In the age of automotive downsizing...

Discussion in 'General' started by fastfreddie, Feb 6, 2019.

  1. Prospect

    Prospect Hayai

    "Still a whole lot of Wrong in their" In their what?
     
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  2. SPL170db

    SPL170db Trackday winner

    Negative....chicks dig nitrous oxide. Both for and not for the reasons you're thinking


    [​IMG]
     
  3. Funkm05

    Funkm05 Dork

    Actually, they do. While temps do vary, they average between 1800-2300 degrees C ... do the conversion and you get your average range of ~3200-4100 degrees F. That’s for standard gas ic engines.
     
  4. fastfreddie

    fastfreddie Well-Known Member

    If you're forming measurable amounts of NOx worth mentioning, you need to fatten up your mixture. The small amount of Nitrogen consumed in the endothermic process when combining with unused Oxygen is what gives you NOx. If you're giving up Nitrogen to unused Oxygen, you're giving up power. Power that would be produced by the addition of that combining Nitrogen in its ability to expand rapidly when exposed to high heat.
    You're losing about 10% Nitrogen during a combustion process anyway, why give up more with a poor state of tune? Nitrogen is what drives your engine, not the precisely controlled explosion. The "explosion" is merely a catalyst for heat generation.
     
  5. stangmx13

    stangmx13 Well-Known Member

    the chemical energy for ICE combustion is supplied by gasoline and oxygen. U don’t get more energy from nitrogen. In fact it takes some energy to heat and expand the nitrogen. It’s likely that an ICE running on just O2 and gasoline would be more efficient than one with air and gasoline because that loss wouldn’t exist.
     
  6. tropicoz

    tropicoz Well-Known Member

    All this talk of oxygen and nitrogen and speed and power and yet NO ONE mentions the most critical component....NOS!
     
  7. fastfreddie

    fastfreddie Well-Known Member

    You don't get any energy from Nitrogen itself. It needs to be acted upon to convert it to mechanical energy, or, an action might also convert it to a useless compound for mechanical work but great for fertilizer.

    O2 and fuel alone can't be tested in an ICE outside a vacuum. So, let's say you're in this vacuum...
    What's gonna be there to push against the piston, a momentary but very hot flame? It's not a rocket thruster, it's not gonna push shit. Inert gas needs to be present in order to react, by expanding, to the heat that's generated by your flame for any meaningful pressure to be applied to a piston.

    I won't go on trying to educate anyone, so y'all do some digging on your own...it's the best way to learn.
    If you can explain how it's an air/fuel mixture providing the push on the piston and not the heat from that mixture expanding the real driving force against those pistons, I'm all ears but I'm done talkin'.
     
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  8. rd49

    rd49 Well-Known Member

    It is not heat moving the piston but it is the expanding combustion gases from the air/fuel mixture. By the way how much does air weigh? :D
     
  9. Motofun352

    Motofun352 Well-Known Member

    A small amount of cold liquid hydrocarbons (admittedly in vapor form) combusts (not explodes) with the O2 in the air forming a hot gaseous mixture of CO2, H2O and little CO/NOx. This hot pressurized gas is what does the work on the piston. The cold N2 in the chamber robs heat (and thus pressure) from the burning mixture. It's not much and the N2 does stabilize the burn so it is important.
     
  10. stangmx13

    stangmx13 Well-Known Member

    ^^ yes that.

    its funny that u try to talk down to someone when your point has a big gaping hole in it.

    are u imagining that the gasoline and O2 vanishes or something? combusting gasoline and O2 produces CO2 and steam. both expand tremendously just like nitrogen. those expanding gases will do plenty of work without the presence of an inert gas. assuming perfect combustion with air, they make up about 29% of the exhaust gases (mole ratio). there's nothing inherent in the design of an ICE that would prevent it from functioning without an inert gas to push the piston.

    the Otto cycle's maximum efficiency is solely based on compression ratio. the fuels, any inert extras, the displacement, etc etc do not factor in at all. so let me clarify more. an ICE optimized to run on solely gasoline and O2 would likely get closer to that maximum efficiency than an ICE optimized to run using gasoline and air. N2 is just not necessary and creates loss. loses due to pumping N2. heat lost from the CO2/H2O to the N2. there are prob more losses that I cant think of. And u simply cant beat the 2nd law of thermodynamic, so the optimized case with air MUST be less efficient.
     
  11. fastfreddie

    fastfreddie Well-Known Member

    @Moto...
    Where's all the Nitrogen in this hot gaseous mixture? Did it just step aside to let the flame do the work?
    The stuff you're talking about is what, 8-9 % of the contents within the combustion chamber after combustion? That's not work-producing pressure, it's the garbage remaining after a burn. Do you really think that stuff has anything to do with producing work?

    WTF is the Nitrogen doing this whole time? Remaining at room temperature and minding its own business?
    Hell no! Someone lit a fire under its ass and it got up and moved...but it had no where to go...so it pushed in all directions with extreme amounts of pressure that could only be achieved in an enclosed, high heat induced environment.

    C'mon, man, you're a frickin' engineer. Does a flame have enough mass to move anything? It's a chemical reaction. It needs to act on something to convert that energy into a mechanical reaction. All a flame can do is incite molecules to get farther apart from each other. Since we're talking the molecular level, these momentary heat flashes from the "power stroke" don't have the longevity to act on the pistons in a way that will push their molecules anywhere...we're not melting pistons and cylinder walls in one stroke of the four-cycle process. What's left that can be effectively acted upon to do work and react rapidly to this high heat that's been induced? Inert Nitrogen.

    Let's pretend to do science-y stuff, you know, put things into perspective...
    - Take a stoichiometrically perfect mixture of fuel and Oxygen in a vacuum and ignite it.
    Result: Momentary heat flash and slight pressure development from O and fuel solids partially expanding due to rising heat as they're being consumed/converted to chemical energy...a slight pressure spike.
    - Take that same vacuum, the same amount of Oxygen and fuel, and add four times as much Nitrogen (or any other inert gas of your choice to mimic the atmosphere) to give the heat something to react with that won't be consumed by combustion.
    Result: Momentary heat flash with coinciding extreme pressure development. The same pressure spike would be there as in the first scenario, but completely overshadowed by a pressure wave of rapidly expanding Nitrogen.

    Disregarding the coincidence to reality that the second science-y scenario presents, which scenario moves a piston more effectively, thus proving what is doing the actual work?
    The one that is little more than a fart in an empty room, or the one that's a fart in a crowded and soon empty room?
     
    Last edited: Feb 7, 2019
  12. stangmx13

    stangmx13 Well-Known Member

    u really didnt comprehend my post.
     
  13. Tristan

    Tristan Well-Known Member

    Who's gonna sweep up all the sequins on the ground after this purse fight?
     
  14. fastfreddie

    fastfreddie Well-Known Member

    I wasn't talking to you.
    But you may want to visit my fourth paragraph.
     
  15. Kurlon

    Kurlon Well-Known Member

    If you start with JUST a stoich perfect volume of O2 and fuel, when it combusts the O2 and fuel don't collide and then disappear, they form new compounds, ideally CO2 and H20 if everything burns cleanly. That volume of new gas can expand to do the work you're ascribing to nitrogen. You don't need a vacuum to test this in, a test chamber full of O2 at 14psi will work just fine.
     
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  16. stangmx13

    stangmx13 Well-Known Member

    heres a hypothetical that might make sense to u.

    1. take an ICE in air and run it at WOT. measure how much fuel (and O2) is being used.
    2. seal the intake to an O2 bottle and run it at part throttle so that the same amount of fuel and O2 is being consumed. maybe its at 21% throttle because thats the proportion of O2 in air.
    3. now downsize the engine so that at WOT using only O2, it uses the same amount of fuel as #1 and #2.

    which scenario produces more HP: #1, #2, or #3? ignore issues like knock and blowing shit up.

    #1 def produces more than #2 because it creates higher cylinder pressures. this is what uve been saying.

    #3 produces more power than #1. this is what ive been saying. assuming ideal gas law, cylinder pressures are at least same as #1. but I suspect that they are higher in #3. N2 is compressible, so pressure will rise less with more compressible stuff in the cylinder. and the heat used to expand the N2 must create a loss. so that heat would expand the CO2 and H2O more anyways.

    efficiency is output/input, so lets say its HP/fuel. all used the same fuel. so #3 is the most efficient.
     
  17. turner38

    turner38 Well-Known Member

    Guess what Temperature NOX begins to spike...
    2800F typically, Which is normally around 14/1 AFR and climbs significantly at 14.7 then rockets up when the AFR gets to 16/1.

    Ive always argued the PERCEIVED Stocheometric number of 14.7/1 is misleading, engines are far more effecient at 13.2/1 AFR and you get more power out of the fuel consumed.

    Nitrogen being present in the combustion Chamber doesnt provide much of a benefit. There is just nonway to get the Oxygen there easily without it hitching a ride also.
     
  18. fastfreddie

    fastfreddie Well-Known Member

    Way too much math for me to contemplate at the moment...I might get around to it. For starters, your Oxygen/fuel ratio would be about 2.5::1.
    I get what you're saying, but you're proposing a bomb. The engine would have to be so overbuilt as to make it inefficient due to its own heft...which means it would have to be over-sized to get any meaningful power out of it.
    I don't disagree about the NOx. We're on the same page. Lean is bad.
    I do disagree with Nitrogen not providing a benefit. It's what does the work. You have to have something inert and appropriate for the job (pushing a piston) to convert the heat into a working force that pushes the piston. That the "something" just happens to be Nitrogen, in abundance, is gravy.
    Remove the Nitrogen and there is nothing to be converted into a usable work force. You're just melting pistons.
     
  19. stangmx13

    stangmx13 Well-Known Member

    math? there was 1 number in that post that wasn't even relevant. its all conceptual.

    so now its an engineering problem, that u cant use more O2 because the engine cant be build and/or ud melt pistons?? someone above already said that N2 "stabilized the burn" and no one is disagreeing with that. but that has nothing to do w/ N2 "doing the work". N2 does provide a benefit, but its not doing work. there is no physical requirement for an inert gas to push the piston.

    go watch Episode 3 of Grand Tour. Jeremy Clarkson pipes O2 directly into his engine when driving at very high altitude. theres less nitrogen up there. but guess what he gets from the O2... haha, its a silly comparison because of everything else thats different. but oh wells.
     
    Last edited: Feb 7, 2019
  20. fastfreddie

    fastfreddie Well-Known Member

    It's an engineering problem because you can use more Oxygen...superchargers and turbos being the obvious examples. But we're not using pure Oxygen alone in combination with an appropriate amount of fuel in the the current crop of engine design. You'll just grenade the thing.

    What season for episode 3?
     
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