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Floram
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Cylinder coatings for an ICE

01/02/2023 3:15 PM

Hard chrome has been popular due to its high hardness and porosity that is claimed to hold oil and help with lubrication.

For small engines such as mopeds, suppliers are using cast iron cylinders besides other coatings such as nikasil in combination with aluminum pistons. An alternative to chrome is electroless nickel that has no porosity but is very uniform without edge build up and does not require mechanical after treatment after coating. Its hardness is just slightly less than that of chrome. As applied near 56 HRC that can be increased to 60-62 HRC by hardening.

My question is if EN (electroless nickel) would be suitable to apply to small cylinder of 50 cc displacement. The thickness is between 0.0005 and 0.0008 inches without porosity. Will this be a detriment to lubrication using oil-fuel mix to provide oil?

As far as I know, EN has not been applied in engine cylinders.

Thanks for comments.

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SolarEagle
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#1

Re: Cylinder coatings for an ICE

01/02/2023 4:55 PM

The crosshatching of the cylinder wall is critical to the ring lubrication, which is a common point of failure, so if the coating process compromises this in any way, then it's a no-go....Once the rings seat, there should be no further wear on the cylinder walls from that point on they ride on oil...regardless of direction of lubrication...

Proper crosshatching pattern...

..."A new generation of honing technology is playing a vital role in improving product performance for fluid power components, providing manufacturers a unique ability to size and finish valve bores precisely, with exceptionally high Cpk(process capability) levels. The new honing technology, known as precision bore machining, can control bore size with quarter-micron accuracy (0.00001 inch), can correct geometric errors in the bore and can produce a specific surface finish with lubrication and seal-enhancing properties."...

https://www.productionmachining.com/articles/when-the-bore-needs-more

https://www.enginebuildermag.com/2000/09/cylinder-bore-surface-finishes/

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SolarEagle
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#2
In reply to #1

Re: Cylinder coatings for an ICE

01/02/2023 5:36 PM

https://www.nickelinstitute.org/media/1769/propertiesandapplicationsofelectrolessnickel_10081_.pdf

It would probably work, but what's the point? What is the goal? I would be more keen to coat the valves and valve seats with something super hard and corrosion resistant..maybe spark plug threads...

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SolarEagle
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#3
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Re: Cylinder coatings for an ICE

01/02/2023 6:08 PM

https://bryansgarage.com/acceptable-cylinder-wall-scoring/

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Floram
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#4
In reply to #3

Re: Cylinder coatings for an ICE

01/03/2023 12:26 AM

Thank you SolarEagle.

All of your replies are much appreciated, especially the last link which is very informative.

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SolarEagle
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#5
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Re: Cylinder coatings for an ICE

01/03/2023 5:33 AM

It strikes me as being very important to completely filter the air entering the engine without restricting the airflow....and of course a good filter for the oil itself...but there should be some sort of way to monitor the air filter instead of just time interval changeout...and you never see figures on filter effectiveness like you do with home furnace filters...seems to me the air filters in cars are just too small and poorly located in most cars..but maybe they are deemed 'good enough' like most stuff nowadays...any air filter is going to be somewhat restrictive to the airflow, if it is indeed an effective filter, and you get around that by increasing the size...I would like to design an air filter that was built in under the entire width of the hood with damper control that could draw from the outside air or under the hood, for different weather conditions....

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Floram
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#8
In reply to #5

Re: Cylinder coatings for an ICE

01/03/2023 10:27 AM

To confirm your comments on air filters. I have seen pictures of worn piston rings of a heavy duty off-road machinery that was exposed to sand dust due to its operation.

The engine was still quite new but the rings of the 4 inline pistons were progressively worn down the closer they were to the air intake and therewith to the air filter that was surely overloaded or likely had an opening. The difference between the wear rates was enormous on one of the four cylinder banks of the V8.

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#13
In reply to #5

Re: Cylinder coatings for an ICE

01/14/2023 12:09 AM

The sample size is small, but even so it is worth a look...

https://youtu.be/sJ3L-E-ufYo



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Trees4Life
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#6
In reply to #3

Re: Cylinder coatings for an ICE

01/03/2023 8:22 AM

"It’s important to remember that if new piston rings are being replaced, you should also install a new cylinder head."

Who ever follows that will soon be out of business.
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Floram
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#7
In reply to #6

Re: Cylinder coatings for an ICE

01/03/2023 10:10 AM

Just for fun.

I never replace "new" piston rings only old ones. :-)

What you mean by the last sentence may or may not be true. Perhaps only the same customers will not come back.

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SolarEagle
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#9
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Re: Cylinder coatings for an ICE

01/03/2023 3:25 PM

You get what you pay for...

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Brave Sir Robin
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#10
In reply to #9

Re: Cylinder coatings for an ICE

01/03/2023 10:38 PM

Where labor is cheap and parts are expensive. Amazing work with relatively crude tools and equipment. I wonder what the reliability is like?
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SolarEagle
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#11
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Re: Cylinder coatings for an ICE

01/04/2023 3:18 AM

I wonder how old those heads are? I imagine it works good enough to justify the effort..I also have to wonder if that's been done before to those heads, I thought I saw some previous repairs...I found a refurbished head on Ebay for $4k that looks similar...

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HiTekRedNek
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#12
In reply to #10

Re: Cylinder coatings for an ICE

01/06/2023 2:55 PM

Probably as reliable as a new refrigerator.

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