors cures that midrange surge or flat spot in the power-band. It is essential to eliminate the sensors when using a PCIII or you will get FI errors. Using an aftermarket silencer some have had success in curing the surging by eliminating the O2 sensors. When in constant throttle the ecm puts the fuel curve into stoichiometric mode and it burns with lower emissions, saves fuel, this seems to produce a flat spot or a surge when coming out of it.

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Thanks HS. I was looking for a bit more ed-u-ma-ca-shun on how it actually worked in terms of various throttle situations so I appreciate the help. If I understand this correctly, the O2 sensors "tell" the system to richen/lean mixture as needed depending on the readings before and after the Cat. So my question is, if the Cat is not there (ie 99 header pipe) and the sensors are eliminated, does the bike run leaner, regardless of throttle state (steady, WOT) or does the bike run richer? What actually controls the fuel/air mixture on the bikes, other than the stock map and O2 sensors? It seems the removal of the Cat would decrease the restriction enough to require a change in the mixture (assuming factory exhaust and no PC III). So, to complete my ramblings, if I were to get 99 headers, with no aftermarket pipes and no PC III for my Vtec, would I notice any positive or negative performance changes (hp) or will it simply be enough to address surging problems for those unlucky owners that have them?

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Map Sensor is what controls the fuel air mixture mostly, but it hands off to the O2 sensors when in open loop during those steady throttle sessions then it goes very lean into stoichometric, it think its 14 parts air 1 part fuel. Map sensor measures the manifold vacuum pressure which is what controls the fuel mix when tied with the throttle postion sensor - its a three dimensional map tp sensor vs map sensor air temp sensor in the airbox - it is when one of these variables is held constant that the O2 sensors is used, TP constant input for so many seconds loops in the o2 sensors.

It is an excorize in Boyle's law

PV=C

and adjusting for temperature

V=CT

The computer needs to know the volume of air at what pressure and temperature in the cyclinder to inject the right amount of fuel based on the throttle input at the time of the intake stroke.

It reads temperature from the temperature sensor and reads pressure with the map sensor, and then calculates the amount fuel - it is not 100% correct so there is not always an effiecient burn so when the throttle postion is held constant it can read the O2 sensor reading and inject stochometric fuel loads. Its of course more complicated than I explain but basically thats the idea.

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When I installed mine I ended up nipping off a little of each lead so that the resistor can sit right on the end of the connector. Makes for a little cleaner tape job. :D

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When I installed mine I ended up nipping off a little of each lead so that the resistor can sit right on the end of the connector.  Makes for a little cleaner tape job. :D

Indeed. This was more for demo purposes, so a person could see what terminals to plug in to. I also want to mention that there is no need to mummify the connectors with electrical tape to keep water out. Just use a little bit to 1) retain the resistor and 2) insulate any metal from shorting out. Too much tape will likely trap water inside the connectors and lead to corrosion (someday). And water won't really hurt anything, anyway. Instead, let them be "self draining". Engine heat will dry 'em in a minute. Besides, once you pull that clear plastic boot back down over the connectors, water won't be an issue anyway.

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I think it is all making sense now. So if I put on the new -old headers, and used the O2 sensors, I wouldn't really see much on the bike performance wise. My bike would just run closed loop at all TP and I might get a bit more sound from the stock cans? Correct? Sorry if I sound like a dumbass asking this many questions. I am just trying to squeeze as much bang-for-the-buck out of the silver bullet as possible. +1.gif

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I think it is all making sense now.? So if I put on the new -old headers, and used the O2 sensors, I wouldn't really see much on the bike performance wise.? My bike would just run closed loop at all TP and I might get a bit more sound from the stock cans? Correct? Sorry if I sound like a dumbass asking this many questions.? I am just trying to squeeze as much bang-for-the-buck out of the silver bullet as possible.? +1.gif

HS is basically right, but to boil it down....there's no real reason to eliminate the O2s if you're NOT running a Power Commander. That is, unless you're putting any kind of "headers with no sensors" on an O2-sensored bike. In that case, you'll have to do the O2 elims to keep the FI light happy.

As a practical matter in the real world, you won't see power increases and such by O2 elimination. You don't get power increases at steady-state throttle.....where the O2's "live".

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HS is basically right, but to boil it down....there's no real reason to eliminate the O2s if you're NOT running a Power Commander.?  That is, unless you're putting any kind of "headers with no sensors" on an O2-sensored bike.? In that case, you'll have to do the O2 elims to keep the FI light happy.?

As a practical matter in the real world, you won't see power increases and such by O2 elimination.? You don't get power increases at steady-state throttle.....where the O2's "live".

Sweet- thanks for all the free knowledge. Now I just have to decide if the weight savings of going Cat-less will make my ride scary fast- lol

One last thing- will the change in restriction have any negative effect on the bike? I assume the bulk of the exhaust restrict comes from the cat, not the stock pipes. I have fears that such a change may cause problems? Any comments?

Edited by VFRquig

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From everything I've read, most people seem to be happy with o2 sensor eliminators or 330 ohm resisters. So, I decided to try it. My results were less than favorable. Now when the bike stumbles/surges in the 4k-5k range, it feels like I lose all of my power. When I twist the throttle a bit to get out of the stoichiometric mode or when the RPMs get above 5k, it feels like someone just rear-ended me as the bike lurches forward violently. sad.gif

My pretty sure I plugged the resistors into the correct spots since the FI light doesn't come on. My only guess is that I grabbed the wrong resistors from Radio Shack. The package says 330 ohm, but I'm going to check the colors on the resistor just to make sure. :huh: Until I can figure it out, I'll be removing the resistors and plugging my o2 sensors back in. <_< YMMV.

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How do you arrive at a value of 330 ohms for the resistors? Is it in the manual, spec for the O2 sensor? Just curious. Thanks!

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How do you arrive at a value of 330 ohms for the resistors?  Is it in the manual, spec for the O2 sensor?  Just curious.  Thanks!

I think someone actually measured the dynojet branded eliminators.

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How do you arrive at a value of 330 ohms for the resistors?? Is it in the manual, spec for the O2 sensor?? Just curious.? Thanks!

Dunno. It's just been "common knowledge" since forever. O2 elims are very common in the aftermarket world, so it's not any real secret as to what is in those $15 (each) items from DynoJet. I'm sure sombody just laid an Ohm meter on one, took the reading, made their own.

Edited by Trace

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Now when the bike stumbles/surges in the 4k-5k range, it feels like I lose all of my power.  When I twist the throttle a bit to get out of the stoichiometric mode or when the RPMs get above 5k, it feels like someone just rear-ended me as the bike lurches forward violently. 

I take it you don't have a PC? Again, there's no reason to remove the O2s unless you do.

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I take it you don't have a PC?  Again, there's no reason  to remove the O2s unless you do.

Yup no PC. I was under the impression that the O2 eliminator merely kept the bike from enter stoichiometric mode when holding a constant throttle. How does a PC keep the bike from stumbling if the ECU is always trying to adjust the air/fuel ratio at constant throttle? I thought all the PC did was allow you to dump more or less fuel into the cylinders at given throttle openings. Wouldn't the ECU still try to fight with the PC then? I'm confused. :unsure:

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Yup no PC.? I was under the impression that the O2 eliminator merely kept the bike from enter stoichiometric mode when holding a constant throttle.? How does a PC keep the bike from stumbling if the ECU is always trying to adjust the air/fuel ratio at constant throttle?? I thought all the PC did was allow you to dump more or less fuel into the cylinders at given throttle openings.? Wouldn't the ECU still try to fight with the PC then?? I'm confused.?

Yes, you are confused.

The PCII simply "fools" the ECU into thinking it's happy, so there's no fighting each other under your seat! +1.gif It does this by providing the ECU with bogus input data at various throttle and rpm points, most noteably as HS said above, the MAP sensor. The ECU interprets this bogus data and acts accordingly. The trick is to give it "good" bogus data so it does what you want. The O2s try to undo what you're tricking....and it can try to go either way. O2s don't just lean things out....they can richen them from a lean condition, too. I suspect that's what happened in MFP-2214's case....but dunno for sure.

So, there you have it. Buy a PC and do the 330 ohm trick....and save $30!! :thumbsup: :P

I urge you to go to the DynoJet website and mouse around there for awhile. They explain the differences between PCII, III, IIIusb, etc....and much other info as to how these things work.

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I installed the resistors two weeks ago on a stock 2003, no PC. It almost completely did away with the slight feeling of power loss between 4500 and 5k at a constant throttle that I was noticing before.

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I installed the resistors two weeks ago on a stock 2003, no PC. It almost completely did away with the slight feeling of power loss between 4500 and 5k at a constant throttle that I was noticing before.

Now THAT's interesting!! Dunno.

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Yes, you are confused. 

The PCII simply "fools" the ECU into thinking it's happy, so there's no fighting each other under your seat!  :goofy:  It does this by providing the ECU with bogus input data at various throttle and rpm points, most noteably as HS said above, the MAP sensor.  The ECU interprets this bogus data and acts accordingly.  The trick is to give it "good" bogus data so it does what you want.  The O2s try to undo what you're tricking....and it can try to go either way.  O2s don't just lean things out....they can richen them from a lean condition, too.  I suspect that's what happened in MFP-2214's case....but dunno for sure.

So, there you have it.  Buy a PC and do the 330 ohm trick....and save $30!!  :thumbsup:  :P

I urge you to go to the DynoJet website and mouse around there for awhile. They explain the differences between PCII, III, IIIusb, etc....and much other info as to how these things work.

This is not really correct. The Power Commander does not alter the inputs to the ECU. It sits between the ECU and the injectors...It intercepts the injector control pulses from the ECU, modifies them to achieve the desired trim based upon the custom map, then sends them on to the injectors. The ECU still gets normal input data and does whatever it does with that to generate a base injector pulse for those conditions. The PC stretches or shortens the base pulse to achieve the desired fuel trim. (Remember...Injectors are a pulse-width modulated device. The longer they are "on" the more fuel they will deliver -> richer mix)

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From everything I've read, most people seem to be happy with o2 sensor eliminators or 330 ohm resisters.  So, I decided to try it.  My results were less than favorable.  Now when the bike stumbles/surges in the 4k-5k range, it feels like I lose all of my power.  When I twist the throttle a bit to get out of the stoichiometric mode or when the RPMs get above 5k, it feels like someone just rear-ended me as the bike lurches forward violently.  sad.gif

My pretty sure I plugged the resistors into the correct spots since the FI light doesn't come on.  My only guess is that I grabbed the wrong resistors from Radio Shack.  The package says 330 ohm, but I'm going to check the colors on the resistor just to make sure.  +1.gif  Until I can figure it out, I'll be removing the resistors and plugging my o2 sensors back in.  <_<  YMMV.

MFP, when I first put in the O2 sensor eliminators which I purchased for 30 bucks on my Vtech I had the same problem as you described as did a few others on the board. The lurching was terrible. However, I discovered that by turning the ignition on, letting it go through it's whine, then turn it off and then back on and then start the engine, the surging and flat spot are completely eliminated. Why does this happen? No f ing clue. Some think that the computer resets itself after you shut down the bike each time. By "rebooting" the computer it seems to read the open loop. I think Das Bone has documented this too. So leave them in and just on/off/on your bike each time. Beats spending 300 bucks on a PC111.

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This is not really correct.  The Power Commander does not alter the inputs to the ECU.  It sits between the ECU and the injectors...It intercepts the injector control pulses from the ECU, modifies them to achieve the desired trim based upon the custom map, then sends them on to the injectors.  The ECU still gets normal input data and does whatever it does with that to generate a base injector pulse for those conditions.  The PC stretches or shortens the base pulse to achieve the desired fuel trim. (Remember...Injectors are a pulse-width modulated device.  The longer they are "on" the more fuel they will deliver -> richer mix)

Yes, it IS correct for the PCII, which is what I was addressing. Sorry, should have been totally specific. From the DynoJet website:

The Power Commander II was introduced in 1999 and featured the latest surface mount electronics. Additional features were added like the faceplate button adjustment. The Power Commander II also allowed fuel and ignition adjustment on select models. The PCII utilizes "sensor offset" technology to adjust the fuel curve. Signals from the various sensors on the bike are monitored by the PCII and these signals are recalculated and sent to the ECU in order to achieve the required fuel curve.

And the PCIII operates like this, as kerplode said:

The Power Commander III was introduced in 2000 and is externally similar to the PCII. The PCIII utilizes "direct injector control" technology to control the fuel curve for models that do not possess the appropriate sensors to allow sufficient fuel adjustment using the PCII technology. The PCIII takes the injector pulse from the ECU and changes the pulse width signal to the injectors.This unit allows "Fuel Only" adjustment.

For my money, I'll take the PCII, which allows me to tinker with timing and two other sensor inputs.

More at for the other versions, such as USB at: http://www.powercommander.com/featversions.shtml

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MFP, when I first put in the O2 sensor eliminators which I purchased for 30 bucks on my Vtech I had the same problem as you described as did a few others on the board. The lurching was terrible. However, I discovered that by turning the ignition on, letting it go through it's whine, then turn it off and then back on and then start the engine, the surging and flat spot are completely eliminated. Why does this happen? No f ing clue. Some think that the computer resets itself after you shut down the bike each time. By "rebooting" the computer it seems to read the open loop. I think Das Bone has documented this too. So leave them in and just on/off/on your bike each time. Beats spending 300 bucks on a PC111.

:blink: Ok, I'll give it a try then. :thumbsup:

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Yea the PC2 would alter the sensor inputs before they went into the ECM, but the PC3 is after the ECM actually altering the input to the injectors directly.

That is the main difference between the older PC's and the new ones. Still need to eliminate the O2 sensors when using the PC3 though, the PC2 is for the first generation of fuel injection like my 98vfr that did not have O2 sensors, later in 2000 when the yellow bike came out they went to using O2 sensors and the PC3 came out for that bike

USING only O2 elmininators will prevent the bike from going into stocimetric mode and is said to smooth out the throttle responce like I said earlier. but I have no experience with that so take it at face value.

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