Over the years REC has experimented with different cermet and ceramic products which can benefit a rotary engine by reducing friction, heat and wear, as well as control engine temperatures.
The most common coating process performed to internal combustion engines is ceramic coating the pistons, or in this case, the rotor. This process is performed only on the combustion faces of the rotor. The application thickness can vary from 1 or 2 thousandths of an inch all the way to 3 to 4 thousandths of an inch. The purpose of ceramic coating is to provide a thermal barrier, which helps much of the heat that develops in the combustion process not transfer directly onto the rotor surface, keeping the rotor as well as the motor oil, cooler. Some ceramic coating products are also specifically designed to prevent carbon cooking on the combustion faces of the rotor. REC primarily recommends this coating for high horsepower and high boost applications to help prevent detonation.
Because of the odd and non-symmetrical shape of the combustion chambers, the rugged finish within the chambers attracts heat causing hotspots. These hotspots can cause a type of pre-ignition called dieseling. This ceramic coating allows the combustion chamber to hold heat evenly and thus reducing these hotspots. We choose and also recommend having the coating applied on the thinner end of thickness tolerances as we believe it is necessary for some of the heat to be transferred into the oil, however the rotor surface will still benifit from reduced and even heat distribution.
Cermet coatings are coatings which are primarily used to bond riding surfaces, areas of metal to metal contact or other areas where friction takes place. In a rotary application, the most common area to apply these coatings are to the riding surfaces of the housings themselves. Much like the way that the factory and housings are nitrated for extra hardness, cermet coatings act in a similar way. However, this coating procedure actually takes the place of the stock chrome plating of the rotor housing and the nitrated surface of the end housing.
The cermet product applied to just the side housings alone will work to reduce friction dramatically when compared to a factory nitrated surface. This procedure is a fundamental key to reliability in all road race applications. Some of the top winning Mazda sponsored race cars have successfully used this product and it helped bring thes cars to victory.
REC has developed special techniques to remove the factory chrome from the rotor housing which is then etched, prepped, and then finally sprayed. The end housings can undergo two different types of preparation before the product is sprayed.
1) the end housing surfaces are ground on a surface grinder, prepped and then this spray is applied all the way across the end housing face including the water jacket area.
2) the end housing riding surface is milled to create a counter bore area (or step) then prepped, and sprayed within this contained area only.
Although method 1 requires less prepping and millwork, there is more cermet material required to spray a larger surface area. Hence the cost of materials is more. The second method will use less material but the additional costs of prep work and mailing makes this method and overall more expensive process.
When working with aluminum side housings, cermet coatings are one of the only options which will provide a reliable and durable riding surface. REC’s own two-piece aluminum 20B replacement center plate is prepped and milled as mentioned in method two. This method is by far the superior way to achieve the best reliability and longevity. Once this product is applied to aluminum parts, a special refinishing process called "diamond lapping" is performed. REC offers this in-house service.
Cermet Coating Cost Range: $395.00-690.00 - Please inquire for accurate quote
Similar to our conventional side housing lapping cermet lapping is designed strictly to resurface the housings coated with our race cermet coating. Because cermet surfaces are substantially harder than traditional nitride treated housings, a slightly different process is needed. Cermet coated housings need to be lapped on a riding surface which is coated with cermet itself. We then need to apply diamond lapping compound which is substantially more expensive than traditional aluminum oxide compound. The lapping time required to do each face is also higher.
Cost: $115.00 per face