I was searching for information on Thermal barrier coatings from SAE, and purchased 1 paper. The problem is almost all the only info I can find on TBC's is on diesels, mostly low heat rejection deisels, which I think isnt similar enough to a gas application to get decent information from.

Rich or anyone found any papers that would more suit our 4s or 2s performance engines in regards to TBC's?

Like you, all the SAE papers that I've seen address thermal coatings have been diesel specific. There is a paper that looks at a Chromium/Nickel based coating for piston crowns but not as a thermal coating, but as a way to toughen up the crown for ragged edge tuning. It's pretty interesting and worth a read.


SAE paper # 900453 Nickel coated pistons for improved durability in knock control engines

Abstract:
Gasoline engines achieve maximum efficiency when operated at the knock limit. Knock control ignition systems enable an engine to operate in either continuous or intermittent light knock. Laboratory research has indicated it is harmless to run an engine within this range. Experience with knock control engines in passenger cars has shown erosion damage on pistons. Typical examples of knock erosion damage and ways of influencing severity of damage are discussed.

Nickel coating has been developed as an effective and reliable technique to protect pistons from combustion knock erosion. Additional benefits of nickel coated pistons include: reduced piston deposits, increased wear resistance in the top groove, and reduced cylinder head temperature.

Engine text results and an analysis of engine efficiency increase due to nickel piston coatings is also presented.

If Sean Hilbert or Phil McDowell from Cobra ( and REV! ) sees this they can shed a lot more light on this. They worked with this type of nickel based coating in the high end shifter kart arena. I'm sure Dave "Doc" Montgomery from Bombardier has some thoughts as well.

The thermal coatings seemed to fall out of favor a few years back. I heard various reasons why like ring related problems (the heat energy has to go somewhere) and lower volumetric efficiencies from increased intake/cylinder temps .

The testing I heard about that Poeton was doing with F1 teams lead them to conclude that the coating didn't provide enough advantage to make it worth the cost and trouble. Unfortunately the interesting testing done in F1 camps rarely gets published, so it seems we are stuck with rumors and poorly documented tests at best.

damn, I hate that

I got SAE paper # 970204, Coatings for improving engine performance.

By the title I hoped it would be on SI engines, but was on single cylinder low heat rejection diesel.

ABSTRACT
Thermal barrier coatings are becoming
increasingly important in providing thermal insulation
for heat engine components. Thermal insulation
reduces in-cylinder heat transfer from the engine
combustion chamber as well as reducing component
structural temperatures. Containment of heat also
contributes to increased in-cylinder work and offers
higher exhaust temperatures for energy recovery.
Lower component structural temperatures will result in
greater durability. Advanced ceramic composite
coatings also offer the unique properties that can
provide reductions in friction and wear.
Test results and analysis to evaluate the
performance benefits of thin thermal barrier coated
components in a single cylinder diesel engine are
presented. The procedure includes the performance
testing of a reduced cooling partially air gap insulated
metal baseline engine, a coated cylinder liner build
and a fully insulated build where the cylinder liner,
piston top and cylinder headface are coated with a
thin thermal barrier ceramic composite material.
Test results indicate that coatings on the cylinder
liner bore produced a reduction in fuel consumption
while coatings on the piston and cylinder headface
surface were more effective in reducing heat rejection.

I have also heard rumors about ring life suffering, but that dosent make sense to me if the coating is doing anything to reflect heat away from, and therefore entering the piston. If cylinder walls are treated preventing heat transfer, I could see problems.

Taking info from the paper I read (effectively making it rumor), TBC's do definatly effect heat transfer into the piston. The paper refers to a pistons "thermal impedence" and its reactions to TBC's, noting that the TBC treated piston had a surface temperature that more closely followed the 4s cycle temperatures, cooler on intake and hotter during combustion, compared to and untreated piston. Cylinder pressure charts show that that caused a problem and theorized that it was caused by delayed ignition of the diesel charge due to cooler piston and associated compressed charge temps.

While the paper showed that it did nothing to improve performance of the diesel, it adds to my SWAG that it could help a SI engine or more specifically a 2s by reducing intake charge temp. But then again I dont know.........

I would love to hear from Sean re: this topic, his responses are always worth reading a few times.

It makes sense to me. Normally the piston crown and cylinder head would work as a heat sink. If a coating were to work effectively there would be additional heat rejection through the cylinder walls. With the rings working as a heat transfer conduit between piston and the cylinder wall, it's seems possible that the rings could see additional heat and possibly fail prematurely. The coatings I've played with have never been effective enough to be able to determine this on my own. Lack of proper resources have left me at the mercy of what's published, and in this case it seems as though it's lacking for our purposes.




It's usually required too. It usually takes me a few practice laps through his stuff to really grasp it completely.

So the thinking is, that the cylinder walls see the heat not absorbed by the piston and dome, and the rings in turn ride on the heated cylinder.

*But* the cylinder would enjoy the extra time (relativly speaking) and cooling of the intake charge before the rings see the same area of cylinder wall, and the rings will theoretically have less heat to transfer from piston side to the cylinder. Again just guesses

speaking of practice laps, I have been rolling the Blair 2s track, I cant tackle the tripples yet.