Scion FR-S ZN6 Build Guide: FA20 Mod Order That Works

The 2013–2016 Scion FR-S (ZN6) is one of the most rewarding sport-compact platforms to build — but only if you spend money in the right order. The FA20 makes roughly 155 whp stock, and the internet is littered with FR-S builds that stalled out because the owner chased the wrong mods first. Headers and a tune do more for this car than any other single bolt-on combination, and everything else — suspension, wheels, fueling — should stack on top of that foundation. Here's the complete Scion FR-S build guide, from first dollar to finished car.

Quick links

• Headers First, Everything Else Second
• Keep The Suspension Honest
• 18x9.5 +35 Is The Setup
• Drivetrain & Supporting Mods
• The Whole Build, One Page

Headers First, Everything Else Second

Skip the cold air intake. Owners on FT86Club and every dyno comparison thread consistently report minimal gains from an intake alone — the stock airbox flows fine until the exhaust side of the FA20 can actually breathe. The move is an equal-length header and front pipe paired with a flash tune via the OpenFlash Tablet (OFT) or EcuTek. On 93 octane, this combination gets you to roughly 170–180 whp and — critically — fixes the notorious torque dip around 4,000 rpm that makes the stock car feel anemic in the mid-range.

Add an E85 flex-fuel map and you're looking at 200–220 whp. That's the realistic naturally aspirated ceiling for the FA20 without touching internals, and it completely transforms how the car pulls from mid-range to redline. The Speedhunters-documented Mortensen drag FR-S build used Delicious Tuning flex-fuel maps even at extreme power levels, confirming that E85 is the single best bang-for-buck fuel upgrade on this platform. If you're planning to eventually go forced induction, the Grams Performance 550cc Fuel Injectors for BRZ/FR-S at $385 are worth noting now — they support E85 and mild turbo setups without going to the 1000cc+ injectors that make idle quality miserable on a street car.

For more on the FA20 platform's reliability weak points — including the oil pump cover Phillips screws that every owner should address — read our 6 overlooked reliability mods for FA20/FA24 BRZ/GR86 owners. That article covers the preventative maintenance side that most build guides skip entirely.

Keep The Suspension Honest

Don't slam it. The ZN6 chassis communicates beautifully when it's set up right, and it punishes you when it's not. Daily and canyon builds in the 86 community run 6–7 kg/mm front and 7–8 kg/mm rear on coilovers — compliant enough to live with, firm enough to rotate. BC Racing BR Series at 8/8 kg/mm is the common entry-level choice if you want one setup for street driving and occasional track days. The Speedhunters drag build used D2 coilovers with Whiteline poly bushings and Voodoo13 rear lower control arms — proof that even at extreme power levels, the suspension philosophy stays the same: control the chassis, don't just lower it.

Pair your coilovers with front camber plates for adjustment range. Budget for rear lower control arms if you're chasing alignment accuracy at lower ride heights — without them, you're limited in how much rear camber you can dial out. The target is a 1–2 inch drop with approximately −2.5° front camber and −2.0° rear camber. At those numbers, the car starts communicating through the steering in a way stock suspension never does. If you want to understand why cheap coilovers can actually make the car worse, our breakdown of whether coilovers are overrated is worth reading before you buy. And for the alignment theory behind those camber numbers, check out our camber setup guide.

Browse the full suspension catalog at ThreePiece.us for coilover options across platforms.

18x9.5 +35 Is The Setup

The FR-S runs 5x100, 56.1mm center bore, M12x1.25 lug pattern. The proven aggressive-but-streetable fitment is 18x9.5 +35 wrapped in 245/35R18 tires. That gets you flush without excessive poke at a reasonable drop. You'll need to roll the fenders — especially the rears — and watch for inner liner contact at full steering lock. Trimming the liner or running a small front spacer fixes it. Stock suspension doesn't have the travel control for this width, which is exactly why coilovers come first in the build order.

If you want zero fender work, 18x8.5 +38 on 225/40R18 is the clean conservative play that still fills out the arches without rubbing. The American Roadstar Sport AS 225/40R18 at $128 per tire is a solid all-season option for the conservative setup — affordable enough to not feel guilty about daily driving on them. For the wider 245/35R18 setup, search 245/35R18 tires to see what's currently in stock.

For wheels, browse 18-inch wheels in 5x100 to find options that clear the FR-S brakes without spacers. If you're considering stepping up to a multi-piece wheel, our guide on why 3-piece wheels cost $4K+ and whether they're worth it breaks down the real advantages — on a lightweight chassis like the ZN6, unsprung weight savings from forged barrels are actually noticeable. The Work Emotion series and Work Meister line both offer 5x100 configurations that look right on this platform. For the full comparison, read Volk TE37 vs Work Meister and cast vs forged wheels explained.

If you're running spacers on any setup, read our deep dive on whether wheel spacers are safe before bolting anything on.

Drivetrain & Supporting Mods

The FR-S 6-speed manual is surprisingly durable — even the Mortensen drag build running 700+ whp kept the factory gearbox and differential, upgrading only the clutch and axles. But at street power levels, the stock clutch starts slipping once you're past 200 whp on E85, especially if you're aggressive with launches. The ACT Heavy Duty Clutch Pressure Plate for 2013 Scion FR-S at $320 is the sensible upgrade — it holds more torque without destroying daily drivability. If you're planning forced induction down the road, the ACT Xtreme Clutch Pressure Plate at $359 gives you more headroom. While you're upgrading the clutch, the Chase Bays stainless clutch line for BRZ/FR-S at $95 replaces the soft rubber factory line and improves pedal feel noticeably.

On the cooling side, the stock FA20 cooling system is adequate for naturally aspirated street use, but if you're pushing the car on hot days or doing back-to-back canyon runs, budget for an oil cooler. Oil temps are the usual limiter on this engine — the Speedhunters build added a Mishimoto aluminum radiator and oil cooler once boost entered the picture, but even NA builds benefit from oil temperature management during sustained high-rpm driving.

For brakes, the stock pads fade quickly under spirited use. The Hawk ER-1 Rear Brake Pads for 2013–2016 FR-S at $271 are an endurance-compound upgrade that handles heat far better than stock — a worthwhile investment once you're on wider, grippier tires that load the brakes harder.

The Whole Build, One Page

Here's the FR-S build in order, the way the platform actually responds:

1. Equal-length header + front pipe + OFT/EcuTek tune on E85 — that's your power. 200–220 whp naturally aspirated, torque dip eliminated.
2. Coilovers at 6–8 kg/mm with front camber plates and rear lower control arms — that's your handling. Drop 1–2 inches, dial in −2.5° front / −2.0° rear.
3. 18x9.5 +35 on 245/35R18 with rolled fenders — that's your fitment. Or 18x8.5 +38 on 225/40R18 for zero fender work.
4. Clutch upgrade once you're past 200 whp — the ACT HD pressure plate holds without ruining your commute.
5. Oil cooler and brake pads — supporting mods that keep the car reliable under the increased demands of better tires and more power.

While you're in there, swap the soft Phillips screws on the oil pump cover for proper hardware — it's a known weak point covered in our FA20 reliability mods article. You end up with a 200+ whp, naturally aspirated FR-S that handles, looks right, and still drives to work Monday. That's the build.

If you're shopping wheels for your ZN6, start with the full wheel catalog or browse the vehicle gallery for real-world fitment examples. Need inspiration from other platforms? Our 9th Gen Civic Si canyon build guide follows the same philosophy — mod order matters more than mod budget. Go find a clean FR-S and build it right.