BMW 420d: Stage 1 + xHP Stage 3, 230bhp

This BMW 420d came in for the combination we recommend on almost every automatic BMW diesel: our Stage 1 custom dyno tune for the engine and an xHP Stage 3 calibration for the ZF 8-speed gearbox, both developed on the same visit.

The numbers

On the baseline run it made 180bhp and 390Nm. It left making 230bhp and 496Nm, measured on the rollers, not estimated:

Why the gearbox matters on a 420d

An extra 106Nm is only useful if the gearbox lets you use it. xHP Stage 3 lifts the factory torque limits and sharpens the shift strategy, so the 8-speed changes quicker and firmer and the car holds the right gear instead of hunting for one. The result feels sharper everywhere, not just at full throttle.

How it was done

Health check and diagnostics first, then baseline runs on our 4WD linked dyno, then a calibration developed around this car with live data logging and repeated runs before the final verification pulls. No generic files. Original software backed up and fully reversible.

Got a 4 Series or 3 Series diesel? Check your car’s gains and price, or read how xHP gearbox tuning works.