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I saw Mad Max: Fury Road this weekend, its an incredible film that relies heavily on storytelling through visuals. A lot of the film is open to interpretation but what I want to know is:

When fuel is being spat into the engine I want to know if that would actually do anything. In the film it significantly increases the vehicles' speed. Now I'm not a mechanic, but I would like to know if there is any real-life truth to this. And if there is... how exactly does it work?

  • Petrol is fine in your mouth. If you've ever had to use a hose to syphon gas, you've probably had it happen. However, you have to be extremely careful not to swallow it. Other than that, I think the above comment is pretty much on-target from what I know, though I'm no mechanic either. – Johnny Bones May 26 '15 at 17:09
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    I, too, am not a mechanic. ;-) But I'm pretty sure those were air intakes, not exhaust pipes. I thought they sucked air in to cool off the engine. – BrettFromLA May 26 '15 at 17:12
  • Yes, those are air intakes and petrol wouldn't kill you. I'm also not sure it was petrol...may have been pure alcohol or the like. – DA. May 26 '15 at 21:40
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    @BrettFromLA they're not to cool the engine (that's what the radiator is for) but rather to 'feed' the engine. Just as it needs fuel, it needs oxygen. The more fuel, the more oxygen it needs. – DA. May 26 '15 at 21:40
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This question is likely better asked over on https://mechanics.stackexchange.com/

My non-mechanic understanding is that, first of all, most of the vehicle accouterments in Mad Max are mainly there for show rather than practical purposes.

That said, what the warboys are spitting into are the air intake valves. This is what feeds the engine its combustion oxygen. When they show above the hood, they are often air ram intakes and/or part of a supercharger.

The more oxygen the engine can 'eat' the more fuel it can also 'eat' and therefore increase output. My guess is that the spitting of fuel into the intake is to replicate adding fuel via fuel injection. It's obviously more dramatic to do it manually while riding on the hood in the middle of the desert.

In addition, my guess was that it wasn't necessarily gasoline they were spitting in but perhaps pure alcohol.

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    I am a mechanic and can say you are exactly right: there is no real work equivalent. What they do in Fury road is almost entirely there for show rather than practical purposes. No one should worry about this ... it happens all the time in the movies. Even the original Mad Max with the switch button "on" for the roots style blower is completely fictitious and cannot work that way in real life. It absolutely adds to the drama though. – Pᴀᴜʟsᴛᴇʀ2 Sep 5 '15 at 15:35
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Note that I am no mechanic, and I do not recall specifically the lead-up to that scene in the film, but I do know that there is such a thing as "water injection" which is really methanol+water injection (or humorously "meth injection").

I think the idea is that the methanol is higher octane (or rather increases the fuel octane, slowing detonation) and the water plays some role in cooling the fuel-air mixture enough to prevent premature detonation, which leads to some minor efficiency boost.

I think that these systems are banned in racing sometimes, probably because if they fail to cool things down properly, and the engine is tuned up to work tightly with them (for racing/max performance), then you get what some folks describe as an "engine grenade."

Presumably the vehicles are (at least fictionally) using the hood scoop to grab cool air and funnel it into the carburetor, and so they are doing the equivalent of wiping the sweat off the brow of the surgeon in a melodrama.

Beyond that, I don't know if the specifics of what they are doing adds up (there are several places in the engine chain to inject the water), nor do I think they tell us what the fluid is. 160-proof Methanol or ethenol would still be distasteful, but probably more pallatable than gasoline.

further reading here (4. Pre Throttle Body/Carburetor Injection) and here

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    There is nothing fictional about the hood mounted air intakes. They are a regular sight at drag or classic car meets en.wikipedia.org/wiki/Supercharger They are also awesome! – Gusdor Jun 12 '15 at 8:56
  • "Fictionally" means that the intakes are not actually functional on many of the vehicles used in the making of the movie (i.e. they were props). – Yorik Jun 16 '15 at 15:07

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