06/11/2026
A little dyno correction lesson for those following yesterday’s discussion.
Some people pointed to the humidity difference between the baseline and final pull and suggested the results were misleading.
So let’s look at the actual numbers.
The graph was printed using STD correction:
Baseline: 164.09 hp / 153.36 tq
Final: 170.23 hp / 158.77 tq
Gain: +6.14 hp / +5.41 tq
The dyno weather stack reported:
10:28 AM
Temp: 81.6°F
Baro: 29.19
Humidity: 69%
6:02 PM
Temp: 96.2°F
Baro: 29.18
Humidity: 22%
Now compare that to KPIE.
KPIE is St. Pete-Clearwater International Airport, the closest official airport weather station to my shop.
KPIE around the baseline pull:
10:53 AM
Temp: 81°F
Dew point: 73°F
Humidity: 77%
Altimeter: 30.14
KPIE around the final pull:
5:53 PM
Temp: 88°F
Dew point: 62.1°F
Humidity: 42%
Altimeter: 30.06
6:53 PM
Temp: 86°F
Dew point: 70°F
Humidity: 59%
Altimeter: 30.06
So what stands out?
The morning dyno stack reading was believable.
The evening dyno stack reading was the problem.
The dyno stack claimed 96.2°F and 22% humidity at 6:02 PM in Pinellas County, Florida, in June.
The closest official airport station showed 88°F / 42% humidity at 5:53 PM and 86°F / 59% humidity at 6:53 PM.
That is nowhere near 22%.
The barometer also matters. The dyno stack showed almost no baro change from baseline to final, 29.19 to 29.18. KPIE also showed very little pressure movement during the same window, 30.14 earlier and 30.06 later.
So the real issue was not some massive atmospheric swing creating fake horsepower.
The issue was a questionable humidity reading from the dyno weather stack.
Now here is where it gets funny.
Using SAE correction and trusting the dyno stack’s questionable 22% humidity reading:
Baseline: 161.39 hp / 150.83 tq
Final: 166.57 hp / 155.36 tq
Gain: +5.19 hp / +4.52 tq
Using SAE correction with nearby KPIE historical weather data instead:
Baseline: 161.96 hp / 151.37 tq
Final: 169.26 hp / 157.86 tq
Gain: +7.30 hp / +6.49 tq
Read that again.
The questionable 22% humidity reading did not inflate the final number.
It actually reduced it.
In other words, if SAE correction had relied on that questionable humidity input, it would have made the final result look worse, not better.
That is one of the reasons I prefer STD correction. STD relies primarily on temperature and barometric pressure and is far less vulnerable to questionable humidity data from a weather stack.
The takeaway is simple:
Same motorcycle.
Same dyno.
Same operator.
Same correction method.
Baseline recorded.
Final recorded.
The gain did not come from humidity.
The gain came from the work performed.
And for those who think dynos are random number generators, I also posted a graph today showing the same motorcycle tested more than a year apart. Different day, different mileage, different firmware version, and the curves were nearly identical.
Anybody can post a hero pull.
Repeatability is what matters.
