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Tech said to remove O2 sensors with fuel pak

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  #11  
Old 03-25-2011, 08:12 PM
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PC III here, I cut the wires to mine cuz I didn't have any plugs to replace them...bike runs great.
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Old 03-25-2011, 08:13 PM
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I will be honest i called them the other day as wel to talk about the fuel pak. The guy i spoke to didnt seem to sure of things. I then called my dealership to ask what harley has to off when puttin on a set of big shots. He said dont use the fuel pak, or power commander 5. He said he has seem many issues with the fuel pak. He said to go with TTS from mastertune. He said this is the best.
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Old 03-25-2011, 11:53 PM
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Hehe that's what the dealer told me. To go with the TTS..

Commenting on the OP, doesn't o2 eliminators take care of the sensors?
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Old 03-26-2011, 04:39 AM
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The reason some tuners suggest removing the O2 sensors for bolt-on fuelers is because otherwise the bike tends to lose its tune in the closed-loop operation area (low throttle & cruising).

What happens is that the mechanic gets things nice on the dyno and then once you leave the shop and run the bike for a few miles the closed-loop system plus sensors reads the extra fuel the fueler is adding as a too-rich condition and drops the fuel back to more like stock. In fact, with HD ECUs, this also tends to have a knock-on effect on open loop AFRs too.

You don't get these problems if using a SEPST or TTS to do a proper job because you re-program the ECU and tell it what new AFRs to set for both closed and open-loop.

If you do fit a fueler and disable the sensors you should use eliminator plugs. This fools the ECU into thinking the sensors are still there and reading an ideal AFR and the ECU won't try to adjust the tune. Don't use the eliminators and the ECU thinks the sensors are faulty and the results are unpredictable. It might just throw a code and switch to open loop all the time or it might switch to limp-home mode with a very safe AFR and timing across the entire throttle range - not good.

The trouble with the relatively cheap solution of a fueler and no O2 sensors is that you have just disabled the most useful and adaptive part of the EFI. The engine will no longer be able to adjust as well for variations in air temperature, altitude and fuel. In other words, the tune might be spot-on for the exact conditions in the dyno shop but the tune will be immediately wrong as soon as you drive away and a lot wrong in the winter, up a mountain or if you put in a tank of US-winter-grade fuel.
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Old 03-26-2011, 06:58 AM
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Well I'm not saying this is the case, but if memory serves, the pcv and pcIII both control , cold and hot fuel ratio as well as the percentage of fuel delivered based on the grade you put each gear and speed etc....isn't that what the o2 sensors do with the ecm. Read the amount of 02 within the exhaust and signal the ecm to compensate by thinning or enriching the mix.
If so, then it makes sense to pull the o2 sensors out. In my pcv setup, my o2 sensors are disconnected from the ecm altogether. Only reasons I left them in llace, was just in case some HD tech cried foul if I ever went in for warranty work. I'm not certain how the fuel pak operates, but i cant imagine it being any different than the pcv. Or even the pcIII.
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Old 03-26-2011, 07:19 AM
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Thats a bit of a confused post. You are comparing apples and oranges by comparing the gear input feature of the PCV and an ECU/O2 sensor combo. I think you need to do a bit more reading on how these things work.

The closest you can get in comparison is to use the 5V input feature of the PCV and set up an alternative adjustment table. But you would need a sensor to drive that input...Hey, an O2 sensor would be good! Now you are back to the start and have spent a bunch of money on a system that's still not quite as good as if you had done the job properly in the first place.
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Old 03-26-2011, 07:45 AM
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Ok lemme try it this way.....

The o2 sensor reads the exhaust and signals your ecm to change its fuel delivery if needed. all the while your ecm is following a predisposed table of fuel delivery factors. These based on a variety of factors ....ambient outdoor temperature, altitude, engine temperature, and in some cases your plugs, like a knock sensor In your car.
When you install a tuner , tts, pcv or the pcIII, you input a set of measurements through your tuned into your ecm that your ecm will use bypassing or eliminating the measurements from your o2 sensor.
If you use both a tuned, and your o2 sensors, you're gonna get conflicts within the ecm, and eventually something is gonna give.

I'm no techy, but it only makes sense to remove , disable , dismantle, cut, or whatever you wanna do with your 02 sensor.

It's not written in stone, but it certainly does make sense. Hope I made better sense this time. Tunes , maps, stage 1's, afr's are all very complicated ...I'm just scratching the surface
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Old 03-26-2011, 08:30 AM
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I agree that in theory , it makes sense to remove the O2 sensors . But....in all on V&H's literature regarding the F.P. they nowhere tell you to remove the sensors . If that is the proper route....then you'd think that would be a part of the instructions , and perhaps even offer O2 eliminators , like Dynojet .
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Old 03-26-2011, 08:47 AM
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Ok. I see where you are coming from.

You are in error on one point: "When you install a tuner , tts, pcv or the pcIII, you input a set of measurements through your tuned into your ecm that your ecm will use bypassing or eliminating the measurements from your o2 sensor". There is no input back from a tuner to the ECU from a bolt-on fueler like a PCV.

Here's a bit more info...

When you bolt-on a fueler like a PCV it sits between the output of the ECU and the injectors. It alters the signals out of the ECU to increase or decrease the timing of the injectors to lean or richen the mixture.

They are popular with tuners (especially indies) because they can be fitted to most bikes and they only have to know how to work a PowerCommander, not understand or be able to work with the stock EFI system with its proprietry and, in some cases, locked-down ECUs.

The downside to them is that if the O2 sensors are left enabled the ECU tends to try to override the extra fuel the fueler is adding and the tune drifts. So eliminators are added and the O2 sensors disabled. The downside to this is as I said before, the engine loses a major self-tuning ability and can no longer cope so well with variations in temp, pressure and fuel i.e. external things that effect the AFR.

This limitation is well known by the manufacturers. Dynojet offer a solution to this by selling an additional piece of kit: the AutoTuner. This puts O2 sensors back into the picture, but connected to the PCV rather than the ECU. If you invest in this then you have a good solution. However the price for this is now around $750.

So what a lot of people do is put on a fueler, eliminate the stock O2 sensors, then either just load a canned map or else get the bike tuned. The numbers look OK whilst on the dyno and everyone is happy. Even after the it goes out of tune afterwards its still better than stock so its still OK.

However, for similar money to just a PCV, you can fit a TTS or SEPST and still make use of the stock O2 sensors. The downside to this though is that the tuner needs to understand the ECU and that skill is rarer but if done properly then you get a very good tune that stays put.
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  #20  
Old 03-26-2011, 08:53 AM
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Here is an article from a fairly respectable tuner . I talked to him last summer at the Carlisle(Pa) bike fest . I think we are approaching a thread hi-jack, lol .
http://www.drdyno.com/AIM_2010-09.html
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