Theoretical engine material efficiency improvements
 

This morning I was reading on wikipedia about yield and tensile strength of various materials, and it got me to thinking - there are plenty of materials out there which have different properties, which might lead to lighter or more durable or more efficient engines.

Surely most of manufacturing is what it is because of cost and complexity reasons, but I'm curious just what could be produced if cost were less important, or not important at all.

I considered briefly a block sleeved with a titanium alloy. While it likely wouldn't be any stronger than a good steel, titanium weighs less and its thermal conductivity is very significantly lower. In a reciprocating piston engine, is it not the case that the less heat is lost from the cylinder, the more of it can be made useful? Ceramic might be another contender here.

I've read of manufacturers using magnesium to save weight in certain components - e.g. Honda's use of it in transmission cases and oil pans. Reading about its properties leaves me confused, because it appears aluminum is stronger at a given weight, magnesium is just lighter at a given volume. Or, in other words, the same transmission case made out of magnesium would be lighter, but you could make a stronger one with a given weight with aluminum if you were clever with your design.

I'm not sure what properties make for more durable and lower friction bearings, but my guess would be a combination of hardness and Young's modulus.

This is not even getting into the more exotic materials one could make a chassis out of, of course, or things like superconductor wiring.

Polimotor experimented with a plastic 2.0L Ford engine years ago:


https://youtu.be/d3m6snKelAM

https://thekneeslider.com/plastic-en...ne-interested/

and more recently:

https://www.permatex.com/permatex-pa...ngines-future/

When someone says magnesium referring to structural parts ("mag wheels" etc.) they always mean an alloy. The particular alloy is probably stronger and lighter than a more common, lower magnesium, aluminum alloy. Magnesium content is usually between 90% and 98%, aluminum content 1% to 8% But some aluminum alloys are also called magnesium if they are high in magnesium - the alloy Magnalium is 5% magnesium
-mort

Pure magnesium has a nasty tendancy to "burn" furiously once ignited unlike most other metals.

When I was a kid I converted a Microbus from 6v to 12v; the VW 12v flywheel is bigger such that the transmission bell housing on a 6v car needs to be clearanced. I got out the grinder and thought gee, these sparks are HOT. Magnesium.

I believe one of the Japanese manufacturers was working on this back in the 90's. Engine was supposed to be half the size, less than half the weight and a lot more effiecnt(much less heat loss). At the time the ceramics were way to brittle and kept breaking. Maybe the problems were never resolved.

Self-Insulating Ceramics Could Replace Metal in Car Engines
Sudden temperature changes, the classic weakness of ceramics, are no problem for these high-strength materials

From PopSci:

By Jeremy Hsu March 22, 2010


METAL CASTING

New ceramics have the ability to resist sudden temperature changes, just like metals

EPA

Metal alloys have served as the proverbial backbone for car engines and jet turbines alike because of their high strength and ability to resist sudden temperature changes. Now a lighter, cheaper ceramic material that also resists temperature changes may become a viable replacement for expensive metal, according to New Scientist.

Most hot ceramics will fracture and crack if dunked in cold water, because the material contracts too quickly. But the Chinese Academy of Sciences in Beijing has come up with a new family of ceramics that wrap themselves in a buffer layer of insulating air, which protects against the sudden temperature changes.

The new ceramics held their strength even after reaching temperatures of 5,810 degrees F and then being quenched in cold water.

Chinese researchers created the self-insulating ceramic by roughening the surface with plasma etching and acid treatments. The ceramic surface ended up with repeating fin shapes similar to the nanoscale patterns of lotus leaves -- a hydrophobic surface that repels water. The roughened surface also traps pockets of air that become the buffer against sudden temperature change.

On the other hand...
JJ

The real trick isn't using a different material to allow higher efficiency, it is to also be able to produce them at a reasonable cost.

Unless you are doing a theoretical, money is no object exercise.

Valid point

Heh.

If I have my history correct, 25hp VW engine cases were 'aluminum', then the went to 'magnesium' with the 36hp vevision and finally Type IV and aftermarket cases were aluminum again.

What the question reminds me of is that rotary engine seals were either cheap and low-mileage or expensive and lasts-forever. There's an opportunity for a cheap but lasts forever solution.

The other thing is additive manufacturing. Even given the gamut of alloys and plastics, being able to integrate them at the mesoscale at scale means metamaterial alloys with programmable features.

Printing a bronze bushing in a steel bracket is only the beginning. Object with a solid skin and Voronoi cell infill will be superinsulative, and light.

Inserting different metals for the crystals within a structure?

The plastic in question was Torlon, but all I’ve found(back when I had an old Ford 2.0) was that it was significantly lighter than even aluminum and the engine was made mostly from it except the rotating assembly and made some pretty big power for a normally aspirated engine...

If we could get Ti sleeves at the same hardness as steel, but save weight and have lower thermal conductivity, put them into a Torlon block... don’t get me wrong, we’d have a half million dollar engine but it would be remarkably efficient and powerful for its capacity...

Weaving crystalline lattices into a composite alloy?

My car already has a plastic valve cover and intake manifold. The dipstick is made from carbon fiber, the oil pan, magnesium. These materials seem to hold up just as well as their metal counterparts and save weight too.

One idea I'm surprised didn't take off sooner is the offset crankshaft. That seems to me really low hanging fruit for efficiency.

Crank offset has been around for 100 years; I don't know the pros and cons of it or why or how much it is implemented.

It started going into a lot of mass production engines in the mid to late 2000's. My understanding is that the forces on a piston are highest during the power/expansion stroke, so by improving the angle during that stroke you can cut internal friction pretty significantly. It also saves on piston ring and cylinder wall wear.

It doesn't show up in a lot of high revving engines, or those in luxury cars. My guess is that it's harder to balance, if that can be done at all.

Old Tele Man already brought up the old Polimotor.
 

But truthfully, the majority of the current materials work is not in making the engine that much lighter or the reciprocating mass lighter, it is reducing friction and heat loss. Those are what help you gain efficiency.

Ceramic coatings are already common and have improved to the point they are used in race and production environments. Simply coating the piston heads and combustion chambers of an engine gain several horsepower with no other changes if detonation is controlled. Coolant temperatures also go down.

I worked with a project where the wet cylinder sleeves of a Cummins diesel N14 were replaced with ceramic sleeves. Engine power increased by almost 20 horsepower with no other changes and engine coolant temperature decreased. Problems with piston ring life and wet cylinder sealing are still being worked on.

The single biggest contributor to internal combustion engine friction is the cylinder walls and piston ring interface. Material make up of the ring face as well as the cylinder surface can gain horsepower.

A practical engine we had prepared for the AutoXprize utilized heavily ceramic coated combustion chambers and piston domes. The piston rings had an exotic plasma coating as well as the iron cylinder liners. This reduced the ring to cylinder wall friction considerably.

None of this is so exotic and costly that it cannot be implemented today.