Piston top and combustion chamber coatings

Unless they increase the compression ratio by reducing the size of the combustion chamber, it's all codswallop.

Thermodynamic efficiency is related to the difference between the cylinder gases' temperature and the exhaust temperature.

The power given out by the engine is related to the expansion of the cylinder gases. Get more in (with either a super- or turbo-charger) and one gets more out - provided the engine is built to withstand it, that is.

I've read several independant tests on various substances. many have been tested by big manuafacturers. The concept is by preventing heat transferring to the cylinder head and piston top it remains in the cylinder to do work. this is also what actually happens. the effect is more marked on certain head/piston designs with large combustion chamber surface/volume ratios or non-square bore/stroke ratios.

The cheapest solution is simply to use electroless nickel/chrome plating. combined with Capacitor discharge igniton and 'flat' gapless plugs this will resist detonation better and keep the internals slightly cooler. The ceramics or cermets work much better, normally being applied by metal spraying. Silicon Nitride was an early one; it also provides a very hard wearing cylinder wall surface.

More important benifits come from cooler operating temperatures and cooler exhaust valve heads and , most important - cooler piston tops temperatures allowing lighter pistons.

Hi, some years ago we raced a Cotton Telstar (Villiers two stroke), burning holes in the piston became a real issue. After looking at pistons with ceramic crowns, nitrided bores and heads we finally talked to Champion about spark plugs and cured the problem by fitting plugs two grades cooler, no more detonation (pinking) no more holed pistons. The moral here is for sparkling performance get the heat ot of the engine as fast as possible. As a side issue if each cylinder has a displacement of greater than 500cc then the problem will almost certainly be flame spread, cured by Honda using an oval piston and by every one else by fitting two spark plugs per cylinder.

Surely you want to get rid of the heat? I can see what you are getting at, but I don't believe it would work. consider - the heat has to go somewhere. Try managing the cooling more accurately, then you should be able to run at optimum efficiency. Remember, the original purpose of an exhaust was to remove the heat, not the noise.

I think they refer to reducing heat transfer to the metal = less burning and the charge temperature and pressure stay a little higher = more work from the engine = hotter exhaust too. http://www.azom.com/details.asp?ArticleID=53

Heat wasted to water is only done to stop the metals from melting and the oil from boiling away.

An engine that could run at red heat would be more efficient. Hard to achieve, but we might have it in 20-30 years if work persists and we stay with IC and not go to fuel cells.

Yes I've just re-read my post, and I feel I didn't make a good stab at explaining myself. I was thinking managing cooling as in getting the hot gas out fast! I don't think I'd bother putting some exotic coating on, or even nikasil, as I think over time it'd burn through. Polish the parts, get the heat out quick.

work does go one with these coatings.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TVV-4KM46KT-B&_user=10&_coverDate=02%2F26%2F2007&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=2ab6fce8ee13f3a68b029fd36a892eab

and more to drill here. Theoretically I agree with the concept. Less heat lost to walls is better as you can have longer strokes to the same end pressure

http://www.google.com/search?hl=en&q=%22ceramic+coating%22+%2B%22engine+efficiency%22&btnG=Google+Search

I'm clearly thinking petrol engine not diesel engine here! Amazing how calcium zirconate-based materials usually found in high temp sensors find new uses.

Theoretically, if you keep the heat in the cylinder, the gases will expand more and therefore you will produce more energy from a given quantity of fuel.....e.g. efficiency goes up!!

Cooling reduces the efficiency, but stops motors melting!!!

I would expect that a complete engine from ceramic might be very fuel efficient!!

Hello back; You seem to have received some very good answers that probably have left you, well, still unsure.As I recall I was in a similar spot with a slightly different end application. The problem seemed to be that I knew what I had but didn't really have the best of luck because it seemed that temperature was allways the unkown factor. By that I mean, you add a coating and the performance changes but only for the better at a specific operating temp. As we all know the more work the engine does, the hotter it gets. Therefore what seemed to happen was the coating that improved the 'power, at one temperature caused a negative effect at another; Almost as if you needed differnet coatings at different temperatures to maintain the correct coating to be using the one that improved the power at that specific temperature. My solution was to elliminate the variable by manufacturing the critical components from ceramic.This gave the whole varrying equation a constant that could be used as a baseline for developement of coatings et al. I think that, if looked over by others may put a different twist on your question that others could pass thoughts on. I hope. Good luck.

They use water/air to cool engines so they do not melt as they cool incoming charge cannot overcome the heat of combustion. If you could make an engine that would run at 2000F it would be more efficient than anything we have now. The trick is to get something that will run at high temperatures and not break. Turbines do this because they do not have the impact loads of gas/diesel engines.

Very good insulation on all faces that see hot gasses will also add to efficiency.

Of course all gas engines are carnot limited. A good engine will have a downstream turbine in the exhaust to get extra out,.

In the 70's I used teflon applied to the piston and cylinder head and walls. After glass peening the surfaces it was applied and baked.

The results included longer time between ring changes, cleaner piston tops and combustion chamber, as well as more power.

Spark plug selection was trial and error, but the longer tips were better to a point, then pre-ignition was a problem. They did have a sorter life span, however.

One other thing was using a "L" shaped ring. It was available as an enduro bike part, but Sealed Power used to make them for car engines. The piston would have to be a modified one to accommodate the ring.

General Magna-Plate still coats all kinds of parts.

http://www.magnaplate.com/coatings/tufram.html

Water injection will help, but the water has to be very finely atomized. Ever notice how much better your car engine performs when the air is cool and humid?

Adding methanol to the water will help cool the air and add power. Some windshield washing fluids have water and methanol and can be used.

Hi Bill,

Interesting post.

You wrote:

"Some windshield washing fluids have water and methanol and can be used."

I just wonder what this might do to oxygen sensors and other engine components.

John