Impact of water grain and % oxygen
 

Just want to understand and input will be really appreciated.
What is the relation between those ?
More grain of water per pound of dry air mean less air molecule in that pound of dry air.
I know that some area own more % oxygen than other (degree of pollution, tree, altitude, near ocean...) But do they serve the same goal in weather calculation or they have their own impact on calculation.

Re: Impact of water grain and % oxygen
 

How does one measure for % of 02 ?
Is there a gauge for that?

Re: Impact of water grain and % oxygen
 

In may be over simplifying but both indicate the same thing: The amount of oxygen available in a defined volume of air.

In the 2000s O2 was seen as a good indicator but sensors required re calibrating regularly. Previously Density Altitude calculation was the ticket particularly when O2 sensor reading was included.
Many were for years looking at vapor pressure, humidity & temp to indicate available O2. In the last 10 years grains of water has become the indicator of favor since I believe does the VP/H/T calculation for you.
Am sure with some time will find one is more reliable than the other these days grains is favored.

Re: Impact of water grain and % oxygen
 

You can use a oxygen meter or a chart like the one below.
But be aware that % of oxygen in the air is going down in our world...
https://milehightraining.com/altitude-to-oxygen-chart/
https://www.oxygenlevels.org/

Re: Impact of water grain and % oxygen
 

Thank Mr.Sigman for your explanation.:)

Re: Impact of water grain and % oxygen
 

I don't think a % of anything is a good measure for predicting performance. You'd need an absolute measurement of the 'amount' of Oxygen in the air. I don't know how that is done.

Much like how most racers have moved away from Relative Humidity % and are now using Grains. Dew Point is essentially the same thing as Grains for ET prediction purposes, but on a different scale.

Re: Impact of water grain and % oxygen
 

Air density index vary with altitude above sea level, temperature and barometric pressure.
I am thinking of (as an example) the same air density index with different % of oxygen in that same pound of air will give me a different result.
But, I may be totally wrong...

Re: Impact of water grain and % oxygen
 

Charles if it was more Oxygen it would help you go faster.

Re: Impact of water grain and % oxygen
 

Charles,
If you want to learn all about weather correction, get Patrick Hale's book, "Motorsports Standard Atmosphere and Weather Correction Methods".

https://dragracingpro.com/books

The book is considered the best on its subject.

Also, for software, I recommend Performance Trends "Weather Wiz".
Extremely accurate, as long as data inputs are good.

http://performancetrends.com/Weather-Wiz.htm

Re: Impact of water grain and % oxygen
 

PerformAIRE Weather systems calculate Density Altitude(Air Density) and is the only system that actually measures oxygen content, by use of an optional Oxygen sensor. The Oxygen percentage is influenced by the surrounding area (Pollution, Vegetation)

When we talk about Density Altitude it is a calculation based on the Temperature, Humidity, and Barometric Pressure alone in the air. Typically, we ASSUME a constant percentage of oxygen (20.90%) within that density. The only way to determine the actual percentage of oxygen and therefore the actual amount of oxygen per volume is by specifically measuring the oxygen level independently from the temp, hum and press.

An internal combustion engine does not burn "air density", it burns Oxygen with Fuel to create power. Knowing the actual amount of oxygen is very important and is the main factor a PerformAIRE weather station is providing to determine the performance.

Secondary, the amount of water in the air density also influences the performance of an engine. Generally, the more water in the air, the worse it is for performance. Not only is it displacing the amount of oxygen but it also can dilute the fuels energy potential.

Water grains is an ABSOLUTE calculation of the amount of water in the air. Unlike RELATIVE humidity (water % based on temperature), think of grains as the weight of the water in the air.

Without getting into too much detail, the PerformAIRE systems use Patented measurements and algorithms to determine not only the air density, the amount of oxygen, the water content, and how that all effects the engines performance.

Re: Impact of water grain and % oxygen
 

It’s is the system to with the optional Oxygen meter.

Re: Impact of water grain and % oxygen
 

Thanks for your precious input SSDiv6,
I own a copy of Mr. Hale book and I have read and re-read that book quite a few time.
May be it's time to do it again because I'm mssing something here.
I will also take a close look at the Weather Wiz.
Keep on,

Re: Impact of water grain and % oxygen
 

"Typically, we ASSUME a constant percentage of oxygen (20.90%) within that density. The only way to determine the actual percentage of oxygen and therefore the actual amount of oxygen per volume is by specifically measuring the oxygen level independently from the temp, hum and press."

Thanks Mr. Bartoli for your precious input.
That was exactly the purpose of my question. I doubted something was missing in my weather calculation and I was also assuming a constant percentage of oxygen.
keep on coaching us...

Re: Impact of water grain and % oxygen
 

When we were monitoring Oxygen at the track we were at the Texas Motorplex on Saturday the wind was blowing from Dallas towards the south on Sunday morning it had changed to coming up from the gulf with same Baro and temp. On the Oxygen meter there was a 1% increase oxygen available and it showed in performance of Fuel Cars and Pro stock.

Re: Impact of water grain and % oxygen
 

I was going to suggest a decent weather station, but Altronics beat me to it.. I have a Crew Chief Pro system in my trailer, and couldn't believe all the options available for predicting the weather, pertaining to throttle stop and ET predictions.. you will not be dis-satisfied making that move, if you haven't already..

I always looked at density altitude, (DA), while trying to dial, but learned that it is the formula that goes into arriving at the DA that is more important.. that being said, I'll tell you that grains of water and vapor pressure are pretty important.. the higher they go, the slower you go..

Re: Impact of water grain and % oxygen
 

I must add this previous post from Don Sofranko to this fact:
Re: "Live From" Indy US Nationals The Big GO 2022
Just a curious question after watching the big race from home on NHRA tv

As a past racer at the big go, its always a challenge with the big delays in hours or days between rounds. I was amazed that a bunch, if not all the guys on Monday slowed more than expected, from the early Monday R4 to R5 (3:30 PM) in super stock, and also similar in R5 to R6 Stock. It seems like with all the modern weather stations, and other data that it would have been detectable, to see a slowdown.

Am I wrong or is there another reason for everyone missing the dial by what looks like .03-.04?

Why do the modern weather stations not always tell the picture?
This was from early Monday to the 3:30 afternoon round

Re: Impact of water grain and % oxygen
 

I’m curious if there were any other apparent changes when this happened. Especially pertaining to Grains/Dew Point.

Re: Impact of water grain and % oxygen
 

No but you could haze coming out of Dallas