fuel question
Intermediate
Joined: Oct 2013
Posts: 26
Likes: 0
From: California
Closed loop fuel injection is capable of making real time adjustments based on exhaust gas composition sensed by the O2 sensors. Standard carburetors (not electrically adjusted) cannot adjust for altitude, temperature, humidity which all effect air density/mixture. It is my THEORY that the ECM can adjust fuel flow to adapt to changes in total flow up to the per-programmed adjustment limit. When that limit is exceeded it trips the engine light, most likely in this case with a "too lean" code. The ECM will increase injector dwell to maintain the factory air fuel ratio until the "that's not right" limit is reached. IF the factory tune is OK for a particular owner, why can't the air cleaner and mufflers be changed without a re-tune UNTIL the check engine light comes on. Now it really is too lean, but until that happens, the factory A/F ratio can be maintained.
Road Warrior
Joined: Dec 2012
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From: CT
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Outstanding HDF Member
Joined: Dec 2008
Posts: 2,007
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From: Ohio
The AFR you are refering to is only maintained while the bike is operating in closed loop mode. At certain RPM's, accelerating, decelerating, at idle, the ECM is not in closed loop mode. Replacing the somewhat restrictive stock A/C with a more free flowing one can then result in lean running periods when not in closed loop mode. The end result might be more heat and some reduction in power during acceleration. But you'll be OK for general riding around.
Ultimate HDF Member
Joined: Jan 2008
Posts: 6,532
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From: SoCal
Closed loop fuel injection is capable of making real time adjustments based on exhaust gas composition sensed by the O2 sensors. Standard carburetors (not electrically adjusted) cannot adjust for altitude, temperature, humidity which all effect air density/mixture. It is my THEORY that the ECM can adjust fuel flow to adapt to changes in total flow up to the per-programmed adjustment limit. When that limit is exceeded it trips the engine light, most likely in this case with a "too lean" code. The ECM will increase injector dwell to maintain the factory air fuel ratio until the "that's not right" limit is reached. IF the factory tune is OK for a particular owner, why can't the air cleaner and mufflers be changed without a re-tune UNTIL the check engine light comes on. Now it really is too lean, but until that happens, the factory A/F ratio can be maintained.
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Dooley
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Aug 17, 2008 12:15 PM