Big hood size, engine optimism ?‍♂️

[eBronco]

Okay fine, but air/fuel ratio is necessarily measured as a ratio of masses because air density is highly variable, so the fuel specific energy is what really matters to the combustion process.

You did say energy density and not specific energy so you were technically correct on that count, but again, it's specific energy that makes the magic happen.

Yes diesel has longer hydrocarbon chains but those chains require more energy to be broken apart to take part in combustion so the net energy gain is lower.

Unfortunately, a portion of the energy in gasoline is lost due to thermal losses. If you could recover the waste heat and turn it in to useful energy, it would make it much more efficient.

I also think we should stop putting hydrophillic ethanol in our fuels.

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[Superds]

This is good nonBronco discussion, maybe if Ford catches wind that we’re not taking about Broncos anymore they’ll release more info on the Bronco.

 

[RupertH]

I think we should stop putting hydrophobic anything in our fuels...

 

[securitysix]

I would be shocked if they offer a diesel. I am actually shocked they finally decided to put one in the F-150.

But, I must have a manual option. Diesel would just be the cherry on top.

Ford at least makes a diesel engine that would fit the Bronco. While they probably won't put it in there, if they did, you'd have an oil burner straight off the lot.

Ford does not make anything that runs CNG straight off of the lot. You can get the CNG prep package on the Coyote, but that just gives you hardened intake and exhaust valves and valve seats. You still need the tank(s), lines, etc., so you're still needing to get aftermarket work done to run CNG, which is just cost added to the purchase price.

Since we're not getting the Coyote in the Bronco (I'd be happy to be wrong about that), that means EcoBoost engines and maybe the 3.3L NA. There's not much out there about CNG conversions on EcoBoosts, and even less info on the 3.3L.

Regardless, I'm not going to be driving an CNG powered vehicle off the dealer's lot.

 

[Stampede.Offroad]

I think we should stop putting hydrophobic anything in our fuels...

??

No gas in your gas?

Or did you mean philic.

 

[RupertH]

??

No gas in your gas?

Or did you mean philic.

Exactly what I said...

Unfortunately, a portion of the energy in gasoline is lost due to thermal losses. If you could recover the waste heat and turn it in to useful energy, it would make it much more efficient.

I also think we should stop putting hydrophobic ethanol in our fuels.

Also, perhaps limit ourselves to fuels that don't have thermal losses.

 

[frinesi2]

Exactly what I said...



Also, perhaps limit ourselves to fuels that don't have thermal losses.

Okay sunshine

 

[RupertH]

I see the problem, I forgot my sarcasm tags...

 

[eBronco]

??

No gas in your gas?

Or did you mean philic.

That was my fault, yes hydrophillic.

 

[JimmyDean]

OK, you opened the can. First, I want to let you know that I am a Mechanical Engineer and I have rebuilt engines, do all my own engine work and have restored classic mustangs.

So, let's get started.

Diesel fuel (DFM, heating oil) is 15 percent more energy dense than gasoline. On the molecular level it’s comprised of more long-chain hydrocarbons. It is a fact that it has more energy in it than a comparable quantity of gasoline and that will never change.

Gasoline (regular unleaded) 114,100 BTU/gal 33.44

Diesel #2 129,500 BTU/gal 37.95

In addition to burning a more energy dense fuel, diesels almost always have much higher compression ratios than their Otto-cycle counterparts. The typical gasoline engine clocks in anywhere between eight- and 12-to-one depending on whether direct injection is part of the equation. But diesel compression ratios on the other hand typically start at 12 and can hit 16-to-one or more.

Of course ridiculously high compression is a required part of the diesel-combustion process. Air in the cylinders gets superheated by pressure, so that when the fuel is sprayed into the combustion chambers it instantly ignites, which is why these engines can operate without spark plugs.

One benefit of these tremendous compression ratios is that the engines can extract more power from the fuel. Not only is this great for performance but it also improves efficiency.

Common-rail fuel injection is a technical advancement for diesel engines as is piezoelectric technology. With these systems very precise amounts of fuel can be sprayed into the cylinders at extremely high pressures.

Aside from all of this, diesel engines also lack throttle plates found in their gasoline-burning counterparts. These air-restricting components cause losses; energy wasted as an engine tries to suck air past a partially closed throttle plate. Diesels have no such restrictions.

With variable vane turbocharging you can alter the amount of boost they provide at different engine speeds. This gives you an even delivery of torque instead of one gigantic lump.

Finally technology like selective catalyst reduction (SCR) eliminates harmful byproducts like oxides of nitrogen. In this system a urea solution is injected into the exhaust stream where it reacts in a special catalyst, breaking up dangerous NOx into harmless nitrogen and oxygen.

The other benefits of diesel is that it is a lubricant rather than a solvent (like gasoline). Generally, the operating temperatures are much lower and a well designed diesel engine can last 2-5 times longer than it's Otto-cycle counterpart. The downside is that the high pressure injection systems are not servicable by most back yard mechanics.

Even with gasoline direct injection, diesel still has more energy than gasoline. That fact will never change. Period.

I seriously doubt Ford will be offering a diesel, but if they did, I would be first in line.

You want to know the real reason people are rejecting diesels? The global climate change / warming crowd. They have made diesel's ugly. I agree that there has been great technological progress with gasoline engines, but those don't change the underlying fact that diesel has more energy and will always be more efficient, especially when towing or hauling.

I don't have time to reply tonight, will do that tomorrow. Also a BSME here, with one of my specialties being in IC engines, the other Nuclear power, but I've been out of the loop there for years so pretty sure my knowledge on that is old tech. Been working in the control valve world as of late however.

 

[JimmyDean]

Unfortunately, a portion of the energy in gasoline is lost due to thermal losses. If you could recover the waste heat and turn it in to useful energy, it would make it much more efficient.

I also think we should stop putting hydrophillic ethanol in our fuels.

all right, this'll take a few hours to write because I am at work.

on energy density, as discussed earlier, gas has more density per mass, whereas diesel being denser has more per volume.

And stoichiometric combustion doesn't care about either. It is looking at a molecular level. (we are looking at ethanol free here, even though that's not what we use anymore, because then things just get fucky…).
And while a single molecule of diesel has more energy than a single molecule of gas, in the refining process you can make slightly more gasoline products than diesel from the same crude. generally speaking about 3:2. which is were the efficiency needs to be compared from (similar to comparing electric cars, the original power source is what needs to be considered, and the energy input to create/transfer that power) And this more than makes up for the increased efficiency by volume of the diesel, as you can make more gas using the same base.

On to the cycle, the theoretical cycles have always had Otto as more efficient, but in practice the diesel cycle won out because of the higher pressures and temps it could be run. But it had to be run at those pressures and temps in order to even function, so the tech to do that was developed and refined as it was needed. Gasoline engines however did not have this restriction, so had a much slower development cycle, only receiving development due to pressures from environmental concerns (and a little from power output concerns). At the same total compression, Otto is significantly more efficient. But for decades, you could not get Otto anywhere close to the diesel compressions so the diesel won out on the efficiency here.

Until recently. increased tech used on gasoline engines has been allowing higher and higher compression ratios. not so high as diesel, where you could be running 18:1 base compression with a turbo adding an additional 3:1 ratio for final cylinder pressures of >750 psig prior to combustion. this more than made up for the 11-12:1 compression ratios in a streetable gas engine, or even the 20:1 on a boosted race engine. Now they are building gas engines with cylinder pressures reaching over 500 psi easily before combustion, even seeing 450psi cylinder pressures on strictly tuned street engines.

This increased in real world efficiency of the Otto cycle, combined with the real efficiency of gasoline over petrol per unit of crude used for manufacture, has gotten modern gasoline engines above diesels in efficiency. And there are still places it can be improved (same with the diesel though).

Now, give me a diesel in a truck, and a gas in my cars, and I'll be happy. But that is more due to how the engines behave differently.

and yeah, I',m a backyard mechanic working on the high pressure oil and injection system on my diesel..it is a PITA, and I had to modify my air compressor to near the point of failure to get it to output 200 psi so that I can do better tests on the system, still doesn't approach the 1500 psi it can see during operation, but the failure are occurring before 300 psi anyways.

 

[JimmyDean]

I'll add, a lot of what you have down is completely correct, there are certain things like the waste heat and throttle body that decrease gasoline efficiencies significantly. But it's not that these problems do not exist on diesels, they've just been worked around years ago. There have been methods designed to utilize some of this, but due to potential risks they have not been implemented, This is also one of the reasons turbos have increased efficiency, they utilize much of that waste heat. Once we see VGTs really make their way to production turbo gas engines we'll see another large increase in efficiencies. another option I've discussed here before is a system to vary the octane rating of the fuel being delivered to the engine. This will not necessarily increase efficiency, but would decrease the use of higher octane fuels at points in the performance curve where high octane isn't necessary, near idle, low boost, cruising, etc.

 

[eBronco]

Jimmy, I think you and I are on the same page. Just remember there can be advancements on both sides of the equation, meaning, there are technologies that are making the Diesel-cycle better just like the Otto-cycle. Pretty amazing that we have so many engineers on this forum. I wonder what makes engineers like the Bronco so much?

So, what is a Bronco? A truck or a car? I consider it more in the truck line, so give me an oil burner.

On turbos, they actually use the waste pressure vs waste heat. If you could come up with a way of using the waste heat (through maybe a mini steam turbine), it would really help the gasoline engines. That would be especially helpful with a hybrid. Just think of all the heat wasted through the radiator..

Oh and diesel is much less volatile than gasoline. That is why they don't use it in airplanes. But I am sure you already know that.

 

[JimmyDean]

Jimmy, I think you and I are on the same page. Just remember there can be advancements on both sides of the equation, meaning, there are technologies that are making the Diesel-cycle better just like the Otto-cycle. Pretty amazing that we have so many engineers on this forum. I wonder what makes engineers like the Bronco so much?

So, what is a Bronco? A truck or a car? I consider it more in the truck line, so give me an oil burner.

On turbos, they actually use the waste pressure vs waste heat. If you could come up with a way of using the waste heat (through maybe a mini steam turbine), it would really help the gasoline engines. That would be especially helpful with a hybrid. Just think of all the heat wasted through the radiator..

Oh and diesel is much less volatile than gasoline. That is why they don't use it in airplanes. But I am sure you already know that.

we used to scare the new guys back my air force days by throwing lit matches into buckets of JP8.

A Bronco is a beast. It's own category, categorically better than everything else out there.

A turbo motor keeps some of the potential energy from being converted to thermal energy, and then it uses that potential energy from the exhaust and transfers it to the intake. On an N/A engine all of that potential is converted to thermal and kinetic, and un-utilized (well, some of that kinetic is technically utilized if your exhaust points out the back of the car...but we're dealing with number so small there I think we can just consider it wasted...)

 

[RupertH]

There are several diesel aircraft options- unless you're talking about turbine aircraft that use JetA. I believe the military replaced JP-4 (old formulation, now they use JP-8, more like JetA with some extra additives) with diesel in tests and it ran fine, but destroyed the engines. I think it's more about the heavies you can't separate as you get closer to the bottom of the column, and the particulates (like sulfur) that were harder to remove years ago.

Hard to concentrate on that now, picturing the world's smallest cogen plant poking out of the hood like a '70s-style blower horn!!

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