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I've always been leery of this kind of stuff. Strikes me as a bit "snake-oilish". I particularly like this one:

KoolKote is an aerospace quality hard anodize applied to all surfaces of the piston with a buildup of .001". This coating is designed for use in nitro-methane engines such as Top Fuel Drag Racing to endure the corrosive effects of this fuel type.

I've been going to the drags since I was a kid, and have never seen a piston with this coating in a fuel car. To this day, every top fuel or funny car piston I have ever seen is plain, bare aluminum. I mean, c'mon - these guys get maybe 8-12 runs on a piston before it's a souvenier. No piston gets run twice in the same race weekend. They are replaced every run, and the used ones go in the "check" pile, to be dye penetrant inspected back in the shop before they are pronounced "good" for another run. Even with no cracks, they are discarded somewhere between 8-12 runs, depending on how much money the team has. Any sort of coating is going to inhibit this inspection. In other words, this sounds like a load of b.s. from JE. No one is worried about "corrosion" with that short of a service life.

Speaking of which, it strikes me that if any of these coatings are useful at all, it would be in a low service life race motor. Something that gets torn down and freshened up often. Otherwise, I would be worried about this stuff flaking off after too many heat cycles or something like that.

I wonder if anyone has ever done a long term, high milage test on a street engine with any of these coatings. It would be easy enough to coat half the pistons, run it for a few years and a couple hundred thousand miles, and then tear it down to check. I have a hunch there would be no measurable difference between coated and uncoated.
 

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I've seen that web site. Remember, they are a supplier of these coatings. A quick google search will turn up many such suppliers, touting the virtues of their products. Many will even have "professionals" providing testimony as to the effectiveness of the product. Do they really work? Maybe. I've never met anyone who uses them, or knows anyone who uses them. Of course, all of this can be said for "male enhancement" products as well...
 

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typically a 996 will have a squish distance of 1.4mm or so (piston crown 0.90mm down from the top of the cylinder, head gasket 0.5mm thick), so taking that down to 0.90 - 1.0 will get you an extra 1/2 point of comp. 11.5:1 up to 12:1 sort of thing. but because they have 0.6mm base gaskets and you can't get the old corse ones anymore you need to machine or get some from cometic if they'll send them to you for not outrageous postage costs.
So, removing 0.5mm of squish increased CR by 1/2 point? That's a lot, isn't it?
 

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I've seen that web site. Remember, they are a supplier of these coatings. A quick google search will turn up many such suppliers, touting the virtues of their products. Many will even have "professionals" providing testimony as to the effectiveness of the product. Do they really work? Maybe. I've never met anyone who uses them, or knows anyone who uses them. Of course, all of this can be said for "male enhancement" products as well...
Here's one:
"Tests of NASA ceramic thermal barrier coating for gas turbine engines"

"Abstract
A two-layer thermal barrier coating system with a bond coating of nickel-chromium-aluminum-yttrium (Ni-16Cr-6Al-0.6Y, in wt.%) and a ceramic coating of yttria-stabilized zirconia (ZrO2---12Y2O3, in wt.%) was tested for corrosion protection, thermal protection and durability. Full-scale gas turbine engine tests demonstrated that this coating eliminated burning, melting and warping of uncoated parts. During cyclic corrosion resistance tests made in marine diesel fuel products of combustion in a burner rig, the ceramic cracked on some specimens. However, metallographic examination showed no base metal deterioration."

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TW0-46T3F1M-TH&_user=10&_coverDate=12/03/1979&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1256496531&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9c5793ba39ee08ac07ee22d0a41a3a25
Also, see the "related articles" in the upper right hand corner for more.

and another:
"Ceramic-coated components for the combustion zone of natural gas engines"

"Abstract The use of ceramic coatings on the combustion zone surfaces of large,natural gas-fueled,internal com-bustion engines is discussed. Unique handling and quality control systems are required for plasma spray-ing thin (0.25 mm,0.0010) in.coatings on up to 48.25(cm19)-in.diameter piston crowns and cylinder heads weighing up to(1200 lb).The in-service performance characteristics of two types of natural gas-fu-eled combustion engines powering natural gas compressors that had thin zirconia ceramic coatings ap-plied to their combustion zone surfaces are presented. Their performance was measured in the field be-fore and after coating. It was determined that the durability,power output,fuel consumption,exhaust emissions,and other operating characteristics all improved due to ceramic coating of the flame side sur-faces of cylinder heads,power pistons,and valves."

http://www.springerlink.com/content/h537680jm2552687/
 

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So, removing 0.5mm of squish increased CR by 1/2 point? That's a lot, isn't it?
no, that is not a lot.
As Brad said, there is usually not so much to take away with the 2 Valve
ducati engine, so a compresson raise from 9,2:1 to let's say 9,5:1 is
not even noticeable while riding.
and as said by others before: you do not look at the compression while
setting the squish clearence, you set the squish clearence for its own rea-
sons and check the static compression afterwards.
If you want to raise the compression then, you need different pistons, if
you want to lower it, you need to machine material from the top of your
existing ones.

who is that guy in your avatar, do we need to look at that picture for longer now ?

:think: ;)
 

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no, that is not a lot.
As Brad said, there is usually not so much to take away with the 2 Valve
ducati engine, so a compresson raise from 9,2:1 to let's say 9,5:1 is
not even noticeable while riding.
and as said by others before: you do not look at the compression while
setting the squish clearence, you set the squish clearence for its own rea-
sons and check the static compression afterwards.
If you want to raise the compression then, you need different pistons, if
you want to lower it, you need to machine material from the top of your
existing ones.

who is that guy in your avatar, do we need to look at that picture for longer now ?

:think: ;)
OK, thanks.

That's me! who'd you think it was?
 

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i thought that is Flavio Brivatore, Renault formula one team manager.

:think: ;)
 

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During cyclic corrosion resistance tests made in marine diesel fuel products of combustion in a burner rig, the ceramic cracked on some specimens.
That is, to me, the most important line in that paragraph. I well remember the old Slick 50 debacle, where that and similar products were touted as the be-all and end-all of engine lubrication. The idea behind them was to coat internal friction surfaces with teflon, decreasing wear on them to an almost neglidgable amount. Problem was, once it built up to a certain degree, it started flaking off. These hard, crystalized chunks tore the bejeebers out of the insides of motors. Made a real mess.

Granted, the application process is different with these baked-on coatings. But the fact that they can crack, and possibly even seperate from the parent surface, concerns me. Is the performance gain worth the risk?

Their performance was measured in the field be-fore and after coating. It was determined that the durability,power output,fuel consumption,exhaust emissions,and other operating characteristics all improved due to ceramic coating of the flame side sur-faces of cylinder heads,power pistons,and valves."
"Improved" is a slippery term that guys like me - engineers - like to brandy about quite freely. It works really good with non-engineering audiences, what we call "lay people". Managers and accountants, and other folks that we need to convince to fund our projects. Other engineers, however, will always say "quantify that for me". They will also be very suspicious of the presence of other contributing factors - how controled was the test? It's human nature to want to see improvements delivered by our efforts. It takes a good deal of discipline, and often peer review, to get an honest, unbiased answer.

So, I will follow that path - quantify "improved". Will it even be noticable in our application? As Muschi quite correctly points out, half a point in compression in our motors will never be felt. I'll add that it probably wouldn't even show up on the dyno. No one would argue that half a point of compression will "improve" power, but once we know how much, we are not likely to go to great lengths to persue it.

Same with thermal and friction coatings. I have no doubt they "improve" things. But how much, and for how long? Is it worth the cost and risk in our engines? I don't think it is. I'll spend my money elsewhere, and sleep better at night knowing I will never again tear down another "Slick 50 engine". Some were a real mess...
 

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no, that is not a lot.
As Brad said, there is usually not so much to take away with the 2 Valve
ducati engine, so a compresson raise from 9,2:1 to let's say 9,5:1 is
not even noticeable while riding.
and as said by others before: you do not look at the compression while
setting the squish clearence, you set the squish clearence for its own rea-
sons and check the static compression afterwards.
If you want to raise the compression then, you need different pistons, if
you want to lower it, you need to machine material from the top of your
existing ones.
Well, if you go the other way, adjusting squish may lower the CR enough to avoid pinging.
 

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So, I will follow that path - quantify "improved". Will it even be noticable in our application? As Muschi quite correctly points out, half a point in compression in our motors will never be felt. I'll add that it probably wouldn't even show up on the dyno. No one would argue that half a point of compression will "improve" power, but once we know how much, we are not likely to go to great lengths to persue it.

Same with thermal and friction coatings. I have no doubt they "improve" things. But how much, and for how long? Is it worth the cost and risk in our engines? I don't think it is. I'll spend my money elsewhere, and sleep better at night knowing I will never again tear down another "Slick 50 engine". Some were a real mess...
They have quantified "improved", but I guess you want to remain skeptical about it, that's fine. Those were engineering papers I presented also, not meant for lay people. I'm sure if you read the entire article, you'd find plenty of quantified data. I'm not skeptical about this, so I don't have a need to pay for the article to prove to myself that it is a good idea.

Also, just because a coating cracks does not mean it flakes off. The next line says "However, metallographic examination showed no base metal deterioration."

There are also enhanced emissivity coatings available for external surfaces. Coating the inside of the exhaust port with heat barrier coating would count as "external" to me as well.
 

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Well, if you go the other way, adjusting squish may lower the CR enough to avoid pinging.

no, no, another no from the pink rider. :) ;)

you can ( logically ) only "adjust" the squish clearence in one direction,
reducing it, that is, to get it to the "correct" 0.040" / 1mm value.

if you would need to adjust it in the other direction, from let's say 0.6mm
up, your pistons would call for a replacement anyway, as they would have
hit the heads while running. There is no need under no circumstances to
get more squish clearence, the engine will not run as well then.

get this now: stop searching for a connection between squish and
compression, there is one, but it just doesn't matter.


:)
 

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No.

You could reducing the CR slightly, but the lack of correct squish will increase the tendency to knock!

Tom
Yup. We have covered this extensively; now we are just going around in circles.

Dirk, there may or may not be any correlation between degredation of the base metal and adhesion of the ceramic coating. Saying "However, metallographic examination showed no base metal deterioration." is not the same as saying the coating did not flake off.

Remember the craze a few years ago with everyone wrapping exhaust pipes with asbestos cloth? The theory was that it kept heat in the exhaust, leading to higher exhaust velocities and improved scavenging. An "improvement". Notice how pretty much no one does this anymore? In spite of the touted "improvement"? It's all about return on investment for effort and cost spent towards an "improvement". Most decided this one wasn't worth it.

Again, I would like to see "improvements" quantified. Not in a jet turbine, not in some marine diesel application, not in a sprint car - in one of our motors. I'll bet you a new hat it's so inconsequential as to be worth neither the money nor the risk.

These fads come and go in the high performance world. The "real" ones prove their mettle over the years, with a large number of folks applying them. Many fall into the "couldn't hurt to try it" category, so it's fun to play around with them. Others fall into the "some risk" category, like this one. To me, the risk (and cost) outweigh the potential benefits. I rather suspect no one will ever hop on a hot Super Sport, one that goes like a raped ape, and exclaim "wow, you can really feel those coated pistons..." I do, however, have visions of some poor guy tearing one down some day, one that had a chunk of cermamic break loose, and start posting here "wanted: one set of 900 SS cases...".
 

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Dirk, there may or may not be any correlation between degredation of the base metal and adhesion of the ceramic coating. Saying "However, metallographic examination showed no base metal deterioration." is not the same as saying the coating did not flake off.

Remember the craze a few years ago with everyone wrapping exhaust pipes with asbestos cloth? The theory was that it kept heat in the exhaust, leading to higher exhaust velocities and improved scavenging. An "improvement". Notice how pretty much no one does this anymore? In spite of the touted "improvement"? It's all about return on investment for effort and cost spent towards an "improvement". Most decided this one wasn't worth it.

Again, I would like to see "improvements" quantified. Not in a jet turbine, not in some marine diesel application, not in a sprint car - in one of our motors. I'll bet you a new hat it's so inconsequential as to be worth neither the money nor the risk.

These fads come and go in the high performance world. The "real" ones prove their mettle over the years, with a large number of folks applying them. Many fall into the "couldn't hurt to try it" category, so it's fun to play around with them. Others fall into the "some risk" category, like this one. To me, the risk (and cost) outweigh the potential benefits. I rather suspect no one will ever hop on a hot Super Sport, one that goes like a raped ape, and exclaim "wow, you can really feel those coated pistons..." I do, however, have visions of some poor guy tearing one down some day, one that had a chunk of cermamic break loose, and start posting here "wanted: one set of 900 SS cases...".
Well, say what you want but ceramic coating of engine parts has been around for 30 years or so. I'm not here to convince you one way or the other. I don't understand why you are arguing with me anyway when I provided engineering reports on these things that you can read yourself and draw your own conclusion. Even further, there are people on this list that have done this to Ducati engines, so you should ask them if it was worth it. I have no idea myself, but I am convinced that the marginal cost of doing this is worth it to me. I think I recall it costs all of $25 to coat a piston top. So, you're arguing with the wrong person. Go attack the authors of those articles if you have issues with what they are saying. I don't have the time or a access to a dyno or the money to bother with this kind of testing. I'm convinced it is good engineering practice to provide enhanced thermal management of an air cooled engine. I'm also convinced that this kind of coating is just as durable as the Nikasil coating on the cylinder bores of our engines. It's not my job to convince you or anyone else of anything.
 

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You have only addressed half of my concern - cost. I see the other half as more significant - risk. Or, put in a different way, risk vs. reward. If this process would double the power and/or longevity of these motors, I would say it's worth the risk. If it only adds a few percentage points to either, then it's not worth the risk.

I have seen these used for years in race applications. Long enough to have come to the conclusion that no one wins or loses based on the use of these coatings. No one gets more or less service life on a race motor based on the use of these coatings. A 20 hour race motor is still a 20 hour race motor, coatings or not. I've seen it first hand.

My concern on a street motor is longevity of the coatings, and what happens when they fail. Or, perhaps more accurately, what the failure mode may be. Flaking off in big chunks or wearing off? That probably depends on whether it is a thermal coating (piston domes and combustion chambers) or a friction coating (piston skirts and main or rod bearings). I'm not aware of enough people running these coatings in a street motor long enough to develop a very good database on this. So, I choose to err on the side of caution. Especially in light of the minimal gains promised.
 

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Dirk, take this from the pink rider, no one is arguing here, no one
is attacking here either.
this is a friendly discussion between like minded adult people.


now we are just going around in circles.
yes, technically and mentally.

:)
 

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from memory, a 996 has a 34cc chamber and 2.6cc of valve cutouts. if the piston is 0.90mm down the bore the deck vol is 6.8cc. the gasket vol is 3.8cc. so total clearance vol 47.2cc. swept capacity is 498cc. comp is clearance + swept / clearance, 47.2 + 498 / 47.2 = 11.55:1. reduce the deck height from 0.90 to 0.50, deck vol drops to 3.8cc, clearance vol drops to 44.2. comp is now 44.2 + 498 / 44.2 = 12.28:1 . both sound too high, maybe my chamber vol is too small. but you get the idea. when i measured one it was 11.5 up to 12.

pulling the base gaskets out of a 888 (94mm bore) for instance gets you from 11.2 to 11.7, as they have the old thick 1.3mm head gaskets, 0.3mm base gaskets and usually 1.3mm squish. the same 0.3mm reduction on a 9.3:1 92mm bore 900 2v motor would get you up to 9.6:1. and probably bent valves based on measurements i've done, but then i do know people who have done that to early 900ss motors. with je pistons they've all been between 1 and 1.1m when i've checked them i think.
 
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