I've heard about these coatings for a while to be used on pinstons. you know the ceramic coating on the top and the moly stuff on the skirts and then coat the combustion chamber in ceramic and the valves.

but in all honest does this stuff really work? yeah it sure sounds good and the info I have read from the companies look good but then again there are those trying to sell tornado intakes and sure it might sound good but it isn't.

how much can one expect to gain in power AND gas mileage using these coatings to the pistons, chambers and valves and such?

is it worth it?

If used how thick does the coating need to be? how quick would it wear away or will it stay?

piston skit and top, combustion chambers, valves and so forth coated? how much gain?

when done does the motor need to be retuned a little bit because of the way the car now runs?

 

I do know that ceramic doesn't retain heat as well as metal. It helps eliminate hot spots in the combustion chamber.

The main things that cause knock is an uneven burn (some areas burn faster than others), too many ignition sources in the combustion area, uneven fuel distribution, ignition timing set too early, and pre-ignition.

An uneven burn, too many ignition sources and pre-ignition are caused by hot spots.

An uneven burn basically means the burn isn't uniform. There are areas that burn easier than others. These can be caused by hot spots, like around the exhaust valve. The more heated the mixture is, the quicker it will burn once it's lit off. The burn then moves toward the intake valve. That's why a lot of spark plug holes, either angled or not, are biased more toward the exhaust valve. It's not just because there's more room over there because of the smaller valve.

Too many ignition sources are things like the spark plug AND an edge of the chamber (hot metal). While the hot metal may not be able to ignite the mixture without the spark plug ignition, once the mixture is lit the flash point of the fuel is changed and now that hot metal lites the fuel near it. The different areas of the burning fuel meet and cause a disruption in the burn pattern.

And of course if the hot metal does get hot enough, the spark plug doesn't need to ignite the fuel. The hot metal will. Pretty much resulting the same as above.

Ceramic coating evens out the surface temps of the combustion area eliminating hot spots.

I have no idea how long it lasts or what kind of power increases you're looking at. It would only make sense that if the engine is running with an optimal advance curve, and does not experience "knock", then the gains would be minimal. You can't get a whole lot better than great.

As far as the coating on the skirts goes, I don't know if it really works or not. The only company I've seen that does this is Speed Pro. I have those pistons, but I can't tell what it'll do just by looking at it.

 

my other wonderning on top of does it work and how thick does it need to be is on the ceramic in the combustion chamber. what happens if you detonate? does it just fall apart of hold together?

I know withe rx7's the cermic apex seals are prized for there resistance to stuff like that but it's a lot thicker and might be a different type of ceramic

 

does anyone one else have any ideas?

 

This should help. Read this thread.

 

The coating on the piston tops keeps combutstion chamber temps down. They're also smoother so both of these help supress detonation. Some of the coatings are also harder than the aluminum so I guess theres a marginal bit of strenth gained.

The coating on the skirts cuts down on friction between them and the cylinder walls. It tends to wear off quick. There's only a few times that I've torn down a motor with coated skirts and the majority of the coating wasn't worn away.

Where you pick up more signifigant gains with coatings is on your bearings. Big time loss of friction, pick up a few HP and oil temps drop.

 

The coating on the piston crown is there as an insulator -- it helps retain the combustion heat inside the combustion chamber so that the cylinder pressure is higher and more work can be done on the crank. It doesn't keep the combustion chamber temps down.

 

Well, for my sake, as well as Speed Pro's, I hope you're wrong since the piston-to-cylinder wall clearance is based on the coating being there.

 

you think the skirts never touch the cylinder walls? Look at any piston that came out of a running motor and you'll see vertical scuffs.

 

Piston, combustion chamber and exhaust port coatings are usually ceramic and are designed to keep the burning charge from transferring heat into the metal - thus keeping combustion chamber temps (and pressures) higher. This effect can be seen as an augmentation of the engines compression ratio and hence efficiency. At best on a low compression motor you might see a 3-5 percent gain in peak combustion chamber pressure but anything approaching 12:1 it is almost a wash.

The one thing that coatings DO help with though is they keep the metal surfaces under them cooler. Ceramic coatings have been used for decades in the aerospace industry to allow jet engine hot parts to withstand the high temperatures they now regularly see. In addition to air film cooling these coatings help turbine blades and combustor linings to withstand constant gas temperatures north of 3000 degrees farenheit.

Molybdenum (sp) coatings are alot like graphite dry lubricants - they are applied so that the layers of moly are oriented paralell to the surface and are more slippery (coef of friction) than the base metal (aluminum).

Moly coatings are even being used by OEMs these days so I would say they are good stuff. Ceramic coatings on hot parts are good for low compression motor performance augmentation but are much more valuable as heat insulators -- keeping your parts cooler!

 

I don't believe I ever said that, did I?

Quote:

Look at any piston that came out of a running motor and you'll see vertical scuffs.

Yea. Seen it many times. That's not what you said.

You said...
And...

Then I said...
I don't believe I ever said...

"I think the skirts never touch the cylinder walls."

Or...

"I've never seen vertical scuffs."

I've been misquoted, once again.

I was simply pointing out tha Speed Pro is going to be giving me new pistons and whatever else gets messed up from the clearance being to much if
And something else breaks or wears quickly because of the increased clearance. That ain't cool if that happens.

Can you be a little more specific as to what brand you've seen "wear off quick" along with proof that it was "X" brand?

Thanks.

 

the coating spead pro puts on the skirts of the pistons is there to help limit wear durring the breakin and before operating temp is reached. i dont think you have anything to worry about.

 

It'd better be for more than just break in and cold start, as much as I paid for them!!

From Fed-Mogul's site...

Sums-a-bichez better honor their stuff.

 

well i was going by what was used a few years ago. I would say it does the most good during start up and break in to minimize cylinder wear. i never saw the coatings wear off. but if its as good as it says it is maybe i should get a set. i still say you should have no problem and your cylinder walls will thank you

 

You have my sincerest apologies, Great One.

I was offering up my experiences, not trying to call you out or prove you wrong. Sorry you took it the wrong way, maybe I should have put a at the end. Either way, I don't know what brand they were or how the motors were assembled where I saw the worn coating. They were used motors that customers had built by other engine builders and had run/raced and brought to me to freshen up.

 

That's Mr. Great One to you, pal.

By your post it seemed as if you were trying to prove something, just wanted to make sure you understood that I had a genuine question. I'm sure you can tell that I'd be a little concerned if I was going to have problems with something I paid extra for. That's all.

As you were, peasant.

 

ok so lets say I have a car that is running 8:1 compression and the fuel setup is set to run around 16-17:1 A/F ratio peaking at points close to 20:1 on the A/F for very light cruise. going thorugh a carbed setup.
would ceramic on the pistons, combustion chamber, and valve faces help much?

 

You might notice a diff if you ran two Identical motors side by side one with coatings and one without. Like I said -- if your motor runs close to 12:1 CR (INCLUDING BOOST!) then the benefit is very small.

If you are acutally running 8:1 however I would think it would help noticably.

 

get back to your dungeons and dragons game Corky

 

hey I used to play AD&D third edition back in the day