VB WRX Build Guide: From Stock to 400+ WHP

Platform Overview

The 2022+ Subaru WRX (internally designated VB) is powered by the FA24DIT — a 2.4-liter turbocharged flat-four producing 271 bhp and 258 lb-ft of torque from the factory. On the dyno, the VB WRX puts down approximately 225-245 whp at the wheels. It is available with a 6-speed manual or CVT automatic, paired with Subaru's symmetrical AWD system.

The FA24 is a significant departure from the EJ257 that powered the STI. It features a closed-deck block, direct injection, and a single twin-scroll turbocharger. The closed-deck design gives the FA24 significantly better strength at the cylinder walls compared to the open-deck EJ, which means it handles boost better from a structural standpoint.

The aftermarket for the VB WRX is growing rapidly. COBB Tuning has been the primary pioneer, with comprehensive Stage 1 through Stage 2+ power packages already available.

Stage 1: Tune Only

The FA24 responds well to tuning, though gains are more modest than the older EJ platform due to the factory calibration already being relatively well-optimized. The primary tuning platforms are:

• COBB Accessport V3 ($770) — THE Subaru tuning platform for the VB generation. Full-color touchscreen ECU flash with Stage 0/1 OTS maps for 91 and 93 octane. Expect +25 whp and +23% peak torque on Stage 1 93 octane OTS. 50-state legal (CARB D-660-125). Supports both 6MT and CVT.
• COBB Stage 1 Power Package ($845) — Accessport V3 bundled with a high-flow drop-in intake filter and Stage 1 OTS maps. Same power gains as standalone Accessport since the filter alone adds minimal power. Good value bundle.
• Burger Motorsports JB4 ($529) — Plug-and-play piggyback tuner with up to 50 whp (70 hp crank) on the stock car. 8 preloaded maps with on-the-fly switching. Not VIN-locked, transferable. No ECU flash required.

For flex fuel capability at Stage 1, the COBB Stage 1+ Flex Fuel Power Package ($2,075) includes the Accessport, CAN gateway module, flex fuel kit with ethanol sensor, and fuel pressure sensor. Gains jump to +40-100 whp depending on ethanol content.

Cost: $529-$2,075
Risk: Low. Stock hardware handles Stage 1 power without issue.
Expected power: 250-345 whp depending on fuel and tune.

Stage 2: Full Bolt-On

Stage 2 on the VB WRX is anchored by the COBB ecosystem:

• COBB Stage 2 Power Package ($2,290) — Includes Accessport V3, COBB top-mount intercooler kit, charge pipe, high-flow intake filter, and intake tube. Maximum bolt-on power while maintaining 50-state emissions compliance. Stage 2 OTS maps included. Targets 320-330 whp on 93 octane with a custom tune.
• Downpipe: A high-flow downpipe replaces the restrictive factory cat. The biggest single hardware gain. +15-25 whp with a retune.
• Intake: A full intake system (beyond just a drop-in filter) improves airflow to the turbo.
• Intercooler: The COBB top-mount intercooler included in the Stage 2 package is the benchmark. It dramatically reduces intake temps compared to the undersized stock unit.

Full bolt-on with a custom tune on 93 octane puts the VB WRX at 300-340 whp. With flex fuel on E50+, expect 340-380 whp.

Cost: $2,500-$5,000 on top of initial tune setup
Risk: Low-moderate. Stock turbo is approaching its limit.

Stage 3: Big Power

The stock FA24 turbo tops out around 340-360 whp. To push past 400 whp, a turbo upgrade is required. The VB WRX turbo upgrade market is still developing, but options are emerging:

• Hybrid turbo upgrades: Drop-in upgraded turbo units that retain the factory location. Targeting 380-450 whp.
• Full turbo kits: Larger frame turbo setups for 400-500+ whp. These require comprehensive supporting modifications.

The FA24's closed-deck block is structurally stronger than the EJ257, which gives confidence at higher power levels. However, the long-term limits of the FA24 bottom end are still being mapped by the community. Forged internals are recommended for sustained power above 400 whp as a precaution.

Cost: $8,000-$18,000+
Expected power: 400-500+ whp

Known Issues

• CVT limitations: The CVT automatic is the weak link for power builds. COBB supports CVT tuning, but the transmission has lower torque limits than the 6-speed manual. Serious power builds should be on the 6MT.
• Fuel system limitations: The stock fuel system (direct injection only) runs out of headroom at higher power levels. Port injection kits are being developed for the FA24 to support bigger turbo builds.
• Intercooler heat soak: The stock top-mount intercooler is undersized and heat-soaks quickly. An upgraded TMIC is essential for Stage 2+.
• Plastic intake components: Some stock intake components are plastic and can warp or fail under increased boost pressure. Upgraded metal components are recommended at Stage 2+.
• Developing aftermarket: The VB WRX is still relatively new (2022+), so the aftermarket is not as mature as the EJ257 STI platform. Parts availability and tuning knowledge are growing but not yet at EJ-level depth.

Budget Breakdown

Recommended Build Order

1. COBB Accessport V3 — The foundation for all VB WRX tuning.
2. Stage 1 OTS map or custom tune — Immediate power and drivability improvement.
3. Intercooler upgrade — COBB TMIC or equivalent. Fixes the biggest thermal weakness.
4. Downpipe — Biggest single hardware power gain.
5. Intake — Feeds the turbo better air.
6. Flex fuel kit + E30 tune — The biggest power-per-dollar upgrade. COBB's flex fuel package makes this easy.
7. Clutch upgrade (6MT) — Required once power exceeds stock clutch capacity.
8. Turbo upgrade — When you hit the stock turbo ceiling around 340-360 whp.

Ready to build your VB WRX? Use the StageUp Build Creator to configure your build and see real-time WHP estimates based on your fuel and mod combination.