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Discussion Starter #1
Ok tec guy's here's another dumb question.... I know that Nos supports combustion better then 21% oxygen... What if I were to use 100% O2 medical gas? It's the higher cocentration of oxygen in the nos that supports to combustion... so what's up.... I have access to medical gas... is this possible? Your O2 sensory would go crazy... can someone explain this?
 

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Well NO2 is not volatile in the current state. O2 is EXTREMELY flammable/explosive. You don't want this in your car and you certainly don't want it pushed into your combustion chamber. Its too dangerous used purely..this is why NO2 is used. It provides a lot denser, oxygen-rich charge, but its not explosive
 

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More is not always better. People blow things up with NO2......adding something with 80% more volitility sure isn't going to help things.
 

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Discussion Starter #4
91TB78 said:
O2 is EXTREMELY flammable/explosive. . It provides a lot denser, oxygen-rich charge, but its not explosive
OK.... now first off... thanks for the impute... I really am not a mechanic... BUT I am a med student interning in respiratory medicine....and I have to correct this... O2 IS NOT flammable... It only supports fire... you need a source material to combust... The cylinder is at 2200 psi(g) [gauge] therefore it has potential for explosion only at 73 degree C.

Now I understand that O2 would add volitility, maybe too much, but how does density of the gas effect things? wouldn't a lower density gas like a heliox (40% O2 and 60% He) flow faster therefore burn faster?

Sorry, once again i'll state..... I know little about enignes... but alot about gas physics...


P.S.- I'm totally not trying to flame! PUN intended!
 

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Re: WHAT WAS YOUR FIRST CAR

Goose said:
OK.... now first off... thanks for the impute... I really am not a mechanic... BUT I am a med student interning in respiratory medicine....and I have to correct this... O2 IS NOT flammable... It only supports fire... you need a source material to combust... The cylinder is at 2200 psi(g) [gauge] therefore it has potential for explosion only at 73 degree C.

Now I understand that O2 would add volitility, maybe too much, but how does density of the gas effect things? wouldn't a lower density gas like a heliox (40% O2 and 60% He) flow faster therefore burn faster?

Sorry, once again i'll state..... I know little about enignes... but alot about gas physics...


P.S.- I'm totally not trying to flame! PUN intended!
I am not 100% sure on properties of each gas, but I do know that O2 adds volitility compared to a "safer" NO2. Density of oxygen is important b/c you want a very oxygen dense air-charge to get the most power. This is why you would add NO2 in the first place..it is more oxygen dense compared to normal ambient air. So going back to your original question..you wouldn't want to go one step ahead of NO2 and go with straight O2 b/c of safety.
 

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Goose is correct - partly!

You need three components to start a fire; oxidant (air, NOS, oxygen), fuel (gas, wood, paper) and an ignition source (spark, heat). This is the fire triangle - remove one component and the fire is extinguished.

With NOS you have a more concentrated source of oxygen than air (33% vs 21%). Try this site for some tech details on NOS

http://www.dynopower.freeserve.co.uk/nitrous_oxide/

As you increase the oxygen concentration the requirements for the other two fire triangle components become less restricted. So for a bottle of medical grade oxygen (99-99.9% O2) a large proportion of metals become viable fuels and the ignition source could be something as simple as the heat generated by the flow of the oxygen round a too sharp bend of piping. For safe oxygen service all the materials of construction that come in contact with the oxygen need to be carefully selected and cleaned of all debris and organic contaminants (grease, oil etc). Not really possible in an automobile.

In summary - DO NOT TRY THIS AT HOME (that means you Goose) :eek:

Jon

P.S. I'm an engineer at a major industrial gases company that along with NASA has done most of the research on this. If you think about it pure oxygen plus fuel is what launches most rockets out of Earth's atmosphere. I know the STi is AWD but it's not meant to be that off-road.
 

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You can do some searches on the net for more info. One issue that some people talk about is the flame speed -- basically you need to be really careful or the flame will happily propogate back into your bottle, and boom. Nitrous has a pretty low flame speed making it more suitable. In addition, I would guess from my cursory reading that controlling the resulting combustion temperature would be harder and you'd be running a much greater risk of heat damage.

I do wonder why one couldn't bump up the oxygen content a bit, say to 40% oxygen. My guess is that one normally get enough with nitrous, and you can always inject some more. Cheaper and easier to stick with readily available products too.
 

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TypeUKinUSA hit it dead on. The reason combustion temperatures are reasonable in a car is due to the fact that the air is mostly N2. But, if you have a pure hydrocarbon and oxygen flame, the temperature can sky rocket and you can have molten metal. Think what an oxy-acetylene torch can do to your engine block. Acetylene is a simple hydrocarbon, C2H2...

So, this brings up a major reason that people use NOS; it has two nitrogen molecules for everyone one oxygen molecule. Nitrogen is a great diluent since it has a large heat capacity. As the NOS expands from high pressure, it's temperature drops considerably (anyone use compressed air bottles to clean their comuter?) and it cools the intake charge, making it more dense. So, even though N20 is only about 36% oxygen by volume, you can cram even more N20 in, thus more oxygen in.

Like everyone else has said, pure oxygen would be great, but it's too hard to handle safely.
 

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Discussion Starter #9
Thanks guys!!!


The gas density makes alot of sense to me...

I think I'll just stick with a normal fuel/O2 mixture till my extended warr. expires.

Good to see people who have a good grasp of gas physics... I Had to take 12 credit hours! Yuck!!!
 

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So, would anyone reccomend the use of nitrous with the STi? If so, what would you gain? Would you want to use it to help low or high end acceleration (or both)? Are there better/worse times (withing the rev range) to use it?

All I know about nitrous is what we have said here, but I know that there is more to it. Is there a good web site to learn more? I'm looking for something more in-depth than a howstuffworks type of thing.
 
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