1msfyter

How much does this affect you et's. Reason Im asking the local track here is 2800', always hot (85-90 at 5:30pm) and almost no humidity. Next week the weather is supposed to be cooler with 20% humidity and should be about 80* when racing starts and cooler around 8:30pm.
My best time there is a 13.8@104 uncorrected using DR's.

WS Sick

I'm at about 1500 feet and I see at least 4 tenths going from 90 to 60 degree weather. The humidity will also play havoc , the higher the humidity the more it hurts the air.

I know someone has the conversion table link here somewhere.

1msfyter

Normally its always 0 humidity in palmdale.The track isnt the greatest either

marshall93z

heat is worse than humidity, but the less humidity the better!

Stephen 87 IROC

But there is more moisture in 90* air at 50% humidity than the is in 60* air at 50% humidity so you can't just go by the humidity. It's those extra water molecules in the air that hurts engine performance.

That's why during the heat of the day you'll have low humidity but as the sun sets and the temperature drops, the humidity increases. There's no difference in how much moisture is in the air but the percentage in relation to the temperature is what changes.

It's better to track due point to see how much that changes than it is to track humidity. If the due point increases then there's more moisture in the air.

Injuneer

What you need to know is "absolute humidity". What you get on the weather report is "relative humidity"..... the amount of water in the air compared to the amount of water the air can hold before it is saturated (water starts to condense and drop out - precipitation). You can calculate absolute humidity from the ambient air temp and relative humidity. You can also get it from the ambient temperature and dew point.

The easiest way to see how much the change in altitude, ambient air temperature or humidity will affect your timeslip is to take the timeslip, and go to one of the timeslip "correction" calculator websites, and start plugging in various temperature, humidity, etc. That will give you an idea of the impact of going to the temperature and humidity extremes you might see at your local track.

Raptor1

I'm waiting for "Bob C" to chime in on this one...

Anyway, as any good drag racer does, I've kept logs of all my runs. However, in addition to all the normal weather parameters (temp., PH, bar.) that most everyone monitors, one thing I keep track of is dew point. I have noticed that a change in DP affects performance more than a change in temperature and/or humidity.

There is also "vapor pressure". But we won't get into that, right "Bob"?

ScreamnChicken

I know last time I ran my car at BIR, I ran a 13.03@108. It was around 85 with a dewpoint of 72, elevation 1600'.(Not sure about those exact numbers anymore as it was a couple months ago.) Anyways, the DA was 3200, and when I used the NHRA correction factors my time went down to 12.61@112, which is what I was actually hoping to run with mods, hp/tq numbers in sig.

Raptor1

Please don't take this as a flame or anything, but I think you should be running better than that. We have similar mods except you didn't list ported heads, which I have. But you have a bigger cam which should offset the heads somewhat. We have the same converter. Different gears, but there's always a debate whether 3.73's or 4.10's are better anyway. When I run in similar air to what you described I usually run ~12.6. Oh yeah, IF your dyno numbers are SAE corrected you also have more HP and TQ at the wheels.

Is your PCM dyno tuned to your combo?