You may be surprised to hear that there is yet another Rear Motor Mount available for the Mazdaspeed 3 platform in a market with more than a handful of options; however, this one is different. This RMM takes the idea box and kicks it to side as it makes a great leap towards style, performance and refinement. Ladies and Gentlemen, this is the new CorkSport Stage 2 Rear Motor Mount.
If you are even remotely familiar with the OE style (and many aftermarket options) RMM then you can clearly see that the CorkSport Stage 2 RMM is drastically different. Now let me explain why this is a good thing.
We all understand that the engine mounts isolate the engine from the chassis in an attempt to reduce and/or eliminate undesirable vibrations and noise experienced by the driver. That’s great and all, but what is really important is how the isolation is executed, specifically by the RMM. First, some background information.
There are three motor mounts working together to suspend the engine so let’s talk about the other two real quick. The transmission and passenger side motor mounts reside on the furthest ends of the assembled transmission and engine, respectively. These do most of the work supporting the engine given their positions, but a side effect of that is the aggressive rotational force they allow the engine to exert due to their transverse setup. This is where the rear motor mount comes in by managing the rotational force from the engine when applying power to the axles/tires.
Let’s take a look at the diagram below:
In the diagram we are looking at the OE RMM installed on the vehicle. This view is looking at the RMM from the right hand side of the vehicle. The diagram also attempts to show the general location of the transmission mount which is approximately where the transverse pivot point of the engine lies.
The engine exerts the rotational force onto the RMM shown with the double end red arrow. This can be further broken down into directional components as shown with the blue arrows. The forward force is unavoidable due to the design of the system in a whole, but the downward force can be reduced or even eliminated with a clever design such as relocating the damping material from the OE location to a location closer the engine pivot point. Note the length of the blue arrows as it will be different in the following diagram.
There are two key aspects of the CorkSport Stage 2 RMM that contribute to its superior performance and low NVH (noise, vibration, & harshness). First is the rigid design of the mount that installs into the sub-frame. This nearly eliminates any up and down pivot capabilities at the sub-frame thus reducing the magnitude of the up/down motion the RMM will allow. This feature has been used by a couple other manufacturers in the community because of is superiority. Second, and more importantly, is the location and orientation of the polyurethane bushings. The horizontal orientation of the bushing allows the bushings to function and support load in the same direction the engine exerts force. This results in a more durable design with less NVH.
Now comes the big game changer…the location of the bushings are in a location never done before in the Mazdaspeed 3 platforms. Comparing the OE RMM pivot location vs the CorkSport pivot location you will see that the CorkSport design moves the pivot point of the RMM forward in the vehicle. This is important because of how it relates to the natural pivot location of the entire engine/transmission. Moving the RMM pivot location further forward reduces the amount of downward force applied to the RMM at the sub-frame, thus reducing the NVH without compromising performance. This is shown with the different length blue arrows in the diagram. This allowed us to use very stiff 95A durometer polyurethane without compromising driver and passenger comfort.
Anyways, enough with the technical stuff; check out this video comparing the OE RMM and CorkSport Stage 2 RMM in action.
If this hasn’t blown you away already then let Jason Atwell’s Beta test review set it in stone for you…
“Tested out the new CS RMM and I’ve gotta say; I was dead set on the gold RMM I was currently using. Once I got the CS one, I installed it right away. The fitment was spot, I hoped in the car and took it for drive and noticed an even more solid feel in the shifts. The vibes are about the same as the gold RMM so all in all I’d have to say it’s a fantastic product and would recommend.” – Jason Atwell