piston coatings

[Anonymous]

what i would like to know is if you have to allow extra clearance for the piston skirt coatings,and do they work?also what about the thermal barrier coatings for the piston domes ? i`m asking because of an impending rebuild not only on my sled this fall but my bike this winter ,so if it saves a little $$$ over the long run or add`s a few hp i`m interested. i`m asking out of ignorance so thank`s for any input you may have 8) Mark

[Mastiff]

I've done some looking at various coatings for friction resistance and thermal transfer. The web sites I looked at said you don't need to allow for the coatings, they are thin enough to have no effect on clearances.
I was looking at using the friction reducers for the valves stems, bearings and cylinders. I'd use the thermal coatings on the combustion chamber and the piston dome and the valve faces. The makers claim they reduce wear by 2 to 10 times. The possibility of not having to rebuild the engine for the rest of my life, and then leave it to my grandson on top of it, appeals to me. It would also be cost effective. The makers also claim a horsepower increase.

[focus frenzy]

where is the heat of combustion suppose to go??
It has to go someplace??
I have seen some showing up on some new engines, but only on the piston skirt to reduce friction from the skirt rubbing the cylinder.

[Mastiff]

The heat of combustion that is blocked off by the thermal barrier ceramic coating winds up going out with the exhaust gases. The exhaust will be hotter. I would also get ceramic coated headers if I went this route.
There are more than one type of ceramic coating. Some are thermal blockers, and hold heat in. These would be used in combustion chambers and on exhaust headers. Some absorb heat. You would use them on the inside of the block to draw heat out of the oil. Some radiate heat. You would use them on the outside of ths cylinders and the outside of the block to more effectively release heat away from the engine and keep it running cooler inside. Still others are friction reducers. You would use them anywhere in the engine where metal parts rub against each other, such as the piston skirt, the cylinder bore, the crankshaft, the valve stems, etc.
The themal blockers raise the heat of combustion, which raises horsepower. The friction reducers free up horsepower normally lost in the engine, as well as increasing the longevity of the engine. Just my 2 cents.