New Reliability Mod
07-24-05, 03:12 AM
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New Reliability Mod
I'm sure most of you already know that tire pressure plays an important role in handling, gas mileage, tire wear, etc.. I'm sure you also know that the regular compressed air in your tires makes the pressure fluctuate with heat and other factors. Well, I seen on the news the other day that some tire shops are filling their tires with Nitrogen instead of regular air. They said racers swear by it, so this may not be news to some. Anyhow, the biggest advantage of Nitrogen over regular compressed air is that each molecule of Nitrogen is significantly larger than air, therefore keeping tire pressure more stable all around which then leads to better gas mileage, tire wear, and even better handling to an extent. Some shops (like Cosco) will fill your tires with Nitrogen for free, while others charge a small fee (I won't even try to quote a price b/c I don't know). Anyways, I figured you guys would like to know every little thing possible that may help with gas mileage, God knows these aren't economy cars, lol.
PS-- Speaking of gas mileage related to our beloved 7's, I have a very funny pic to post. I found it browsing around on a certain used car website. It's sort of an inside joke, but we're all insiders here. (If you don't get it, put 5$ worth of gas in your RX-7 and see how long it lasts) :P.
PS-- Speaking of gas mileage related to our beloved 7's, I have a very funny pic to post. I found it browsing around on a certain used car website. It's sort of an inside joke, but we're all insiders here. (If you don't get it, put 5$ worth of gas in your RX-7 and see how long it lasts) :P.
07-24-05, 03:58 AM
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Amazing how people start talking about whats been talked about (gas milage) on this forum since the begining. Why don't we start talking about how this nitrogen thing works, sounds kinda hoky to me...
07-24-05, 04:07 AM
#7
Haven't we ALL heard this
No, you don't need to do this.
It is just a waste of money. Besides air is like what ... 78% nitrogen to begin with? Isnt that enough for joo
James
Edit - Here is a good forum thread on it
http://www.eng-tips.com/viewthread.c...=120996&page=1
Got this from that site:
The question about nitrogen in tires has come up in other lists on the web as well. Let me clarrify a few points.
1. Air is 78% nitrogen, N2, and 21% oxygen, O2. So even if you put air in the tire, it's already 78% nitrogen. Many of the so called nitrogen generators don't produce much more than 90% nitrogen.
2. At relatively low pressures (ie tire pressures) N2, O2 and water vapor will all behave as ideal gases, and follow PV=nRT. Pressure will increase or decrease to the same extent as the temperature increases or decreases regardless of which gas is in the tire. (Even at 300 psi, which is about 20 atm, there is little deviation from ideality.) Therefore the comments about N2 not changing in pressure as the temperature changes are without merit.
3. The rate of effusion (or diffusion) of a gas through a porous membrane depends on the molar mass and to some degree on the molecular diameter. N2 and O2 are almost the same size and N2 is lighter than O2 (28 g/mol vs 32 g/mol) so if either gas were to effuse out of the tire, nitrogen would do it more quickly. Luckily, tires are designed not to be porous membranes.
4. N2 and O2 both have essentially the same specific heat capacity, about 1.0 J/gK, and thermal conductivity, about 0.00026 W/cmK. Water vapor has a specific heat capacity of about 2 J/gK. But remember, water vapor will constitute less than 1% of the air in the tire. So the idea that N2 has different heat handling properties is also without merit.
5. The ozone, O3, in the atmosphere, which is a ground level pollutant, will do a great deal more damage to your tires than the O2 inside the tire. For instance, don't leave a condom out in the air in Los Angeles for a few days. It will develop lots of tiny holes and weaken.
spdracer22 says that dry air is preferably to air with a lot of water vapor. As a tire heats up, the very small amount of H2O present will be in the vapor state which may contribute to the overall pressure very slightly.
Several have suggested that N2 in a high pressure tank is more portable and requires no electricity. That would make sense, particularly for aircraft tires.
I find no reason to believe that N2 is going to produce a "better ride" or "better handling".
The bottom line is that for general passenger car tires or truck tires there is nothing to be gained (other than portability) by using nitrogen rather than air. The biggest gain will be $$$ by the companies that sell nitrogen handling equipment and the tire merchants that appeal to ignorant customers. And who is the biggest loser? Yep, the consumer.
It is just a waste of money. Besides air is like what ... 78% nitrogen to begin with? Isnt that enough for joo
James
Edit - Here is a good forum thread on it
http://www.eng-tips.com/viewthread.c...=120996&page=1
Got this from that site:
The question about nitrogen in tires has come up in other lists on the web as well. Let me clarrify a few points.
1. Air is 78% nitrogen, N2, and 21% oxygen, O2. So even if you put air in the tire, it's already 78% nitrogen. Many of the so called nitrogen generators don't produce much more than 90% nitrogen.
2. At relatively low pressures (ie tire pressures) N2, O2 and water vapor will all behave as ideal gases, and follow PV=nRT. Pressure will increase or decrease to the same extent as the temperature increases or decreases regardless of which gas is in the tire. (Even at 300 psi, which is about 20 atm, there is little deviation from ideality.) Therefore the comments about N2 not changing in pressure as the temperature changes are without merit.
3. The rate of effusion (or diffusion) of a gas through a porous membrane depends on the molar mass and to some degree on the molecular diameter. N2 and O2 are almost the same size and N2 is lighter than O2 (28 g/mol vs 32 g/mol) so if either gas were to effuse out of the tire, nitrogen would do it more quickly. Luckily, tires are designed not to be porous membranes.
4. N2 and O2 both have essentially the same specific heat capacity, about 1.0 J/gK, and thermal conductivity, about 0.00026 W/cmK. Water vapor has a specific heat capacity of about 2 J/gK. But remember, water vapor will constitute less than 1% of the air in the tire. So the idea that N2 has different heat handling properties is also without merit.
5. The ozone, O3, in the atmosphere, which is a ground level pollutant, will do a great deal more damage to your tires than the O2 inside the tire. For instance, don't leave a condom out in the air in Los Angeles for a few days. It will develop lots of tiny holes and weaken.
spdracer22 says that dry air is preferably to air with a lot of water vapor. As a tire heats up, the very small amount of H2O present will be in the vapor state which may contribute to the overall pressure very slightly.
Several have suggested that N2 in a high pressure tank is more portable and requires no electricity. That would make sense, particularly for aircraft tires.
I find no reason to believe that N2 is going to produce a "better ride" or "better handling".
The bottom line is that for general passenger car tires or truck tires there is nothing to be gained (other than portability) by using nitrogen rather than air. The biggest gain will be $$$ by the companies that sell nitrogen handling equipment and the tire merchants that appeal to ignorant customers. And who is the biggest loser? Yep, the consumer.
Last edited by Wankel7; 07-24-05 at 04:10 AM.
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07-24-05, 04:11 AM
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Originally Posted by jacobcartmill
i get about 23mpg on the highway with my 89 TII. i'd say its not bad considering its got haltech and a big turbo and stuff.
07-24-05, 04:32 AM
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The most I can get a full tank is 184. Sadly, I never have time to actually get my car tuned up. For example, get injectors cleaned, new tranny, brake, and some other fluids, O2, etc....
07-24-05, 05:29 AM
#17
Haven't we ALL heard this
I think of the main reasons it is used on aircraft tires is because the pressure that some of the tires are pumped up to. Over 100 psi on some...and it is easier to bring nitrogen out of a 1500psi bottle than air compressors.
James
James
07-24-05, 11:36 AM
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I don't see how anybody gets over 20 mpg. I'm guessing thats on the freeway but still, i get around 13-14 mpg in the city and about 15-18 mpg mixed city and half freeway.
07-24-05, 11:40 AM
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i used to work at a tire warehouse for 2 years and they did that type of air, is was 4.88 per tire.. for a car or light truck... and it's 99% not 70 something...and u can feel a lil diff, i would run it and did
07-24-05, 12:44 PM
#21
Haven't we ALL heard this
Originally Posted by slip_N_slide83
i used to work at a tire warehouse for 2 years and they did that type of air, is was 4.88 per tire.. for a car or light truck... and it's 99% not 70 something...and u can feel a lil diff, i would run it and did
James
07-24-05, 12:58 PM
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I agree with WANKEL7.
I've had several physics courses in university, college, and high school, and I can personnaly confirm that, at these pressure, every single gaz will act as a perfect gas...
as for the tire from aircrafts, it's easy to understand.... Imagine the INSTANT pressure that the gaz has to take. A plane hits the ground HARD and it's ******* damn HEAVY. There must be absolutely insanes pressures for a short period of time.
for our cars, this is absolute bullshit. physics, mathematics and rationality will tell you that nitrogen will not have any SIGNIFICANT effect on handling and/or gas mileage
if someone can prove me wrong, I want the physic laws and equations to back it up
l-p
I've had several physics courses in university, college, and high school, and I can personnaly confirm that, at these pressure, every single gaz will act as a perfect gas...
as for the tire from aircrafts, it's easy to understand.... Imagine the INSTANT pressure that the gaz has to take. A plane hits the ground HARD and it's ******* damn HEAVY. There must be absolutely insanes pressures for a short period of time.
for our cars, this is absolute bullshit. physics, mathematics and rationality will tell you that nitrogen will not have any SIGNIFICANT effect on handling and/or gas mileage
if someone can prove me wrong, I want the physic laws and equations to back it up
l-p
07-24-05, 01:01 PM
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Originally Posted by porsche4786
I don't see how anybody gets over 20 mpg. I'm guessing thats on the freeway but still, i get around 13-14 mpg in the city and about 15-18 mpg mixed city and half freeway.
And this is with a fair amount of "spirited" driving, not driving around like an old woman
