Custom Performance Engineering, Inc. has chosen to think outside the box on this and come up with a completely new Focus ST RMM design. To do this, cp-e™ carefully studied the layout of the stock Focus ST rear motor mount. Immediately after removing the rear mount it was decided that a better design could be achieved.
The Ford Ecoboost engine mount system contains two side mounts that provide a rotational mounting point. The rear motor mount is added to help prevent the engine from swinging like a pendulum. However, the design of the stock mount orients the bushing horizontally; allowing applied stresses to act along two planes in the bushing. These types of bushings are not really meant for this and it has been found that the rear mount may be inadequate in preventing the engine from moving.
cp-e™ has come up with a way to apply stress to the bushing in only one plane. By redesigning the whole Focus ST RMM, cp-e™ was able to mount the bushing vertically so that the pendulum effect of the engine is compressing the bushing properly. Orienting the bushing in a way that allows it to be compressed properly has allowed us to create a mount that provides a stiffer system while still using a low 65 durometer bushing.
cp-e™ goes a step further by using EPDM, a sort of rubber bushing. Urethane begins to fail at temperatures as low as 200°F and generally the bushings need a higher durometer rating to hold together. The Focus rear motor mount is a perfect example of when not to use urethane. The location of the mount allows a large amount of heat to be transferred to the bushing. EPDM holds up to this heat, and doesn’t begin to break down and fail. EPDM has a higher density than urethane, so the bushing can have a lower durometer rating while keeping high reliability and support. Why is that good? Higher durometer ratings transfer vibrations through the vehicle and into the cabin, raising the NVH (noise, vibration, & harshness) value.
To give you these benefits, the two 17.1lbs blocks of aluminum are put in our CNC machine to be whittled down to only 2.17lbs. This process takes a lot of time but was necessary to provide the design necessary for the application.
Through initial testing our mount has shown to help hold the engine properly in place while providing a low durometer bushing in order to keep the in cabin vibrations low. It is to be expected that vibrations will be added in some points of the driving experience, but this effect comes solely from stiffening up the engine mounting system.