VT21x – 2021 Subaru WRX STI Rallycross Supercar

At first glance, the VT21x appears similar to the VT21r with the addition of a more aggressive body kit. But the 21x features significantly more engineering prowess and power. It’s designed for the rigors of mixed surface, high flying Nitro Rallycross competition.

The closed-circuit series pushes Subaru’s performance to the limit. In 2021, Subaru Motorsports USA scored a 1-2 podium finish in the Nitro RX driver’s championship with drivers Travis Pastrana and Scott Speed in a thrilling tie-breaker and in matching VT21x race cars. In 2019, this car drove the team to victory in the Americas Rallycross Team’s Championship with four wins in six rounds. What’s the secret?

Starting with the same solid bones as our VT21r, we create the VT21x with supercar levels of speed and engineering. Nitro Rallycross is a crowd favorite for huge power slides, big jumps, and breakneck acceleration. The rear doors are sealed, the side mirrors are tiny and mounted on the polycarbonate windows, and the complete vehicle weighs just 2600 pounds dry (with ballast added to meet the 2915-pound series minimum). The frame is seam-welded for extra strength and has a steel roll cage welded to it (with more safety including onboard fire suppression and a Kevlar fuel cell). As a drift king and a champion long-jumper, the VT21x has a special body kit that allows for both extra downforce and maximum wheel travel on its Reiger suspension. VSC fabricates its own suspension arms, links, cross members, hubs, and spindles to handle extreme loads. Aluminum skid plates for the oil sump and differentials, along with a full composite underbody covering, ensure the VT21x can run smoothly lap after lap.

There’s another reason the rear doors don’t open: The radiator is mounted behind the front seats in a position that’s optimized for the mud-slinging, bumper-car-bashing style of Nitro Rallycross. We blocked off the lower bumper intakes and moved the whole system to the middle where it is better protected from impacts and can inhale a cleaner stream of air. It also allows us to install a larger intercooler up front in the engine bay with more surface area (water-spray cooling is not allowed). Feed and return pipes, installed with the fewest bends and joints as possible, circulate water back to the engine. And about that engine: With a larger Garrett turbo and a 45-mm restrictor (that’s nearly a third larger than what’s allowed in the VT21r), the custom Subaru BOXER belts out over 600 hp and 680 lb-ft of torque.

A six-speed Sadev sequential gearbox connects to a triple-plate clutch and two limited-slip differentials. The VT21x can decouple the rear axle with a special clutch pack in the center differential that opens when the driver pulls the handbrake. Depending on the track, VSC can modify the torque split and clutch engagement at both axles. The brakes are significantly larger than that of the VT21r’s 12-inch rotors, at 13.8 inches in front and 12.6 inches in the rear. Our no-compromise approach to design and testing results in a one-of-a-kind car that’s among the world’s fastest and most capable at handling the twists, jumps and impacts of rallycross.

For more details go to: https://www.subaru.com/content/subaru/en/motorsports/cars/rallycross.html

SRTUSA 2021 Rallycross Supercar   
2021 Subaru WRX STI Rallycross Supercar (VT21X)
Prepared by Vermont SportsCar

ENGINE
Horizontally Opposed 4-cylinder
Turbocharged and Intercooled
Approx. 600 bhp and 680 lb-ft torque with NRX Mandated 45mm Restrictor
Garrett Motorsport Turbocharger

ENGINE MANAGEMENT
Cosworth Pectel ECU

ELECTRONICS
Lightweight Motorsport Wiring Loom
Cosworth Programmable Power Management System
Cosworth data logging system GEMS LDS4 Display

WEIGHT
Regulated Minimum Limit of 1,300kg

TRANSMISSION & DRIVE SYSTEM
SADEV 6-speed Sequential Dog-engagement Gearbox
RCV Custom Driveshafts
RCV Custom Propshaft

CLUTCH
Triple Plate Carbon Racing Clutch

DIFFERENTIALS
VSC (Front) SADEV (Rear)

COOLING
PWR Radiator Mounted in Rear and Ducted
PWR Intercooler Front-Mounted and Ducted

SUSPENSION
Reiger Competition Suspension
Vermont SportsCar Tubular Front and Rear Cross Members
Vermont SportsCar Suspension Arms and Links
Vermont SportsCar Hubs and Spindles

BRAKES / GRAVEL SPEC
Alcon 350mm Front Brakes
Alcon 320mm Rear Brakes
Endless Brake Pads
Vermont SportsCar Hydraulic Handbrake

EXHAUST SYSTEM
VSC Custom Exhaust Manifold
VSC Stainless Steel 4-inch Quick-Change System

WHEELS
KMC “KM-199” Rallycross Wheel

TIRES
Yokohama ADVAN AO54 Rallycross Tires

ROLL CAGE / SHELL PREP
Seam-welded Shell Custom FIA Specification T45 Roll Cage

SEATS
RECARO Ultima with HANS (Head & Neck Restraint)

INTERIOR
Carbon Fiber Dashboard
Carbon Fiber Door Cards
Carbon Fiber Driver Footplate
Schroth Enduro Harnesses

FUEL CELL
FIA FT3.5 Fuel Cell (25+ Liters)

BODY
Composite Bumpers, Fenders and Rear Doors
Composite Under-floor Protection
Carbon Fiber Rear Wing
Aluminum Sump Guard
Aluminum Differential Guard

MISC
Polycarbonate Front Windshield
Polycarbonate Side and Rear Windows
Custom Motorsport Steering Rack (11:1 Ratio)
Motorsport High-flow Power Steering Pump

Subaru Motorsports USA Dust Erruption
2021 VT21X Interior Cockpit
Subaru Motorsports USA NRX Lineup
2020 VT20X Interior Driver Display
NRX Jump Sequence
21x Wheel Close up
21x Testing Pan
2020 VT20X Interior ECU
Subaru Motorsports USA Sunset Lineup NRX
2020 VT20X Interior Cooling Ducts
Subaru Motorsports USA NRX Jump Test
21x Subaru Motorsports USA Gravel Spray