Will Tier 4 lead to gas tractors again?

[BXpanded]

A lot of forklifts and man-lifts run on diesel as do skid steers.

With the exception of airplanes, the engines in the vehicles you mention are cheap and relatively light weight.

Diesels have heavier parts because of the higher pressures and temperatures experienced by the components. Special coatings on the piston crown reduce the oxidation caused by high gas temperatures. All this adds up to higher costs and weight. NASA had a program to develop a light weight diesel aircraft engine as well as a cheap tubofan) for light aircraft in the late 1990's and I believe it was completed. As far as I know, no engine manufacturer has taken the technology and utilized it in a commercial venture yet.

Excerpt from Continental website:Continental Diesel - Home
Altogether, the some 3,500 plus Continental Diesel engines operated in General Aviation have to date successfully completed more than 3.5 million flight hours. The weight of all Continental Diesel engines 1.7 and CD-135 is identical so that each 1.7 l engine can be replaced by a CD-135 engine.

The need for diesel engines in aircraft is primarily driven by the cost and lack of availability of the 100 octane low lead gasoline used by most FAA certified engines. The diesels use the same relatively inexpensive, Jet A fuel (kerosene) as larger turboprop and jet engine planes. Airports in many parts of the world, and even many US airports do not offer 100 LL as the comparably small quantities used by small aircraft do not make it economically justifiable. 100 LL is also on the EPA's list of targeted materials. Although research is ongoing, there is no really good substitute available at present. Due to the low demand for 100 LL, only about 10 refineries produce it. The price is quite high.

The diesel engines are very expensive. They can be somewhat cost justified by flight schools or charter operations that fly many hours and use large quantities of fuel.

 

[CobyRupert]

Pick up owners with diesels don't operate or use them to what they are meant to do.

Uhhm...that's one way to look at it!

"Doc, my arm hurts when I do this".
"Well, don't do that!"

 

[buickanddeere]

For the price of a reciprocating air certified diesel . A PT-6 gas turbine starts looking attractive .

 

[Jerry/MT]

Excerpt from Continental website:Continental Diesel -*Home
Altogether, the some 3,500 plus Continental Diesel engines operated in General Aviation have to date successfully completed more than 3.5 million flight hours. The weight of all Continental Diesel engines 1.7 and CD-135 is identical so that each 1.7 l engine can be replaced by a CD-135 engine.

The need for diesel engines in aircraft is primarily driven by the cost and lack of availability of the 100 octane low lead gasoline used by most FAA certified engines. The diesels use the same relatively inexpensive, Jet A fuel (kerosene) as larger turboprop and jet engine planes. Airports in many parts of the world, and even many US airports do not offer 100 LL as the comparably small quantities used by small aircraft do not make it economically justifiable. 100 LL is also on the EPA's list of targeted materials. Although research is ongoing, there is no really good substitute available at present. Due to the low demand for 100 LL, only about 10 refineries produce it. The price is quite high.

The diesel engines are very expensive. They can be somewhat cost justified by flight schools or charter operations that fly many hours and use large quantities of fuel.

Thanks for your response. While 3500 engines in the GA markes is relatively tiny, I'm glad to hear Continental is using the technology. Hopefully this will lead to more users as av gas becomes more difficult to obtain. I was a member of the NASA Air Breathing Propulsion Advisory Committee in the mid -90's and we received regular progress reports on this program at our meetings at LERC.

 

[truckdiagnostics]

Would a shorter stroke diesel be able to achieve gas engine equivalent RPMS?

The determining factor is the length of time it takes the fuel to burn. Diesel fuel takes longer to burn hence lower rps. There are ways to cheat like a pre combustion camber.

 

[MHarryE]

Think of the crankshaft as a lever being pressed on by the connecting rod. The further the rod is pushing away from the crank centerline, the greater the leverage or torque. Short stroke high rpm diesel equals poor performance.



Attached is a perfect diesel cycle. Piston reaches top dead center and heat is added (fuel injected) keeping cylinder pressure high until mid stroke. The result is lots of leverage but a controlled burn. In basic terms, heat added at a constant pressure. The Otto cycle (gasoline engine) has heat added at a constant volume (TDC) and that peak pressure drops as the piston goes down. The result is lower torque, and to make up for it add cycles (higher engine speed). It's a simplification but for comparison, a Ford Ecoboost 3.5 has 365 HP and 420 ft lb while the 6.7 Powerstroke has 420 HP and 925 ft lb. both are direct injection. Max power at 5,000 vs 2,800. Remembering the old days and our gas tractors (maybe not so old as we still have 4 gassers around the place) they don't really get down and grunt when we hit a hard pull. They die. Most of our diesels really bear down and pull through.

 

[roadhunter]

I can see it now, the Ecoboost Tractor.

 

[truckdiagnostics]

Think of the crankshaft as a lever being pressed on by the connecting rod. The further the rod is pushing away from the crank center line, the greater the leverage or torque. Short stroke high rpm diesel equals poor performance.
Correct, the reason a short stroke diesel is inefficient is because you need the longer stroke to take advantage of the longer burn time. One needs a longer stroke than the other.

 

[adventure bob]

late to this...
We don't have small fuel efficient diesels because the big three don't make small fuel efficient diesels. They also have problems bringing affiliate diesels to the US because diesels are contrary to big ags position on ethanol. The EPA enforces that political position with anti diesel regulation.
We don't have great bio diesel from algae or other secondary waste sources because diesel doesn't have a great lobby in congress like corn does. Bio could solve several problems all at once: One of the best sources for algae is sewage waste runoff ponds. Turn human waste into bio, since we seem to be pretty good at creating more humans and waste this seems beneficial on many levels.
We don't have electric tractors or good cars for that matter, because Battery technology just isn't there yet. Electric motors however are awesome 100% torque at 1 RPM. Infinitely flat powerband up to the motors physical limitations. When someone comes up with a battery, neigh an energy storage mechanism, to power electric motors for a realistic run time, then well have something.

 

[buickanddeere]

The determining factor is the length of time it takes the fuel to burn. Diesel fuel takes longer to burn hence lower rps. There are ways to cheat like a pre combustion camber.

Actually not . It is the short direction cam timing and the small valves from a small bore/long stroke design that choke of high rpm power due to the engine not being able to empty and fill the combustion chambers .