Bored at work thoughts: With enough octane booster, could you run diesel in a gas engine?

"Sir_Stig: and toxic masculinity ruins the party again." (sir-stig) 04/28/2016 at 15:08 • Filed to: Work thoughts.

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Based On my (poor) knowledge of ICE’s and octane ratings, high octane prevents pre-combustion, and diesel doesn’t work in gas engines because of pre-combustion. If one was to accidentally put diesel in their gas vehicle, would there be a ratio of diesel to gas to octane booster that would work to not require a fluid flush?

dogisbadob > Sir_Stig: and toxic masculinity ruins the party again. 04/28/2016 at 15:16

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I don’t think this would work. The flash point of diesel is too high, and the car wouldn’t start. Also, you can’t accidentally put diesel in a gas engine because the larger diesel nozzle won’t fit in the smaller gasoline filler tube.

SidewaysOnDirt still misses Bowie > Sir_Stig: and toxic masculinity ruins the party again. 04/28/2016 at 15:22

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I think you have it backwards. Upping the octane increases knock resistance which would be handy with a 22:1 ratio like in a diesel, but useless in your 10:1 gasser. All you’ll do is make it more impossible to work. Theoretically you could put gas in a diesel that way...

Sir_Stig: and toxic masculinity ruins the party again. > SidewaysOnDirt still misses Bowie 04/28/2016 at 15:24

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Ah, I see.

Übel > dogisbadob 04/28/2016 at 15:24

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Also, you can’t accidentally put diesel in a gas engine because the larger diesel nozzle won’t fit in the smaller gasoline filler tube.

That’s only a deterrent, people still find ways to make it happen.

Dave the car guy , still here > dogisbadob 04/28/2016 at 15:25

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I’ve seen diesel get into gas cars in another fashion. When the tanker refills a service stations fuels and picks the wrong cap. Happens often enough in both gas to diesel and vice versa for us to see it about twice yearly where I work. It hardly ever turns out to have an easy fix. We see water in the fuel less often than contaminated mixed ones.

HammerheadFistpunch > Sir_Stig: and toxic masculinity ruins the party again. 04/28/2016 at 15:26

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To say nothing of the fact that octane booster is basically meaningless garbage.

Sir_Stig: and toxic masculinity ruins the party again. > dogisbadob 04/28/2016 at 15:26

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you say that, but a coworker managed to do that to a work truck earlier this month.

Why they give flex fuel vehicles yellow gas caps when diesel pumps are yellow I’ll never understand...

Leadbull > Übel 04/28/2016 at 15:30

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RallyWrench > Sir_Stig: and toxic masculinity ruins the party again. 04/28/2016 at 15:31

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Among the other reasons mentioned as to why this won’t work, diesel is too heavy to atomize properly in a gas engine.

SidewaysOnDirt still misses Bowie > HammerheadFistpunch 04/28/2016 at 15:35

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Not really. It’s mostly ethanol IIRC. Overpriced? You betcha. Boosts octane? Yep. Does that too. Does boosting the octane matter (ie will it get you ALL THE POWER and make your VEE-techs kick in yo?). Not usually. It’s only useful if you’re running high boost, have a super high compression ratio, or are driving an old car designed for leaded gas and it’s not for power, it’s to prevent knock.

dogisbadob > HammerheadFistpunch 04/28/2016 at 15:37

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especially if it has MMT which isn’t safe for your engine

MasterMario - Keeper of the V8s > HammerheadFistpunch 04/28/2016 at 15:40

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Most people use it wrong thinking it “adds like 50HP bro” but it can be useful. If you have a car that requires premium, it’s a good idea to keep a bottle in your trunk in case you can’t find a gas station with premium. It doesn’t happen often, but on road trips, in the middle of no where it can happen.

HammerheadFistpunch > SidewaysOnDirt still misses Bowie 04/28/2016 at 15:48

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no...most boosters use MBTE and they do not work.

HammerheadFistpunch > MasterMario - Keeper of the V8s 04/28/2016 at 15:50

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well the trouble is that it wont actually raise your octane, they claim “up to 9 points!” but the fine print is that a “point” has a decimal in front of it. i.e. 9 points! is .9 octane number boost.

AMGtech - now with more recalls! > dogisbadob 04/28/2016 at 15:54

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Tell that to the customers I’ve seen do it.

jimz > Sir_Stig: and toxic masculinity ruins the party again. 04/28/2016 at 16:01

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no, it’s not volatile enough to be ignited via spark.

Sir_Stig: and toxic masculinity ruins the party again. > jimz 04/28/2016 at 16:03

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Ah so I have it backwards then? would there be a way to combust diesel in a gas engine (if only as a percentage of the actual fuel combusting?)

jimz > SidewaysOnDirt still misses Bowie 04/28/2016 at 16:05

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you’ve got that backwards. You basically want gasoline and diesel to behave in almost exact opposite ways. with gasoline, you want to make sure it doesn’t autoignite, so the higher the octane rating the more resistant the fuel is to auto-ignition. With diesel, you want it to autoignite, and the faster the better; so the higher the fuel’s cetane rating, the more easily it autoignites.

adding octane booster (or just straight gas) to diesel fuel in a diesel engine will just make the fuel harder for the engine to ignite; increasing ignition delay which makes the engine lose power and run dirtier. and noisier.

jimz > Sir_Stig: and toxic masculinity ruins the party again. 04/28/2016 at 16:08

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you would have to pre-heat the fuel to where it gets above its flash point. The flash point is the temperature the substance has to be to start giving off flammable vapors, it’s not the temperature where it’ll spontaneously ignite (that would be the autoignition temperature.) The flash point for gasoline is around -25°F, the flash point for middle distillates like diesel and kerosene is about 140°F.

gogmorgo - rowing gears in a Grand Cherokee > dogisbadob 04/28/2016 at 16:08

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Not every gas station uses a high-flow nozzle on the diesel pumps. There was a few years, late 90's, early 2000's, when the diesel vehicles were produced with just standard-sized fill holes. It friggen sucked, cause the full-serve gas station I worked at in highschool only had a high-flow nozzle for filling big rigs. Filling a Duramax, VW, or Smart meant that you stood there holding this massively heavy nozzle for 20 minutes trickling the fuel in and trying real hard not to spill.

MasterMario - Keeper of the V8s > HammerheadFistpunch 04/28/2016 at 20:03

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Haha...I’ve never actually looked closely at octane booster as I’ve never used it, but that doesn’t surprise me. But still, it’s better than nothing in a pinch. Raises your 89 to 90

samssun > jimz 04/28/2016 at 20:14

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Intake charge, especially for a turbo engine, should be say 100 degrees, and as compression occurs it should easily exceed the flash point. Assuming you could get a cold engine started, once it’s running there should be diesel fumes to ignite, right?

jimz > samssun 04/28/2016 at 22:26

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no. you have to be able to put enough energy into the fuel to overcome its enthalpy of vaporization (meaning, the energy to transform it from a liquid into a gas) and get it hot enough to be flammable. the problem with diesel/kerosene is that it carries a lot of energy away just from the phase change (going from liquid to gas) and that makes it difficult to ignite easily. if you’ve ever seen an older diesel engine try to start cold, you’d see a lot of white/blue-white smoke come out of the tailpipe while it’s cranking. that smoke is diesel fuel which got hot enough to vaporize, but didn’t get hot enough to actually ignite. Here’s an example:

SidewaysOnDirt still misses Bowie > jimz 04/29/2016 at 07:16

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Interesting. I figured that the higher compression would make the gasoline prone to detonation, especially with the heat of the combustion chamber in a diesel engine and the glow plugs.

jimz > SidewaysOnDirt still misses Bowie 04/29/2016 at 07:49

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Well, to be fair I was talking about blending gas into diesel fuel. Trying to run pure gas in a diesel has a host of problems, not the least of which is its near total lack of lubricity which would be death to anything with an injection pump or unit injectors.

SidewaysOnDirt still misses Bowie > jimz 04/29/2016 at 08:51

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Conceptually though assuming the ancillary equipment wouldn’t fail, what other problems would you have with increasing gas’ resistance to detonation in a diesel engine? It seems to me like in theorey it could work if you could get it to consistently detonate at the top of the stroke.

SidewaysOnDirt still misses Bowie > HammerheadFistpunch 04/29/2016 at 08:53

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That’s all based on how much you put in. Assuming that it raises it one point per bottle in a 12 gallon tank (usually they measure them for 20), a few of them of them will get you to 93 from 87. My BRZ don’t like 87.

jimz > SidewaysOnDirt still misses Bowie 04/29/2016 at 09:36

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The problem is that the chamber temps under compression in a diesel are far above the gasoline’s autoignition temp, but its resistance to autoignition means there’ll be a delay between injection and ignition. And after that delay its likely the vaporized fuel will detonate. By the time you modify gas to be safe in a diesel you might as well just use diesel or kerosene.