Stage 2 remap: ECU calibration for modified hardware

Stage 2 is a calibration for modified hardware: intake, a larger intercooler, a downpipe or an exhaust without the catalytic converter and particulate filter, and where needed the fuel system and clutch. The file takes into account that the engine now breathes more freely and the air after the intercooler is cooler, and runs more boost and fuel than Stage 1 allows. For tuners: send the original file and a list of modifications, and get a finished file with corrected checksums, on average in 30–60 minutes.

What limits Stage 1 on stock hardware

The ceiling of Stage 1 is set by the hardware around the engine. The higher the boost, the more the compressor heats the air, and on a long pull the stock intercooler stops keeping up. Hot air is less dense, and on a petrol engine it also invites knock: the ECU pulls timing and power drops while you drive.

On the exhaust side the problem is back pressure behind the turbine: the catalytic converter and, on a diesel, the particulate filter, whose resistance grows as soot builds up. The higher the pressure behind the turbine, the less energy it takes from the gas and the hotter the exhaust runs. The engine spends more work pushing gas out, and fuel use and the temperature of the valves and turbine go up.

Two more limits are fuel and the drivetrain. If fuel pressure stops holding its target under load, power cannot go any higher: the pump or injectors need more capacity. On many diesels, rail pressure is already close to what the high-pressure pump can deliver in stock form. The clutch and gearbox hold torque up to their rated limit.

Why hardware without a new file gives so little

The ECU does not know that anything on the car has changed. It holds boost to the same target, limits torque with the same maps, and a MAF sensor in a new housing may read something other than what is really there. So a downpipe or an intercooler on the stock calibration gives little: the turbo spools a bit earlier and the air is cooler, but the ceiling stays where the factory put it. A removed catalytic converter or particulate filter without a new file means fault codes, and on a diesel without its DPF, limp mode as well.

Which hardware goes with Stage 2

Each modification removes its own limit, and the file has to know exactly what is fitted to the car:

Any combination is possible, so there is no single Stage 2 file that fits every car: it is built around the specific set of parts. A turbo larger than stock is already the next stage. Send the file with a detailed description and we will check whether there is a solution.

Diesel

On diesels, Stage 2 is usually done on cars with the particulate filter and EGR removed and a larger intercooler. The reason is soot: more fuel means more soot, and accumulated soot is what causes most of a DPF's flow resistance. Regenerations come more often, back pressure rises, and exhaust temperature rises with it. Disabling the filter in software is a separate option, DPF Off, and EGR is disabled the same way, in the same order.

Petrol

On turbo petrol engines the main modification is the downpipe. With no catalytic converter in it, and sometimes even with a sports cat, the rear lambda sensor shows that the exhaust is not being cleaned and the ECU stores fault P0420. Its monitoring is disabled with the CAT/Lambda Off option. On engines with a gasoline particulate filter (GPF/OPF), say whether it is still fitted. Fuel octane matters more for Stage 2 than for Stage 1, because it decides how much timing the engine can take at high boost.

How Stage 2 differs from Stage 1

The gain depends heavily on the hardware and the engine, so the percentages in the table are only a guide. You can go straight to Stage 2 if the hardware is already fitted, there is no need for Stage 1 in between. And if fuel consumption matters more, neither stage is the right tool: that is what Eco Tuning is for.

What to put in the order

A Stage 2 file is written for a specific car. In the order comment, list:

• intake and intercooler: what is fitted instead of stock;
• exhaust: downpipe with or without a cat, what happened to the DPF or GPF;
• EGR: working or blanked off;
• fuel: 95 or 98 RON, whether the high-pressure pump or injectors have been changed;
• gearbox and clutch: manual, DSG or automatic, and whether an uprated clutch is fitted;
• what was flashed to the ECU before, if it is no longer stock.

First drives: logs over repeated pulls

The values to log are the same as after Stage 1: boost, knock, temperatures, fault codes. The difference is how you log them. A single pull tells you little: the intercooler heats up gradually, and intake temperature problems show on the second and third pull in a row. So log several long pulls, and for Stage 2 pay particular attention to:

• intake air temperature after the intercooler: how much it climbs from pull to pull;
• knock retard per cylinder (petrol): whether it grows along with intake temperature;
• fuel pressure: whether the high-pressure pump holds its target up to the limiter with the extra fuel;
• full-load lambda (petrol): actual against requested.

When boost or fuel pressure falls short, or knock retard grows with every pull, stop testing. Describe what the log shows and we will look into it.

Clutch and gearbox

Stage 2 adds more torque than Stage 1, and the stock clutch is often the first weak point: it is replaced with an uprated one along with the rest of the hardware. On DSG and automatic gearboxes the torque limit lives in the gearbox control unit, and the engine file does not remove it. It is raised with the Torque Unlock option, if that particular gearbox has margin.

How to order the file

1. Read the original file via OBD or on the bench with the tool you use, and keep a copy.
2. Upload it to the portal and select STAGE 2. List the modifications in the comment and add any disables (DPF, EGR, cat) to the same order.
3. Get the finished file with recalculated checksums, on average within 30–60 minutes.
4. Flash the file, clear the faults and log several pulls in a row.

If your ECU is not in the list below, send the file with a request: we will check the software and tell you whether Stage 2 is possible.

Stage 2 usually goes together with removing the particulate filter, EGR or catalytic converter. This increases emissions and changes the vehicle's emissions class. In the EU, the UK, the US and a number of other countries this is prohibited on public roads and may cause an inspection failure. The service is intended for tuners and is used where the law allows it: motorsport, off-road, export, vehicles not used on public roads. Responsibility for using the file lies with the vehicle owner.