Diesel engines
On a diesel the ECU controls injection quantity, injection timing, rail pressure and turbo boost. Re-calibrating them usually gives the larger torque gain, which is why remapped diesels feel strong from low revs. In our catalogue diesel engines average 34 bhp and 73 Nm.
Petrol engines
Petrol engines are remapped through fuelling, ignition timing and, where fitted, boost. Turbocharged petrols respond best; naturally aspirated petrols usually gain less because there is no boost to re-calibrate. Petrol engines in our catalogue average 27 bhp and 51 Nm.
Which is better to remap?
Neither is better: the best result comes from a healthy engine and a remap written for that exact engine. Turbocharged engines of either fuel typically see the biggest improvement.
What the gains feel like
On a diesel the improvement is mostly felt as strong, effortless pulling power between 1,500 and 3,500 rpm: motorway overtaking, towing and pulling away on a hill. On a turbocharged petrol the improvement is felt as stronger acceleration through the mid-range and sharper response, with a livelier top end.
- Diesel: biggest change is torque, felt low down
- Turbocharged petrol: stronger acceleration and a higher percentage power gain
- Naturally aspirated petrol: smaller, mainly throttle-response gains
Looking after a remapped engine
Both fuel types benefit from regular servicing and good oil. Diesels with particulate filters also benefit from the occasional longer run so the filter can regenerate. A remap does not change those needs, but a healthy engine is what lets the extra performance last.
A note on diesel emissions equipment
Modern diesels have particulate filters (DPF) and EGR valves. A lawful remap leaves them in place and working. If you have a DPF or EGR fault, see our guide on diagnosing and repairing them.
Questions
Do diesels gain more than petrols?
Diesels usually gain more torque; turbocharged petrols often gain more as a percentage of power. It varies by engine.