Impact of water grain and % oxygen

[Charles Stewart]

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.

[L.Fite]

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

[Signman]

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.

[Charles Stewart]

Originally Posted by L.Fite

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

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/

[Charles Stewart]

Thank Mr.Sigman for your explanation.

[Lenny5160]

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.

[Charles Stewart]

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...

[Ralph A Powell]

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

[SSDiv6]

Originally Posted by Charles Stewart

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.

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

[Altronics]

Originally Posted by Charles Stewart

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.

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.