autocross

The testing of our Fiesta ST rear strut brace involved three different driving conditions.

Cornering: 30-40 mph, slalom

Braking: 50-0 mph, stop with ABS engaged

Acceleration: 0-60 mph, full-throttle run

Each setup (with and without brace) was tested on the same day on an identical surface and with the same driver. The tests are repeatable and will provide an accurate comparison of rigidity in the rear body portion of our Fiesta.

Results

Check out the plot below to see our testing results.

Fiesta ST performance results

These data points confirm our theory that the addition of bracing in this area of the ST does indeed have an impact on flex. Although flex in these conditions was not excessive, we did see a bit of movement.

Once the trunk brace was bolted into place, the results were very impressive; the brace reduced overall movement substantially. The acceleration and braking test saw less overall movement compared to our handling test. Movement during the acceleration and braking conditions

In our last update, we left you with some mock-up prototype pieces that we used to create and refine our Fiesta ST rear strut brace design. Since then, we've worked up a couple of functional prototypes to test our ideas for stiffening the rear of this hot hatch.

Initial Prototypes

We constructed two prototypes of this trunk brace. The first prototype is finished in a black powder coat, and we'll use this unit to evaluate for aesthetics and fitment. The unfinished ("raw") prototype is going to be used for testing purposes, meaning it will be modified.

First, check out our powder-coated unit bolted into place.

Mishimoto Fiesta ST performance parts

Mishimoto Fiesta ST performance parts

Everything fit nicely and bolted into position as designed. Check out a close-up shot of fitment with the lower tray support.

Mishimoto Fiesta ST parts

With the lower tray in place the bracing is barely visible.

Mishimoto Fiesta ST parts

Although this unit fit well and is extremely robust, we are going to make

We left off development with a neat look at our first prototype, when we determined the shape and path of our brace and printed out mounting brackets for each side of the piece. By using specific angles with our square material, we were able to avoid modification of the seat mounting bracket, retain rigidity, and provide a bar that is easily hidden by the rear tray.

Our last image showed our fabricator tacking together the material. Below is what we ended up with.

Prototype Fiesta ST rear strut brace installed

We then installed the floor panel mounting covers.

Prototype Fiesta ST rear strut brace installed

Let's take a closer look at how the plastic interior components sit with respect to our brace mounts.

Prototype Fiesta ST rear strut brace installed

As you can see, the height of our mounts will prevent use of the lower mounting position for the rear tray. We want this bar to allow the tray to fit in both the lower and upper positions, retaining all intensions from the factory design.

Chassis rigidity is extremely important for on-track handling, response, and feel. Ford provides a well-designed chassis with the Fiesta; however, as you can imagine, there is always room for improvement. Within the short time that this car has been available, the aftermarket has provided some great options, including better dampers, stiffer springs, and thicker sway bars, to enhance handling.

Our company will not likely dip into struts or springs, but we are certainly interested in helping stiffen the chassis. Our Mustang EcoBoost front strut tower brace is underway, and we recently launched development of a Fiesta ST rear strut brace. Time to get started!

What's The Plan?

Our goal here is to link one side of the rear trunk area to the other. You may wonder why this is needed. Doesn't the floor/body connect the two sides? Yes, but keep in mind, the floor is not made from a thick material. During aggressive cornering, the floor will see some pretty substantial flex. By connecting one side

Interested in purchasing our WRX radiator stays? Check out our product page for more information!

Mishimoto Subaru WRX/Sti Aluminum Radiator Stay Set

Now that we had our battery tie-down finalized, we could focus on the next component we wanted to tackle in the engine bay. Our next target would be the radiator stays, the small stamped steel pieces holding the radiator to the radiator support. We offer anodized aluminum radiator stays for a variety of vehicles including the previous generation WRX/STI, Honda Civic, and Ford Mustang.

For this particular project, we would be following a similar route. Our stays would be produced in aluminum and then anodized in a variety of colors to match an engine bay accent color. Before we get into the Mishimoto design, take a look at the stock components.

Stock 2015 WRX radiator stay

Stock 2015 WRX radiator stay

Following our standard product development procedure for smaller components, we designed our stays in Solidworks and printed them using our 3D

Interested in purchasing our Subaru battery tie-down? Check out more details on our product page linked below!

Mishimoto Subaru CNC Battery Tie Down

Mishimoto is not only interested in improving the performance, reliability, and power output of your new Subaru, but we also care about aesthetics. Small touches in the engine bay can make a big impact on the overall appearance and also provide a sense of personalization. Our first targeted component is the battery tie-down. The stock tie-down is rather bland, its main purpose being functionality, which is fine for a stock unit. For those looking to upgrade, a stylish aluminum replacement is ideal. In case you haven't yet peered into the engine bay of your "15, here is what the stock tie-down looks like.

Stock 2015 Subaru WRX battery tie-down

Our first task was to design a few prototypes and see what design we thought was most appealing. This is much easier said than done. Check out a few renderings of the design ideas from our team.

Mishimoto

Interested in purchasing our WRX catch can kit? Check out more details on our product page linked below!

Subaru WRX Baffled Oil Catch Can System

The final kit is ready for installation! After months of development and test fitting, we finally had our completed prototype components ready for fitment verification prior to mass production. Check out all of the components below!

First, the passenger side catch can bracket for the PCV system.

Final PCV catch can bracket

Next up is the finished version of our dual port catch can!

Final catch can

A cool shot of the internal components of the catch can.

Final catch can internal components

And finally we have the catch cans and both brackets included in this kit. The black finish is subtle and works well with the WRX engine bay.

Kit catch cans and brackets

We then attached the brackets to the cans in preparation for the full kit installation.

Catch cans with brackets installed

Now that we had all of the components ready to go, we performed one final

Interested in purchasing our 2015 WRX aluminum radiator? Check out our product page for more information!

Mishimoto Subaru WRX Performance Aluminum Radiator

Now that we had a finalized prototype, it was time to test this component to ensure that our improvements over the stock unit resulted in real-world advantages for our customers. An aluminum radiator provides the instantaneous benefit of increased reliability over the stock plastic unit. Despite this, cooling performance is always our primary goal with a heat exchanger.

Prior to actual road testing, our engineering team put together a few charts illustrating the improvements over the stock radiator.

Comparison of coolant surface area in Mishimoto and stock radiators

Coolant surface area refers to the space occupied by the tubes in the radiator. The amount of coolant surface area affects both fluid capacity and overall heat transfer contact points. A larger coolant surface area results in greater heat transfer and lower temperature.

Interested in purchasing our WRX catch can kit? Check out more details on our product page linked below!

Subaru WRX Baffled Oil Catch Can System

Time to start designing brackets! After a quick recap of the project goals, our creative engineering team began brainstorming. First, they selected a location for the catch can on the PCV valve side. It would need body mounting points for the can bracket, and preferably a short route for the hose so as not to complicate the engine bay. Our goal is a clean installation that appears stock-like, not a medusa of hoses routed about the engine bay.

The PCV valve on the 2015 WRX is located under the intercooler toward the rear of the engine block. You can see it in the image below, taken during a later stage of development of this kit.

2015 Subaru WRX PCV valve

We also needed to consider the differences between the RHD and LHD vehicles. In our US spec LHD model, both the brake booster and master cylinder are located on the left side of the engine bay.

Interested in purchasing our 2015 WRX aluminum radiator? Check out our product page for more information!

Mishimoto Subaru WRX Performance Aluminum Radiator

No need for an introduction, let's check out our second prototype!

Mishimoto prototype 2 radiator

Mishimoto prototype 2 radiator

Mishimoto prototype 2 radiator

So what can we tell from these images? The unit as a whole is very precise, and the TIG-welding is straight and accurate. All mounting points and adjustments to the previous version should make this a drop-in fit. One major difference you will notice from the GR radiator is the lack of an overflow port on the passenger top tank. On the previous generation, this line would run to the expansion tank located on the intake manifold. The FA20 does not utilize such a reservoir, so this port is removed.

Let's take a closer look at the core of this prototype!

Mishimoto prototype 2 radiator core evaluation

Mishimoto prototype 2 radiator core evaluation

The fin height is a touch shorter