I know this topic was discussed off and on.

However, I like to revisit it and since I am considering doing just that for these reasons:

1. it smooths the surface out and fills in imperfections to (hoepfully) make it difficult for carbon to build up on the rotor face.

2. reduce rotor temp heat since it probably has the greatest amount of heat due to direct heat from the combustion event and inferior cooling properties compared to the rotor housings which has cooling passages.

Both should help minimize the possibilities of detonation.

How much? I don't know.

There are a few cases that I know of people coating their piston heads and these people have noticed that there is less detonation and knocking in there modified cars.

The rotor face and piston face should be tantamount with respect to their functions.

At this point I am concern if the material will chip off and if so, will it break apart without any ill-effects to the engine?

let's keep the flame down on this discussion since it's really intended for fact finding.

thanks.

 

i would think one concern here would be durability. i've had ceramic coated headers peel after two years of use and they are not subjected to the same abuse a rotor face is. i also have a friend with a drag car that had coated headers on it. the car has done 85 runs with them installed and they are peeling. even if the material that peels off does not hurt the motor, i don't think the coating would last long enough to justify doing it. also, who wants to do the experiment to see if the peeling material doesn't cause damage? i know i don't.
just my $.02
andy

 

I think if you are building a race engine that will be torn down on a schedule it may serve some benefits. However for a daily / longevity driven engine, i would hesitate for similar reasons as stated above.

 

Uh..."The rotor face and piston face should be tantamount with respect to their functions."? Nice try at sounding eloquent, but I think you need a verb in there somewhere...

You're confusing detonation with pre-ignition. Detonation is an uncontrolled burn of the intake mixture caused by spontaneous ignition; pre-ignition is an uncontrolled burn caused by the intake mixture being ignited before the desired time by hot spots in the combustion chamber. That is what you're trying to prevent with the ceramic coating (not sure that JetHot coating will work with combustion chambers).

That said, I think that any way you can keep combustion heat from transfering to the engine internals is a good thing. However, ceramic coating is a pretty expensive process (at least for the types of processes I've seen). Not sure if just coating the rotor face will be beneficial enough in the long run to justify the cost.

 

I have seen many applications of ceramic coating on pistons that have worked fine. No problems with durability. However, I doubt that the ceramic coating that was applied in this case is the same as the ones advertised for usage with headers. I've heard of many companies advertising their ceramic coatings for headers, when they were nothing more than a spray-applied paint. Actual ceramic coating uses a plasma or flame spray to fuse the coating with the piston.

 

also depending on the thickness of the coating, wouldn't also slightly increase your compression ratio. From 9.0 to 1 to something higher, not much but still there 9.1 or 9.2?

Tim

 

Also you have to make sure that the temperature to Put* the coating on exceeds way above the regular everyday use temperature. I don't know that I would do this myself.

 

The "proper" ceramic coatings I've seen are pretty damn thin-- like 0.08-0.12 in. thick. Not enough to change compression ratio in any appreciable manner.

 

yeah........ increase in compression ratios is another concern that I had.

durability of ceramic coating has alot to do with the prep work.

 

Again, "real" ceramic coatings for usage with components in the combustion chamber aren't sprayed on like paint and baked in an oven. For lack of a more simplistic term, real ceramic coatings are literally "welded" onto the surface by an expensive process.

 

I can get ceramic coating at a reasonable cost..... It's about $50 per ft.

If the benefits are there, then it's worth the cost.

What about coating the ouside of the engine block to reduce temps in the engine compartment?

I have a koyo radiator. Is that suffice enough to maintain lower engine temps?

 

"$50 per ft."? How are they applying this particular "ceramic coating"?

 

not sure.......... I know that they prep it by baking the metal at 800 degrees to burn of the oil.

And then it's blasted.

Then the liquid solution is applied and baked at 800 degrees.

So considering the amount of work, energy, and materials it's really a good deal.

 

Hmmm....I'm not so sure that this is the correct "ceramic coating" you want. All of the ceramic coatings I've seen were applied in what appeared similar to an autoclave used to make carbon fiber parts. The components to be coated are enveloped in an inert gas, and then the coating is literally "exploded" onto the part. This ensures a complete bond.

Plus, I'm sure there are areas in the combustion chamber that get hotter than 800 degrees at some point.

 

What are we talking about here boys !? Celcius or Farenheit... (Hint: There's a difference)
I know I was reading well over 1200 deg. F on the exhaust manifold, so likely that the interior gets that as well, I think the trick is adhearing the ceramics at a temp where the metal won't melt and high enough where the engine won't reach that temp, I can't remember the exact figures, but as I recall the temps at where an engine melts and what some engines can produce are like 100-200 degress F appart... or less...

Also the thickness deal, the only concern would be milling out the slots for the apex seals so that the seals can be re-applied to the roror, without scratching or compromising the process you just paid so much to do... once the seals fit, why would there be a change in compression ratio !?
Also I'd think to a slight degree weight would be a concern, you're adding a layer of ceramics, which could weigh a couple of ounzes, and I'd try and possibly reduce the weight of the rotor to compensate...


But This Sounds interesting

 

800 degrees is the curing process.

once it's dried it can handle 1300 - 2000 degrees (depending on the kinda ceramic coating u choose)

 

We are talking F since we are in Amerika

 

That's absolutely right. Ceramic coating headers etc. is more akin to a high temp paint. True ceramic coating fuses fine particles of (you guessed it!) ceramic material to the surface of a part. Vaguely similar to a diamond coated cutting tool for instance. True ceramic coating is by no means a painting process nor is it related to the Jet-Hot process in any way.

I would think the rotary would benefit even more from ceramic coatings than a piston engine would given the higher amount of exposed walls inside the combustion chamber.

Batman, I don't think the guys you are talking with are on the same page as you. I don't think what they are offering is the same thing I have seen on piston crowns.

 

Then it's definitely not the correct ceramic coating you need for use in a combustion chamber. True ceramic coating for internal engine components exposed to the combustion chamber does not need "curing" or "drying". Once the the coating is flashed on, it's done.

 

With the correct ceramic coating applied, you don't need to mill anything. The coating is applied in a manner that affects only the surfaces exposed to the application "blast". Plus the coating is thin enough in outlying areas that it shouldn't affect the clearance of apex seals-- remember, it's been used on piston engines (with accompanying ring lands) for years. Compression ratio is not affected.

The layer is thin enough that weight is not a concern; it will be nowhere near a couple of ounces, even on all three faces of a rotor. Plus, the ceramic you're thinking of (like a vase or plate) isn't quite the same composition as the coating used in this process.

 

The ceramic coating I have used is thick enough that if u were to coat the entire rotor it would fill part of the gap where the seals would go.

 

"You have used..." On headers, right? Not in a combustion chamber. True ceramic coating is, once again, 0.08-0.12 inches thick, and I've been told the newer types are even thinner (while providing equivalent or better heat insulaton properties).

 

.10 inches thick = .254cm or 2.54mm thick, look at a ruler and I can't imagine that amount being coated on the entire rotor facing NOT making the available space in the combustion chamber smaller, raising the compression ratio.

Tim

 

Whoops, I meant 0.008 to 0.012" thick... apologies for the mistake.

 

DOH!

I left that for someone else to catch