# Thread: How much RPM you loose when the humitity is 90%

1. ## How much RPM you loose when the humitity is 90%

Hi Guys,
I have made today a test with my ski and i had the following conditions barometric pressure 1022,humitity 90% and temperature 64F and i would like to know how much does the humitity affects the loose of the RPM how many RPM.
Thanks!

2. I also depends on your mods if any.

3. Originally Posted by h2jim
I also depends on your mods if any.
stage 3

4. The only time where I have run into issues is when there is a huge change in humidity. Like tuning if 90% humidity in Florida and then going to Havasu at near 0 humidity.

Andy

5. Relative humidity changes ONLY make little difference. It's the combination of other factors like air temp, humidity, dew point, elevation, that greatly effect horsepower and Relative Air Density (RAD).

Play with this calculator to see the effect on horsepower, density altitude and Relative Humidity.

http://wahiduddin.net/calc/calc_hp.htm

High relative humidity with cool air temps and high pressure, like 1022 hPa yields good performance. Change the humidity from 94 to say 34 and you will not see much of a change. BUT, raise the air temp or lower the pressure and you lose performance.

You know you will have a great performance day with cool temps, low relative humidity, lower dew point, and high pressure ( above 30.00").

Simply going from a day with 30.10" to a day with 29.78" pressure will easily kill 200 rpm!

6. ## +1 by:

7. My ski can loose 3 mph with ease with high temp and humidity swings over cool dry conditions.

8. ## +1 by:

9. Alright let's get this humidity thing settled. Humidity is when the temperature equals the dew point. It can be 45 degrees out and if the dew point is 45 degrees you have 100% humidity. The thing you want to look at is dew point. When the dew point is over 64 degrees it starts feeling humid. A dew point about 68 degrees will produce miserable 'humidity'.