Why nitrogen fill?
10-29-2007, 11:12 AM
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Why nitrogen fill?
As we all know it is quite common to use a nitrogen fill over a compress air fill in racing applications. My questions will be posed from my limited knowledge of gases.
I will pose the first set of scenario, and then I ask that you pose other benefits of using a Nitrogen fill and I will ask you some questions that have been bothering me about why it is "beneficial"
1. There is less of a temperature change in the tires when it is filled with Nitrogen over Air.
Considering the specific heats (kJ/kg * K) of both gases, we find that there is very little difference and that there is less than a 3.5% difference. This leads me to believe that the difference in temperature between the two gases when compared to hot and cold tires is very minimal. I have considered the fact that there is moisture in the air and thus this can also play into it, but how big of a difference does it really make?
2. Less rotational Mass
Nitrogen has a MW of 28.013 and air has a MW of 28.97. The difference is very little and I understand that they are looking for every edge, but really?
3. More consistent tire pressures from track day to track day.
Isn't Nitrogen a smaller molecule than air, so wouldn't it diffuse more easily out of the "holes"?
Please feel free to comment and criticize, I'm pretty thick skinned, so if you feel the need to "bash" feel free to.
I will pose the first set of scenario, and then I ask that you pose other benefits of using a Nitrogen fill and I will ask you some questions that have been bothering me about why it is "beneficial"
1. There is less of a temperature change in the tires when it is filled with Nitrogen over Air.
Considering the specific heats (kJ/kg * K) of both gases, we find that there is very little difference and that there is less than a 3.5% difference. This leads me to believe that the difference in temperature between the two gases when compared to hot and cold tires is very minimal. I have considered the fact that there is moisture in the air and thus this can also play into it, but how big of a difference does it really make?
2. Less rotational Mass
Nitrogen has a MW of 28.013 and air has a MW of 28.97. The difference is very little and I understand that they are looking for every edge, but really?
3. More consistent tire pressures from track day to track day.
Isn't Nitrogen a smaller molecule than air, so wouldn't it diffuse more easily out of the "holes"?
Please feel free to comment and criticize, I'm pretty thick skinned, so if you feel the need to "bash" feel free to.
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