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Old 05-06-2013, 07:18 PM   #3329
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Joined: Apr 2003
Location: Long Beach, CA
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Originally Posted by RAL88 View Post

Ok. So I have fitted a cat eliminating exhaust on my R850r-gs. I have tried all the configurations that I could find of the ccp and in conjuction with the IIce air. All but one results in a lot of afterfire to varying degrees. It seems that the one that works the best is the removal of the ccp completely which I found is suppose to be done for no cat on the 850r.

Now, from my understanding in this mode the motronic does not use the O2 sensor in the exhaust and uses 1.8%CO2 as the reading for the motronic to use.

My question is will the IIce Air still be able to adjust the fuel ratio in this configuration since it is measuring the incoming air temp or is this disabled also when the ccp is removed.?
Yes. The ECU always uses the air temperature input and barometric pressure to calculate air density. With that information it determines the length of the fuel injector pulse necessary to create the desired fuel/air density ratio.

Regarding the afterfire (aka backfire) popping from the tailpipe, that issue is primarily a function of the inconsistent Overrun Fuel Cutoff routine in the ECU.

Moving the throttle around within the range of fully closed to slightly decelerating is what creates the unburned combustible mixture in the exhaust tubing, and causes the backfires. Tailpipe popping can be greatly reduced or eliminated with careful operation of the throttle.

To describe the 'workaround' throttle operation as simply as possible, the throttle should be either holding the bike at a constant speed, or opened more to cause acceleration. If you want to decelerate at more than a slight rate, close the throttle fully. When you want to accelerate, or hold the new lower speed, open the throttle quickly and directly to where you want it.

The above takes practice of course. And I don't like the idea of having to adapt to the ECU. But without other electronic measures there's no way around it.

The reduced air temperature input has some slight effect on backfiring, I don't know that I'd call it significant, but there is an improvement. As you have seen however, some bikes experience more improvement than others. I ascribe the difference more to the rider, which I suppose is a good example of 'Your mileage may vary.' (YMMV)

Regardless the name, there are better ways around the problem of tailpipe popping, afterfire, or backfire.


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