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Old 05-07-2013, 11:03 AM   #3334
RAL88's Avatar
Joined: Feb 2011
Location: Albuquerque, NM
Oddometer: 77
Originally Posted by Poolside View Post
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.

Thanks for that great explanation. So what is the ECU doing when I completely remove the ccp and this stops the tailpipe popping?

'96' K1100LT-SE
'97' R850GS-R
"If it ain't broke take it apart and make it work better"
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