The turbo (turbocharger) is the component that revolutionized modern engines. Using the energy of the exhaust gases, a turbine drives a compressor which pressurizes the incoming air. More air = more oxygen = more burnable fuel = more power.
Turbo types
- Fixed geometry (FGT): vintage
- VGT/VNT (Variable Geometry): modern diesel standards, moving vanes
- Twin-scroll: two separate flows to reduce lag
- Bi-turbo: two turbos (sequential or parallel)
- Electric turbo: electrically assisted turbo (Audi, Mercedes)
Turbo and tuning
Stage 1 makes better use of the original turbo by increasing the supercharging pressure (boost). Stage 2 optimizes the flow (downpipe). Stage 3 replaces the turbo with a larger one.
Popular acronyms
- K03/K04: BorgWarner, on VAG TFSI
- GT/GTB/GTD: Garrett
- IS20/IS38: BorgWarner for VAG MQB (2.0 TFSI/TSI)
- BMW M-series: Mitsubishi MGT, BorgWarner
Supercharging and management
Modern diesels are dominated by the variable geometry turbo (VGT/VNT), whose moving vanes adapt the response to all speeds, reducing lag; on petrol turbos double-volute turbos or specific groups are often used to reduce lag. The ECU regulates the boost pressure by acting on the wastegate or vanes, based on the required torque map.
Limits and stages
Stage 1 makes better use of the original turbo by raising the boost within safety limits; pushing too much takes the compressor out of the efficiency zone, resulting in overheating of the air and stress. Stage 2 improves the flow (downpipe), while Stage 3 replaces the turbo with a larger one, an intervention that requires adjusting injection, fuel supply and clutch for a reliable result.
Turbo care
The turbo is a component that works at extreme temperatures and speeds: quality oil and regular changes, in addition to cooling before switching off after intense driving, extend its life, even more so on a remapped engine. In the advanced stages, replacing the turbo without adapting injection, fueling and clutch does not bring real benefits. The rule, as with pressure, is not to push the compressor out of its efficiency zone.