Nitrogen instead of compressed air

Nitrogen instead of compressed air

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Discussion

77racing

Original Poster:

3,329 posts

154 months

Monday 15th March
quotequote all
Just going to start using Nitrogen this season. Just a quick question what rise in pressure can i expect from cold to hot tempreture ?

sherman

8,883 posts

182 months

Monday 15th March
quotequote all
Less than normal air I would assume.

77racing

Original Poster:

3,329 posts

154 months

Monday 15th March
quotequote all
yes but by how much ?

mmm-five

9,182 posts

251 months

Monday 15th March
quotequote all
What problem are you trying to solve?

Scientifically, rather than purely in a tyre-filling scenario...

If you're comparing completely dry gases, then there's less than 1% difference in heat-related pressure increases between compressed air and pure nitrogen.

Moisture levels would make more difference as temps rise as this will expand more than any of the other gases in there.

It might matter in Formula 1 where 1% is meaningful, but probably not in club/national racing levels.

carl_w

6,707 posts

225 months

Monday 15th March
quotequote all
I'm planning to run a 78% nitrogen, 21% oxygen and 0.9% argon mix this year.

77racing

Original Poster:

3,329 posts

154 months

Monday 15th March
quotequote all
mmm-five said:
What problem are you trying to solve?

Scientifically, rather than purely in a tyre-filling scenario...

If you're comparing completely dry gases, then there's less than 1% difference in heat-related pressure increases between compressed air and pure nitrogen.

Moisture levels would make more difference as temps rise as this will expand more than any of the other gases in there.

It might matter in Formula 1 where 1% is meaningful, but probably not in club/national racing levels.
i,m trying to find a good start point of inflation from cold, if i wanted to end up at 35psi hot what should i start with . I used to start on compressed air 22psi cold to reach 30psi hot.

Dan BSCS

1,016 posts

203 months

Tuesday 16th March
quotequote all
77racing said:
i,m trying to find a good start point of inflation from cold, if i wanted to end up at 35psi hot what should i start with . I used to start on compressed air 22psi cold to reach 30psi hot.
I think he meant, why are you switching to Nitrogen inflation rather than just using air. Although asking you to justify your decision is not particularly helpful to your quest for answers.

In answer to your question, this is not really something anyone will be able to answer particularly accurately for your given situation so you will just have to test really.

Start at a good guess (slightly on the high side) then just keep bleeding air out over a 20-30 minute run till you reach a stable level of your desired hot pressure. Let them cool right down then make a note of the cold pressures and Bob’s your uncle. biggrin

bigothunter

1,366 posts

27 months

Tuesday 16th March
quotequote all
carl_w said:
I'm planning to run a 78% nitrogen, 21% oxygen and 0.9% argon mix this year.
hehe

Nampahc Niloc

799 posts

45 months

Tuesday 16th March
quotequote all
carl_w said:
I'm planning to run a 78% nitrogen, 21% oxygen and 0.9% argon mix this year.

Same, but I’m also going add a smidgeon of CO2.

bigothunter

1,366 posts

27 months

Tuesday 16th March
quotequote all
Nampahc Niloc said:
carl_w said:
I'm planning to run a 78% nitrogen, 21% oxygen and 0.9% argon mix this year.
Same, but I’m also going add a smidgeon of CO2.
0.038%

Any more and the world will end whistle

TimCrighton

995 posts

183 months

Wednesday 17th March
quotequote all
Ideally use it on newly fitted tyres.

The benefit of it, to those nay sayers above, is that in many cars tyre pressures are in effect part of the combined spring rate (as the tyre compression and side wall movement allows some initially element of damping and movement before the suspension components are engaged). Also it can be desirable for example to maintain a softer tyre pressure and allow the tyre sidewall to roll and/or the contact patch to be enlarged - sidewall movement also generates heat which increased pressure and therefore reduces this element over time. Additionally where a car is running over long periods it can be advantageous to control or help to control the growth in tyre pressures over a long stint.

We use it in several of our cars and it serves a purpose.

Like everything you need to test it to see what it will do in your car but for us where as we might have seen a 6-7 psi increase cold to hot that might be reduced to 2-3 psi with Nitrogen.

77racing

Original Poster:

3,329 posts

154 months

Wednesday 17th March
quotequote all
TimCrighton said:
Ideally use it on newly fitted tyres.

The benefit of it, to those nay sayers above, is that in many cars tyre pressures are in effect part of the combined spring rate (as the tyre compression and side wall movement allows some initially element of damping and movement before the suspension components are engaged). Also it can be desirable for example to maintain a softer tyre pressure and allow the tyre sidewall to roll and/or the contact patch to be enlarged - sidewall movement also generates heat which increased pressure and therefore reduces this element over time. Additionally where a car is running over long periods it can be advantageous to control or help to control the growth in tyre pressures over a long stint.

We use it in several of our cars and it serves a purpose.

Like everything you need to test it to see what it will do in your car but for us where as we might have seen a 6-7 psi increase cold to hot that might be reduced to 2-3 psi with Nitrogen.
Tim I take compliments and insults from those that know no better LOL, your point about stabalising pressure over a period of time is going to save a lot of faff. I was thinking that an advantage to already been at pressure from the get go would give me an advantage into the first few laps all be it heat will still take time but less to come up,using nitrogen. There is obviously an advantage other wise why would all the top teams with top cars be using it. I use 305 645 18 tyres so will as you surgest start 3 psi down and wave good bye to the nay sayers LOL

liner33

8,672 posts

169 months

Wednesday 17th March
quotequote all
We used to use dry air from dive cylinders when drag racing gave more consistent results which were key when you are talking about 1/4 of a psi and less than 8 psi to start with . Easy to source also

77racing

Original Poster:

3,329 posts

154 months

Wednesday 17th March
quotequote all
Tim will see you in anglesey later in the year i hope i,m using it on this LOL................................................



20200820_070241 by flat chat, on Flickr

77racing

Original Poster:

3,329 posts

154 months

Wednesday 17th March
quotequote all
liner33 said:
We used to use dry air from dive cylinders when drag racing gave more consistent results which were key when you are talking about 1/4 of a psi and less than 8 psi to start with . Easy to source also
i had thought of that and went for nitrogen because it is more stable over time.

carl_w

6,707 posts

225 months

Wednesday 17th March
quotequote all
77racing said:
i had thought of that and went for nitrogen because it is more stable over time.
Could you explain further?

77racing

Original Poster:

3,329 posts

154 months

Wednesday 17th March
quotequote all
divers dry air expands less than compressor air usually

stevieturbo

15,488 posts

214 months

Wednesday 17th March
quotequote all
carl_w said:
I'm planning to run a 78% nitrogen, 21% oxygen and 0.9% argon mix this year.
Good job there's no co2 or they'd overheat like mad and destroy everything

stevieturbo

15,488 posts

214 months

Wednesday 17th March
quotequote all
So nobody uses Helium to make the unsprung weight lighter ? lol

TimCrighton

995 posts

183 months

Wednesday 17th March
quotequote all
77racing said:
Tim will see you in anglesey later in the year i hope i,m using it on this LOL................................................



20200820_070241 by flat chat, on Flickr
Love that!! It'll be exciting up through Church and School!

It's still a great looking car the Sag. I nearly raced the car in period and had it not been for a last minute swap it might be a very different story. One for the bar at Anglesey!