The Great Dyno Runs Part Deux

By: Don Eilenberger
March 1999

This is the second dyno run report run on my 1985 K100RT (the FINEST year!)

Thanks to Jeff DeCarlo for the loan of his Luftmeister sport exhaust system, and for the sound level measurements.
Thanks to Sun Cycle of Manasquan NJ for the use of their dyno.
Thanks to Brian Curry for the loan of a spare L-Jetronic brain.
Calibration Runs calibration and mixture RPM.gif (11998 bytes)
Chart 1: There are three horsepower runs illustrated in the chart above. Some explanation:
  1. The run plotted in red (#21) was a base run. No changes or modifications to the engine/bike.
  2. The run plotted in green (#22)was done with the starter button held in. Holding the starter button in on an L-Jetronic bike results in enriching the mixture by approximately 10% as it activates the start-enrichment circuit. The L-Jetronic brain prevents the starter motor from operating since it knows the engine is already running.
  3. The run plotted in blue (#23) was done with a different L-Jetronic brain in place (Thanks to Brian Curry). The additional power may also have been a result of a full warmup of the engine at this point (the cooling fan was now cycling). This brain remained in place for the remainder of the runs.
Exhaust comparison: stock vs lufty hp RPM.jpg (39940 bytes)
Chart 2: Stock System (run 23) vs Luftmeister (run 26) - Horsepower plot.
This chart should be self-explanatory. Over a wide range of RPM the Luftmeister exhaust resulted in less HP. It did produce a small increase in horsepower from 4,200 to 5,500 RPM and above 7,500 RPM, but the loss of HP at other RPM exceeds the gains for a net loss of power.
stock vs lufty torque rpm.jpg (39418 bytes)
Chart 3: Stock System (run 23) vs Luftmeister (run 26) - Torque plot.
Once again - self-explanatory. Little gain by the Lufty over a very narrow RPM range.