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Old 09-29-2013, 03:57 AM   #503
roger 04 rt
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Joined: Nov 2011
Location: Massachusetts
Oddometer: 2,362
I'm not singling out the dyno operators, who I have no reason to mistrust. All I'm commenting on is the AFR test method. The tailpipe AFR probes can't do a good job at the start of an short inertial dyno burst. The exhaust flow is low and they are too near fresh air. The engines would likely stall if the AFRs were that high.

The better test method is an upstream probe such as an innovate (or other) LM-1, LC-1 or LC-2. (I'm not basing any of these AFR comments on GS-911 data.)

Think of It this way: you're running down the road at 2000 rpm in 4th gear. Your stock bike would be running a Closed Loop AFR of 14.7:1. At that point you crank the throttle to WOT. The BMSK goes Open Loop instantly and changes fueling (much faster than a tailpipe probe can respond). It picks its new fueling point based on TPS of 100% and RPM 2000. I would estimate that point is 12.8-13.2:1, and it adds an acceleration enrichment. I have measured this on F800S, R1200GS, R1150, and R1100. They all instantly go to an AFR between 12:1 and 12.8:1 approximately.

This is why I say that those high AFR numbers are in error.

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