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Reducing fuel consumption, PS200 Thermal coating

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Cass256

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I like rotary engines, and when I heard about the fabled "Rotapower" engine I had to do some digging. One of the marketing claims of the Rotapower is an efficient coating that reduces fuel consumption - Quite a claim, so I went a little deeper and found the NASA Contractor Report (#195445, which I've uploaded here but you can find it online) of the coating they use, called PS200.

It's a very interesting read, and I highly recommend you check it out if you're interested in the research. The portion that interests me the most comes from the conclusion section on page 8;

1.) The use of a TBC [Thermal Barrier Coating, aka PS200] on the side-walls with an iron rotor reduced specific fuel consumption (SFC) by 8.6%. Using TBC on both the side-walls and the rotor face of a titanium rotor reduced the SFC by 16.1%

16% is a big difference in fuel consumption. This study was done in 1995, when computerized coating tech wasn't nearly as precise as it is today; According to the paper, a more uniform surface than they could achieve would give even greater gains. So I guess these are my questions;

Would adding a thermal coating to a production piston engine achieve similar results? Is ~15% better fuel burn enough to make people consider overhauling their entire engine?
Do you think modern coating techniques could achieve a better uniform surface, maybe even further reduced SFC?
 

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Vigilant1

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Has Mazda done it? This info was available 7 years before the introduction of the RX-8, and these car companies are scrounging for even tiny MPG improvements due to market and CAFE pressure. That was especially the case for the RX-8. Mazda engineers and management would have sold their grandmothers for an 8-16% improvement in efficiency, if it could be had without reliability or maintenance issues.
There's a LOT of hokum in the thermal barrier coatings biz.
 

Cass256

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Mazda engineers and management would have sold their grandmothers for an 8-16% improvement in efficiency, if it could be had without reliability or maintenance issues.
I think that's the real kicker behind any thermal barrier, my guess is they're all somewhat fragile & wear quickly. It'd be nice to see actual data from longevity tests, though
 

rv6ejguy

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I don't think they are applied to any mass produced engine and if the fuel savings were that significant and they were durable enough, I believe they'd be in widespread use today...
 

Daleandee

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I just opened the attached report to read it, but, after seeing who the author is, decided not to waste my time.
I was always taught, "If it sounds too good to be true ... it is!"
 

wsimpso1

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Wankel rotaries do have a LOT of combustion chamber surface area per swept volume, which means a lot of energy loss to the walls. Anything that reduces the losses to the walls can have big effect on thermodynamic efficiency. Trouble is most of that big area is sliding surfaces for seals, so yeah, coatings will get scraped off. Coatings of this sort do work pretty well in Wankel rotors and piston crowns, but the incremental improvements are then small... They are played with.

Anything by Moller is immediately suspect...

Billski
 

daveklingler

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I had the same thought about PS200 several years ago. I did a lot of research on it and got more and more excited. I saw that Moller had noticed it and (surprise) done some grant research, but that didn’t mean much.

One of the lead NASA researchers died a few years ago, and the other one is semi-retired. After many tries, I was finally able to have a conversation with him about using any of the PS series coatings on a Wankel. He told me he thought it would last 8-10 hours, max.

Note that this isn’t a ceramic coating so much as a solid lubricant system, which is pretty different and has a different purpose. You might use PSxx on top of something else.

That’s not to say that there isn’t a ceramic coating out there that would do great for Wankels. It just probably isn’t this one. I think regular old Nikasil is the best I’ve found thus far.
 
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