BMW M5 F90: 3.3" exhaust and Stage 1
The most underrated step on the S63B44 is the exhaust. We measured what downpipes give before any remap.
The usual order on an M5 is a map first, exhaust "later". We did it the other way round and measured each step separately, so the contribution of the hardware is visible.
Exhaust only, stock map
3.3" downpipes and 3" midpipes on the stock calibration gave +18 hp. Not much. But exhaust gas temperature dropped by 60–70 °C, and that is exactly what later lets the map run harder without risk.
Exhaust plus Stage 1
After calibration: 720 hp. For comparison, the same map on the stock exhaust makes about 680 hp and pulls timing much earlier on long runs.
The conclusion is simple: on this engine the exhaust is not about sound, it is about thermal headroom.
Tuning stages
| Parameter | Stock | Tuned | Gain |
|---|---|---|---|
| Power | 600 hp | 618 hp | +18 |
| Exhaust gas temp | 980 °C | 915 °C | −65 |