Why don't they use Compressed Oxygen instead of Nitrous Oxide in Drag Racing?

[St. Phatty]

This is one of those Fast & Furious type questions.

Plus, I watched Maloof Racing on Netflix.

They use Nitrous Oxide - for Racing AND for Dental Anaesthesia ?

Now that is one Versatile Chemical Compound ! !!

"The purpose of a nitrous oxide system is **to increase the power output of an engine** . It does this by increasing the amount of fuel that can be burned, by increasing the oxygen supply."

So, if they want more Oxygen - why not use a tank of Compressed Oxygen, and fold that into the inflow of Atmospheric Air, 80% Nitrogen 20% Oxygen 420 ppm CO2 ?

Does anyone know the formula/ Stoichiometry for burning Gasoline with Nitrous Oxide ?

 

[exploziv]

I think the key is not blowing up the engine. Nox also cools the engine in a predictable ratio quite fixed in relation to oxygen given. In a forge, you pump oxygen to get higher temps, but you want the metal to get hotter. In an engine, dilatation from the fast temperature increase would be killer. Compressed oxygen would work if you managed to move the heat away fast enaugh.. maybe in some kind of older style airplane turbo engine. In a car, we would need better materials that don't change size with temperature increase.

 

[Douglas.Curtis]

exploziv has it correct.

While the more oxygen you have, the more efficiently the fuel burns, the engines are only made of metal and unable to handle extreme temperatures. What's more, detonation of fuels becomes significantly easier in a pure or close to pure oxygen environment.

 

[Three Berries]

Aluminum pistons can't take it. Their only cooling is oil squirted on the underside of them.

 

[flylowgethigh]

A nitrous system also adds fuel when the booster is on. Typically timing is also pulled. The concept is liquid added displacement… adding fuel and air in a ‘forced’ manner by spraying.

Safety is one reason I can think of. O2 is dangerous. Liquid O2 is more so. The NOS bottle is full of liquid. They have to heat the bottles to keep the pressure up around 1000 PSI.

A mixture of nitrous and fuel in an intake manifold of an engine that has stalled is a bomb. Try to start it, and the spark will sometimes blow the intake manifold off the engine in a spectacular manner.

 

[Douglas.Curtis]

A mixture of nitrous and fuel in an intake manifold of an engine that has stalled is a bomb. Try to start it, and the spark will sometimes blow the intake manifold off the engine in a spectacular manner.

Wait... that's *not* what funny car drag racing is all about? I remember watching just to see something like that happen to a $100,000+ engine. heh Very pretty, very destructive, veeery dangerous, and (of course) very awesome!

 

[chilliwilli]

O2 is so reactive the fuel would ignite mixed with gasoline in a turbo.

 

[Brother Nature]

All the above guys are kind of right. Their concerns could be engineered out though. Even a proper drag engine running NOS has to be seriously beefed up to cope with the load and rebuilt often, theoretically this could be done for an oxygen intake too.

The issue is the ratio of petrol to oxygen and the bulk of O. The ratio is something like 1:15 and O is a very light gas, one pound fills something like 12 cubic feet of space. Doing the math, even highly compressed, it's not efficient enough to be worth it, the containers needed to store enough for even a 400m blast would defeat the entire purpose.

 

[St. Phatty]

So, besides using aerodynamics, how could a person get a 1/2% to 5% increase in performance with a REALLY souped up dragster.

Either the street legal kind that still has a factory chassis, or the Camaro body on the super-light chassis.

I think the exhaust pipes on the standard V8's look congested. Sharp bends and little jiggles in the exhaust pipe are BIG NO-NO's in the realm of expensive military hardware.

See those multiple jiggles in the exhaust duct on the right ?

They have a cost that I suspect robs the engine of a few horsepower.

In the aerospace design world, where you pay $5K for a 4 inch cube of a fan to move the air, you are super-conservative about how the ducts are routed.

The ducts on the left are better than the ducts on the right.

I might know Ducts, but I don't know much about cars.

Do car engines NEED to have a constriction in the exhaust pipes for some car technology reason ?

Does a car engine benefit from some kind of back-pressure "pushing back" on the engine exhaust ?

 

[Douglas.Curtis]

Yes, back-pressure has a definite impact on pressures, exhaust exchange and more. The supertrapp(sp?) mufflers use multiple disks you can add or remove to adjust the amount of pressure, basically allowing you to 'tune' the exhaust to the engine it's attached to. Side note: they blow exhaust residue 90 degrees from the pipe, instead of straight back.

 

[St. Phatty]

Yes, back-pressure has a definite impact on pressures, exhaust exchange and more. The supertrapp(sp?) mufflers use multiple disks you can add or remove to adjust the amount of pressure, basically allowing you to 'tune' the exhaust to the engine it's attached to. Side note: they blow exhaust residue 90 degrees from the pipe, instead of straight back.

I found this picture of what would be an optimal header for simply moving air with the least resistance.

The picture with the red painted engine.

The most airflow with the least pressure drop, is the goal when you are designing cooling ducts for electronics.

It sounds like, at the higher RPM, the engine somehow gets more acceleration to the Rubber tires, if the exhaust tubes are longer.

This makes me wonder if an Adjustable length header might be best - a Shorty with clean ductwork, like in the first picture with the red engine, off the line.

Then growing in length after a few seconds, so that the 18 inch long duct becomes a 30 inch long duct (or whatever length is found to be optimal) - about 5 seconds into the 10 second race.

Doing a web search for
"adjustable length automotive racing header"

I got the second picture, the one NOT painted red, with the black tubes.

I look at the spider web of black tubes in the second picture, and it looks like they are purposely increasing the length of the exhaust duct.

 

[Three Berries]

So what would happen if you just had the engine on an engine stand, running & driving a big load like it would in a car, and gave it the ultimate no-back-pressure situation: NO header.

Will the Torque or Power be lower with No Header at some RPM with some loads ?

Probably burn up the valves with no manifold. I suppose that could be gotten around. The easy way is an exhaust turbo charger which it uses the further expansion of the hot exhaust gasses after it leaves the head to raise the intake manifold from vacuum to 20-30 psi pressure.

 

[Douglas.Curtis]

Even running "open headers" still has a bit of back pressure from the way the engine block is configured. I don't think you'll find much variation there. May I ask... what is your end goal with this discussion?

On a side note... Have you seen Koenigsegg's new 3 cyclinder (only 2.0 liter) motors with dual turbo? Absolutely insane HP and torque from such a tiny engine. Imagine putting 600 horsepower and 443 pound-feet of torque in a mazda miata or something that size. lol

https://www.topspeed.com/cars/car-news/is-koenigsegg-s-600hp-three-cylinder-engine-the-key-to-the-survival-of-the-internal-combustion-engine/

 

[Tynehead Tom]

Now I'm just spitballing here but I'm guessing that the thing about Oxygen is the temperatures would exceed the limitations of the metals the engine is made of. Perhaps too volitile of a reaction when used as an accellerant with a combustable such as race fuel or even pump grades of gasoline.
The more O2 the hotter the fire.
Think about a cutting torch , a flammable gas is combined with O2 and you can cut steel with fire. Without the 02 the gas ignites but only burns as hot as the atmosphere it is in. You can heat the steel up and never melt it where as you add a bit of 02 to that mix and steel becomes motlen in seconds.
I'm not that knowlegable about this topic or the nature of Nitrous Oxide but my guess is that it is an accellerant that was found to be the safest for temperature reasons so horsepower could be harnessed without melting down the engine components

 

[Douglas.Curtis]

@Tynehead Tom You're quite correct about O2 and heat. Even a cigarette burns at 750F to 1300F in pure oxygen. Gasoline burns at over 3800F in regular air, and many 'coolant' systems can have issues keeping an engine cool on super hot days. I'm having difficulty finding the temperature of a gasoline flame in pure oxygen, but I did find propane (which is slightly lower in energy) can reach temperatures around 5000F in pure oxygen.

Nitrous Oxide cools things down quite a bit, while it also adds oxygen to the mix as the nitrogen breaks down. (IIRC that is... lol)

Exotic ceramic/aluminum alloys might make it possible to use pure oxygen one day. I remember reading about some experimental engines using O2 and diesel to run submerged submarines. The design I read about used exhaust gasses to mix with pure O2 and keep temperatures from melting things rather quickly.

 

[St. Phatty]

Even running "open headers" still has a bit of back pressure from the way the engine block is configured. I don't think you'll find much variation there. May I ask... what is your end goal with this discussion?

To see if I can find a way to help an experienced drag-racing pro to get an extra 1% of horsepower.

Partially because I think his team would be fun to work with.

 

[exploziv]

The snaking you see in the black parts is to mantain same lenght exhaust on all pistons, for even pressure. The extra lenght compared to first picture also keeps noise down.

 

[Brother Nature]

Not advice, but fun to watch

 

[Ibechillin]

Alepa Racing C7 corvette lol

 

[St. Phatty]

Not advice, but fun to watch

I'd like to try that with 20 horsepower roller skates on my feet.

Not roller blades, roller skates.

When I was out skating at one of the local trails near the river, I talked to a woman who skates in the local Roller Derby.