n468ac

n468ac

Well Known Member
http://www.swaintech.com/

So today I?m walking over to another building in our complex and I run across one of our neighbors. His hobby is racing classic and custom snowmobiles; his shop has a very impressive collection. So I stop by and ask him about ceramic coatings, our hanger neighbor coated his RV8 but yet has to fly and has really sparked my interest in this technology. Too my surprise he shows me ceramic coated pistons, vales, the dome on the heads, and exhaust systems for 2 and 4 cycle engines. He claims on the pistons that have been coated he hasn?t been able to burn a hole in one yet! On the exhaust he sees 30% to 50% reduction in temps. He didn?t think that it increased performance ? just reduced temps in the engine and under the hood. So after talking awhile he recommended Swain Technology, I gave them a call ? they were nice, but they don?t want to touch anything with aviation on it. Can?t blame them, I?m sure the insurance company has something to say about it (sometimes I think the insurance companies really run the world ? another rant for another day). They were nice enough to say if I sent them an exhaust system that didn?t ?look like? it came off an airplane they would coat it. They didn?t want to make any claims on durability or temperature reduction, as they didn?t work in the aviation field.

Has anyone tried ceramic coatings? Did it help reducing temps? Did it just flake off within a few hours?

Just thinking out loud ?
 
I know a couple of guys who had their Rotax exhaust pipes done with 'Jet-Hot' coatings. Still look new after more than 5 years. You can check them out at
www.jet-hot.com
 
Cradin Technologies, in Boerne, Texas coated my exhaust and intake tubes. They are aviation friendly and the owner is an A&P and does a lot of aircraft coatings, including internal engine parts.
Since I had it done from the beginning, I can't tell if it improved anything or not. I like to think it does.
 
Ceramic Coated Exhausts

Just listened in on a conversation about this recently. Seems there may be evidence that the coating keeps heat inside the pipe and can then burn exhaust valves. Would be good to hear input from someone with the expertise in this area (long term). :rolleyes:
 
.....just what I heard.....

RVadmirer said:
Just listened in on a conversation about this recently. Seems there may be evidence that the coating keeps heat inside the pipe and can then burn exhaust valves. Would be good to hear input from someone with the expertise in this area (long term). :rolleyes:
Click to expand...

Ditto RVadmirer, but it's what I heard in a conversation between other aviators. Might warrant more investigation.
 
Not an aircraft

Chris,

Remember, when dealing with outside vendors, you're not building an aircraft, you're building a "dune buggy".

Tracy.
 
coatings

Go to VAF home page, scroll down to vetterman on left side and click to see what he thinks about coatings or wraps.

Bill Woods
RV 8 QB
 
Thinking out loud ...

Maybe ceramic coatings are good for racers ... short time, high power, high fuel flow.
 
There is a very long history of coating in the racing world. Not a big history of aviation use, excluding turbine components that is.

My neighbor had his IO-320 in his Lancair coated by Lycon a few years ago. His motor is modified and puts out 190hp and Lycon said it was the "coldest" IO-320 they had ever run on their dyno. I think, ECi is starting to coat some of their pistons, so inroads are being made. I had my pistons coated, and am still waiting to get the exhaust and cylinders done (my choice no problems) by Cradin. It is not that expensive and I think well worth it to keep the heat out of the engine. A few hp is nice, but not the primary goal.

The only downside of coating, in my opinion is that it must be done by a professional shop with a good history of it. If it is not done well, the coating could peel and those bits that come off would be a very hard abrasive and do a good job of tearing up a cylinder.
 
Talk to the Man!

A few years back I spoke to Larry Vetterman about having this done to my exhaust as I had done it on the header in my track car with good results.

Larry had two comments, the ceramic coating may cause the the exhaust to crack due to different expansion rates.

More importantly, he said that exhaust works as a heat sink to draw heat away from the head and by adding the coating you reduce its ability to do that.

I have no idea if this is true or not, just repeating what he told me.

This would be on a completly stock engine, no ceramic coated pistons or other internals.
 
Ceramic coated naturally

Interesting fact.

Why do new Lycs run hot during break-in? You could say they're tight during break-in, but the biggest reason is the combustion chamber, piston top and valve face have no carbon coating (from combustion). After many hours of operation, the carbon coating acts like a ceramic coating! Cool (pun intended). I wounder if the pipes get their own natural "coating" from the carbon deposits.

Vetterman's assertion that ceramic coating causes valve and exhaust pipe problems is interesting, but it would be nice to prove it.

The heat sink affect of the head by the pipe...never heard of that. Could be? Would you not notice higher CHT. Is the valve temp and CHT related? Could we not do a before and after and not CHT? Would CHT difference not show up?

External coating only on the pipe might keep the heat in the pipe, not transferring or shedding to the air.

What about just an internal pipe coating. That should keep the heat out of the pipe, but just increase it down stream.

If you are using high quality 321 SS you should have less cracking issues if the basic design and construction of the pipes are not deficit, coating or not, is my opinion. 304 SS does not have the same heat fatigue quality. Vetterman does use 321 tubing.

Wraps and coatings likely add more thermal STRESS to the pipe; Cracks, in my opinion occur from the mechanical shaking, poor support-installation, poor or no slip/flex joints-design and poor welds-manufacture. Stainless is not easy to weld properly. NOT SAYING Vetterman's product is less than outstanding, but in general these are causes of cracks.

If your pipes have a weakness in any area, coatings and wraps are likely to make it worse. Aircraft is pretty demanding and its flight safety. If your pipes fail, hot exhaust impinging on the fiberglass cowl or systems could cause serious grief.

Here's Mr Vettermans input with two comment's I added:

Can I wrap my exhaust with automotive type of wrap material and obtain more power?
Any material on the exhaust will shorten it's life and failure will occur. We are using air cooled engines and one the best heat sinks on the engine is the exhaust system. The mass air flow comes in and is forced down and around the cooling fins and then is directed over the exhaust system and then exited out the bottom. If the exhaust is covered it cannot aid in the cooling process. Our tests show that any type of wrap on the exhaust makes both the cylinder head and exhaust temperature run higher. (how much) The stainless steel used (type 321) will degrade if the surface temperature is over 1250 degrees F. We also did not find a power increase of any kind by wrapping the exhaust.

How about ceramic coatings?
The jury is still out on them as to whether there is any benefit, however as stated above, they have the same effect as wrapping the exhaust. We do know that once a ceramic coating is applied, the system can never be repaired as it gets into the pores and welding is not possible. (you can grind the coating off) How about cooler cowl temperatures with either of the above? Yes, the temperature in the cowl will probably be cooler, but the engine produces so many BTU's of heat so it either is kept cool by the mass air flow or it stays in the cylinder heads.

Clearly there are some questions. Where are the myth busters? :D
 
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I heard Larry give his opinion at SWRFI one year. And repeated his thoughts on a post a couple of years earlier. I also asked him about a 4-1 and he did not think it provided any benefit (CAFE says different). SkyDynamics also drops the warranty if the exhaust is coated. But when talking when talking with AET about their 4-1 they had no such issues. Simply stated to coat both inside and out. The actual amount of metal contact surface of the exhaust flange is the only way heat could be conducted away from the cylinder and that contact area is rather small, so how is that going to significantly contribute to cooling? You don't see any "cooling fins" on exhaust pipes. Plus if the pipes are radiating half of the heat, would not the cooling air flow around and through the cyl fins not be cooler?

Then talked the Cradin in Beorne and there seems to be alot of misinformation. Verified that their coating CAN be welded, not all coating are the same. Given the severe competion at NHRA and the ungodly amount of hp and rpm those engines see, they wouldn't do anything that did not work or provide a benefit. Well, all of the engines are coated.

I think that heat rejection is more critical on an air cooled engine and anything (safely within reason) we can do to keep the heat down is a good thing.
 
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