How badly does the humidity affect our trucks at the track?

I know that with high humidity, the amount of O2 in the air is less and the affect is the same as reducing the air density. However, I've also heard that blown engines 'like' the humidity as it serves to cool the intake charge more - like nature own water injection - and helps reduce detonation.

In real world terms, what suffers more? HP,torque, ET, MPH...

I ran 4 runs at SAR saturday night at Midnight Madness. It started off real good with the hot off the highway pass at 9:43 pm(13.37@104.4, 2.1011 60') near equalling my previous best. Humidity was about 70% and the temps were mid 70's.

I let it cool, changed lanes and got my best ever of 13.16@104.77, 1.988 60' at 11:38 pm. Similar temps, better tire heat, MORE humidity. HERE COME THE 12's!

Last 2 runs were 13.22 @104.48 at 12:55am and 13.31@103.93 at 1:52am. The temps were consistant, but the humidity was so high that I had water on the roof, hood and bed cover. I thought a lifted a head on the 3rd run when a big drop of water hit the windshield at 3/4 track.

Any ideas - & sorry about rambling I'm bored @ work,
Herb

 

Herb,

Humidity does adversely affect Density Altitude. It is not good for racing. Not only is air quality affected, but so it traction due to moisture on the surface. Track temps are usually much higher than air temps, and it starts to show dew early.

When calculating DA, temp/barometer/humidity(dew point) are all calculated inwith actual elevation. It will adversely affect your times.

joe

 

herb i'm with you, i live in a very dry climate. when the humidity picks up so does my E.T.

 

Good point on the track surface Joe.

My 60's dropped off after the second run. Too damn many variable

I tried to roll out of the lights, then floor i after I got traction and I think that worked on my best 60' but hell I could hear a thing - open headered Big Block Nova trailer Queen in the next lane!

One of these days, I'm gonna see good track weather. Most likely it won't be in San Antonio - Damn hot humid tropical jungle weather in mid October

Lightninquick - I've never actuall run mine in 'dry' air. When I talk about the humidity goin up, it goes from 70% to 100% - freakin San Antonio...

Herb

 

With a D\A of 500 or under I run a several tenths faster.

Here is the one I use.
http://wahiduddin.net/calc/calc_da.htm

 

I plugged the #s into the calculator in your link and I got the following:

Run 1 - D/A - 2116, ET - 13.37@104.43
Run 2 - D/A - 1998, ET - 13.16@104.77
Run 3 - D/A - 2198, ET - 13.22@104.48
Run 4 - D/A - 2295, ET - 13.31@103.93

Sounds pretty swampy....

The track is at 600' and I got the weather data from weather underground's historical data for the area.

Herb

p.s. - I am assuming this means that I am running in air equivalent to an altitude of X instead of the fairly dense air at the 600' elevation I 'should' see.

 

That's exactly what I do.

I run an 1\8 mile track and I am also around 600'. With DA's like yours above I run 8.3's to 8.5's which would be right at what you are running in the 1\4.

I noticed a huge difference in my 60' also with lower DA's.
1.9-2.0 vs. 1.8's