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Exhaust O2 sensor bypsss...

Discussion in 'Technical and Troubleshooting Torque' started by Arran, Jul 12, 2006.

  1. I've bought an aftermarket can for my new fireblade and when I was pulling the old exhaust off noticed that the new exhaust didn't have a provision for the Oxygen sensor.

    I've bought a bypass plug for the sensor but want to know if the sensor isn't, uh, 'sensing' the O2 level of the exhaust fumes, will there be any consequences?

    Any thoughts?
  2. As I understand it, the 02 sensors only work when the bike is running in cruise mode ie high intake vacuum small thottle opening. Referred to as closed loop. So you may not get quite as good fuel economy as the ECU will have no idea how much to lean off the AFR. The ECU will just use a standard fuel/ignition map to suit the load & revs the engine is running at.
  3. Roarin,

    I would have thought the opposite. i.e. the O2 sensor comes in when you are try to get more performance out of your bike and the sensor is modifying your map to get the mixture right.

    I've been out to the FI loop for a while, but I would never bypass an O2 sensor. Though I must admit sime bike FIs are different to typical car ones.
  4. How easy is it to incorporate the O2 sensor in the new exhaust? If the thing's designed to work with the EFI/engine management system, then bypassing it may be counterproductive.
  5. I'd probably take your exhaust and the O2 sensor to an exhaust place and get a bung welded into the pipe for the sensor.

    Regards, Andrew.
  6. your biggest problem is the computer throwing an error (missing sensor) - this is what the replacement plug fixes.

    That said, the system only runs closed loop (tries to maintain stochiometric fuel burn - ie not rich or lean but baby bear's just right - at less than WOT, where it reverts to open loop (ie no feedback and just preset injector timing pulses).

    You might find your fuel consumption goes up, or down or doesn't move at all - but if you stick an EGT probe into it, it'll probably do much worse.

    If you buy a power commander et al for a bike with lambda sensors (O2), you have to remove the sensor or the ECU will override the PC by learning the new offsets.
  7. Hmmm...

    I'm not getting a good feeling about this.

    Can anyone suggest a bona fide expert I can contact?... Not that I don't value your input guys!... but,

    Contradicting advise make baby Jesus cry.
  8. Just be sure that the plug that you should get welded in place THE SAME DISTANCE from the head as the stantard pipe.

    They are designed to run at a given temprature range and if its not in the right spot it will either cook or not get hot enough to run.

    The O2 senser is there to give the ECU feedback on the mixtures that are being used. Leaving this out (of exhaust gas flow) will cause faults in the ECU and you'll run the risk of focking your engine because the mixture will be way outta whack.

    You wouldn't run your bike without the airfilter, oil and so on, would you?[/quote]
  9. I can understand your concern. Some of the posts here seem to have technobabble that us mere mortals can only guess at.

    My view is - you're putting a non-standard muffler onto your bike. That's likely to affect how the engine runs. By taking taking away one of its sensors that helps to control the air-fuel mixture you're risking an out of tune engine.

    In the old days, fitting less restrictive exhausts tended to make carby'ed engines run lean. I can't see why this would be any different. EFI helps to maintain the right balance by sensing the amount of excess air or O2 in the exhaust gases.

    My recommendation, other than seeking professional advice - get your local machine shop to weld in a recepticle for the 02 sensor and fit it back on with the new exhaust.

    Oh, and seeing as it's a new bike, presumably brand new, there are warranty issues. If you stuff the engine because of this, it could cost you big bucks. Why take the chance? Get it done right.

    What does your dealer say about this. Or indeed, the retailer who sold you the can?
  10. all i can say is when we changed exhausts on the GTP race cars we always installed the O2 sensor back in the race exhaust, if we didnt we had all sorts of probs remaping the standard computer. aftermarket puters weren't so much of a problem.
  11. Hi Arran
    Check out 1000rr.net.
  12. As I said at the start -the 02 sensors only work when the throttle is held at a fixed setting ie cruising, & then trim back the AFR for good economy. They do not respond fast enough to provide the ECU information when accelerating etc. The ECU uses throttle & gear position along with MAP (manifold absolute pressure) sensing for this. But as others have stated, removing the sensors may cause the ECU to go into a limp home mode. No idea if your bike will do this. You may be able to wire in some sort of resistor to fool the ECU into thinking the sensors are still there. If you are worried about it then get someone to check your AFR whilst the bike is under load ie on a dyno. Or as someone else suggested, find someone that has already done it.
  13. I agree with Sleepa, go to 1000rr.net. Someone there may have a solution.

    Good idea.

    Minor problem. The O2 sensor produces a voltage between 0.1V for lean and 1.0V for rich (typical outputs).

    Its true, I doubt that it will react quick enough under 'race' conditions, but this depends on what the ECU can manage.

    As for crusing, the output varies between 0.3-0.8V (roughly) to aid in reducing emissions.

    If your bikes got it, well it's there for a reason.
  14. certainly - emissions

    nothing to do with power, response, fuel economy or anything else. Same as cat's.
  15. Tell me again why you didn't check all this out before you bought the aftermarket can??I would have...... :shock:
  16. What's the old saying about hindsight being twenty-twenty vision....?
  17. Because I have one on my R6 and love the look & the note...

    That and I have contacts. ;)

    It's all sorted now. Essentially all the lambda sensor does is tell the EFI to lean out the mixture at cruising speeds. If there do happen to be any residual effects from bypassing the lambda sensor it's easy to do a re-map.

  18. YOU WROTE: Because I have one on my R6 and love the look & the note...

    so you've had this problem b4??

    YOU WROTE: That and I have contacts. ;)

    so your expert isn't "bona fide" maybe

    Thats good mate.....a happy ending

    maybe talk with your "contacts" sooner and you wouldn't have to go through all this pain...I'm sure Roarin was tell you the same thing.....
  19. Some people just keep asking questions until they get the answer they want to hear :roll: Makes you wonder why you bother at times huh? :LOL:
  20. Is that directed at me?