Piston thermal coating

[digger]

the engine is a heat pump and the more heat that is contained in the combustion chamber the more HP you make. that is why uncoated aluminum heads require 0.5 increase in CR to get the same HP a CI head engine with the same parts

Heat is used to raise combustion chamber gas pressure. It is the change in gas pressure that produces the downward force on the piston. A glance at the pressure curves of a PV diagram will clearly show this.

An increased inlet air temperature will not change the compression pressure at all. It will change the compression temperature and the resulting combustion flame speed leading to a higher combustion temperature and combustion pressure. This may or not be beneficial to performance.

By far, the best way to cool a piston is to use oil spray jets directed to the underside of the piston.

The ability of a metal to conduct heat is given by its thermal conductivity value.
For cast aluminum it is 92 BTU/hr/ft^2/F/ft.
For cast iron it is 23 BTU/hr/ft^2/F/ft.
Aluminum will conduct heat at a rate four times faster than cast iron.

As far as insulating properties of materials the conductivities are:
Alumina (aluminum oxide) is 6-12 BTU/hr/ft^2/F/ft. This is often called hard coat anodize.
By far the best insulating coating would be zirconium dioxide at .6-1.0 BTU/hr/ft^2/F/ft. (if you could get it to stick)

Thermal conductivity is affected by the material, time in hours, area in square feet, temperature and thickness in feet.
Piston coatings are not usually applied to a depth measured in feet but rather in a few thousandth of an inch. Which is why the ceramic tiles on the space shuttle were nearly an inch thick.

David my I understanding is that most heat will be transferred by radiation like applying a flame to a body and thus the fact that the coating is thin is relatively immaterial for this mode of heat transfer.

[digger]

note the thin coating does 95% of the work, the main difference between a piston a space shuttle is the time of continuous heating vs 'pulsed' heating

[David Redszus]

The two primary forms of thermal transfer that we are concerned with are radiation and conductivity.

Radiation
For aluminum with an emissivity value of 0.07, one square inch at 400F will radiate, or shed, .007296 BTU/min.

For porcelain with an emissivity value of 0.92, one square inch at 400F will radiate, or shed, .095895 BTU/min.
For a given area and temperature, thermal radiation is directly proportional to emissivity of the material.

Conduction
For aluminum with a thermal conductivity of 204, one square inch, with a temperature differential of 3600F, 1mm
thick, will conduct 14,965 BTU/min.

For porcelain with a thermal conductivity of 1.6, one square inch, with a temperature differential of 3600F, 1mm
thick, will conduct 117.4 BTU/min.

In air with a thermal conductivity of 0.026, one square inch with a temperature differential of 3600F, 1mm
thick, will conduct 1.9 BTU/min.

Heat transfer via radiation is not sensitive to thickness but is sensitive o surface area and VERY sensitive to temperature.
Heat transfer via conduction is sensitive to area, temperature and material thickness.

Interestingly, the space shuttle tile outer coating (borosilicate) is actually a type of cheap glass with a very low thermal conductivity of 1.11 which is lower than air.

[piston guy]

If it did something ( in general) to increase power Nascar teams would be using it and they don't. Nuff said.
YES it will provide a "band aid" for a compromised design power adder combination and possibly keep it from failing.

[Frankshaft]

If it did something ( in general) to increase power Nascar teams would be using it and they don't. Nuff said.
YES it will provide a "band aid" for a compromised design power adder combination and possibly keep it from failing.

For a few extra seconds

[lemons racer]

I didn't expect such an intense response to my thermal coating question, leaves me with allot to study. Keeping in mind my intended use for this engine (24 Hrs. of LeMons, Chump Car, & some fun track days) cost is a consideration.
Gary C did state he had used this product with good results. Going to check if the other coatings mentioned also offer their products to the public.
Saved money everywhere I can, used poly engine & trans. mounts, used trick flow pushrods & Performer intake, 1904 Edelelbrock (Qjet) carb, Lots of parts from Pick and Pull on their half off days. The only place I spent money was the 21 4N 1.94 1.6 valves, springs, retainers, keepers, & pc seals from Alex's Parts, that was less than $200.00 plus an Elgin cast hyd. roller cam. With the 081 305 58cc heads milled .060 that I ported ALLOT .015 shim head gsk. 4" bore 3.52 stroke (don't ask) should be right at 11-1. The machine work except the crank was free from a friend.
While I'm thinking about it remember I'm not trying to gain HP, just trying to keep a little heat out of the inexpensive pistons so maybe they can last a little longer before they do melt down. Normally LeMons runs 7 hrs. on Sat. then another 7 hrs. on sunday. I'd be happy to get 75-100 Hrs out of it but if not it's on me for being cheap!

[swampbuggy]

Hey piston guy, do the NASCAR engine builders have anti friction and or scuff applied to the piston skirts what little skirt there is ?? Mark H.

[piston guy]

Not the last time I made some . Coatings were on the top ring groove and pin bore only ( hard anodize). Things probably changed since then.

[MadBill]

I believe this is a Ford NASCAR piece, circa 2000. Ring grooves appear to be hard anodized. Skirts have some kind of anti-scuff coating.

NASCAR Piston 004.JPG

[DCal]

Until I retired, the test and sample pistons from Nascar teams that I got to see were coated on the skirts at Calico after we shipped them to the teams. They wanted to inspect them before the coating so that if the sizing of the skirts varied they knew who to blame I guess. Now we do a lot of OEM parts and very little Cup stuff. The business has grown and profit is up. But together we learned a lot so it was mutually beneficial to both parties.

[roc]

I didn't expect such an intense response to my thermal coating question, leaves me with allot to study. Keeping in mind my intended use for this engine (24 Hrs. of LeMons, Chump Car, & some fun track days) cost is a consideration.
Gary C did state he had used this product with good results. Going to check if the other coatings mentioned also offer their products to the public.
Saved money everywhere I can, used poly engine & trans. mounts, used trick flow pushrods & Performer intake, 1904 Edelelbrock (Qjet) carb, Lots of parts from Pick and Pull on their half off days. The only place I spent money was the 21 4N 1.94 1.6 valves, springs, retainers, keepers, & pc seals from Alex's Parts, that was less than $200.00 plus an Elgin cast hyd. roller cam. With the 081 305 58cc heads milled .060 that I ported ALLOT .015 shim head gsk. 4" bore 3.52 stroke (don't ask) should be right at 11-1. The machine work except the crank was free from a friend.
While I'm thinking about it remember I'm not trying to gain HP, just trying to keep a little heat out of the inexpensive pistons so maybe they can last a little longer before they do melt down. Normally LeMons runs 7 hrs. on Sat. then another 7 hrs. on sunday. I'd be happy to get 75-100 Hrs out of it but if not it's on me for being cheap!

lemons racer, I'm a shoe string car enthusiast but nonetheless I like to try things and maximize yields where possible. I've been studying piston coatings for a long time and my conclusion is that for my use (low budget racing) it's just not justifiable. Piston coating is one of those things that 'feels right', but the fact of the matter is that has very specific uses (e.g.: anodized ring lands is good for long term durability).

A lipstick on a hog may make her look better, but it doesn't alter the taste of the bacon.

PS.: Keep us posted on you racing adventures. Once my kids grow up a little more, I'd love to try LeMons or similar.

[Bos's5.0]

I think alot of people including myself were/are under the illusion the ceramic piston/chamber coating just magically make HP. But if you take away the ability of the aluminum piston and/or head to absorb heat, then you have in effect increased the chances of detonation?

That's the whole reason you can run more compression with aluminum heads.

Short of piston and head abuse that is on the edge of melting the aluminum, say in high boost race gas situations, just what would a person who has to run normal pump gas get from ceramic coating the pistons/chamber? It's the exact OPPOSITE of what you are looking for. The fuel is the weakest link.

Also, If I had a 9.5:1 aluminum headed engine and coated the chamber and piston, would it now be the same as a 10:1 un-coated engine?

Yes---No?

[peejay]

I think alot of people including myself were/are under the illusion the ceramic piston/chamber coating just magically make HP. But if you take away the ability of the aluminum piston and/or head to absorb heat, then you have in effect increased the chances of detonation?

If it doesn't absorb heat, then the surface won't be hot for the next cycle.

I suspect that the reason why people don't see real world gains in power is because the layer of carbon deposits that form will still absorb heat and reflect it into the next cycle. The piston will still be protected from extreme heat, though.

[John Wallace]

That's the whole reason you can run more compression with aluminum heads.

It's a MUST to increase CR to make the same HP as a cast iron head.
The loss of heat to the heads/block/piston loses efficiency and thus HP.
The aluminum head is inefficient because of the heat transfer.

[David Redszus]

I think alot of people including myself were/are under the illusion the ceramic piston/chamber coating just magically make HP. But if you take away the ability of the aluminum piston and/or head to absorb heat, then you have in effect increased the chances of detonation?

Since carbon is a much better insulator than a heat conductor, the risk of excessive chamber temperature is a potential problem, except for diesel engines.

I suspect that the reason why people don't see real world gains in power is because the layer of carbon deposits that form will still absorb heat and reflect it into the next cycle. The piston will still be protected from extreme heat, though.

Excessive carbon build-up will slow the heat flux into the piston and to the cylinder walls. But carbon in a running engine acts like a glow plug causing local ignition spots and potential irregular combustion. At higher operating temperatures, the carbon will burn off since carbon is a combustible fuel.