F90 M5 Tuning Stages: S63 Twin-Turbo Power Guide

The F90 generation M5 (2018–2023) is the one that finally put a proper twin-turbo V8 behind xDrive and an 8-speed auto, and the S63TU4 underneath it is stupidly underrated from the factory. BMW lists 600 hp for the standard car and 617 hp (625 PS) for the Competition, but independent dynos have put Competition cars around 617 whp — wheel numbers, not crank — which suggests the real flywheel figure is closer to 700 hp bone stock. That headroom is exactly why the F90 has become one of the easiest cars in the M lineup to make genuinely fast without touching the bottom end.

This is a tuning-stages breakdown, not a marketing pitch: what Stage 1 and Stage 2 actually get you, what parts each stage assumes you already have, and what tends to break first when you start pushing a factory-fresh cooling and fueling system past its comfort zone.

Stock S63TU4 Numbers: Where You're Starting From

Every tuning conversation should start from the baseline so the gains actually mean something:

• Standard F90 M5: 600 hp @ 5,600–6,700 rpm, 553 lb-ft @ 1,800–5,600 rpm
• F90 M5 Competition: 617 hp @ 6,000 rpm, 553 lb-ft @ 1,800–5,800 rpm
• Engine: 4.4L twin-turbo V8 (S63TU4), two mono-scroll turbos in the valley, 8HP76 automatic, M xDrive
• Independent dyno results on Competition models have shown around 617 whp / 606 lb-ft at the wheels — strong evidence BMW's crank rating is conservative

That built-in margin is why a Stage 1 flash on a completely stock F90 gets such disproportionate gains compared to naturally aspirated M cars — you're not fighting a tune that's already maxed out the hardware, you're unlocking boost and timing BMW left on the table for warranty and market reasons.

Stage 1: What a Flash Alone Gets You

Stage 1 on the F90 means a bench or OTS (off-the-shelf) ECU flash with no supporting hardware changes — the car stays 100% stock underneath the software. On 91/93 pump gas, tuners are consistently reporting:

• Roughly +100–130 whp and +140–200 lb-ft over stock, landing most Competition cars in the 680–715 hp range at the crank
• No parts required — this is a flash-and-drive stage, which is why it's the highest value-per-dollar move on the car
• Meaningfully sharper throttle response and reduced turbo lag from revised boost and ignition maps, independent of the peak number
• On race gas or E85, several tuners report Stage 1 software pushing gains as high as +200 whp over stock — a genuinely different car

The catch: Stage 1 leans on the stock downpipes and catalytic converters, which start to choke exhaust flow as boost climbs. It's the right first step for almost every F90 owner, but it's also the stage where you'll feel the car asking for more air out the back before it asks for anything else.

Stage 2: Downpipes, Fueling, and the Next Jump

Stage 2 software is tuned specifically around catless or high-flow downpipes, which is the one mandatory hardware change at this level. With downpipes and a matching Stage 2 map on 99/100 RON fuel, shops are seeing:

• 790–830 bhp and roughly 900–950 Nm of torque, a substantial step over Stage 1
• Combined with catless downpipes and no other hard-part changes, some setups land in the 770–800 hp / 950–1,000 Nm range depending on tuner calibration and fuel octane
• A noticeably louder, more aggressive exhaust note — factor that in if you daily-drive the car or live somewhere with noise ordinances
• Check-engine and OBD-readiness considerations if your state does emissions testing; catless downpipes are a street-legality question you need to answer before you buy, not after

Beyond Stage 2, builds chasing 850+ hp typically add a bigger intercooler, upgraded fuel pumps or injectors, and sometimes hybrid turbos — at which point you're no longer in bolt-on territory and you should be working with a shop that's built S63 cars specifically, not just tuned them.

What Breaks First: Cooling, Fueling, and the Clutch Packs

The S63TU4 is tough, but three systems get exposed fast once you're consistently running Stage 2 power on track or in hot weather:

• Cooling: the factory heat exchangers and charge pipes are sized for stock output. Repeated pulls at Stage 2 power in warm ambient temps will show up as heat soak and pulled timing before anything mechanical fails — an upgraded intercooler and auxiliary cooling are usually the first supporting mods people add after downpipes.
• Fueling: the stock high-pressure fuel pump has headroom for Stage 1 but gets marginal on E85 or sustained Stage 2 pulls. Lean fuel trims under boost are the fastest way to hurt pistons on this engine.
• xDrive transfer case and clutch packs: the M xDrive system is durable, but repeated launches at big torque numbers will wear the transfer case clutches faster than BMW's engineering assumptions. It's not a Stage 1 concern, but it's real once you're deep into Stage 2 and launching regularly.

Track-Day Prep Before You Chase Bigger Numbers

A tuned F90 is a genuinely quick car in a straight line, but power is the easy part — the car is heavy (over 4,300 lbs) and that mass shows up under braking and in sustained corners long before it shows up on a dyno sheet. Before a track day, prioritize in this order: fresh brake pads rated for track temps and fluid with a high boiling point, a cooling system check (coolant condition and hose integrity, especially if you're already running elevated boost), tire pressures set cold and monitored hot, and a full torque check on wheels and suspension hardware. None of that is glamorous, but it's what actually keeps a tuned M5 on track for a full session instead of in the pits after two laps with cooked brakes.

FAQ

Do I need downpipes for Stage 1?
No. Stage 1 is software-only and runs on the stock exhaust, stock turbos, and stock fueling. It's the cleanest, most reversible upgrade on the car.

Will Stage 2 downpipes trigger a check engine light or fail emissions?
Catless downpipes typically will on any state that does OBD or visual emissions testing. High-flow catted downpipes are the street-legal middle ground if that's a concern where you live.

Is the M xDrive system strong enough for Stage 2 power?
Yes for street driving and the occasional spirited pull. Repeated hard launches at Stage 2 torque levels will accelerate wear on the transfer case clutch packs faster than at stock power, so it's worth budgeting for that as a wear item, not a defect.

What's the realistic ceiling on bolt-ons before I need turbos?
Most Stage 2 builds on pump or 100 RON fuel top out in the low-to-mid 800s at the crank. Going meaningfully past that reliably means bigger turbos, which is a different conversation than bolt-on tuning.

Ready to start building yours? Browse F90 M5 parts at Iconic Garage, including F90 M5 exhaust and downpipe options and F90 M5 cooling upgrades to support your tune.

Sources: evo.co.uk F90 M5 Competition review, Bimmerpost: "What's the real hp on the f90 comp?"