"Busted" Tune

[whittlebeast]

The only time I could run the Sporty in closed loop was trailing throttle (coasting down or speed decreasing) or idle.  Any time the motor was holding speed constant, the motor throbbed in a totally unacceptable way.  Take the ECU out of closed loop and everything felt great.

This appears to only be an issue with the Sporty version of the Harley code.  The big twins behave way different.

Note that the Sportsters have a nasty trait and the motor gets richer as the ride goes on.  At 15 min into the ride, they are about 3/4 AFR leaner then at an hour into the ride.

[glens]

Better than the other way 'round, no?

I'm not (necessarily) trying to argue with you, Andy.  To me that trace you showed is a textbook example of how closed-loop works.  It may be exaggerated as you say and cause a sub-optimal experience with a Sportster, I have no clue about that (never ridden a recent sporty).  But it perfectly illustrates what goes on.

[whittlebeast]

Most closed loop Cat systems swing the AFR at real close to 4.5% swing in fueling.  The Sporty in those days, did not have a Cat.  I was told it was don on purpose by the Harley engineers to make the bike throb as you ride down the road as they made the VRod run too smooth.

By "averaging" 14.7 AFR, the EPA was happy.  That worked out to close to a full AFR swing every 2 sec for each cylinder at 40 MPH.

Andy

[whittlebeast]

Glen, This is far more typical of a a closed loop feedback loop.  This happens to be a GM left and right bank.  Notice the scales are the same on both plots.

http://www.nbs-stl.com/HarleyTuning/GM%20ClosedLoop.png

Vs the Sporty

http://www.nbs-stl.com/HarleyTuning/SportyClosedLoop.png

A way different look.

Andy