Nitrogen finding it's way into marketing...smoke and mirrors?

I don't know if others have noticed the trend but some auto makers are now selling tires ythat are nitrogen filled. At least one gasoline manufacturer is pushing it's new 'nitrogen enriched' fuels.

If I remember my high school chemistry and physics, 3/4 of the earth's atmosphere is made up of nitrogen.

So how does replacing the last 25% in my tires make a difference to the fuel economy? And how does 'enriching' fuel with nitrogen that is automatically enriched when the engine intakes air; help?

Call me a sceptic but this sounds like a lot of snake oil to me!

Maybe Bob P. can shed some light on the 'enriched' gasoline thing...

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Archeo-peteriX
I don't know if others have noticed the trend but some auto makers are now selling tires ythat are nitrogen filled. At least one gasoline manufacturer is pushing it's new 'nitrogen enriched' fuels.

If I remember my high school chemistry and physics, 3/4 of the earth's atmosphere is made up of nitrogen.

So how does replacing the last 25% in my tires make a difference to the fuel economy? And how does 'enriching' fuel with nitrogen that is automatically enriched when the engine intakes air; help?

Call me a sceptic but this sounds like a lot of snake oil to me!

Maybe Bob P. can shed some light on the 'enriched' gasoline thing...

I don't know what they're doing with the fuel, but the nitrogen in the tires thing is pure snake oil. As soon as somebody can show me the version of the ideal gas law that makes an exception for nitrogen I'll retract that statement. Air behaves like an ideal gas until the temperature is up around 1000 degrees F. our tires will all be a pile of ash at that temperature, so filling the tires with nitrogen instead of air only makes a difference in the profits of the company that sells it.

PV=nRT

V stays the same no matter what (volume inside your tire - OK, some slight change with temp, nothing that would be different for air vs nitrogen so it's irrelevant).
n stays the same no matter what (number of moles of gas).
R stays the same.......... (gas constant - can't change, it's a constant).

The only things that can change are the pressure and the temperature (P &T). As the temp goes up, the pressure goes up, and vice versa. Simple. No exception for nitrogen.

John

Nitrogen in tires is an expensive fad that is silly for normal road use. If your tires come filled with nitrogen it certainly won't hurt anything. But, given the option, I wouldn't pay extra to have them filled that way.

There are two primary "benefits". One is that nitrogen molecules are larger than oxygen molecules. Nitrogen makes up something like 78% of air, with oxygen being the only other major component at something like 21%. The rest is too small to worry about. The theory is that the larger nitrogen molecules don't escape as easily through the rubber of your tires, whereas the smaller oxygen molecules leak through about three times faster. Big deal. If you regularly check your tire pressure this makes no difference whatsoever. Does using nitrogen somehow imply you can go three times as long before needing to check your pressures?

The other "benefit" of pure nitrogen over normal air is that atmospheric air contains moisture whereas bottled nitrogen supposedly does not. John pointed out the Gas Law of PV=nRT. However that equation does not take into account the effects of humidity, which very much complicates the equation. Depending on the level of moisture contained in the air, it can be much more difficult to calculate precisely how much the pressure will change relative to a given temperature change. In some types of racing, i.e. 200mph+ IndyCar oval racing, tiny imbalances in tire pressures will have an enormous effect on how the car handles. For that reason it makes sense to use more stable pure nitrogen, rather than gamble on using air with an unknown moisture content. For normal road use though, you're never going to notice the difference. There will probably be a bigger difference in tire pressure created depending on which way you're headed on the highway and which side of the car is being heated by direct sunlight.

Enriched fuels are also a crock. They can be enriched with various detergents to clean your engine, or other additives. But essentially no fuel additive is going to magically make your engine produce more power, unless it is an "oxygenator".

All of our engines are limited, not by the quality or quantity of fuel that can be pumped into the engine, but by how much air can be inhaled by the engine. To properly burn a certain quantity of gasoline, you first need to add 14.7 times the amount of air by mass. Picture a drop of gasoline and how heavy that is. Now picture 14.7 times that amount of mass in air!

And, only about 21% of all that air is useful oxygen, which is what is consumed in burning the gasoline. You want more power out of your engine, you first need to figure a way to get more oxygen into it, then it's dead simple to squirt a tiny bit more fuel in too.

More nitrogen is completely counter-productive, since nitrogen is inert, will not burn, and simply takes up useful space that would be more productive holding oxygen.

Nitrous Oxide (N₂O) however is very useful at producing more power for a couple of reasons. When heated, the nitrous releases oxygen. That helps. The extra oxygen means you can burn that much more fuel to make more power. Also, when the nitrous expands it helps cool the intake charge, thereby increasing its density, meaning you can pack in that much more air. That's another bonus, allowing you to add even more fuel.

Otherwise the nitrogen in Nitrous Oxide is pretty much only useful for carrying the extra oxygen. On its own, the nitrogen does squat.

Archie, Ferdinand beat me to it! What ferdinand said is pretty spot on. I haven't looked into this 'nitrogen enriched' fuel thing, although I am curious. I suspect that it has more to do with the use of ammonia or an amine in the fuel processing than adding N2 to the fuel, which would just end up taking up space and adding no value. Even spraying H2O to the fuel charge will give a 'boost' to the combustion, but N2 - No!

As for N2 in the tires, if it is true that the O2 in air would 'leak' more quickly through the tire and therefore the pressure in the tire would reduce, we have just found a molecular sieve which, if we keep making up with air, we will end up with pure N2 in the tire. Clearly that does not happen, so I really don't see where 100% nitrogen is better than 78% N2. It is true that the N2 that you will buy is much drier than ccompressed air, but even if the air were saturated there is only so much water that condenses and might be a worry if you are removing air in the winter and the vapour freezes in the valve.

Ain't marketing great?!

Salut, bob p.

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Archeo-peteriX
I don't know if others have noticed the trend but some auto makers are now selling tires ythat are nitrogen filled. At least one gasoline manufacturer is pushing it's new 'nitrogen enriched' fuels.

If I remember my high school chemistry and physics, 3/4 of the earth's atmosphere is made up of nitrogen.

So how does replacing the last 25% in my tires make a difference to the fuel economy? And how does 'enriching' fuel with nitrogen that is automatically enriched when the engine intakes air; help?

Call me a sceptic but this sounds like a lot of snake oil to me!

Maybe Bob P. can shed some light on the 'enriched' gasoline thing...

Do we get a cool window sticker if we bite on this?, if so count me in

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rkj
Do we get a cool window sticker if we bite on this?

No, but you get really cool GREEN valve-stem caps.

Yes, green is the official colour used for labelling N2 pipelines and containers.

Bob P.