The short answer is no, a tuning box cannot damage a modern turbo petrol engine, with two provisos.
The first proviso being that the car manufacturer made their software so that the engine cannot operate in a condition that it unsafe when the engine is under load ie towing, high speed up steep hill etc
Ultimately a tuning box exploits the safety margin built into the factory ECU.
The second is that the tuning box is built correctly ie the circuits do not allow voltages and currents to go through circuits that they were not designed to work with.
Assuming the cars factory software is good and the tuning box is built well how does a car’s ECU allow an engine to operate correctly?
On a petrol engine there are two main conditions that will cause catastrophic engine damage.
- Detonation. When the fuel mixture in the cylinder combusts in an uncontrolled manner. This causes massive spikes in combustion chamber pressures which can damage connecting rods, pistons and many other mechanical components in the engine.
Modern engines have knock sensors. These detect detonation before it becomes damaging, the ECU receives the signal from these knock sensors and retards the ignition timing and/or reduces the boost pressure.
2. Lean Air:Fuel Mixtures. When insufficient fuel is mixed with the air entering the engine combustion chamber temperatures can sky rocket. This can damage pistons, valves and the turbo.
Modern engines have wideband lambda sensors which constantly monitor the air:fuel ratio and alter the amount of fuel entering the engine to maintain the required air fuel mixture.
The tuning boxes from Street & Circuit are built to the highest standards and are only available on cars which are capable of adapting to the increased boost pressure that a tuning box creates