Revvolution Project BRZ Tear-Down and Seam Weld

Article by Brian Hannon. Photography by Corey Davis, Ryan Randels and Nathan Leach-Proffer.

Last week, we introduced the Project BRZ, and outlined the partners involved and our overall build objectives. As you will recall, the goal for the Revvolution Project BRZ is a progressive performance build that is oriented toward high-performance street driving and moderate track applications. This week we will dive into the project with hands-on feedback as we outline our first objective: strengthening the chassis.

While our donor engine sits in a million pieces waiting for the delivery of our upgraded components, we turned our attention to strengthening the chassis and related components to support the power we need it to handle. To do this, we had to strip the car down to its most basic form to really understand the platform in its bare essence, as well as assess the performance strengths and weaknesses of the BRZ. We plan to address the chassis’ strength components piece by piece, while keeping in mind our end objective.

The first component we’re addressing is chassis strength, and how to reinforce it properly as it is a crucial, yet often overlooked, component for a performance application. Essentially, chassis stiffness and strength have everything to do with how predictable the car is. The more predictable your car is, the easier it is to control. When you preload the suspension into a corner, and power out of the apex, you want a predictable outcome.

A leading culprit of unpredictability is chassis flex. This is when the vehicle is functioning like a spring when stressed by cornering g’s, and unloads forces in directions you may not want. While cars from the factory are relatively stiff, they’re not designed to take the loads that performance enthusiasts repeatedly place on them. A day at the track or a spirited drive down a familiar back road can put excess loads and stress on the vehicle that may be outside what the factory originally planned for. Also, cars out of the box may be tight for a while, but in two to three years, the chassis can relax a little and the flex will increase.

Before we get into the details of the build’s progress, let’s take a closer look at the chassis design we are dealing with. The BRZ / FR-S is a unibody design that integrates the frame into a sheet metal body (check out our look into different frame types and their strengths here). The front is an assembly structure where everything is bolted together to bring in structural strength, while the rest of the car is a "canopy” structure. Canopy structure is akin to an eggshell where the body of the car functions as a structural component and is tied in with the main chassis. The assembly structure’s rigidity is like that of a rectangle, while the canopy structure is more akin to that of a triangle. As we noted previously, rigidity is compromised slightly because the whole assembly is made of sheet metal, which is often spot-welded together. While the entire cabin and trunk can certainly benefit from increased rigidity, the front two "stabs” are exactly where the support is needed in this platform. Our plan for the BRZ is to increase chassis rigidity by bracing, and supports (to come later) and seam welding, which is the focus of today’s article.

So what is seam welding? Taking a step back, we need to understand how most chassis seams are put together in the factory. Typical manufacturing processes include spot welding (or stamping together) the unibody sheet metal, and then using the seam sealer to seal the joints to keep out air and moisture. This saves manufacturing dollars but isn't exactly the best process in terms of performance. After removing the factory sealer from the trunk area, for example, there was about a 1/8" gap visible, so you can get an idea of how much flex there could be from factory sealing. The seam sealer is there to prevent debris and precipitation from invading the cabin. Seam welding replaces the seam sealer with stitch welds at all structural intersections and connections. You can take it a step further and weld all of the associated unibody structures and panels together.

Seam welding is a strength and consistency upgrade, and helps keep the chassis tight for longer. This results in a strong and reliable chassis, which reduces body flex and provides reinforcement for key structural points. Some performance critics will sight that one downside for seam welding is, every time you weld, you’re adding weight. However, we are hoping for a net decrease since we removed all of the factory seam sealer.

To start the process of seam welding our BRZ, we brought the car to our interior and aesthetics partners, Elite Auto Salon (EAS), to remove the entire interior.

They pulled out everything to reveal the underlying unibody chassis with the intention of sending it off to SLVA Automotive Studio for seam welding. We also used that opportunity for EAS to address the strengths and weaknesses of the interior and trim.

Once EAS had stripped down the interior, we brought the barren BRZ over to our friends at SLVA for removal of the factory seam sealer to be followed by starting the seam welding process.

After completely removing the sealer, SLVA took to stitch-welding all the interior seams. We were impressed with the welding and thoroughness SLVA applied from the rear bumper all the way up to the firewall.

You may have noticed we didn’t add any additional welding to the engine compartment or front stabs. Fret not, that’s coming. We haven’t yanked the engine yet since we are still ferrying the car from shop to shop, so we didn’t have the luxury of a bare engine bay. Once we get the car over to SCR Performance to pull the drivetrain, we’ll get it back to SLVA for the finishing touches. The next step for chassis strengthening will be the installation of supports and braces that we have slated for the build in the near future.

On the drive home, the effects were immediately realized as the chassis felt much tighter and, though this was hard to believe, the already responsive chassis became borderline telepathic. We can only imagine what the car will feel like on the track.

Next week we’ll take a more in-depth and technical look at the FA20 as we pull it completely apart and document the entire process. SCR will assess the FA20’s strengths and weaknesses, as well as the primary differences between the FA20 and EJ-series. Expect copious amounts of photographic support for that article!

While we wait on a couple of critical components to arrive, the build continues on schedule. Be sure to follow our progress on Facebook and Instagram, and stay tuned for next week's installment!

The Subaru BRZ / Scion FR-S Platform Series Partners

Please take a moment to check out our partners, whom without, none of this would be possible:

The world's most enthusiast-friendly Subaru dealership.

SCR Performance
The Performance Expertise Behind the BRZ / FRS Platform Series.
Visit them on the web @

SLVA Automotive Studio
Where Form meets Function.

Our Audio and Aesthetics Partner aka the Architects of Fidelity.
Visit them on the web @

AR Design
The Fabrication Masterminds Behind our Forced Induction Systems
Visit them on the web @
Our Sport-Compact Performance Parts Source. . . Never Compromising Quality or Customer Service.
Visit them on the web @
Visit them on Facebook @

Air Lift Performance
The Progressive Behind the Build
Visit them on the web @

Maintaining Integrity & Strength through CUSCU Performance
Visit them on web @
Visit them on Facebook @

Wilwood Engineering
The Stopping Power
Visit them on the web @

Advan Racing
Bringing Together Performance & Aesthetics
Visit them on the web @

Turbo By Garrett
Forced Induction at its Finest
Visit them on Facebook @


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Brian Hannon (BHRP)

Grew up around cars and racing, a passion fueled by my whole family. Participated in numerous track days with cars and motorcycles as well as covered the NASA East Coast Honda Challenge for Grassroots Motorsports. Now that I'm in Colorado I'm enamored with the Pikes Peak International Hill Climb... borderline obsessive...
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Write a CommentCOMMENTS

Really nice article and its awesome to see such a new BRZ/FRS being gone through so thoroughly!

Rockysds's Profile Image

Amazing progress. An even more amazing team making it ALL happen. #keepitup