Didn’t that DeLorean already have its own fuel too?
Possibly. But Marty gets there one day after Doc hides it in the cave. It’s likely that Doc drained all the fuel for such long-term storage.
Not only likely, I believe Doc and Marty did have to put gas in the Delorean in 1955. If I recall correctly, they also had to put on a new set of (whitewall) tires.
Yes. Though arguably, they would have had to drain the tank and put new fuel in there regardless. So the scene where they are adding fuel to the car isn’t very conclusive one way or the other. I believe he would have drained it though. He probably made use of the fuel for other tasks over the past 8 months, like heating and lighting.
You know, if you had to achieve a relative velocity to the earth’s surface of 88 mph, you could do it much more easily without a car.
You could just mount the flux capacitor onto a rig lifted by a helium or hot air balloon. Ascend to 10k feet. Disconnect from the balloon. Once you have fallen fast enough to time travel, deploy parachutes once you are in the different time period.
Little risk of materializing in a place where you are about to hit someone, relatively simple and reliable. Pack a few extra balloons into the time travel gear.
Of course, in the universe of Back to the Future, this era has flying cars crowding the skies, so there’s still ways this could go wrong.
IIRC the DMC-12 had a carburetted engine - which means that if the movie car’s engine was fuel-injected, then this was an aftermarket/shadetree modification by Doc, so anything’s possible.
“Fuel injection manifold” is an ambiguous term, anyway. There is an intake manifold which directs air from the throttle body to each cylinder. If the engine has port fuel injection, then there is one fuel injector per cylinder, positioned to spray fuel directly into the intake port of each cylinder, and those injectors are typically supplied by a fuel rail. It’s possible that when they said “injection manifold” they were talking about the fuel rail, but it seems more likely the screen writer was just making up some cool-sounding shit to say.
The penetrations into the intake manifold by the fuel injectors typically are of rather small cross-sectional area; each injector tip (with O-ring) is maybe a 1/2" in diameter, so any intake manifold overpressure due to a backfire event probably wouldn’t generate a lot of force to blow the injectors back out. However, the intake manifold itself is fairly large, and modern manifolds are often plastic; a friend of mine had a backfire event on his 2002 Lincoln LS that actually cracked the intake manifold. But this shouldn’t be a showstopper; if the DMC-12 in the movie had a cracked intake manifold, it would be a simple task to slather on some sort of sealant that should last long enough for one 88MPH run. Moreover, the intake manifold on an early 1980’s car was almost certainly cast aluminum or cast iron rather than plastic; a crack from a backfire event would have been unlikely.
IANAOrganic Chemist, but… from what I’ve read…
Gasoline (and many other petroleum products) are a mix of long chain molecules of carbon, with hydrogen attached to the “sides” of each carbon atom. Methane - 1 atom, ethane -2, etc. The debate above revolves around the fact that gasoline is a specific mix of assorted carbon chains of different lengths. (Hint - octane =8) If the mix is not right, the mix blows up prematurely during compression (like small molecule ethanol did to the manifold), or does not blow up at all or too slow. So it’s not just a matter of getting the source material, it’s a matter of refining it in exactly the right mix. Fractional distillation relies on extracting more of a certain length of molecule by the fact each boils out of the crude at its own temperature. (There’s also, IIRC, cracking which heats the mix under pressure with catalysts(?) to break down the extra-long carbon chains -tar - into shorter, more desirable chains.) Some of the components do not condense conveniently to liquid at room temperature like moonshine does, so a sealed system is better.
I heard the story of someone who decided to go cheap and use (now obsolete) 80-octane aircraft fuel in his car. The premature detonation destroyed the engine in short order.
As others have pointed out, if the 88mph is pushing the limit of the car’s capability with optimum product, the odds of starting from scratch and making anything capable of more than turning over the engine and gumming up the works - pretty remote.
Plus, Doc refining and distilling flammable and explosive vapours using an open flame and home-made equipment - what could possibly go wrong?
The consensus I’m getting here is that the science fiction part of Back to the Future was hitting 88mph in a DMC-12 at all…
that’s why I said “pre-heated.” Diesel and kerosene become flammable at their flash points, about 140°F. at that point it can more easily be spark-ignited. It’d be pretty low in octane number, but the DeLorean’s engine was such a miserable, low-compression piece of shit that it’s possible it wouldn’t care. For a “one run and done” situation, who cares about longevity?
The whole “blowing off the intake manifold” is a stupid movie trope. Detonation tends to crack pistons.
the issue with ethanol in a gasoline engine is air:fuel ratios. petroleum’s stoichiometric air:fuel ratio is 14.5 to 14.7:1. Ethanol’s is ~ 9:1. so if you fuel up a gas engine with eth and don’t adjust the air:fuel ratio, if it even runs at all you’ll be way too lean and asking for trouble.
If a basic crude gasoline were indeed available, it doesn’t seem to be that big a jump to build a basic fractional distillation rig and try to fraction out the octane (as MD2000 points out above, octane is just the alkane with 8 carbon atoms) and lighter alkanes. Cars mostly like to run on a mix of alkanes. One thing we know about octane, is that it has an octane rating of exactly 100. A few cups of passably refined octane (and shorter alkanes) should make the Delorean purr like a kitten. Probably little more than careful distillation would be all that is needed to remove the worst of the longer chains and cyclic hydrocarbons that cause the grief. A whisky still and a thermometer should be all that is needed (plus a lot of care to avoid blowing the entire shebang up.) All Doc needs is to know the right temperature, ant even if he couldn’t remember it - such things were known by then, and and access to a library would be enough.
yeah, I worked with a guy who was a budding mechanic, knew enough to be dangerous. he shaved the heads on his car to increase compression, resulting in “throwing a rod” through the cylinder wall. These mad scientist things where it’s thrown together, works first time, and keeps working throughout the movie, are pretty much fictional.
The PRV V6 was fuel injected. Cite.
Interesting point about the DeLorean the Doc tucked away in the cave to last 70 years.
It’s always been my thought the Doc borrowed Mr. Fusion, the flux capacitor and the time circuits off of it to make his first trip to the future on his steam train to get the permanent parts he needs, so he could then go back to 188x and replace the parts on the DeLorean so they’ll be there when Marty needs them again in 1955 (but then why not just fix the DeLorean’s microcircuits? Well, the Doc had this idea about not changing the STC as much as possible).
That said, why would the Doc drain the gas for long-term storage? Would it be destructive to some internal parts of the car over those 70 years?
When gasoline sits for an extended period the more volatile constituants evaporate while the heavier ones absorb water molecules that are then boiled off when combusted. The result is often referred to as “varnish” and is actually similiar to the acrylic resin component of wood varnish. It will coat valve seats and injectors and harden, forming a solid layer that interferes with fuel flow and seating, as well as lubrication should it slip into the crankcase.
‘Doc’ can’t fix the integrated circuits on the DeLorean from 1985 or 2015 because even if he understands how the circuits function, the technology to fabricate integrated microcircuits and all of the precursor technology to support that (such as making high purity solvents and single crystals from which silicon wafers are manufactured) don’t and won’t exist for seventy years. This is an example of how, even with knowledge of the materials and processes, technologies cannot be reproduced without an adequate industrial base to support all of the supporting manufacturing tools, methods, and materials. He clearly figured out some workarounds because he ended up converting a train into a time machine (and presumably later installing flying circuits) but realistically Brown is clearly in his sixties or later by the start of the first film in 1985 and it seems implausible at best that he could develop all of the necessary technologies to produce even primitive complex logic circuits in the late 19th Century where the technological state of the art is wet electrochemical cells, air gap capacitors, and crude direct current dynamos. To suppose that he could advance the state of both applied electrodynamics and practical manufacture of electrical components by seventy years in his remaining time (all while raising a family and running a blacksmith shop) is unlikely to the extreme. So, really, someone was manipulating things behind the scenes, making it seem to ‘Doc’ that he was discovering the time travel capabiltiy of the ‘flux capacitor’ while really just fumbling about with random components.
I’m seeing a Season 4 crossover of Continuum with the Back To The Future universe here. And it doesn’t look good for the mild mannered Marty McFly.
Stranger
It wouldn’t work. You see, the stainless steel construction of the DeLorean made the flux dispersal… LOOK OUT!!!
You just blew my mind. Heavy.
I think it’s Vern. That kid looked evil-eyed and shifty.
Speaking of, I need to catch up on Season 4…
Another thought about this.
In his 1885 letter, the Doc says most of the components for the logic circuits won’t exist until the 1940s, and proceeds with instruction on how 1955-Doc can build a macro-scale logic board mounted to the hood of the car. Fair enough.
However, he wasn’t concerned about returning himself back to 1985 at the time. He was exceedingly happy to live out the rest of his days in the Wild West. He just needed to tell his 30-year younger self how to build the logic circuits to get Marty back home once and for all. It wasn’t until Marty and 1955-Doc dicovered 1985-Doc’s grave that they decided to change plans and go back for him.
IANAComputer scientist or lab tech, but it seems to me the circuit board would mostly need a few technologies not yet available in 1885. And I’m not talking about making a microchip… only the large-scale version:
Vacuum tubes existed. But I’m not sure about diodes, triodes, and I know the transistor wasn’t invented until the mid 20th century. At this point, I’m not sure what would be needed to be “re-invented” for the Doc to make the parts he needs to make a working circuitboard like the one the Doc builds in 1955. But, at the end of BTTF III, it’s evident that at least 7 to 10 years had intervened between the time the Marty returned from 1885 and the Doc showed up in his time traveling train (since his oldest son, Jules, appeared about 7 or 8 years old).
So, couldn’t the Doc have built the same circuit board he described to his 1955 counterpart, given about that long to reproduce the tech and subsequently crafting his own parts? If he knew how to make a transistor, surely he could work up to making one by, say, 1892?
I don’t see why he couldn’t. Spock made an advanced computer with video display from vacuum tubes while stuck in the 1930’s, so obviously Hollywood old tech is incredibly adaptable.
And don’t forget Scotty making clear aluminum in the 1980s!
You know what’s always bothered me the most about that franchise? In the first movie, when the car needs to connect with the wire to pick up the power from the lightning, why the fuck arrange it orthogonally? Running the wire in line with the car’s travel would have enlarged the window of opportunity by orders of magnitude.
Doc sure loved drama!