Thanks to the Department of Defense and NASA we have an entire family of chemical surface treatments that can be applied to various engine components. Our tax dollars have made all of this possible.
Most of the cutting edge developments in both F1 and NASCAR the past few years have been in ever more sophisticated coating technology. Even after all these decades coatings remain as the cutting edge of engine technology.
These coatings are not just about reducing friction. Coatings won’t make a measurable power difference unless the motor is turning over 6,500 rpm. Thermal barrier coatings and dry film lubricant coatings though don’t need to be spinning high rpms to be beneficial.
High tech coatings will though make a difference in three areas.
- Increased thermal efficiency of the engine
- Decreased amount of internal friction in the engine
- Increased longevity of internal engine parts
Thermal Efficiency: Your racing engine is actually an energy conversion device. It creates thermal energy and converts it into kinetic energy. When you introduce a spark into the combustion chamber of your engine you’re setting a mixture of gasoline and air on fire. It’s not an explosion – it’s a fire. The spark plug starts this fire and it spreads across the combustion chamber. This is thermal energy.
The bad part is very little of this thermal energy is converted into kinetic energy. Most estimates are that only twenty per cent of the thermal energy is converted to kinetic energy. The bulk of the thermal energy is sent to the cooling system or out the exhaust pipe.
Every thing you do to increase the power of your engine is simply a way of improving the thermal efficiency of your engine. Those expensive carburetors and the fancy porting job that cost you a small fortune are simply a way of getting more air and fuel into the combustion chamber. The greater the amount of air and fuel you can pack into the combustion chamber the more thermal energy you can create.
High tech coatings help that energy conversion process by keeping as much of this thermal energy in the combustion chamber as possible. It’s far better to keep the thermal energy inside the combustion chamber than sending it to the cooling system. Coating the tops of your pistons and the roofs of your combustion chambers is critical to capturing all the thermal energy. That will lead to increased power.
Reduced Friction: Anti-friction coatings on piston skirts, valve springs and valve stems reduce frictional losses. There are really two major types of coatings here. We have oil shedding and self-lubricating.
The self-lubricating dry film is normally applied to piston skirts, valve springs, camshaft lobes, wrist pins and valve stems. These coatings are generally some sort of polymer and each company will have a slightly different compound. These coating are generally applied to a thickness of less than .001 of an inch.
It’s difficult to reduce friction beyond what a wet oil film can offer. Swain considers these coatings as solid or dry film lubricant coatings. The primary purpose of these coatings is to provide a solid film of lubrication when the wet lube isn’t there. This could be on a cold start or a momentary instance of oil starvation. This coating also provides additional protection when a load is greater than what the oil film can handle.
These coatings offer minimal reductions in friction because they tend to hold the oil film more effectively than bare metal or bearing material. Their real value is providing a film of lubrication when the wet oil film is insufficient or simply not present.
Piston skirts and rod/main bearings benefit the most with these coatings. With older engines that normally suffer from valve spring fatigue the solid film lubricant coating helps reduce the friction and heat.
Wrist pins are rarely coated because the base metal is so hard it limits the profile that Swain Tech Coatings can put on them in the surface prep stages. Also, the fit between the piston pin and the bore is so tight most of the coating gets removed as the pin is pushed back in.
Camshafts are rarely coated for similar hardness limitations and the type of blunt load the cam lobe takes limits the service life and benefit of the coating on most camshafts. Wrist pins and camshafts can be coated but we rarely encourage this to be done because it offers little benefit.
The oil shedding type of coating is most often found on connecting rods, crankshaft counterweights and oil pans. Again these are usually some sort of polymer. These coatings act similar to Teflon in that oil won’t stick the surface. The oil simply beads up and won’t stick to a surface.
If your motor is spinning over 6,500 rpm and you really want to find those last five horsepower you should consider oil-shedding coatings. The counter weights on the crankshaft and connecting rods benefit the most as they rotate compared to the oil pan where the coating just helps with oil run back. Swain doesn’t feel these coatings should be a high priority. If you’re looking for those last few shreds of power you could consider using coating on the counterweights and connecting rods.
Increased Longevity: If you can reduce the internal heat of your engine some parts are going to last a lot longer. The best example of this might be your valve springs. The coating used here reduces the internal temperature of the spring and thus provide you with increased longevity.
Things That Can Be Coated
Pistons – Pistons are interesting since they require two different types of coatings. The top and the thrust surface require different coatings.
The top of the piston needs a ceramic thermal barrier (a thermal barrier in the combustion chamber also helps the chamber retain heat and the sides (or thrust surfaces) need a coating that reduces friction and scuffing.
Header System – Don’t confuse this type of exhaust coating with the cosmetic coatings that are available. Those low tech coatings are really pretty but do very little to insulate the exhaust or increase power. You want a thermal barrier that keeps the energy in the header. This serves two purposes. It makes your engine compartment cooler and it keeps exhaust gas velocity high.
After the exhaust gases exit the combustion chamber it needs to be kept warm. Hot exhaust gases have greater velocity. As the exhaust temperature cools the velocity slows. Ceramic coatings keep the heat inside the exhaust system. These thermal coatings are usually about 0.15-inch thick as opposed to the cosmetic coating, which are seldom more than 0.002-inch.
Exhaust Ports - All of the things I just said about the exhaust system apply to the exhaust ports in the cylinder heads. Remember your exhaust system begins at the exhaust valve. We want to keep as much heat as possible in the exhaust system.
Valve Springs - using a coating that reduces fatigue and heat can reduce valve spring failure. Cooling and longevity are two of the advantages of the new valve spring coatings. You should see a significant improvement in valve spring life.
Bearings - Coated bearings don’t appreciably change the shell dimensionally, but they do a great job of improving both bearing and journal life. These oil attracting low friction coatings allow parts to move freely and also provide some back up lubrication if oil starvation occurs.
The Value
Let’s think about spending roughly $1,000 here. That will get you into the ballpark. If you have a very basic engine $1,000 you might get more power from a new camshaft or head-porting job. Now if you’ve done all that and you’re looking for the last few horsepower then $1,000 worth of engine coatings will be a very good value.
Thermal barrier coatings offer the most value when power gains are your primary purpose. Making more efficient use of the thermal power from the combustion process is the most effective way to gain power through the use of coatings. Measurable power gains come from coating the pistons, combustion chambers, exhaust ports and the exhaust header.
In some applications you might get a small measurable gain from the solid film lubricants being used on piston skirts and bearings. However, the primary benefit from the solid film lubricant coatings is that you have a solid film of lubrication when the wet oil film isn’t present due to a cold start, oil starvation or excessive load.
The real value for most of us may be in increased longevity. Most (but not all) vintage racers aren’t on the ragged edge of the horsepower curve. We’re more concerned about getting through the season without an engine rebuild than we are about those final five horses that live way out on the horsepower curve. If we can spend less than $1,000 and make our parts last a little longer we’ve found true value. That’s what coatings are all about when it comes to our old cars. The real value may be the increased life span of your engine parts.
