[mike leech]

Originally Posted by 455firebird1969

My initial point was rain is not water vapor. (Mike said he did it in the rain). Water vapor affects density altitude (which affects performance), rain does not. Rain is the result of atmospheric conditions. If he had stated he did it in low pressure air or poor conditions, I would not have provided input. My point is cold air cannot hold as much water vapor when compared to warm or hot air. Simply because it is raining, does not necessarily mean you have a high water vapor content. High humidity does not indicate high water vapor content. If the air is cold, things change. Saying a rainy day has high humidity is vague unless you include the tempurature.

The psychometric chart indicates 50 f. air / at 90% humidity holds 49 grains per pound water vapor.
While, 90 f. air / at 70% humidity holds 150 grains per pound of water vapor.

37 f. air with 100% humidity can only hold 33 grains per pound.

Mikes performance is stellar, and I congratulated him, it's not about his achievements.

All I'm trying to do is help those reading this to understand how meteorology works.

Really? Thats what you're trying to do? I'd rethink that.....


Several credible sources have pointed out the truth about dynoing on a bad air day and its effects. One that owns and runs a dyno. Maybe the learning opportunity is closer to home than you think. No offense. But who the hell thinks the the water grains are not high when its a rainy day. Come on.

A lot dyno cells use shop air for the input. So that adds to the issue as the temp comes from the shop and the water grains and pressure ar fed by the atmosphere.