Why diesel?

"The Opponaut formerly known as MattP123" (mattp123) 10/27/2013 at 22:03 • Filed to: None

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Hello jaloppo kinfolk! I am doing a persuasive speech on why diesels make sense. Can anybody think of any quotable sources that provide some good stats and opinion from an expert? I'm guessing magazines might be a good place to start, but I can't think of any articles off the top of my head.

KillerRaccoon - Group J's Sébastien Loeb > The Opponaut formerly known as MattP123 10/27/2013 at 22:05

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Why diesels are good.

Nibby > The Opponaut formerly known as MattP123 10/27/2013 at 22:08

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"Diesels sound badass and they provide gobs of torque over their conventional gas-powered brothers. This allows for more towing capacity while also returning better fuel economy." - Nibby, Jalopnik Gold member.

JayZAyEighty thinks C4+3=C7 > Nibby 10/27/2013 at 22:12

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Umm I'm a diamond member... Gold is so 2012!

Demon-Xanth knows how to operate a street. > The Opponaut formerly known as MattP123 10/27/2013 at 22:13

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During mountain towing a 6.0 Chevy dually gets half the MPG of a duramax while not performing as well.

Aaron Brown > The Opponaut formerly known as MattP123 10/27/2013 at 22:13

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I consider diesels to be better for a few reasons. Torque, emissions, fuel economy, and everything that came out of this episode of TG .

The Opponaut formerly known as MattP123 > KillerRaccoon - Group J's Sébastien Loeb 10/27/2013 at 22:15

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I already tried the Google chief. We already know the pro's of diesel. I'm looking for real data to back up those statements. Like has any magazine done a comparison of a diesel vs. gas version of the same model? Anybody credible calculated the carbon footprint of a diesel vs an alternative of similar fuel economy in it's class? Has a Top Gear host said anything memorable about a diesel?

The Opponaut formerly known as MattP123 > Demon-Xanth knows how to operate a street. 10/27/2013 at 22:21

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Has this been published anywhere credible?

TheD0k_2many toys 2little time > The Opponaut formerly known as MattP123 10/27/2013 at 22:22

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Rolling coal duh!

Lol jk

Demon-Xanth knows how to operate a street. > The Opponaut formerly known as MattP123 10/27/2013 at 22:27

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First hand experience with my family. Their 4WD diesel duallies get about the same MPG as my 2WD Dakota when empty too.

The Opponaut formerly known as MattP123 > Demon-Xanth knows how to operate a street. 10/27/2013 at 22:32

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Interesting. I'll scour the webernets to see if any magazine has done a similar test.

tromoly > The Opponaut formerly known as MattP123 10/27/2013 at 22:47

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The Diesel cycle is more efficient that the Otto (gasoline) cycle, I want to say something like 5 percent more efficient. Diesel fuel is more "crude" than gasoline, i.e. doesn't take as much refining from crude oil to make the fuel, therefore takes "less" energy to make a gallon of diesel fuel (though not a huge amount of energy saving).

GhostZ > The Opponaut formerly known as MattP123 10/27/2013 at 22:50

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Diesel energy density.

Diesel RON: 15–25 (from wiki) http://en.wikipedia.org/wiki/Octane_ra…

This means it takes very little energy from compression to make diesel burn, and once it does, it produces slightly more power for the same fuel.

It's flammability limits are also wider and better, with a higher flashpoint and a lower autoignition temperature.

http://en.wikipedia.org/wiki/Flammabil…

This means that unlike a gas engine, which has to run a very narrow band of stochiometric ideal Air/fuel ratios, Diesel can run at a much wider variety of air/fuel mixtures and still burn. So a turbo can throw tons of air at a diesel engine without worrying about it overheating (run extremely lean) and a tractor can ignite lots of diesel without having to use lots of heat and compression (which would wear down the parts more).

The reason Diesels provide more "torque" is because of the nature of the 2 stroke cycle. Since the engine fires every other stroke instead of every 4 strokes, the output RPM for a diesel engine is halved. That means that a cylinder at 5000rpm in a diesel engine incurs an explosion at the equivalent of 10000rpm in a gas engine. This lets them run at higher "effective" RPMs than gas engines. Rotary engines are like this too.

However, HP comes from torque conversion over a distance. To keep moving, a certain amount of torque is needed, but to keep moving quickly beyond that threshold, you need to be able to maintain that torque while spinning a longer and longer distance in the same time. Gasoline engines use gear reduction (transmission, differential, tires, etc.) to achieve this.

This means a 5000rpm engine with 400 ft/lbs will perform like a 10,000 rpm engine that only gets 200 ft/lbs of torque, but that the car with 400 ft/lbs can resist twice the added weight that a car at 200 ft/lbs could. Of course, if the weight of the cars are the same, that means that the 400 ft/lbs car will need twice as much grip to keep all of the power to the ground. The myth that torque = acceleration is only partially true. Insufficient torque will sap acceleration because it reduces how quickly you can overcome inertia.

This is why a diesel engine is better for a car that needs high miles-per-gallon, runs extremely lean without overheating, does not have to rev very high to make good torque, isn't super sensitive to the air/fuel ratio (which important in extreme conditions where air can thin, get cold, or dirty) and doesn't need to waste power to get combustion very quickly.

desertdog5051 > The Opponaut formerly known as MattP123 10/27/2013 at 23:09

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A couple of sources for you.

http://www.autoblog.com/2013/06/30/new…

http://www.businessinsider.com/10-reasons-why…

The Opponaut formerly known as MattP123 > GhostZ 10/27/2013 at 23:31

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That's actually pretty good and might be useful in my speech. Don't take it the wrong way, but could you be considered an "expert" that my professor might let me reference? Engineering or physics background?

GhostZ > The Opponaut formerly known as MattP123 10/28/2013 at 00:04

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I've dabbled in some physics, but I'm more in the rounds of marketing things other people invent, so I'm not an 'expert'.

Here's a source you can cite however:

http://solvents.americanchemistry.com/Health-Safety/…

You can also look at emissions data from the EPA. Schools love the EPA, and most of their data is widely available.

twinturbobmw > The Opponaut formerly known as MattP123 10/28/2013 at 00:12

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Try looking up some Audi TDI stuff. They like to brag about their diesels.

Harrycarry250 > GhostZ 10/28/2013 at 00:32

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Wonderful explanation!