Piston, Cylinder and Ring Coating

[supermileage]

I am looking at coating the pistion, cylinder and ring of a Briggs and Stratton Model 9 engine. I am looking for something with very low friction and high oil retention. If you know of a good coating please let me know.

[Christ]

Ceramic.

You can get a jet-coat of ceramic on the head surface (combustion chamber) and piston crown/skirts to allow better heat retention properties and keep skirt friction down.

I don't know how well it would stand up, but a graphite coating may also help.

[usergone]

I think there has been mention of some kind of teflon treatment for engine parts somewhere around this forum.

That may or may not stand up to the temps inside the cumbustion chamber (lol) so probably treating the pushrods and crank/connecting rods/journal bearings and everything else that moves and is not in the combustion chamber would be a better idea.

[Christ]

Originally Posted by thecheese429

I think there has been mention of some kind of teflon treatment for engine parts somewhere around this forum.

That may or may not stand up to the temps inside the cumbustion chamber (lol) so probably treating the pushrods and crank/connecting rods/journal bearings and everything else that moves and is not in the combustion chamber would be a better idea.

DuPont, Inc does not support the use of Teflon in high-temp non-drying applications like engines. It creates a waxy film that can plug small holes and create big problems.

That's why race applications use ceramic instead.

[usergone]

Originally Posted by Christ

It creates a waxy film that can plug small holes and create big problems.

Does that include out of engine treatment? I could see that with a fluid treatment meant for an assembled engine, but what about soaking the parts separately? Remember, briggs and stratton engines can be completely stripped down in just a couple of hours. What about plugging up the small holes while treating?

[Christ]

The rep I talked to said something about the film breaking down and "cooking" into a waxy substance when used in a hot/wet environment. We didn't get too technical about the discussion, I just asked about the use of PTFE in motor oil (some companies use it) and he said they weren't advocating it.

If you look on DuPont's website, somewhere, there's a short blurb about it, also not technically specific.

[Christ]

Taken from Wiki -

PTFE is a thermoplastic polymer, which is a white solid at room temperature, with a density of about 2.2 g/cm3. According to DuPont, its melting point is 327 °C (621 °F), but its properties degrade above 260 °C (500 °F).[6] PTFE gains its properties from the aggregate effect of carbon-fluorine bonds, as do all fluorocarbons.

Won't stand up to heat in an engine for much of anything, that said. I'm still trying to find the exact page where they say that they have no knowledge of PTFE having any advantage for use in automotive engines.

[solarguy]

Teflon is great for engines, on the outside, to keep them from getting dirty.

Sarcasm off.


Teflon has no business inside an ICE under any circumstance, applied hot, applied "cold", applied by magic secret processes, in a vacuum, in a clean room, using special patented process, applied disassembled, applied in the oil, All bad, no benefit. And some versions will actually damage your engine.

The people who make teflon, DuPont, who profit from it's sale, vigorously discourage its use inside any ICE under any circumstance. That should pretty much settle it.


Ceramics are a whole other ball game and might be worthwhile, albeit expensive.

I am interested in what this little engine will be used for...

Hints??

troy

[Christ]

So taking this beyond just the piston, bore, and rings, a few things you can do to make the engine itself more efficient are:

Highly polished friction surfaces (bearings). If you want to try something special, use copper sheet and make your own bearings of the correct clearances. Copper sheds heat well, and for a low-speed engine, friction is already minimal, and since most oils have zinc additives, they will protect the copper from abrasion.

Another thing you can do is swap the rod out for one of a large enough size that you could install roller bearings instead of standard bearings. This might also reduce friction.

The area along the top of the piston, between the crown and the top ring land, is considered a "gap" area. Mixture will gather there and not be ignited properly through the burn sequence. If you have the skills, try to design a top ring that will fill that groove, rather than allowing up to 30% of the overall mixture to occupy that space at TDC.

Consider testing rings made of high-temp nylons instead of metals. Nylon is self lubricating, but wears quickly.

Don't forget the timing gears and cam friction surfaces, as well. Every bit of friction needs to be looked at as a package to get maximum friction reduction.

Helical cut gears reduce noise, but increase friction a good bit. Side or spur cut gears will be noisier, but reduce friction. Side cut gears with a good polish and proper lubrication will give the best performance as far as friction goes. Less teeth per area will also reduce friction, but that can only be taken so far and maintain proper operation.

[autoteach]

classic coatings in sheboygan has what you need. Good luck on your supermileage car.