This guide covers two different WRX generations that share the name but not always the same parts:
- VA (2015–2021) — FA20DIT 2.0T, AWD, 6MT or CVT
- VB (2022+) — FA24 2.4T, AWD, 6MT or “SPT” CVT
If you only remember one rule: confirm your chassis (VA vs VB) before you click “buy” or flash anything.
Platform Snapshot (vehicle-specific)
Quick reality check (what the platform is “good at”)
- Repeatable street speed with AWD traction when temps are controlled.
- Huge drivability upside from a good calibration (better throttle/boost behavior, smoother power).
- Track/autocross friendly with pads/fluid + basic cooling upgrades.
What bites people (what the platform is “bad at” if you ignore it)
- Heat + knock sensitivity: warm pulls, hot summer traffic, or repeated runs can pull timing and ruin consistency.
- Low-RPM torque chasing: big torque early feels great… until it becomes the weak link (especially on stock FA20 rods per IAG).
- Legality-sensitive exhaust mods: catalyst changes are the #1 “don’t get cute” area.
Stock performance baseline (for time-obsessed builders)
- The WRX has been tested around mid‑5s to high‑4s 0–60 depending on year/trans/conditions.
Use these as reference baselines, not promises:
- 2015 WRX manual test reference: Car and Driver.
- 2022 WRX reference: Car and Driver.
Your “real” baseline is your own repeatable run (same road, same fuel, same tire pressure, same temps) plus logs.
VA vs VB quick matrix (so you don’t buy the wrong parts)
| Item | VA WRX (2015–2021) | VB WRX (2022+) |
|---|---|---|
| Engine | FA20DIT 2.0T (direct injection) | FA24 2.4T (direct injection) |
| Stock plug gap reference | Subaru spec 0.020”–0.022” (FA20) | Common OE-style plug listing shows 0.024” pre-gap (NGK 96698 / SILKFR8A6) |
| Most common tuning ecosystem | COBB Accessport + custom tuning | COBB Accessport ecosystem (support evolves by model year) |
| “Biggest limiter” when you chase times | Heat + knock, plus low‑RPM torque management | Heat + knock + drivetrain consistency (SPT heat management if CVT) |
| Parts interchange? | Some universal items (tires/brakes), but many engine parts are VA-only | Many intake/charge/exhaust parts are VB-only |
Baseline & logging checklist (do this before you mod)
- Confirm fuel quality (don’t tune for “93” if you always get “91”).
- Confirm chassis (VA/VB) and trans (6MT/CVT).
- Check maintenance basics: oil level, coolant level, air filter, plugs age.
- Do one repeatable baseline run and log:
- Boost target vs actual
- Throttle angle vs pedal
- Knock/timing correction indicators (Subaru-specific)
- IAT / coolant / oil temp
Glossary (fast definitions)
- IAT: intake air temperature (repeatability killer).
- AFR: air/fuel ratio (fueling safety/consistency).
- MAF scaling: airflow calibration for many intakes; wrong scaling = fueling drift.
- EBCS (3-port): electronic boost control solenoid; helps boost control precision.
- Throttle closure: ECU closing throttle to hit a torque target or protect the engine.
- Boost target vs actual: boost control health check.
- DAM / knock learning (Subaru): platform-specific knock strategy indicators; if these move, your tune/fuel/temps need attention.
- Heat soak: after a pull or stop, temps stay high and power drops. Cooling is how you buy consistency.
3 Build Paths
1) Daily + Reliable (fast street, no drama)
- High-grip tires + performance alignment (free “power”)
- Brake fluid + pads (repeatability and confidence)
- Monitoring + conservative ECU calibration (driveability + safety margin)
- Intercooling upgrade if you do back-to-back pulls
- Oil vapor management (AOS/catch can) if you see oily intake/consumption
2) Tuned Street (strong midrange, repeatable 0–60)
- Everything in “Daily + Reliable”
- Boost control hardware (3-port EBCS) + dialed boost ramp
- Charge cooling priority (TMIC/ducting or FMIC if you live in heat)
- Fuel plan (91/93 consistency or flex-fuel support)
- Drivetrain support: clutch (6MT) or cooler strategy (CVT)
3) Track / Big Power (heat + fuel become the build)
- Oil/trans cooling strategy + brake heat strategy
- Fueling headroom + flex-fuel sensing + conservative knock targets
- Turbo system plan (hardware + calibration + reliability goals)
- Suspension geometry + sway bars + end links (balanced handling)
- Engine safety plan (especially FA20: torque control + temp control)
Highest Performance-per-Dollar (Ranked Table)
| Mod | Why it works on WRX (VA/VB) | Supporting mod(s) | Risk | Direct links |
|---|---|---|---|---|
| Tires (summer / 200TW) | AWD can only use power that the tire can transmit. This is the biggest “0–60 mod” you can buy. | Alignment, tire pressure discipline | Low | Baseline context |
| Brake fluid + pads | Lets you do repeated runs / canyon / track without “one-and-done” brakes. | Stainless lines (optional) | Low | Handling kit context |
| ECU monitoring + staged tune path | The WRX responds strongly to calibration and logging. You also catch problems early (knock/temps/boost). | Better intercooling | Medium | COBB AP3-SUB-004 · Accessport list |
| Intercooler priority (TMIC/FMIC) | Keeps power consistent and reduces knock risk on repeated pulls. | Ducting, heat shielding | Low–Med | VB reference |
| Spark plugs (correct gap, fresh) | Cheap stability: reduces misfire risk as boost/load rises. | Coil health, clean fueling | Low | FA20 gap note · FA24 plug spec |
| Sway bars + end links | Biggest “feels faster” mod in corners; reduces roll and sharpens response. | Alignment, good tires | Low–Med | VA sway kit |
| Oil vapor control (AOS/catch can) | Helps keep intake tract cleaner and reduces oil ingestion under boost. | Maintenance habits | Low | DI deposits context |
| Downpipe/J-pipe (catted) | Can unlock airflow and turbo response, but is the most legality-sensitive. | Custom tune, emissions awareness | High | (See section) |
| Fuel plan (flex fuel / ethanol blend) | Ethanol can improve knock resistance and consistency, but fuel demand rises fast. | Flex fuel sensing/support | Med–High | CAN Gateway mention |
| Cooling beyond IC (oil/trans/rad) | Track days and repeated pulls make temps the limiter, not “peak power.” | Thermostat strategy | Med | (See cooling table) |
Intake / Airflow
Reality check
On the WRX, “intake” is not just a noise mod. Many intakes change MAF scaling and require calibration to avoid fueling drift.
When it matters
- You’re tuning for repeatability and want stable AFR/boost behavior.
- You’re stacking mods and need predictable airflow scaling.
- You want better turbo sound/response (and accept the tuning requirement).
Best practice (what actually keeps you safe)
- Use known-fitment intake options for your chassis (VA/VB) and tune accordingly.
- If your tuner says “don’t change the intake,” don’t.
- Avoid “mix-and-match” MAF housings without calibration.
Fitment-safe links
Intercooling / Charge Cooling (TMIC vs FMIC)
Reality check
Charge cooling is one of the biggest consistency upgrades on both VA and VB. Hot pulls = timing pull = inconsistent speed.
TMIC vs FMIC (simple decision rule)
- TMIC is great for street and many track/autocross setups with proper ducting and heat management.
- FMIC is great if you live in heat, do repeated pulls, or your setup heat-soaks quickly.
What to log
- IAT vs ambient (how fast it climbs, how fast it recovers)
- Knock/timing correction stability during repeat pulls
Fitment-safe links
Downpipes + Exhaust (legality-sensitive)
Reality check
This is the most emissions-sensitive mod for street cars. Don’t plan on bypassing inspections.
When it matters
- Your build goals require airflow headroom.
- You have a proper tune path and understand legality implications.
“Fitment-safe” strategy
- Prefer high-quality catted options.
- Match hardware + calibration as a set.
- If you can’t legally run it, don’t buy it.
Fitment-safe links
Tuning Options (ECU / TCU) + “Bogging” clarity (required)
Reality check
The best WRX tunes are smooth, predictable, and consistent—not spiky.
ECU tuning ecosystems (starting points)
- COBB Accessport ecosystems exist for both VA and VB, with support evolving by year/trans.
CVT / SPT note
CVTs are extremely temperature/strategy sensitive. Heat management and sane torque are the whole game.
Fitment-safe links
“Bogging” / flat response: what’s actually happening
This is usually torque limiting/throttle closure, knock response, or boost oscillation—not “the car is slow.”
What to log/check
- Throttle angle vs pedal
- Boost target vs actual
- Knock/timing correction indicators
- IAT and coolant
Typical fix approach (not a hack)
- Smoother boost/tq ramp in the tune
- Better traction and repeatability
- Fix boost control issues (EBCS, leaks, wastegate behavior)
Boost control (3-port EBCS, leaks, and “hunting”)
Boost control stability is a consistency mod. If boost hunts, your car feels unpredictable.
Practical checklist
- Pressure test for leaks
- Use proven hardware (per tuner)
- Don’t chase peak boost at the expense of stability
Fueling + Ethanol (E30/E85)
Reality check
Ethanol can be great for knock resistance, but it demands more fuel volume and consistent content measurement.
When it matters
- Logs show you’re fuel-limited.
- You want safer timing/boost behavior on hot days.
Best practice
- Don’t “guess” ethanol content.
- Build fuel headroom before chasing numbers.
Fitment-safe links
Ignition (plug gap, coils, and misfire stability)
Reality check
Many “it feels weird” issues on tuned cars are spark-related under load.
VA vs VB plug notes (sources)
- VA FA20 turbo plug spec references often cite 0.020”–0.022” (FastWRX listing note).
- VB FA24 common OE-style listing shows ~0.024” pre-gap (OAKOS/NGK listing).
Your tuner’s file and misfire behavior should decide final gap.
Fitment-safe links
Drivetrain + Traction (0–60 consistency)
Reality check
AWD helps traction, but your times will still vary if:
- temps climb,
- boost control is unstable,
- the tune pulls timing,
- tires are inconsistent.
Practical traction priorities
- Tire compound and pressure discipline
- Smooth torque ramp (calibration)
- Consistent launch method (same RPM, same procedure)
Fitment-safe links
Brakes + Handling
Brakes (repeatability is the real “fast”)
- Street/spirited: high-temp fluid + quality pads is usually the best ROI.
- Track: add heat capacity (pad compound, cooling, rotor strategy) before chasing more power.
Fitment-safe links
Handling quick hits (what actually changes lap/road speed)
- Tires + alignment first, then bars/springs/shocks based on balance goals.
Sway bars deep dive (the “d⁴ rule”)
A sway bar behaves like a torsion spring; stiffness scales strongly with diameter (polar moment: J ∝ d⁴).
Source: Dronacharya PDF — torsion / polar moment of inertia (J = π/32·d⁴)
Fitment-safe links
Reliability / Supporting Mods
Platform weak points / known issues (documented themes)
-
Low-RPM torque on stock FA20 rods (VA)
- What it feels like: strong early shove, then “random” reliability scares as torque climbs.
- What to monitor: knock strategy changes, fuel quality consistency, oil level/condition.
- Common mitigation: conservative torque curve (especially low RPM) + temperature control.
- Source context: IAG notes OEM rods as a weak link when low-end torque is increased.
-
Direct injection intake valve deposits (VA + VB)
- What it feels like: gradual loss of smoothness, idle quality changes, reduced efficiency.
- What to monitor: long-term trims (if available), intake cleanliness over time.
- Mitigation: good oil control (PCV/AOS), periodic cleaning practices appropriate to DI.
- Source context: DI fuel doesn’t wash the valves, which contributes to deposits (AutoTrader).
-
Heat soak / inconsistency
- What it feels like: first pull strong, second pull soft.
- Monitor: IAT, coolant, oil, trans temp where possible.
- Mitigation: charge cooling, radiator/oil cooling as needed (see cooling section).
What to monitor long-term (so issues don’t sneak up)
- Oil level (check often; turbo DI cars can consume oil)
- Coolant behavior (unexpected loss/overheat = investigate immediately)
- Knock stability across temperature swings
- Fuel trims (large changes can indicate intake leaks, MAF scaling issues, or sensor drift)
- Intercooler performance (IAT recovery time is a “health metric”)
Links
Recommended Mod Order
- Baseline & logs (know your current behavior)
- Tires + alignment (consistency + safety)
- Brakes (fluid/pads) (repeatability)
- Intercooling strategy (control IAT so the tune can stay consistent)
- Conservative tune path (smooth torque, stable boost, safe knock margin)
- Ignition refresh (plugs/gap; coils if needed)
- Sway bars + end links (use the power and brake confidence)
- Fuel plan (only after the car is stable on pump gas)
- Downpipe/J-pipe (catted) (if legality and build goals align)
- Advanced cooling + drivetrain support (track / big power plans)
FAQ
Which WRX do I have—VA or VB?
2015–2021 is the VA chassis (FA20DIT 2.0T). 2022+ is the VB chassis (FA24 2.4T). Parts and tunes don’t always cross over—confirm before buying.
What’s the best first mod if I care about 0–60 consistency?
Tires + repeatability (heat management) first. A tune can add power, but it won’t matter if intake temps soar or traction varies run-to-run.
Do I need an ECU tune for an intake on a WRX?
Usually yes on MAF-based intakes—if the intake changes airflow scaling, you want calibration that matches the hardware to avoid lean/rich swings.
What causes the “bog” where I go partial throttle → WOT and it feels flat?
Most commonly torque limiting/throttle closure, knock response/timing pull, or boost control oscillation—log throttle angle, boost target vs actual, and knock/timing indicators to pinpoint it.
Is a downpipe/J-pipe “worth it” on a street WRX?
It can be, but it’s the most legality-sensitive mod. Prefer high-quality catted options and verify local emissions rules before changing catalysts.
What’s the biggest reliability mistake?
Chasing low-RPM torque and peak numbers without temperature control, clean fueling, and conservative calibration—especially on stock internals.
Should I run ethanol (E30/E85) on a stock WRX?
Only with proven flex-fuel sensing/support, additional safety margins, and a tuner who understands your fuel system headroom. Ethanol can improve knock resistance, but it also increases fuel demand.
What plug gap should I run on a tuned WRX?
Use conservative, tuner-proven guidance. As cylinder pressure rises (boost/load/ethanol), the gap often needs to tighten to prevent high-load breakup.
Do I need an intercooler if I’m only doing a conservative tune?
If you do repeated pulls, drive in heat, or track the car, yes—charge cooling is one of the biggest consistency upgrades you can make.
How do I track what’s installed on my car?
Keep a current mod list, notes, and costs. Drivurs Garage is designed for fast, structured tracking.
Related Guides
- Subaru brand hub
- Subaru WRX hub
- Tires for performance driving
- Alignment for street and track
- Brakes for performance driving
- Intercooler guide
- Intake vs intercooler
- Heat management for tuned cars
- Intake myths and real gains
- Mod order explained
- Fuel upgrades (when needed)
- Boost control basics
- Boost vs timing
- Why boost drops under load
- Knock correction explained
- Torque limits (ECU/TCU)
- Throttle closure explained
- What to log on a tuned car
- Spark plugs gap and heat range