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Old 01-12-2009, 05:00 PM   #1
Retiarius
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Default Do coated pistons skirts really make that big of a difference?

I'm not concertned with noise, but in the long run from a wear perspective, will it really help?
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Old 01-12-2009, 07:43 PM   #2
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Yes coated piston skirts help, but they are not coated to reduce wear. The coatings primary intent is to reduce friction (increases usable power, improves fuel economy and reduces engine heat). The increment is small but real.
Reduced wear on the cylinder wall if any is very small especially if using molyfaced rings which also lube the piston ring/cylinder wall contact point.


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Old 01-12-2009, 10:16 PM   #3
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And its also at the least cheap insurance for initial start-up and break-in (if the coating makes it that long).
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Old 01-12-2009, 11:33 PM   #4
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^^Ditto...and from what I've seen, I question whether or not typical skirt coating lasts that long as well. And if the oil film goes for whatever reason, coating won't save it. But cheap insurance for break-in? Worth every penny.
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Old 01-12-2009, 11:53 PM   #5
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the skirt coating wont last very long, my stock pistons wore thru it in some spots in 7,000 miles.
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Old 01-13-2009, 02:07 PM   #6
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No. Neat concept but i have had two very expensive longblocks and neither machinist reccomended skirt coating
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Old 01-13-2009, 04:16 PM   #7
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Quote:
Originally Posted by MS WRX View Post
No. Neat concept but i have had two very expensive longblocks and neither machinist reccomended skirt coating
There's always opinions on the other side as well. I've listened to talented engine builders discuss the importance of coatings in the overall engine design. Not just skirt coatings, but chamber, valve and ports.....

Our skirts aren't all that long to begin with. The coating is going to help.

my .02 anyway
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Old 01-13-2009, 07:53 PM   #8
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Different piston designs of course but I've run Wisecos (coated) and CP's un-coated) and the wisecos seemed to be quieter for the first 5-10k or so. Can't say how those cars are doing now though but my wiseco block is still going strong and ok on noise. (I'm sure this has to do with the build spec too though as these were from different builders).
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Old 01-13-2009, 11:58 PM   #9
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I got my Wiseco's recoated by Embee Performance (pretty much the same as swaintech, just local for me) and the two different types of coatings were a night and day looking difference. After seeing the difference, I would definitely say, it varies depending on what kind of coating you get. If you think about it, there are many different types. You have Cosworth's Xylene Type, Swaintech/Embee's TBC Slippery Tuff Skirt Style, Mahle's GraFal Style, Oil Shedding, TBC, Thermal Dispersant, Anti friction, and etc.... Look at the difference from my Wiseco OTS coatings and the Embee coating:





I wish I had a better picture of the OTS Wiseco skirts, they were nothing special and they chip/scratch very easily... Its almost like comparing rattle can paint vs. powdercoating.

For only (I think) about $20 a piston for tops & sides, IMO you would be a fool not to.
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Old 02-02-2011, 10:04 AM   #10
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Quote:
Originally Posted by hotrod View Post
Yes coated piston skirts help, but they are not coated to reduce wear. The coatings primary intent is to reduce friction (increases usable power, improves fuel economy and reduces engine heat). The increment is small but real.
Reduced wear on the cylinder wall if any is very small especially if using molyfaced rings which also lube the piston ring/cylinder wall contact point.


Larry
doesn't friction produces wear?

https://secure.buschurracing.com/cat...d943c6abd87874
Quote:
These pistons have also been J&E tough skirt coated. This is a special process that helps with the oiling and prevents excess wear.
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Old 02-02-2011, 10:21 AM   #11
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Old thread.

I think Larry meant that the skirts may not contribute to all expected wear, and that rings are also part of the equation.

I am a fan of coatings. After reading reports and various articles from/regarding racing teams, it seems to be proven technology.
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Old 02-02-2011, 10:27 AM   #12
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IMO skirt coatings are a tough call. They often wear off and leave you with a little bit bigger PTW (though minute) than before. In many subaru cases, I've seen them lead to some odd wear patterns/scuffing...unexplained.

I don't run them personally though I may send my pistons down to Calico before putting the engine back together and experiment.
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Old 02-02-2011, 10:44 AM   #13
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Quote:
Originally Posted by ZeroDrift View Post
Old thread.

I think Larry meant that the skirts may not contribute to all expected wear, and that rings are also part of the equation.

I am a fan of coatings. After reading reports and various articles from/regarding racing teams, it seems to be proven technology.
Isn't most of the wear produced on the cold start (especially with a 2618 alloy forged piston) when the piston skirt hits the cylinder wall (piston slap)? now I am even more confused

Quote:
Originally Posted by Homemade WRX View Post
IMO skirt coatings are a tough call. They often wear off and leave you with a little bit bigger PTW (though minute) than before. In many subaru cases, I've seen them lead to some odd wear patterns/scuffing...unexplained.

I don't run them personally though I may send my pistons down to Calico before putting the engine back together and experiment.
some piston coatings are designed to wear over time...

I am going to get my pistons coated for my next built.

Quote:
Tuff SkirtŪ (TS)
Tuff SkirtŪ is a JE Pistons trademark coating that is a lubricating, anti-friction / anti-wear coating applied to the piston skirt only. Unlike our standard Skirt Coating, Tuff SkirtŪ wears slowly over time and is designed to withstand many different types of endurance applications including NASCAR, rally and off-road racing.
http://www.jepistons.com/TechCorner/PistonCoatings.aspx
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Old 02-02-2011, 10:53 AM   #14
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depending on where you go they do in fact work. The swaintech coatings hang tight for a long time. They help with noise alot but more importantly they help with knock and detontation and save the sleeves/skirt and dome of the piston.
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Old 02-02-2011, 11:24 AM   #15
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Quote:
Originally Posted by juanmedina View Post
some piston coatings are designed to wear over time...

I am going to get my pistons coated for my next built.
I'm well aware of that. JE also offers two different skirt coatings

I know what they have and offer and don't run their coatings but I do use their pistons.
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Old 02-02-2011, 01:50 PM   #16
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I was instructed by nick at je not to coat the skirts because it's just going to wear off anyways so why waste the money. He did suggest to have the tops coated tho.

I guess some would say coating the skirts would make the piston slap a Lil less noisy but in a weird way I kinda like the sound of my car at idle.
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Old 02-02-2011, 02:27 PM   #17
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I had mine coated dome and skirt $163 for all 4 (shipping included) I think it was worth it.. OEM pistons come coated...


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Old 02-02-2011, 02:45 PM   #18
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Quote:
Originally Posted by Prevent View Post
OEM pistons come coated...
yup and they are also cast, made on an assebmly line and they also have a factory allowable PTW clearance of about zero

The factory skirt coating also wears quickly.

I'm not saying it's right or wrong but simply that because the factory does it, isn't an argument for a forged piston, hand built, high-performance engine.

I will say that from my only experience on a tear down with the PC-9 (swaintech) coating is that it's pretty tough. The motor is a 102mm stroked (1.47:1 rod ratio IIRC) 4G63...it had spun a bearing so a tear down happened. The motor didn't have a lot of miles (under 8k) on it but the coating still looked good.
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Old 02-02-2011, 02:50 PM   #19
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First time I've had it done so we'll see how much of a noise diff there is.
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Old 02-02-2011, 03:25 PM   #20
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Quote:
Originally Posted by sense of nature
First time I've had it done so we'll see how much of a noise diff there is.
It wont make much difference if any. Loud piston slap would be from excessive piston to cylinder wall clearance. The tighter the tolerance the less noise it will make. Hence why the OEM pistons dont make much noise because the PTW clearance is less than a thousandth. I dont know exactly what it is but its in the ten-thousandths. The reason that they can do that is because the piston material does not expand like forged pistons do.
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Old 02-02-2011, 03:40 PM   #21
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my cp's seem quiet at cold start compared to other non coated, who knows $160 isn't much..
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Old 02-02-2011, 03:48 PM   #22
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Quote:
Originally Posted by Prevent
my cp's seem quiet at cold start compared to other non coated, who knows $160 isn't much..
I used coated CP's in my build... I wont know how loud they are until i do the engine swap in the spring tho... PTW is set to .003" (CP's recommendations) so we will see.
Prevent: What's your PTW tolerances?
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Old 02-02-2011, 03:50 PM   #23
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.003" excluding the coating.. (however the machinist did it) I havent started up the car in cold weather... always plugged in and in a warm garage... I have to get a better map on the car because when it was cold it was idle searching like a mofo.
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Old 02-02-2011, 05:06 PM   #24
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I have always used calico for coating of my cp's for my builds and also for the race acl's(before calico started coating them and keeping them done on the shelf).The motors have always been a little quieter than without a coating and Calico does brg,piston and other engine part coatings for quite a few NASCAR teams.Like Micah said its personal preference but if some of these teams include this in their engine progarms it has to have positive results.Just my .02.
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Old 02-02-2011, 05:30 PM   #25
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I'd say that measuring your piston to wall first, without assumption would be step one before talking about noise and/or wear. I watched a video on here with the CP pistoned EJ "at .003 PTW" and it was much noisier than and forged engine I have had my hands on with that value. Just because "they" say .003 doesn't mean shi#. Don't think from bore to bore, top to bottom it's just "set at .003".... That's a fantasy world.

I have taken apart Modular Ford engines with 100k and still have a decent amount of coating intact. I have also used some aftermarket coatings that wore off quickly.... But if that was their intended lifespan I'm ok with it. I do believe there is a certain amount of time to make the components "familiar" with themselves, and if the coating helps with this relationship it's a win.
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