Air Density Online

Info and Education

Using Air/Fuel Ratio

By Jennifer on November 21st, 2017 in Info and Education, Main News

On this site, we talk a lot about finding your ideal air/fuel ratio. It is the concept that our mechanical fuel injection jetting calculators are built on, and it is the concept used in electronic fuel injection in order to maintain a good fuel system setup. Understanding air/fuel ratio can be very helpful when setting up your fuel system. It can mean the difference between a successful run and a blown engine.

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Tuning with methanol vs nitro

By Jennifer on May 22nd, 2017 in Info and Education, Main News

The basics of engine tuning involve finding the right ratio of fuel mixed with air to get the right amount of power out of your engine. When you have a familiar engine setup and always race with methanol, that task can become tried and true. When you add percentages of nitro, things suddenly get more complex. Following are some of the differences between nitro and methanol.

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Atmospheric water vapor and horsepower

By Jennifer on April 25th, 2017 in Info and Education, Main News

File this one under reasons to keep track of the local weather on race day.

Have you ever noticed that your car runs really well first thing in the morning when it's cool and dry? Have you noticed that performance starts to suffer as the day gets more humid? That's because water vapor in the atmosphere decreases horsepower.

Humidity is a result of water vapor suspended in the air. Any amount of humidity displaces some of the air molecules. Since only about 20% of air is oxygen and oxygen is what is needed for combustion in an engine, anything that displaces air can really decrease the amount of oxygen. Water vapor is not flammable and does not contribute to combustion heat. Any reduction in the amount of air from the suspension of water vapor in the air results in a corresponding reduction in the amount of oxygen and combustion.

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Reading the weather report: When is it about to rain?

By Jennifer on March 20th, 2017 in Info and Education, Main News

How many times have you heard the weatherman say it's going to be a bright sunny day only to get caught in a sudden rainstorm? Conversely, how often have you looked outside thinking there is about to be a downpour only to have the clouds part and the sun appear? There is a lot of science behind weather forecasting but it is complicated and not easy to get right all the time. If you learn how to interpret a few of the variables, it will help you to be better prepared for sudden weather changes.

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Why is it hottest a couple hours after noon? Why is it coldest a couple hours after dawn?

By Jennifer on February 19th, 2017 in Info and Education, Main News

At any given point on earth, solar noon is when the sun is most directly overhead. So why is it not also the hottest part of the day? In the absence of weather fronts to influence the temperature, the hottest part of the day is typically a couple of hours after noon.

In a similar fashion, the coldest part of the day should be right before dawn but it's not. In the absence of weather fronts, the coldest part of the day is an hour or two after sunrise. Why is that?

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Weather changes before and after dark

By Jennifer on January 20th, 2017 in Info and Education, Main News

During a typical day at the races, the weather can fluctuate quite a bit. As the temperature heats up in the afternoon, you can feel the heat radiate from the pavement and the moisture in the air. Then as the day wears on, the night becomes cool and calm. Not only does this influence whether you wear shorts or pants but it also influences how your engine performs.

This is especially an issue in places with extreme temperature fluctuations like in coastal areas. It's not as much of an issue in places where the temperature stays near a median. While you will want to tune your engine according to the local weather, in these places you do not necessarily need to check multiple times per day.

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Air Density And Water Vapor

By Jennifer on December 19th, 2016 in Info and Education, Main News

Air density describes the density of a cubic foot of air in earth's atmosphere. This value changes depending on the altitude because this higher up you are, the less atmosphere you have above you to press down. It also changes based on temperature, which is the measurement of the movement of molecules. This dives into thermal dynamics gets quite complicated but basically, the more molecules move around, the less molecules are present and the higher the temperature gets. Therefore, measuring air density is a matter of measuring the pressure and temperature.

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Understanding the difference between corrected and uncorrected barometer

By Jennifer on November 19th, 2016 in Info and Education, Main News

The value we see as barometric pressure is a way of measuring the pressure of the column of air above us. The higher we go in elevation, the less that pressure becomes. Therefore lower barometer values are correlated with higher altitudes. You might have heard the term density altitude. That is taking the current weather conditions and applying them to conditions at a certain altitude. Similarly, barometer values can be used to estimate altitude.

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