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Whats the story with O2 sensors?

Discussion in 'Cruisers' at netrider.net.au started by snowy, May 10, 2008.

  1. Hey Gang

    Just wondered about others results with bypassing/disconnecting the O2 sensor that is fitted to the standard exhausts.

    I just got a set of Cobras from the states and as known, there is no provision for the O2 sensor. Also got a Cobra FI2000R to deal with changing exhaust and eventual air intake mod.

    From what I can tell, the O2 sensor measures the amount of oxygen in the exhaust and then sends a certain voltage signal back to the ECM which then alters the amount of fuel accordingly. So if it senses high amounts of oxgygen, then as this is a lean condition, it would dump more fuel in, So we would expect this to occur if we just left the sensor tied up somewhere. Is this a correct understanding?

    I rang Cobra and they just said that they dont make a FI2000 that accomodates the O2 sensor yet on the C50/M50. So am assuming if it was left in circuit that such signals would conflict with the FI200R and screw up on the settings. I guess what I'm asking is whether the Dynojet instructions for disconnection work?

    Sorry for th longish post gang, all opinions appreciated

    cheers Snowy
  2. Powercommander sell an O2 sensor eliminator on their website.

    from this I guess that you could buy one from a powercommander testing centre?

    The ECU will run in limp home mode if there is no signal from the sensor, so it must be dealt with, and not just disconnedted.

    I think I remember reading on the M50 hideaway, that there is a pin to disconnect in the ecu connector that does the same thing.
  3. Hi Snowy

    I followed the Dynojet instructions when I fitted the Cobra Streetrods to my M50 and have had no problems

  4. Hey Guys, cheers for the advice, so disconnecting the sensor and removing the black/brown wire from the ECM does the trick?
  5. If you don't remove the wire as well the FI light will stay on. Follow the instructions & all will be good.
  6. Thanks guys, I'm kinda wondering now what value these FI processors are with these closed loop circuits. If the sensor was refitted to the exhaust and kept in circuit, then one would asume that the OEM ECM would make the changes necessary based on the signals from the O2 sensor.

    I realise that our US cousins would prolly need to fit a FI controller as they don't have an O2 sensor, but maybe we dont need to if we have a closed loop circuit that is dynamic rather than static.
  7. An O2 sensor is primarily used for trimming fuel mixtures, it will cause the ECU too lean a bike out whilst cruising down the road resulting in better fuel economy, under wide open throttle the O2 sensor is normally discarded and the ECU will run directly off its predefined RPM vs Fuel Map, which is usually a rich mixture anyways.

    To an extent the computer will adjust the mixtures to compensate for changes, so as long as you still run your O2 sensor, if its running to lean the computer will adjust the mixtures for it to a degree. The O2 has a bit of control over the mixtures, but dramatic changes I dont think it could alter the mixtures enough to compensate.
  8. my cobra pipes and processor arrived yesterday i had them installed at local suzuki dealer as i had no clue about the processor he said when i asked about the sensor he just tapped up the sensor and left connected as it would then not sense anything would this be correct
  9. Get a bung welded into teh pipe somewhere inconspicuous. Will cost about $25-30.
    You bought a bike with fuel injection, may as well take advantage of it!

    Regards, Andrew.
  10. Just taping it up isnt good enough from a dealer.

    I would hope their mechanics would have more of an idea about how the system works then that.
  11. Friend just installed Vance & Hinds Short Shot on his HONDA VT750C2 SHADOW. His Vance & Hinds instructions simply stated to leave them connected and secure them out of the way. :eek:
  12. I dont think taping it and tucking it away would do a closed loop system any good. From my understanding the ECM monitors CO2 and adjust the mixture to compensate, so if left sensing only fresh air then the ECM thinks that mixture is too lean and would wind up fuel intake to compensate. Logic dictates then that the bike would be running far too rich.

    Anyway this was my thinking and decided to get a bung fitted for 20 bucks, bike runs bewdiful, no backfirimg, decelleration poppin, fouled plugs or increase in fuel consumption.

    I would have thought a Dealer would have known about these issues, but there ya go. Anyway i guess if everyone is reporting no problems, then maybe I have overstated its importance
  13. Snowy im with you on this one, I work in the automotive industry and have seen the difference a new O2 sensor can make when you have a faulty one in fuel consumption alone. I would have thought the engineers put it on the bike for a reason, if they didnt need it im sure they would have left it out - same goes with cars - cut things down to keep costs down.

    An O2 sensor doesn't have full control of mixtures but they can "trim" preset mixtures for cruising/ idle conditions. Thats where if its lean when you back off you have less chance of popping and bad running.

    And just for the record snowy, and O2 sensor measures Oxygen, not CO2 :) It looks at the amount of unburnt oxygen thats coming through the system and tries to adjust mixtures accordingly
  14. Do Australian C50s differ from American counterparts? I was lead to believe that they had no 02 sensors which was why they required to have an aftermarked FI controller if we changed the air filter...
  15. From what I understand you do not need an aftermarket FI, the factory unit range will allow for increased air intake. Google the C50 forums for more info.