Can a 4 stroke ICE be oil-less?

[Stormer]

I have seen descriptions of fully ceramic engines that does not need oil or watercooling. But that is expensive and difficult to machine.

So can you apply a coating (TiN or some other PVD coatings? Or maybe hard chrome coating?) on the cylinder walls and the piston rings made from traditional metall to make it so it does not need oil lubrication? For the crankshaft /connecting rod bearing you can make that a ball bearing or roller bearing either from ceramics that does not need lubrication, or you can make it sealed permanently lubed bearings that does not need external lubrication.

I know some firearms parts and roller chains and so on use DLC coating so it does not need lubrication. But from what i read it has a service temperature of only 250 degree C so that will maybe not stand up to the combustion temperatures?

 

[Lnewqban]

Consider that a very important function of the lubrication film is to remove heat from the surfaces in contact.

 

[Stormer]

Consider that a very important function of the lubrication film is to remove heat from the surfaces in contact.

Is that not the task of the watercooling jacket?

 

[Lnewqban]

Is that not the task of the watercooling jacket?

Yes; the film is the medium through which a great deal of combustion heat goes into the cooling fluid.
It works much better that an empty space, even if microscopical.
Also, many surfaces, like some bearings and stem-guides, don't have direct contact with the jacket.

 

[Stormer]

Yes; the film is the medium through which a great deal of combustion heat goes into the cooling fluid.
It works much better that an empty space, even if microscopical.
Also, many surfaces, like some bearings and stem-guides, don't have direct contact with the jacket.

Well i guess the piston can be cooled by the fuel from direct injection. And ceramic bearings don't need cooling.

 

[jack action]

It depends a lot on how hard it works too.

I remember a few decades ago, there was a contest at a local car show: ""Guess how long the engine will turn without oil." There was an old Chevy and they emptied the oil pan. Everybody put their bets and they started the engine, letting it idling. They got tired of looking at it. The engine was still perfectly idling past the longest estimated time. One of the contest organizer got in the car and revved up the engine: The engine was still happy to deliver! If I remember it well, I think they simply shut it off in the end.

Their error was that, with no load, the engine is extremely resistant.

 

[Dr.D]

Is that not the task of the watercooling jacket?

The water jacket does not get close to the crankshaft or wrist bearing pins, and there is a lot of heat to be removed there as well.

 

[Stormer]

The water jacket does not get close to the crankshaft or wrist bearing pins, and there is a lot of heat to be removed there as well.

As i said those can be roller bearings or ball bearings And i wold think that that does not generate so much heat (because that will mean bad bearing with a lot of friction). And the same goes for the valvetrain. And if you use direct injection to cool the top of the piston with fuel there should not be as much heat in the piston either (i saw this on a 2 stroke direct injection engine where the injector sprays on the piston top and cylinder walls and use their heat to evaporate the fuel bacause of the short time for mixing in a direct injection 2 stroke, and at the same time cool them).

But as i said in the opening question i want to know if coatings on the cylinder wall and piston rings can eliminate the need for oil lubrication between them. And if so what kind of coating will be suitable for this? Cooling is a secondary problem not relevant for this.

 

[Vanadium 50]

Can a 4 stroke ICE be oil-less? Sure. In fact, they can run without oil for the entire life of the engine.

An engine that lasts for 100,000 miles at a mean speed of 20 mph (including idling), a mean RPM of 2000 and a 4" stroke means the pistons will have traveled about 1200 miles. That's a lot for a coating.

 

[pbuk]

Can a 4 stroke ICE be oil-less? Sure. In fact, they can run without oil for the entire life of the engine.

I see what you did there

An engine that lasts for 100,000 miles at a mean speed of 20 mph (including idling), a mean RPM of 2000 and a 4" stroke means the pistons will have traveled about 1200 miles. That's a lot for a coating.

I make it about 75,000 miles:

100,000 miles
/ 20 = 5,000 hours
x 60 = 300,000 minutes
x 2,000= 600,000,000 revs
x 2 x 4 = 4,800,000,000 piston travel in inches
/ 12 = 400,000,000 feet
/ 3 = 133,333,333 yards
/ 1,760 = 75,758 miles

At a guess the difference is the x60 to convert from miles per hour to revs per minute.

 

[Dr.D]

Rolling element bearings are difficult to use in an IC engine unless you use a built-up crank assembly. This is not often done. There is little point to eliminating oil on the cylinder walls if it is still needed on the crank and connecting rod bearings.

 

[Stormer]

Rolling element bearings are difficult to use in an IC engine unless you use a built-up crank assembly. This is not often done. There is little point to eliminating oil on the cylinder walls if it is still needed on the crank and connecting rod bearings.

Split bearings is a thing.

So you can run roller or ball bearings on a single piece crankshaft.

 

[DaveE]

It's always dangerous to argue that "since no ones done it yet it won't work." But, I wonder why Toyota, Ford, Volkswagen, GM, etc. haven't put an oil-less ICE one on the market yet. I'm just guessing that they know more about this than everyone here combined. I don't even think you can get one for a lawn mower.

The question "can you do it?" is trivial; of course you can. The real question is does that design meet it's requirements to succeed in the marketplace.

 

[Lnewqban]

Interesting information copied from a catalog produced by a Japanese manufacturer of ceramic bearings, who also shows applications of this type of bearings for cars, trucks and motorcycles (page 15):

https://koyo.jtekt.co.jp/en/assets/file/pdf/catb1013ex.pdf

 

[Lnewqban]

Here, I have found this interesting article about covering some metal parts of internal combustion engines with ceramic coatings, mainly titanium and tungsten, which differ from the materials and manufacturing methods used in modern ceramic bearings:

https://www.thomasnet.com/articles/chemicals/automotive-ceramic-coating/

I have found nothing on cylinder-piston applications.

 

[Lnewqban]

Well i guess the piston can be cooled by the fuel from direct injection. And ceramic bearings don't need cooling.

Any part that is in contact or close to a combustion chamber needs cooling more intense than the evaporating effect of a few grams of fuel.
With heat comes expansion of the material, which affects the clearance between the parts, which is needed to be kept within certain tolerances in order to achieve good compression without excessive friction.

Your question is interesting, and we possibly will see more of that in the future.
Perhaps it is still too expensive to produce big full ceramic parts, like pistons, and the reliability of current coatings of metal surfaces that must work hard regarding friction, impacts and temperature changes is not optimum yet.

The catalog that I have posted above only shows applcations of ceramic bearings in turbo chargers and some other parts of vehicles, where lubrication conditions are marginal.

I know that, in industrial applcations, they are extensively used for high rpm's turbines and where electrical isolation is needed or where pitting of metal bearings is frequent.

Let's keep researching this interesting subject.

 

[Vanadium 50]

I know there is research in using soot as a lubricant. (Usually it gets mixed in the oil and has the opposite effect). I don't know if it has gotten past the "I don't understand it. This should work." phase.

 

[Vanadium 50]

It's probably also worth thinking about what problem you're trying to solve. It may be theoretically possible to save $1000 in lubricants by going from a $2000 engine to a $10,000 engine, but that doesn't mean many people will do it.