A customer asks us for a "Stage 2" for his car. Our first question back: what have you changed on the engine? Silence. It is the most common misunderstanding in this trade, and it occasionally costs a turbocharger.
Stages are not a standard. No body defines them, no manufacturer recognises them. It is workshop vocabulary — convenient and imprecise — describing one thing only: how much hardware has been changed around the engine. The number says nothing about the gain. It says what you have taken apart.
Stage 1: software only
A Stage 1 touches no parts. The engine stays exactly as it left the factory: same turbo, same exhaust, same intake, same injectors. Only the calibration changes — boost pressure, ignition timing, injection quantity, limiters.
The gain exists because the manufacturer deliberately leaves margin. It has to warrant the same engine at 45 °C in Greece and −20 °C in Finland, on fuel of variable quality and with servicing that is sometimes neglected. Nobody consumes that safety margin in normal use.
Across our database, the median Stage 1 gain is +25%. A telling example: the BMW 120d E87 163 hp reaches 200 hp and goes from 340 to 420 Nm. Nothing was removed.
Stage 2: the file follows the hardware
A Stage 2 assumes the hardware changed before the file did. Typically: a freer exhaust line, a better intercooler, a reworked intake, sometimes a sports catalyst. The engine breathes better, so the calibration can go further without leaving liveable temperatures and pressures.
Order matters, and this is where the misunderstanding becomes expensive. A Stage 2 file on a stock engine asks an unmodified part to work beyond what it was calibrated for. The turbo pushes harder, the original exhaust restricts, temperatures climb. This is not commercial caution — it is mechanics.
It is also why Stage 2 remains the exception. Of the 4,558 engine variants from our seven main brands that have a Stage 1, only 521 have a documented Stage 2 — barely 11%. For everything else, there is simply no hardware gain sharp enough to justify a second file.
Where it does exist, the difference is real: the Volkswagen Bora 1.8T 20v starts at 150 hp, reaches 192 hp on Stage 1, then 230 hp on Stage 2 — with torque climbing from 210 to 350 Nm. Those extra 38 hp do not come from the file. They come from what was fitted before it.
Stage 3: this is no longer a remap
At Stage 3, you are no longer calibrating a factory engine: you are calibrating a build. Larger turbo, oversized injectors, sometimes camshafts, a reinforced clutch and gearbox. The file becomes bespoke work, written for that specific car.
This is why you will not find an off-the-shelf "Stage 3 file", with us or anywhere else. Two engines with the same turbo but different injectors do not share a calibration. At this level the dyno stops being a comfort and becomes the only way to know where you stand.
What actually decides the gain
The stage number predicts nothing. Across our database, Stage 1 gains range from +2% to +106% depending on the variant. The engine decides, not the label.
Three factors genuinely matter. First, forced induction: a turbo can be commanded, a naturally aspirated engine much less so — on an engine without a turbo, a Stage 1 rarely returns more than a few percent. Second, factory margin, which varies widely: the same block sold at 122 and 163 hp does not carry the same reserve, and it is often the lower-output version that gains most. Third, the era: recent engines, constrained by emissions standards, sometimes leave less room than their predecessors.
Two examples from the same family make the point. The BMW 118d 122 hp gains 33 hp, or +27%. The BMW 135i 306 hp, already generously served from the factory, gains 64 hp — more in absolute terms, but only +21%.
What the stage does not change
No stage makes a modification road-legal by itself. In Belgium, as in most European countries, changing a vehicle's technical characteristics must be declared, and a non-compliant vehicle can fail its roadworthiness test. Moving from Stage 1 to Stage 2 changes nothing about that rule.
Your insurer applies the same logic: what counts is the modification, not its intensity. An undeclared change can be held against you in a claim, whatever the number of horsepower added.
As for the manufacturer's warranty, it draws no finer distinction either. A "discreet" Stage 1 is still a modification of the engine software, it is detectable, and it is enough to have a claim refused on the affected component.
We say this because it is true, not to cover ourselves: all three points apply as much to a 15 hp gain as to an 80 hp one.
The figures for your vehicle
Rather than an average, look at your own engine. We publish the factory output and the expected gains for every engine variant in our database — brand by brand, generation by generation, with the engine code.
Start by browsing the vehicles: you will find your model, and the figure that concerns you rather than a general range.
And if your variant is not there, or you are hesitating between two levels, write to us. We answer with the exact reference of your ECU, before you commit to anything.