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      07-08-2013, 02:50 PM   #1
PrimeBMW
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Nitrogen

I am about to start using Nitrogen in my track tires to decrease the cold and hot pressure delta. I am thinking that it would have really helped back in the day when I used the PS2 and then the PSS. Now that I run Yokohama race slicks on my E46 M3 I am finding that it will be useful once again. (Yoko race slicks do not have steel belts) Anyone tried Nitrogen yet?
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      07-08-2013, 03:12 PM   #2
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I was going to do this:
But I think I'll do this instead:
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      07-08-2013, 03:50 PM   #3
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5th Gear recently ran an episode of regular air vs. nitrogen inflated tires and measured the lap times and pressure delta. Nitrogen showed no difference. Their test method was not very scientific, however.
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      07-08-2013, 04:34 PM   #4
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Quote:
Originally Posted by Richard@M-World View Post
5th Gear recently ran an episode of regular air vs. nitrogen inflated tires and measured the lap times and pressure delta. Nitrogen showed no difference. Their test method was not very scientific, however.
Was just going to mention that episode. Granted their method wasn't very scientific, but I think to get any real benefit you'd need to be very particular about where you got your nitrogen from. "Air" is already a large part nitrogen anyway.

Do race teams run nitrogen? I'd think if there was a benefit to be gained they would all be doing it.
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      07-08-2013, 04:40 PM   #5
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You'll need a wheel with a purge and a fill valve to completely purge the mixed air inside a tire with the nitrogen fill.
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      07-08-2013, 04:42 PM   #6
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...but but, the GT-R has nitrogen, so it must be awesomesauce!!!111
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      07-08-2013, 04:50 PM   #7
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I've been to track days where nitrogen was being supplied by a tire vendor. I gave it a try and didn't find any major difference in psi after my sessions. I gained approx 10lbs from the heat generated in a 20 min session.
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      07-08-2013, 05:07 PM   #8
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I watched that episode, they showed nitrogen was pointless because most nitrogen filling stations are not pure 100% nitrogen which negates the point.
the "nitrogen" wasn't contaminated by around 21% oxygen by any chance, was it?
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      07-08-2013, 05:30 PM   #9
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Well that is not very encouraging......though I don't think I will just take Jeremy's word for it. My Race shop has a tank of nitrogen so I guess we will see if it helps or not. Like some have mentioned the trick will be getting the air out. At the time I have Apex Arc 8 with only one valve stem.
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      07-08-2013, 05:34 PM   #10
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Quote:
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the "nitrogen" wasn't contaminated by around 21% oxygen by any chance, was it?
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      07-08-2013, 06:25 PM   #11
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According to the ideal gas law there is no difference between Bone Dry Air and Nitrogen in how the pressure responds to changes in temperature. The real difference is that air contains trace amounts of water which condenses at cooler temperatures and could have some marginal impact on pressures. This is more of any issue with airplane tires where water will freeze in the tires at altitude.

As for me, I'll continue to run my custom 79% N2 / 21% O2 mixture.
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      07-08-2013, 08:26 PM   #12
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I did a little reading up/research. It sounds as though nitrogen may only have a small effect on the cold to hot pressure delta. In a HPDE setting it may be of little use......just wait a lap till the pressures come up. In a race setting you may not have that luxury. You want to go 100% from flag to flag. For example we want to run about 30psi hot. That means that we start at 22-25 depending on the corner. That is low......if we can move that cold temp up 1-2 degrees using nitrogen then maybe it makes a difference. **keep in mind these pressures are on a 3000lb. E46 M3 race car and do not translate to the e9x M3.
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      07-09-2013, 12:18 AM   #13
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Quote:
Originally Posted by The HACK View Post
You'll need a wheel with a purge and a fill valve to completely purge the mixed air inside a tire with the nitrogen fill.
Agreed on the purge. Each tire already contains one atm of air with water vapor when not pressurized. We typically pressurize tires to, let's say, 30 psi, which is roughly two atm. So, even when you pump in pure N2 with no water, there is still water in the tire. Therefore doing multiple purges would probably be required to reduce water vapor to a negligible amount to make a difference in pressure/performance.
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      07-09-2013, 07:20 AM   #14
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Quote:
Originally Posted by PrimeBMW
Well that is not very encouraging......though I don't think I will just take Jeremy's word for it. My Race shop has a tank of nitrogen so I guess we will see if it helps or not. Like some have mentioned the trick will be getting the air out. At the time I have Apex Arc 8 with only one valve stem.
It all fairness it was 5th Gear, so it was Tiff's opinion. Which carries more weight than Jeremy's when it comes to driving fast.
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      07-09-2013, 07:29 AM   #15
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Quote:
Originally Posted by ThunderMoose View Post
According to the ideal gas law there is no difference between Bone Dry Air and Nitrogen in how the pressure responds to changes in temperature. The real difference is that air contains trace amounts of water which condenses at cooler temperatures and could have some marginal impact on pressures. This is more of any issue with airplane tires where water will freeze in the tires at altitude.

As for me, I'll continue to run my custom 79% N2 / 21% O2 mixture.
This is correct, the only point in inflating tires with "nitrogen" is to avoid having water in the tire. Water has a great impact on tire pressure because the condensation/evaporation point is right between the cold and hot tire operating points. As Hack mentions, the tire needs to be properly purged, i.e. all traces of water/water vapor removed from inside the tire, for the nitrogen fill to be effective.

This is too much trouble for marginal benefits for me and I will also stick with normal air.
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      07-09-2013, 07:36 AM   #16
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Quote:
Originally Posted by Richard@M-World View Post
Agreed on the purge. Each tire already contains one atm of air with water vapor when not pressurized. We typically pressurize tires to, let's say, 30 psi, which is roughly two atm. So, even when you pump in pure N2 with no water, there is still water in the tire. Therefore doing multiple purges would probably be required to reduce water vapor to a negligible amount to make a difference in pressure/performance.
I am being anal here, but a tire pressure gauge reads gauge pressure and not absolute. So technically 30psi is three ATM .

I agree that multiple purges are required to get most of the water out.

Last edited by CanAutM3; 07-09-2013 at 08:26 AM.
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      07-09-2013, 08:13 AM   #17
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3 purges is adequate. that is what we do with our chemical plant reactors.

as for not getting ultra high purity N2, they are likely using the cheap method of a pressure swing absorption unit which gets you to 98%.

i have access to 99.99% N2 for free and have not bothered filling the tires with it. if i get bored i will, but i do not think the benefit is that dramatic for track days.

i think it is all hype, so dealers can charge $75 for N2 tire fills while the nitrogen is uber cheap.
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      07-09-2013, 11:10 AM   #18
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i think it is all hype
100% agreed.

but you do get those cute green valve caps for your money...those have to be worth something.
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      07-09-2013, 12:15 PM   #19
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Quote:
Originally Posted by apecush
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i think it is all hype
100% agreed.

but you do get those cute green valve caps for your money...those have to be worth something.
Well Thundermoose and I are on the same page and are both 20 year Chemical Engineers, so it is a safe bet we are not both wrong. We could each fill our tires with instrument air at our plants, but it isn't worth the hassle for what we do.
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      07-10-2013, 02:38 AM   #20
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If you want to play around with the temperature and pressure chanches then download "pressurecalculationwithtemp"spreadsheet from next map on my public map on skydrive that belongs to my hotmail adres with same username as here.
https://skydrive.live.com/?cid=a526e...E092E6DC%21793
To download RIGHTclick and choose download.

Made it a while ago for races, and later planted the pressurecalculation to it in part 1 .
Idea of part 2 is to calculate the cold filled pressure that is needed , to get the same warm pressure as for normal conditions of 65/112dgrF Cold/Warm.
Part 3 is to fill in the pressures and it gives the warm inside tire temperature ( or cold if you want).
The calculations assume the tire-vollume not to chanche at higher pressure, wich it will aproximately will not when its pressurised.

Now about Nitrogen filling ( further N2) .
If you fill with 100% N2 , because the empty tire contains 20% Oxigen( further O2) there will be still a percentage O2 in the tire.
Then you can drop pressure to zero and fill again with 100% N2 , eventually in a few rounds, to get a lower O2%.

But whatever you do, in the long while there wil diffuse( and not leaking) O2 from the outside , into the tire. This proces wil give in the end a sertain %O2 belonging to the pressure .
1 bar/14,5psi goes to 10% O2
3 bar/44psi goes to 5% O2.
9 bar/130psi goes to 2% O2.
This has to do with the law of partial pressure wich is then the same inside as outside the tire and about 0,2 bar /3psi. At that point there is a balance, yust as much O2 is difusing into as out the tire.

Water as a gas reacts the same as any gas and by an iteraction of temperature and humidity chanches , its possible that, whatever effort you take to get as less water in the tire as possible, there will be coming water in to the tire or the tire inside gets dryer in the long while.

My idea is that liquid water ( H2O) does not diffuse or much less troug the rubber then H2O as gas.
Once read that O2 difuses 5 times quicker trough the tire as N2 .
What I would like to know is what howmany times quicker H2Ogas goes troug the tire as N2.

So new feed for who is interested
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      07-10-2013, 10:36 PM   #21
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No care about chemistry, all i know is it's a massive PIA. At some point you'll be jones'in for nitrogen, none will be around and then you'll have to use air. You're better off stuffing that $75 in a stripper's thong.
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      07-11-2013, 06:34 AM   #22
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No care about chemistry, all i know is it's a massive PIA. At some point you'll be jones'in for nitrogen, none will be around and then you'll have to use air. You're better off stuffing that $75 in a stripper's thong.
Just not all at once, that would be a serious waste of money.
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