Log Book weather

February 19, 2019, 10:02 AM

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Log Book weather

Running Alky what do most keep track of in your log book. What do you watch the most from day to day as far as the weather that makes your car change ET
Thx in advance

Brian Mollison
2013 American Dragster
2020 Sumerduck Dragway VA Top ET Champion
2017 Sumerduck Top ET & SSS Track Champion
2017 MAC Top ET Track Champion
2009 Sumerduck Dragway Va Top ET & IHRA SSS Track Champion
2008 IHRA Division 1 Top ET Bracket Final Runner-up
2007 Colonial Beach Dragway Top ET Track Champion

February 19, 2019, 11:42 AM

Lenny5160

On a run-to-run basis, the #1 thing I look at is Dew Point. Grains will give you exactly the same thing but I use DP.

An increase of 5-6 grains or 2* of DP will slow me .01 in the quarter.

I'm not nearly as strong trying to predict off the trailer when a lot of things have moved dramatically. Especially a big change in the barometer.

February 19, 2019, 12:19 PM

Big Steve

Water grains for sure at the top of my list

February 19, 2019, 02:57 PM

TOP38

As noted above but you do need to pay attention to temp also and how it effect humidity. If you see temp go down and humidity drop too, your gonna pick up big time vs temp dropping and humidity rising where they may cancel each other out. On a given day the barometer doesn't usually move enough to matter

February 19, 2019, 03:39 PM

Lenny5160

quote:
Originally posted by TOP38:
As noted above but you do need to pay attention to temp also and how it effect humidity. If you see temp go down and humidity drop too, your gonna pick up big time vs temp dropping and humidity rising where they may cancel each other out. On a given day the barometer doesn't usually move enough to matter

Top, you are the first person to mention Humidity. If you are talking about Relative Humidity, measured in a %, you shouldn't be using that.

It can have some value as there can be performance cliffs associated with saturation, but Water Grains and DP give a true measure of moisture in the air and do not move based solely on a change in temperature or pressure.

February 19, 2019, 06:47 PM

Steve from Pa

Water grains for sure is our #1 thing, but were more toward 9 grains / .01, then wind, then DA for us.
I can't stand to look at humidity anymore, just way easier for me to understand water grains.

February 19, 2019, 08:13 PM

ski_dwn_it

Water grains.. But if your serious. Invest in ifamily software.

Hate to even offer that advise as people I race against who are probably reading. Off there trailer it's spot on. Don't even think about it anymore.

Here are some pointers though..I never touch anything and do everything there same. Down to fuel to exact levels every run. In can skip to weeks and hot the track and it's dead on. If I change anything it's time trials and base all runs off that.

My car varies .oox to .01x thru the day. And honestly when I lose its me.

The key is having a very car that works and not touching a thing... Then you have a fighting chance.

Configuration: 3350#, 582 C.I.,

60 - 1.24
1/8 - 5.53@ 126MPH
1/4 - 8.73@ 159MPH

3700#+210lb driver, FULL interior, through mufflers, 10.5 tire.
60'-1.333 (IN 4000ft DA! Joisy Math excluded; 1.25sec using JOISY MATH.)
1/4 - 9.60@144MPH

February 19, 2019, 08:18 PM

Bucky

Water grains is linear with dew point. I use dew point for water. When the dew point approaches the actual temperature, I expect at least one bad run.

February 20, 2019, 08:38 AM

TOP38

quote:
Originally posted by Lenny5160:
quote:
Originally posted by TOP38:
As noted above but you do need to pay attention to temp also and how it effect humidity. If you see temp go down and humidity drop too, your gonna pick up big time vs temp dropping and humidity rising where they may cancel each other out. On a given day the barometer doesn't usually move enough to matter

I was referring to humidity, not relative humidity. RH is OK also if you understand what it means! Bottom line is how much water is in the air is what is important.

Top, you are the first person to mention Humidity. If you are talking about Relative Humidity, measured in a %, you shouldn't be using that.

It can have some value as there can be performance cliffs associated with saturation, but Water Grains and DP give a true measure of moisture in the air and do not move based solely on a change in temperature or pressure.

February 20, 2019, 09:37 AM

Lenny5160

quote:
Originally posted by TOP38:
I was referring to humidity, not relative humidity. RH is OK also if you understand what it means! Bottom line is how much water is in the air is what is important.

I know you've been around and know what you're doing, Al.

I mostly wanted to clarify for anyone reading the thread looking for advice, that what most people refer to as 'Humidity' is not the best thing to use as a reference for racing air quality.

February 20, 2019, 10:51 AM

B Williams

I am on gas what is one of the indicator to use for prediction?

February 20, 2019, 02:29 PM

Bucky

quote:
Originally posted by Lenny5160:
quote:
Originally posted by TOP38:
I was referring to humidity, not relative humidity. RH is OK also if you understand what it means! Bottom line is how much water is in the air is what is important.

I know you've been around and know what you're doing, Al.

I mostly wanted to clarify for anyone reading the thread looking for advice, that what most people refer to as 'Humidity' is not the best thing to use as a reference for racing air quality.

I agree that RH is a pretty bad unit to use. I used it for years, and had to kind of take into consideration the affect that changing temperature was having on the RH...with no real change in the amount of water in the air.

February 20, 2019, 06:07 PM

Steve from Pa

quote:
Water grains is linear with dew point. I use dew point for water. When the dew point approaches the actual temperature, I expect at least one bad run.

X2 forgot to mention that with in 3 or 4 degrees of the D.P. were going to loose .02