Coating Air cooled pistons

[ptuomov]

How is the heat dissipated from the piston? I thought a majority of it was through the rings. A barrier coating on the top would keep more heat in the chamber (and out the exhaust it goes) there-by the rings wouldn’t be as burdened dissipating the heat from combustion as much. Any coating I think would raise the octane requirement if it’s rejecting heat back into the combustion chamber. Piston squirters also help remove the heat from the piston. I’d be interested in the combo of a coating and squirters as far as power production. Using both would certainly be good for the piston.

The engines that I am running take out a huge amount of heat from the pistons with the oil squirters. In one engine, we ran the computations on what was needed with going from 1.5mm to 1mm rings while tripling the stock power — guess what, a lot of oil flow was needed! This was with Mahle Motorsports NA help.

I’m Johnny come lately getting interested in an air cooled engine, and it seems to me that as long as I have enough octane, keeping the piston, cylinder heads, and valves cool is going to allow for more reliable power. I wonder if some people are coating EVERYTHING in these air cooled engines?

[David Redszus]

I’m Johnny come lately getting interested in an air cooled engine, and it seems to me that as long as I have enough octane, keeping the piston, cylinder heads, and valves cool is going to allow for more reliable power. I wonder if some people are coating EVERYTHING in these air cooled engines?

Race engine development is simple. All we need to do is control temperture and temperment. Mahle engineer, Stuttgart, 1984

What happens to the heat when a thermal barrier coating is applied to the piston, chamber, valves, etc? Where does it go?

In an engine the chamber temperature at 15 deg BTC is about 800F deg. About 30 crank degrees later the
chamber temperature is about 4450F degrees (or higher).

The heat has to go somewhere. The exhaust valve opens about 80 degrees later allowing the combustion heat
to escape, but not before soaking into all available metal and fluid parts. Engine parts are intended to absorb
heat and transfer it to the air, directly or indirectly, through fluids such as oil and coolant.

But while engine component parts are transferring heat, they themselves become subject to overheating. And fail.

The engineering task is to construct a thermal path to allow the heat to escape before damaging vital parts.
This means heads, valves, seats, rings, pistons, walls, spark plugs all must carry some part of the heat load.

Years ago, Mercedes built a complete ceramic engine. The ceramic could withstand very high temperatures without
failure. But the engine was a failure. The ceramics did not transfer heat away from their surfaces and the chamber
glowed like a steel foundry furnace. No fuel could be found that would not pre-ignite prematurely upon entering
the red hot chamber.

It is possible to use temperature indicating markers, either wax or paint, to determine just how hot various
engine parts become.

Remember, even the best aluminum pistons lose most of their strength above 350F deg.
And all dimensions change well before that.

[ptuomov]

Ok but what’s the net effect? Aluminum heads seem pretty popular in octane limited engines, but that’s a general and not a model specific observation.

[englertracing]

Grump and Smokey knew what they were doing, but some of the stuff they were doing was because of 1960s technology .Getting the oil hot might of helped more than anything.After we get the best power out of a motor, sometimes we make a "Hero" pull.Dump the water out and refill with cold water as fast as possible and pull. Usually good for 5 to 10hp.

I dont think that works with all fuels

[Bill Chase]

Might consider looking into a water siphon cooled head. When I was still playing with air cooled single 2 strokes we got some pretty impressive results with that setup on a Yamaha 200cc blaster engine.