If you've ever purchased a set of aftermarket forged pistons, usually, you'll notice how shiny and sharp they are compared to your OEM cast pistons. What's probably going through your mind is that they look really nice; nice and polished that is. However, these shiny surfaces can have an ill effect as they reflect energy much like a mirror does with light. One of the first and easiest tricks with pistons is to lightly sand the piston top to a super smooth, but dull finish. This can be accomplished using a 2000 grit piece of sand paper and dry sanding the piston domes/valve pockets. However, make sure this is done carefully. It's not a good idea at all to sand the skirts of the piston as this can cause scratches in the cylinder walls and cause oil consumption.
Now, by sanding the piston tops, you've just dulled this reflective surface, thus creating more area for the reaction to be absorbed and applied directly to the crankshaft. The resulting effect is increased thermodynamic effiency, better heat dispersion, and a piston with a greater defense towards detonation.

Another secret is to remove the sharp angles and edges on the piston dome surface. You might think your new Wiseco's or CP pistons are beautiful and because so, you're reluctant to cut them up. But, it's actually beneficial to remove those sharp edges. These sharp edges can create hot spots, and subsequently a think called "detonation". Now to accomplish this task, you'll need a die grinder and a light carbide roll to do this work. A dremel tool and a coarse carbide cutter will work just as well. Holding the piston by hand, take the die and lightly round off the sharp angles on the piston dome near the valve recesses and indents as well as the dome itself. I also like to wrap the skirts in blue painters tape to ensure that I don't knick the pistons if for some reason my hand slips. Now, don't remove too much material or you will start affecting the compression ratio. Next, sand the areas you remove material from, again with 2000 grit sandpaper to dull them up again.

Last but not least, another way to squeeze a couple more horsepower, as well as improving your motors resistance to detonation is to have the piston domes coated with a ceramic thermal barrier. This effectively distributes heat evenly across the piston dome and increase combustion temperatures. Heat makes power. The more heat you can generate in the cylinder, the more power the engine will potentially make. Unfortunately, internal combustion engines are thermodynamically inefficient by nature when it comes to heat. Most of the energy escapes through your exhaust system or it gets absorbed through your engine and by the cooling system. For obvoius reasons, you can’t eliminate your exhaust system, and the cooling system is a mandatory component to keep the internal parts from melting or coming apart due to extreme heat levels. The only thing we can do to make an engine more thermodynamically efficient is to better contain and manage the heat that’s made when combustion occurs. That’s the purpose of thermal barrier coatings. Increased combustion temperatures and evenly dispursed heat is an easy way to increase thermodynamic efficiency, I.E. power.

When it's all said and done, it would be smart to have the piston assemblies balanced for proper harmonics. It's good practice to do so in engine rebuilding. Also, be sure to remove all sanding particles. You don't want those getting wedged between a bearing and your crank or splashed on your cylinder wall.



Modified by bambam at 5:53 AM 1/16/2007

 

coated rollerwaves might unite that all (and the others I do not know)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by koczeka &raquo;</TD></TR><TR><TD CLASS="quote">coated rollerwaves might unite that all (and the others I do not know)</TD></TR></TABLE>

I've thought of this as well, but i'm not so sure of their overall design besides the smoothing.

 

Make my brand spanking new shiny pistons dull and smooth? Are you high?!
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Just kidding! Some good information in there. A nice change from "How much power is my cookie cutter GSR going to make?"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">Make my brand spanking new shiny pistons dull and smooth? Are you high?!
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Just kidding! Some good information in there. A nice change from "How much power is my cookie cutter GSR going to make?" </TD></TR></TABLE>

Haha...I feel yah.

 

Good info. Ive heard a little about this before but didnt know exactly what was done.

 

Definitely makes sense.

 

You would gain more thermodynamic effiency if you coated the combustion chamber and EX. port in place of the piston tops. Less heat transfered to the water and oil. Doing both would be better. Then you need to tune all-over again. The engine can run leaner, and accept more timing lead.

 

good thread

I venture to guess that the sanding portion would also be a good idea to do with factory pistons as well since the tops are usually not very smooth.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">You would gain more thermodynamic effiency if you coated the combustion chamber and EX. port in place of the piston tops. Less heat transfered to the water and oil. Doing both would be better. Then you need to tune all-over again. The engine can run leaner, and accept more timing lead.</TD></TR></TABLE>
Did you just drop a jewel? I've never heard of that. I've heard all about coating pistons, but never anything else.

 

Poly-Dyn in Texas has been doing that for atleast 15-20 years. The first full coated engine we did included the dry-sump pump, rods, bearings, oil pan, pistons, head, EX. ports, headers, etc. The engine dropped 20C on both the oil and water temp. It did not make big BHP numbers, but we closed up the air inlets for oil and water and picked up top speed. Coating all the gearbox internals made WHP.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">Poly-Dyn in Texas has been doing that for atleast 15-20 years. The first full coated engine we did included the dry-sump pump, rods, bearings, oil pan, pistons, head, EX. ports, headers, etc. The engine dropped 20C on both the oil and water temp. It did not make big BHP numbers, but we closed up the air inlets for oil and water and picked up top speed. Coating all the gearbox internals made WHP. </TD></TR></TABLE>
Neat

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by koczeka &raquo;</TD></TR><TR><TD CLASS="quote">coated rollerwaves might unite that all (and the others I do not know)</TD></TR></TABLE>

I was thinking the same thing, at first I was gonna say this guy just copied off the endyn site.

A good article though, thanks for the post

May I ask why the piston manufacturers don't do this? Cost? Though I know not everyone wants a dull piston....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">You would gain more thermodynamic effiency if you coated the combustion chamber and EX. port in place of the piston tops. Less heat transfered to the water and oil. Doing both would be better. Then you need to tune all-over again. The engine can run leaner, and accept more timing lead.</TD></TR></TABLE>

Ive always wondered about coating the chambers too. Good info.

 

Very interesting.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">You would gain more thermodynamic effiency if you coated the combustion chamber and EX. port in place of the piston tops. Less heat transfered to the water and oil. Doing both would be better. Then you need to tune all-over again. The engine can run leaner, and accept more timing lead.</TD></TR></TABLE>

Hey Don, I've heard of ceramic coating the faces of the valves, but not the whole combustion chamber. It makes perfect sense, but i've just never thought about it. How about teflon coating? I was thinking about teflon coating the valves seats and stems and then ceramic coating the faces. Do you think this would be an issue with the two different coatings on different areas of the same part? Additionally I'd like to teflon coat the piston skirts. I would think that it would also be beneficial to teflon coat the bearings and oil pump. Thoughts? What about the undersides of the pistons...would you choose to coat them with teflon or a ceramic coating? I mean, the possibilities are endless. You could even ceramic coat the entire inside of your intake manifold and throttle body. Maybe cost is the real issue here.

And to add to the piston scuffing, I was wondering about roughing up the quench pads on the P72 castings. I would outline an 81mm bore around the chamber and make sure not to go outside that circle, but remove the mirror finish within it. What are your thoughts on this?

 

its been a while since i read good/new info on HT...

 

Poly-Dyn has two different bearing coatings. One is teflon, but it depends on the material of the crank. The oil pump coating is not teflon but another friction reducing material, as it is a wear item. The valve seats and valve face angles cannot be coated as they are what remove the valve temperatures to the head. Teflon is more of an oil"shedder" that is why rods, crank weights, etc. work well. The best part of teflon coating the pan was cleaning it, 2 teaspoons of mineral spirits, slosh it around and rinse.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">Poly-Dyn has two different bearing coatings. One is teflon, but it depends on the material of the crank. The oil pump coating is not teflon but another friction reducing material, as it is a wear item. The valve seats and valve face angles cannot be coated as they are what remove the valve temperatures to the head. Teflon is more of an oil"shedder" that is why rods, crank weights, etc. work well. The best part of teflon coating the pan was cleaning it, 2 teaspoons of mineral spirits, slosh it around and rinse. </TD></TR></TABLE>

Sounds good. I might look into this Ply-Dyn for my next build.

 

my shop is 30 mins from poly dyn

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crx=si &raquo;</TD></TR><TR><TD CLASS="quote">my shop is 30 mins from poly dyn </TD></TR></TABLE> So what do you recommend? Which of Carl's coatings do you use.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote"> So what do you recommend? Which of Carl's coatings do you use.</TD></TR></TABLE>
gold thermal coating
I have him coated the combustion chambers, exhaust ports, and the top of my pistons

 

is there a site for poly-dyn? sounds interesting.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LSVTEC 91 Civic &raquo;</TD></TR><TR><TD CLASS="quote">Definitely makes sense. </TD></TR></TABLE>

Someone already did all this for you years ago...lol

 

so for a street engine with the occasional track day (drag and circuit), would these oil shedding and thermal coatings be worthwhile?