Abradable Powder Coating- Piston Skirts

General engine tech -- Drag Racing to Circle Track

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Andy Suman
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Abradable Powder Coating- Piston Skirts

Post by Andy Suman » Mon Jul 09, 2012 4:52 pm

Abradable powder coating is a new, low cost, high volume process for piston skirts. It brings substantial benefits to the power cylinder by 1) reducing cleaances and 2) improving the oil film for lower friction. 1% to 2.4% horsepower increases are documented in 'apples to apples' testing using abradable powder coatings on piston skirts in 2strokes and 4strokes respectively. We believe this translates into fuel economy, but have not directly measured it to date. Measurable durability gains are well documented, and peak power lasts longer. google 'Jason Farrell Case Study' for dyno data and parts photos.
The gains come because the APC coated pistons are installed snug (too tight). Upon start-up, APC texture quickly wears in to match the bores. Each piston is uniquely honed in to fit its bore while the engine is assembled, is hot, and is under load. The fine tuned fit is a permanent geometric change to each skirt, because once there is room for the perfect oil film, the wear STOPS. Abradable Powder Coating coating actually locks in the ideal barrel shape for EACH bore. Engine builders normally observe 40-50% reduction in cold clearance at gage point AFTER extended use at peak power...with NO SCUFFING.
Engine Benefits
The improved geometry of each piston reduces clearances and friction -simulaneously. The pistons rock less, less oil squishes(free energy), dynamic ring sealing improves, ring motion and wear is reduced, slap and associated collateral damage is reduced, along with noise. There are design opportunities such as lower tenion rings, smaller crevice volume, stiffer skirts, etc.
The friction of the piston skirt is reduced because of the larger load bearing footprint of an APC coated skirt. The coating assures the minimum oil film thickness across the entire skirt, which corresponds with the lowest friction area on the Stribeck oil film model. The 'leakdown length' of the oil film is lengthened, so the oil film cannot collapse. No boundary lubrication means no wear. RpK is zero, RvK is big- ideal tribological surface after break-in. Thats why it lasts after break-in. Its All About the Oil Film! :)
Thank You for Your Interest
Andy Suman

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Re: Abradable Powder Coating- Piston Skirts

Post by #84Dave » Mon Jul 09, 2012 6:37 pm

Who in the U.S. is capable of successfully applying this coating to the piston skirts? The approximate cost for a set of (8) pistons? -Dave-

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Re: Abradable Powder Coating- Piston Skirts

Post by Andy Suman » Mon Jul 09, 2012 8:03 pm

There are two US facilities that can apply APC. USChrome of Wisconsin, Line2line Coatings near Detroit. Soon another in Quakertown, PA.
Up to 0.002"-.006" on diameter, base price is about $32 per piston, $30 each for 8 or more.
Heavier than 0.0006" on diameter costs extra.
New or Used pistons can be done with surprising results- Dyno-Track-Teardown.

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Re: Abradable Powder Coating- Piston Skirts

Post by MGRoadRacer » Tue Jul 10, 2012 8:47 pm

Have you seen any data on leak down performance?

I generally frown when I get over ~7% and rebuild over 8%; and usually that's the only reason I need to tear it down outside of off-season refresh work.

Best.

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Re: Abradable Powder Coating- Piston Skirts

Post by 427Z06 » Tue Jul 10, 2012 10:26 pm

I take it none of the coating ends up in the oil during "break in"? If it does, how does the coating particles affect other parts of the engine (bearings, cam tappet interface) during "break in".

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Re: Abradable Powder Coating- Piston Skirts

Post by MGRoadRacer » Tue Jul 10, 2012 11:59 pm

I was curious about this too...so I did some searching on their site.

Looking at the thickness/wear data at http://www.line2linecoatings.com/techgeneral.html it appears more of the abradable material stayed on the part than the other coatings. With some of the ridges I've seen in the bores of the A-series motors I've disassembled for conversion into full prep production motors, I'd imagine that cylinder wear and normal break in particles from the metal/alloy components (walls, etc) would be much more voluminous than the coating material, and if the particles are too small to be caught by a good quality filter, likely not something I'd worry about. The largest amount of material loss I saw on the chart was 30 microns, and certainly not all at once.

I'm interested in the "self-machining" aspect. I've got a coolant inlet on the front of an inline 4; and cylinder 4 gets much warmer than cylinder 1, expanding more. I've got the burned, blown out-at-the-back, head gaskets to prove it. Solved that with an aluminum radiator from VW and some fabrication work (radiator supports out, cooling system re-plumbed; it never lines up at first, but that's half the fun), but I'm betting that cylinder 4 is still hotter and has less clearance than cylinder 1 when at temp!

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Re: Abradable Powder Coating- Piston Skirts

Post by 427Z06 » Wed Jul 11, 2012 12:22 am

MGRoadRacer wrote: and if the particles are too small to be caught by a good quality filter, likely not something I'd worry about. The largest amount of material loss I saw on the chart was 30 microns, and certainly not all at once.
Yep...I think your analysis is right on the money. Probably micron or sub micron sized particles, pass right through the filter and just float around until the first oil change.

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Re: Abradable Powder Coating- Piston Skirts

Post by Andy Suman » Wed Jul 11, 2012 1:38 pm

Hi MGRoadracer and 427Z06,
Thanks for the discussion. Answers:

Break-in Particles- The coating is plastic and soft minerals which are used in some break-in lubes- much softer than any metal component. It runs in chain saws to Pro Mods to Nascar engines, and users have never observed any evidence of coagulation or any ill effects of the soft, tiny break-in particles. Even though the coating composition is soft, it holds up long term because it improves the oil film stability to prevent parts from touching...

Leak Down & Compression Durability - check http://www.line2linecoatings.com/testimonials.html for comments by elite racers in many different engines. Summary - Leak down and compression are measurably better AFTER extended duty cycle.

Different Bore Sizes in Engine - Thank You MGroadracer for the question. This is where abradable powder coating really helps. In multicylinder engines, each bore is different from the next when you figure in machining, stack-ups, assembly torques, thermal distortions, and operating stress. The problem is sets of pistons are made the same. When one hole requires a clearance or profile change, why should all the rest suffer? Abradable Powder Coating addresses all these small errors. APC insures that each and every piston becomes the best possible mate for its unique bore. It frees up power and durability by fine tuning each power cylinder.

Best Regards, Andy

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Re: Abradable Powder Coating- Piston Skirts

Post by groberts101 » Tue Jan 10, 2017 6:08 pm

I know Madbill recently mentioned having this process done on one of his motors. Has anyone else around here used APC or have feedback about piston/bore analysis after engine teardown?

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Re: Abradable Powder Coating- Piston Skirts

Post by Jeff Lee » Tue Jan 10, 2017 6:41 pm

I’m just now assembling an engine with this process done to my loose skirts. All I can say is I don’t “feel” the skirts will need scuffing for clearance; I don’t feel they are to tight as delivered. This is a subjective issue after all. Pistons in bore; only a light pressure is required to push them through the bores.
I was under the impression I would need “moderate” pressure to squeeze them in and then scuff to allow less resistance.
Keith Jones at Total Seal turned me onto this coating, followed by Diamond Pistons. Lastly, a good friend who is an AP mechanic stated he was very familiar with APC coatings. He said it made the difference between two jet engines making 17,000# thrust and 22,000# of thrust; the greater thrust due to APC.
I did a lot of research and while some are raving, some are skeptical...I found no negative reviews (from actual users). Diamond suggested it ahead of new pistons and said it would probably make more HP (as did Keith @ TS).
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Re: Abradable Powder Coating- Piston Skirts

Post by cjperformance » Tue Jan 10, 2017 7:34 pm

Anyone know of someone in Australia thats able to apply this coating?
Craig.

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Re: Abradable Powder Coating- Piston Skirts

Post by blown265 » Wed Jan 11, 2017 6:51 am

Hi Craig
Ive used Techline Coatings with good results- havent checked if they do an APC, but they could be a good lead to a supplier who does.
As a side note, an Eaton supercharger I bought recently used/uses a similar coating from the factory to clearance the rotors.
Regards
Paul

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Re: Abradable Powder Coating- Piston Skirts

Post by cjperformance » Wed Jan 11, 2017 6:56 am

Gday Paul and thankyou for that info. I'll follow that up.
Im keen to give it a try on some new pistons as well as some used pistons I have that i think could be reused with this type of product.
I'll let you know how i go.
Cheers
Craig.

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Re: Abradable Powder Coating- Piston Skirts

Post by twl » Wed Jan 11, 2017 8:00 am

We have used Swain Tech skirt coatings which do this. They may not be identical to the OP product, but do basically the same thing from another supplier. Been using it for several years.
We have found good results from this sort of coating in some of our applications.

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Re: Abradable Powder Coating- Piston Skirts

Post by groberts101 » Wed Jan 11, 2017 12:31 pm

twl wrote:We have used Swain Tech skirt coatings which do this. They may not be identical to the OP product, but do basically the same thing from another supplier. Been using it for several years.
We have found good results from this sort of coating in some of our applications.

yeah.. have seen them too, plus they're cheaper. I have to wonder what the composition of that coating is though? Plastic frits like line2line's or ceramic based? They did say their PT-9 or PC-9, not sure which, coatings are not meant to be built up as thick due to potential for coating failures when reaching excessive thicknesses. just under .001 was standard application and max around .002 was the next option up for a few bucks more.

Could you share any firsthand experiences with teardown/parts inspection? While I can imagine they get high spotted away just like any other skirt coating would.. any slight issues with coating delamination or the tiniest bit of oil system debri?

Have wondered for quite some time if these guys>> https://www.oerlikon.com/metco/en/produ ... /sumebore/.. have a hand in the various coatings technology being formulated/applied these days. They have the material database to make nearly anything and work with major aeronautics, OEM's and race teams. Yamaha.. Rotax.. Borg Warner and probably many others.

forgot to add that they do that sumebore on loose liners too. Not stoked to ask about the pricing though. Looks like REALLY expensive equipment. lol

Worldwide based company.. might be able to help some of you guys over on the giant island too. :-D

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