Performance gains from ECU remapping vary significantly depending on the engine type, whether it is turbocharged, and the quality of the calibration. Here is an honest breakdown of what different vehicles can realistically achieve.
Turbodiesel Gains
Turbodiesels offer the most consistent and impressive gains from a Stage 1 remap. These are typical results:
- BMW 320d 2.0 B47 (190bhp): 240bhp / 470Nm — gains of 50bhp and 70Nm
- Audi A4 2.0 TDI (150bhp): 195bhp / 390Nm — gains of 45bhp and 60Nm
- Mercedes C220d 2.0 (194bhp): 240bhp / 480Nm — gains of 46bhp and 80Nm
- Ford Transit Custom 2.0 EcoBlue (130bhp): 175bhp / 420Nm — gains of 45bhp and 85Nm
- VW Transporter T6 2.0 TDI (150bhp): 195bhp / 400Nm — gains of 45bhp and 60Nm
These figures are achieved through OBD flashing on ECUs like the Bosch EDC17 with no hardware modifications required.
Turbo Petrol Gains
Turbo petrol engines see strong gains, though typically a lower percentage than diesels:
- VW Golf GTI 2.0 TSI (245bhp): 300bhp / 420Nm — gains of 55bhp and 50Nm
- BMW M140i 3.0 B58 (340bhp): 400bhp / 560Nm — gains of 60bhp and 60Nm
- Audi S3 2.0 TFSI (310bhp): 370bhp / 490Nm — gains of 60bhp and 40Nm
- Ford Fiesta ST 1.5 EcoBoost (200bhp): 235bhp / 350Nm — gains of 35bhp and 30Nm
Petrol tuning on Bosch MED17 and Siemens/Continental SIMOS ECUs requires careful management of knock thresholds and air-fuel ratios, which is why choosing a reputable tuner matters. Read more about whether remapping is safe.
Naturally Aspirated Gains
Without a turbo, gains are modest:
- Most NA petrol engines: 5-10% power increase
- High-performance NA engines (e.g., BMW M3 S54): up to 15% with optimised timing and fuelling
Naturally aspirated tuning is more about improving throttle response and driveability than headline power figures.
Stage 2 vs Stage 1
Stage 2 gains require hardware modifications (typically a decat downpipe and upgraded intercooler) and push further — usually an additional 20-40bhp on top of Stage 1 figures. For the full comparison, see our guide on Stage 1 vs Stage 2.
What Affects the Gains You See
The numbers above are typical, but actual results depend on:
- Vehicle condition — a well-maintained engine will always produce better results
- Fuel quality — higher octane petrol allows more aggressive timing
- Ambient conditions — hot weather reduces power due to lower air density
- Calibration quality — a custom dyno-calibrated tune will outperform a generic file every time
RemappingWebsite.com provides a vehicle lookup tool that shows customers these specific gains for their vehicle — displaying real figures that help convert website visitors into bookings.