"No, refining gasoline is a very advanced procedure using equipment and chemicals that didn't exist yet. There's no way Doc could have figured out the process and built the equipment in less than a week."
Basic gasoline is just a light petroleum distillate. Making a "still" isn't exactly rocket science. Kerosene was already around at the time, and that's also a petroleum distillate, it's just not as light of a distillate as gasoline is.
"Further, early gasoline was very low in octane. Typical compression ratios of early cars with internal combustion engines that used gasoline was about 4:1. The DeLorean would have been at least 8.5:1 and would have detonated so badly it's unlikely the car would have gotten to 88 before the pistons melted or cracked."
You can boost the octane of gasoline with ethanol (the type of alcohol that people drink), which is also obtained through distillation, except you start with something that has a low percentage of ethanol rather than with a petroleum product.
So, he would need to build a still (a blacksmith shouldn't have any problems doing that, since even "hillbillies" do it) and buy some e.g., kerosene and whiskey. Once he has a light petroleum distillate and some ~200 proof alcohol, he just needs to mix them, say, 9 parts light petroleum distillate to 1 part ethanol, and voila, he has some basic "E10" fuel. It wouldn't have the small amount of additives that modern gasoline has (lubricants, anti-rust agents and anti-icing agents) but that's irrelevant for short-term use.
"Even if he completely understood the chemistry involved in fractional distillation of petroleum"
"Fractional distillation" is just basic distillation, which is a very simple procedure. It's how "moonshine" is made, for example (it's also how legal liquor is made). You can do it in your kitchen with stuff that you probably already have. For example, if you wanted to distill some wine to make brandy, pour some wine into a pan, float a bowl on top of it, put a lid over the whole thing, and bring the wine to the boiling point of ethanol. The ethanol in the wine vaporizes at a lower temperature than the water, and it will condense on the underside of the lid and drip down into the bowl, resulting in a stronger mix of ethanol and water in the bowl, which in this case would be called brandy. If you distilled the brandy again, and then distilled the product of that again, and so on, eventually you get pretty close to 100% ethanol. Better stills aren't hard to build, especially for a blacksmith.
"he would have to first build the apparatus and get hold of some crude oil."
He wouldn't need to start with crude oil. He could start with e.g., kerosene, or any other petroleum based oil.
"Further refining of the gasoline would be required to make the gas close enough for the DeLorean to use without causing detonation and destruction of the engine, particularly when pushing the car to 88MPH."
As I said, ethanol can be (and often is) used as an octane booster, i.e., as a substitute for MTBE, which itself is a substitute for tetraethyllead.
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strntz (10790)
2 years ago
I don't understand your point. I never said Doc couldn't eventually achieve creating a couple of gallons of a fuel that would power the DeLorean sufficiently to get to 88 without engine failure. He (likely) had the knowledge, but he didn't have the time.
As I said:
There's no way Doc could have figured out the process and built the equipment in less than a week.
That is the answer, and it's correct.
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MaximRecoil (4049)
2 years ago
"That is the answer, and it's correct."
No, it isn't. All he would need to build is a still, and he's already a blacksmith. That wouldn't take long even for a blacksmith who couldn't work as ridiculously fast as Doc Brown has been shown to work.
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strntz (10790)
2 years ago
He didn't have the time, and that's assuming he knew all about fractional distillation and getting distilled gasoline from essentially zero octane to at least 75 or so (high enough for one blast before the engine knocked itself to death). Since he tried rotgun in the car, it doesn't appear he knew all that much about refining, but of course, that's a plot device he had to try. But still. If he had the catalysts needed to raise the octane properly, maybe, but they didn't exist in that time period.
Ethanol has octane, but almost half the BTU of gasoline. I don't know if a mix of home brew distilled gas and enough ethanol to keep the engine from detonating would have enough BTU to power the car to 88, which could maybe hit 110 with enough time with real gas. Further, would that mix even have a close enough vapor pressure to modern gas to work properly in a fuel injection system it wasn't designed for?
Since Doc thought rotgut would run the DeLorean, it wouldn't appear he knew all that much about fuels.
In other words, he didn't have the time.
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MaximRecoil (4049)
2 years ago
"He didn't have the time"
He did things in less than a day that would take most people days or weeks, such as building those very detailed models of the town in parts 1 and 3. Building a still could be done in less than a day by any blacksmith, let alone one who works as fast as Doc Brown does.
"and that's assuming he knew all about fractional distillation"
That's very basic knowledge relative to what he should know. Distillation is commonly done in labs:
"Distillation is a common laboratory practice used to isolate and purify liquids on the basis of their volatilities characterized by boiling point differences."
https://lab-training.com/laboratory-distillation-process-will-meet-requirement/
The idea that a multi-field scientist like him, who invented time travel no less, wouldn't know about something as mundane as distillation is absurd.
"Since he tried rotgun in the car, it doesn't appear he knew all that much about refining, but of course, that's a plot device he had to try.
Since Doc thought rotgut would run the DeLorean, it wouldn't appear he knew all that much about fuels."
That was just bad, out-of-character writing. The point of this thread is that it was dumb to do that when he should have been able to just make gasoline.
Also, he doesn't need to raise the octane rating to that of modern gas, because you can always retard the ignition timing to compensate for the pre-ignition you'd get with low-octane gas and factory-spec timing. The DeLorean's engine has a conventional distributor so adjusting the timing is easy to do. Also, you can lower the engine's compression ratio by increasing the thickness of the head gaskets (you can make them out of e.g., copper or steel sheet). You won't get maximum power running low-octane gas with retarded timing and/or a lower compression ratio but it should still be able to reach a mere 88 MPH. Even '80s 4-cylinder econoboxes could go faster than that.
Furthermore, as I pointed out in a post I made here about 5 years ago:
Gasoline was already commercially available at the time. It was first sold as a solvent in 1870, and the term "gasoline" dates to 1863. Prior to being marketed as a solvent it was still being made, but it was considered a useless byproduct of making kerosene.
So he didn't even necessarily have to make it himself.
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strntz (10790)
2 years ago
The DeLorean as delivered was notoriously under powered - a joke really. I drove one of my client's DeLoreans about 20 years ago, and while they had a claimed top speed of 110, this very well maintained example could barely hit 100 and that was after about 3 miles flat out. I would imagine if the timing was rolled back to accommodate a lower octane fue it wouldn't make 80, and that's still assuming the vapor pressure of Doc's fuel would work with the injection to keep the mixture somewhat stoich. His plan the last I talked to him was to put in Buick V6 from a Grand National, but I don't know if they had the transaxle figured out.
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MaximRecoil (4049)
2 years ago
Most any car from the '80s could reach 88 MPH, even ones with a lot less power than the DeLorean's V6. I know that I could do 85 with ease in my '84 Ford Escort because I got a speeding ticket in 1992 for doing just that.
When you start getting past about 90 MPH it starts becoming a lot harder to continue accelerating because air resistance becomes more and more of a factor. The DeLorean has a terrible drag coefficient of 0.54, so it doesn't surprise me that you topped out at about 100. There's a big difference between 100 MPH and 88 because of the air resistance factor; it's not like the difference between say, 45 and 57, speeds at which air resistance isn't nearly as big of a factor. That's because air resistance is proportional to the square of the velocity.
"that's still assuming the vapor pressure of Doc's fuel would work with the injection to keep the mixture somewhat stoich."
E10 (10% ethanol) or E15 (15% ethanol) would work fine. E10, and especially E15, can cause damage to older cars in the long term (because of it potentially damaging hoses/seals that aren't made of a type of rubber that's made to withstand it), but that's irrelevant in this scenario.
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