Thermal Barrier Coatings

[Pat Dolan]

I was just in the process of scraping up the parts to build a Type 4 engine (my first air cooled build in over 30 years!!!!!) and the heads (LN Engineering) come with a baked on thermal coating. I went to their coating applicator (Calico) and they assured me of their performance, but could not as of yet give me any hard numbers on the effectiveness of their coatings.

20 years ago built an ALH that I pushed the limits and managed to melt a piston or two, meant to build it back up with a thermal barrier plasma sprayed onto the piston crowns, but instead dialed back the engine a fair bit to make it street reliable. Have a very different project going on now that I suspect will limit at piston crown temps (not the type 4 gasser, it is going to be a low stress 2.5 litre just for a fun cruiser) so does anyone have any experience, and most of all has anyone got any hard numbers from testing on the effectiveness of thermal barrier coatings? Also, who has what materials applied with what process and by what contractor.

 

[MrBigTruck]

They are effective in keeping the heat in the combustion chamber as opposed to the heat soaking into the piston. When the piston is near the top of the cylinder, there are obviously no exposed cylinder walls to absorb that heat, only the piston crown and the head. The theory is that keeping the heat in the combustion chamber will not only keep your pistons from melting but increase horsepower. I have ceramic coated pistons in the ALH I'm building to swap into a GTI. I had my pistons coated by Swain Tech. Since I had them coated, however, I have started coating my own stuff and have found it to be fairly easy to do. In the future I won't have to send anything out. I also am ceramic coating several pieces for the appearance aspect as well as the ability to keep the engine itself clean. I have a bunch of pics of the stuff I have ceramic coated on my build thread. If you are interested and you can find that thread here:

https://forums.tdiclub.com/index.php?threads/gti-tdi-build.511689/

Here is a pic of a a valve cover and oil filter housing I coated. This particular coating is rated for up to 1800º so it could also be used on exhaust manifolds and downpipes.

 

[Pat Dolan]

"effective" is subjective conjecture. I need actual values for thermal co-efficient and preferrably some measurement data for piston temps before and after treating (that are way beyone DIY level to measure). One project I am working with has been making MMC pistons (FANTASTIC properties) but as it is a 2 cycle, the ultimate thermal limit is ability to cool piston crown and the "bridges" of the exhaust ports.

Most of the coatings I have worked with or made are applied with high energy plasma thermal spray. Are the Swain Tech coatings such or are they painted on and baked (as are Calico)?? What did you go through to make your coatings, and have you done any inside of the engine?