Tegiwa GT86 Rally Build: We’re ready to hit the stage!

Dave VarleyOctober 30, 2025Last Updated: October 30, 2025

7 minutes read

After 5 months of planning, building, and meticulous assembly, our K-swapped GT86 rally car is finally complete. What started as a high-mileage Japanese import has been transformed into a purpose-built rally weapon that combines Honda reliability with Toyota’s chassis dynamics. This is the culmination of everything we’ve learned over the past few months, and we couldn’t be more excited to share the final specification with you.

The Vision

When we set out to build this GT86 for rally, we knew we wanted something different. The platform offered the perfect foundation – lightweight, rear-wheel drive, and fantastic handling characteristics – but we needed more power and the reliability to withstand the rigours of competitive rallying. The solution? A complete K-series engine swap, paired with comprehensive upgrades across every system.

Engine & Drivetrain

The centrepiece of this build is undoubtedly the 4Piston K400 K24 2.5L engine. This isn’t just any K24 – it’s a purpose-built motorsport unit featuring ductile iron sleeves, a 99mm stroke, and an 89.5mm bore, all designed to deliver reliable power in demanding conditions. The increased displacement over a standard K24 gives us the low-end torque we need for rally stages while maintaining the Honda K-series’ legendary high-RPM character.

Getting a Honda engine to work seamlessly in a Toyota chassis is no small feat, which is where the KPower Industries Complete K-Swap Kit comes in. This comprehensive package includes everything from the transmission adapter plate to engine mounts, allowing us to mate the K24 to the factory GT86 six-speed manual gearbox. We’ve upgraded the transmission internals with an MFactory 2-way limited-slip differential for improved traction too.

The Exedy Stage 1 Organic clutch provides the perfect balance of drivability and performance, giving us confidence whether we’re navigating tight hairpins or launching off the start line. Power is delivered smoothly thanks to tuning from Robbie at TDP, but with plenty of bite when we need it.

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Managing this potent engine required serious hardware. The Haltech Elite 1500 ECU serves as the brain of the operation, controlling everything from fuel delivery to launch control. We’ve paired it with a Haltech 82mm electronic throttle body for sharp response and a Skunk2 Ultra Race inlet manifold with a 1-litre spacer to maximise airflow. The Haltech IC-7 digital dash displays all critical engine data at a glance, ensuring we can monitor everything in real-time during competitive stages.

Cooling is absolutely critical in rally, where sustained high loads can quickly overwhelm an inadequate system. We’ve installed a Mishimoto aluminium radiator backed by high-flow fans, plus a dedicated Mishimoto oil cooler with a sandwich plate adapter. The T7 Design alternator relocation kit not only looks trick but also improves serviceability. Tegiwa reflective heat sleeves protect vulnerable components from exhaust heat, while the Milltek catback exhaust system evacuates gases efficiently and sounds absolutely fantastic whilst doing it.

Power means nothing without proper lubrication, so we’re running Torco SR-1R 10W-60 engine oil – a fully synthetic race oil designed for high-stress motorsport applications. The lightweight AntiGravity ATX-30 battery saves precious kilograms up front while providing reliable starting power.

Suspension & Chassis

Rally demands a suspension setup that can handle everything from smooth tarmac to rutted gravel stages, often within the same event. The YSR Tarmac Rally 2-way coilovers form the foundation of our suspension package, offering separate compression and rebound adjustment so we can fine-tune the setup for different stages and conditions.

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We’ve completely replaced the factory suspension geometry with Hardrace components throughout. The front gets Hardrace lower control arms, adjustable drop links, and a 25.4mm anti-roll bar. The rear features Hardrace upper camber arms, rear trailing arms, and toe arms, giving us complete control over alignment settings. This adjustability is crucial for extracting maximum performance from the GT86’s already excellent chassis.

Chassis rigidity has been improved with Hardrace’s rear chassis brace, differential mount brace, and solid rear subframe inserts. These upgrades reduce flex under hard cornering and provide a more direct connection between the driver and the road.

Rolling on Braid Fullrace A wheels in 17×8 ET2, we’ve fitted Yokohama A051T rally tyres in 235/45/17. These are proper competition rubber designed specifically for tarmac rally work, providing exceptional grip and feedback. The Haltech tyre pressure monitoring system lets us keep a close eye on pressures throughout a stage, ensuring optimal performance and safety.

Brakes

When you’re carrying serious speed into tight corners, having brakes you can trust isn’t optional – it’s essential. The YSR big brake kit transforms the GT86’s stopping power, with bigger 330mm discs and 6 piston calipers provide fade-resistant performance stage after stage. Hawk HP+ brake pads deliver the perfect blend of initial bite and consistent performance, even when hot.

HEL braided brake lines eliminate the spongy feel of stock rubber lines, giving us a firm, consistent pedal feel. We’re running Motul RBF660 brake fluid throughout, a competition-grade fluid with an exceptionally high dry boiling point of 325°C. The Motamec hydraulic handbrake provides the precise handbrake control needed for tight hairpins and quick direction changes, a rally essential.

Interior

The interior has been completely transformed into a purposeful competition environment. The Safety Devices roll cage forms a protective cocoon around the occupants, meeting all relevant safety regulations while adding significant structural rigidity. RRS Carbon Control bucket seats keep us secure during cornering, mounted on Planted Technology seat bases with RRS R6 Light Evo harnesses providing proper racing safety restraints.

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Weight reduction was a priority throughout the build, which is why we’ve fitted a lightweight fibreglass dashboard in place of the heavy factory item. This still accommodates all essential controls and the Haltech IC-7 digital dash, which provides a wealth of information at a glance. The Personal Neo Grinta 330mm steering wheel offers the perfect grip diameter and a suede finish for excellent feel, even when wearing gloves.

Communication is critical during rally stages, so we’ve installed a ZeroNoise communication system for clear helmet-to-helmet communication with the navigator. The Tegiwa wide-angle roll cage mirror provides excellent rear visibility without the weight of a factory glass mirror. The Tegiwa PDM-style button pad gives us fingertip control of essential functions, while the Tegiwa 150A kill switch provides emergency shutdown capability as required by regulations.

Safety equipment includes an OMP electrical fire extinguisher system, a first aid kit, and an RRS spare wheel strap to secure the spare during transit. The RRS passenger foot plate provides proper support for the navigator, while the Ricky Evans heated windscreen ensures clear visibility in all conditions – a genuine game-changer for UK rallying.

Exterior

The Tegiwa custom body kit isn’t just for show – every element has been designed with function in mind. The Tegiwa x RuskiWeldFab custom light pod houses 4 Tegiwa LED light bars, providing exceptional illumination for night stages or poor weather conditions.

The RRS carbon roof scoop channels fresh air into the cabin, helping keep the occupants cool during intense stages. A genuine Toyota aero rear spoiler and carbon wing mirrors combine lightweight construction with purposeful styling. TOM’S-style rear tail lights complete the rear end of the GT86.

Weight savings extend to the glazing, with Theia Plastics polycarbonate windows replacing heavy factory glass. RRS 4mm mud flaps protect the bodywork from gravel and debris, while the Tegiwa custom livery ensures we look the part on every stage.

Power Figures

On our Maha MSR500 dyno, the K-swapped GT86 laid down an impressive 333bhp – a massive jump from the 182bhp the factory FA20 produced on the same dyno. Granted, the stock FA20 had covered 316,000 kilometres! That’s a 151bhp gain, transforming this car’s performance completely. But impressive as the headline figure is, it’s the delivery that matters most for rally. The K24’s broad, linear power band provides strong, predictable acceleration out of corners and excellent driveability across the rev range. This is usable, accessible power that translates directly into faster stage times and greater driver confidence.

What’s Next?

With the build now complete, we’re eagerly anticipating getting this GT86 out on stage where it belongs. We’ve built this car to be competitive, reliable, and most importantly, an absolute joy to drive at the limit.

Throughout this build series, we’ve documented every step of the journey – from the initial purchase of a high-mileage Japanese import through to the completed rally weapon you see today. It’s been an incredible project that showcases what’s possible when you combine quality components with careful planning and execution. You can check out the build thread on our blog or watch the series on our YouTube channel.

A Massive Thank You

A build of this scale simply wouldn’t have been possible without the incredible support we’ve received along the way. A special thanks must go to Haltech, who played an absolutely vital role in getting this car running. Their technical support and expertise were invaluable throughout the process – we genuinely couldn’t have done it without them. Huge appreciation also goes to Robbie at TDP for the expert tuning work that unleashed the K24’s potential, and to the teams at 4Piston, KPower Industries, YSR, Hardrace, MFactory, RRS, Milltek, Hawk, Yokohama, Safety Devices, Mishimoto, Braid and all the other companies who provided the quality components that made this build possible. A project like this is only as good as the parts you use and the people who support you, and we’ve been fortunate to work with the very best. Thank you all for believing in this vision and helping us bring it to life.

Check out all the parts that we used to build this car, here:

Dave VarleyOctober 30, 2025Last Updated: October 30, 2025

7 minutes read

The Vision

Engine & Drivetrain

Suspension & Chassis

Brakes

Interior

Exterior

Power Figures

What’s Next?

A Massive Thank You

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