Printable Version of Topic

Posted by: SpecialK Apr 29 2004, 07:18 PM

I just read a pretty interesting article in the new Hot Rod mag that had to do with coatings for engine internals (pistons, cyl. heads...) from a place out in CA:


http://www.techlinecoatings.com/articles/application_guide.htm

They (Hot Rod) performed a test on a coated vs uncoated piston with acetylene torch, and the coated piston lasted three times longer than the uncoated piston (32 sec. vs 97 sec.) before melting a hole through it. They also recommended coating the inside of the cylinder head (particularly aluminum heads) and the face of the valves. All of these coatings can be applied at home, and cured in the oven (send the wife shopping...unless she's VERY understanding of your cause )

Any comments?

Posted by: davep Apr 29 2004, 07:26 PM

Obviously it changes the weights of the pistons so they would have to be trimmed to match.
Also it would increase the compression a bit and may change the deck height.
I would not want it to flake off.

Posted by: SpecialK Apr 29 2004, 07:45 PM

Yeah, the layer on the pistons was .010" - .015" thick, and probably the same (didn't state exactly) on the combustion chamber which would change the comp. ratio some. You'd definitely need to recheck all of your clearances prior to firing it up. If you took the thickness of the coatings into account when setting up your deck heights there shouldn't be any problems......as for cracking/chipping?

Posted by: Jake Raby Apr 29 2004, 08:50 PM

I'm testing "Diamond like carbon coatings" in several engines pretty soon...

The technology sounds great, we'll see what it does.

Doing it to piston skirts changes skirt clearances, and etc... the engine must be designed and toleranced around their use.

Posted by: Mueller Apr 29 2004, 10:39 PM

I've use the Techline coatings, I also had the coating flake off from the surface of my pistons (good chance it was operator error, mine)

My cylinder heads I coated as well, the coating seemed to hold up but I did get cracking at the spot where my cylinder heads had cracks near the sparkplugs.

I only ran the motor for a few hundred miles before pulling it apart for an unrelated reason.

I'd pay someone to coat them if I ever went down that path again......as to the oven, i bought a used oven which I have in the garage.

Posted by: Brett W Apr 29 2004, 11:02 PM

The current issue of Race Engine Technology has an article on the DLC coatings. Rumor has some race teams are not running a bushing in the little end of the rod and just coating the wrist pin with no problems.

Posted by: Jake Raby Apr 30 2004, 07:03 AM

I have heard the same thing and seen it at a NASCAR shop pretty close to my shop..

my 3.0 has received a full dose of it. I'll be able to see some big differences with this engine because I'll be using its girth to test my cylinder heads over the next year..

Posted by: Lawrence Apr 30 2004, 07:41 AM

What about cylinder cooling fins? Would this be a good application for this area?

-Rusty
(who thinks rusted cylinders are UGLY)

Posted by: Brett W Apr 30 2004, 08:51 AM

The fins would not benefit from the DLC but they would definitely benefit from a thermal dispersant. Coatings are a good thing to run but you must understand and apply the fundamentals to the engine first.

One problem that some people won't mention with ceramic coatings on the piston tops is top ring welding itself to the ring lands. There is so much heat passed from the top of the piston into the top ring that it is micro welding itself to the top ring land. Many race engine builders are actually coating the bottom of the top ring and lapping the rings to each piston.

If you are running Nickasil or some other type of Aluminum cylinder I would have them anodized as for cast iron I would sand blast the out side and carefully, LIGHTLY coat the fins with thin black paint. Any more could inhibit cylinder cooling.

Posted by: airsix Apr 30 2004, 11:41 AM

I am sold on the science and benefits of the coatings. My biggest question is durability. Will the coating still be there in 25,000 miles? 100,000 miles? Mike's experience with flaking is exactly what I was worried about. I'm sure that surface prep and application technique have a huge impact, but I'd still like to see before/after tests in the form of a long-term study.

Here's a question: Are any OEM's using this technology? I would imagine if it's effective and it lasts, that you'd find it in engines like the EVO-8 and the WRX-Sti for example.

-Ben M.

Posted by: Mark Henry Apr 30 2004, 12:35 PM

In one of their newsletters the company above said that Ford was testing/using some of their coatings.

Berg offers the dry lube coating on their valve springs, since the mid-90's, they say it doubles the life.

Posted by: Rog914 Apr 30 2004, 01:05 PM

Reading an article about this "flame sprayed coating" that was sprayed on a piston top at mach 6. Has anybody heard of this?

Ralph

74 2.0

Posted by: Britain Smith Apr 30 2004, 01:46 PM

This is what the coatings look like. I had the following done:

Piston Top, Combustion Chambers, Valve Faces, and Exhaust Stub Tubes coated in a Thermal Barrier.

Piston Skirts coated in an anti-friction coating.

Valve Springs coated with a dry-film that absorbes oil.

Posted by: Mark Henry Apr 30 2004, 05:15 PM

Britian, what are the round pieces below the retainers? Spring shims?

They look like they have a raised centre? Or is it just the pic? Got a better shot of them?

Posted by: dmenche914 Apr 30 2004, 05:33 PM

i'd be concerned about a coating that is cured in a home oven, Home ovens just do not get all that hot. parts of the head may exceed that curing temp, and thus the coating may change, or be affected at engine running temps. I would think I would want a coating that was cured at a higher temp than its service temp, that would reduce the possiblilty of the coating still changing (ie flacking, or property change) while in service. Thus I would think you'd be better off with some commercial service, that has the ability to cure the parts hotter than in a home oven. This is just my assumption, but I do have lots of experience in materials engineering.

As far as coating the cylinder fins, I read about a test, between the heat disapation of coated (painted) verses bare metal, verses old rusty, crud clogged cylinders. The bare fins had the best heat disapation, followed by the dirty ones, the painted ones came in last.

In order to stop rust, a THIN coat of high temp flat black paint may help. It might give less heat disapation than a clean bare one, however with the paint, it may not rust as fast, and thus after time, may result in better heat dissapation than a bare one that eventually gets rusty.

Any ceramic coating on the fins will no doubt reduce heat disapation, thus i would not coat the fins, except maybe very thin flat black. Same holds true for the engine case.

Gene Berg wrote a bot about paint and the case and cylinders, and the tests I read elsewhere backed up his claims.


dave