Engine paint question

[Takhli44]

Does a painted black engine run cooler (dissipate heat better) than one with no paint? Air cooled. Flat or glossy? Does a higher surface temp indicate better cooling of internal parts assuming same heat generating conditions internally and air temp externally?

I have always been of the mind that a flat black air cooled engine dissipated heat better but have never tested this and not sure where I came by this information.

[eagle]

G'day mate, i've just been rebuilding a TLR 250 & i've had most of the motor coated by a company called HPC, & have had the exhaust pipes on my Sherco & KTM enduros & 2 TLR coated with there coatings, these coating dissipated heat plus they are quite tough! i find when i ride the exhaust pipes don't seem to get covered in dirt plus they clean up really well!

[Takhli44]

That looks like some interesting coatings eagle, I like the piston coatings. Thanks for the information.

[David Lahey]

Does a painted black engine run cooler (dissipate heat better) than one with no paint? Air cooled. Flat or glossy? Does a higher surface temp indicate better cooling of internal parts assuming same heat generating conditions internally and air temp externally?

I have always been of the mind that a flat black air cooled engine dissipated heat better but have never tested this and not sure where I came by this information.

A higher surface temperature on the same engine means that the internal temperature is also higher
A coating that has a flat black finish may reduce heat transfer from the metal, or may increase heat transfer from the metal, depending on the properties of the coating (the thermal conductivity and the thickness of the coating are the important properties)
Measuring the temperature of the outside of an engine using an infra-red camera can be tricky because to be accurate, the instrument requires adjusting to suit the different surface finishes, and there is no guarantee of getting the adjustment right

[Takhli44]

Thanks David, that pretty well fits with "Relax, nothing is under control."