Boost Control¶
On forced-induction engines, the ECU targets a boost level based on RPM and throttle, bounded by the wastegate spring and shaped by spool and charge-temperature dynamics.
What it is¶
Boost control manages how much pressure the turbo or supercharger delivers. The ECU sets a target boost as a function of RPM and throttle, then works the wastegate to hit it — within the limits the hardware allows.
Why it matters¶
Boost is power, but it's also the fastest route to knock, so it has to be managed, not just maximized:
- Wastegate spring sets the minimum boost the system will make and bounds the control range.
- Spool dynamics — turbo inertia means boost can't appear instantly; the target has to respect how fast the turbo can build it (lag).
- Charge temperature / intercooler — boost heats the air (IAT up), which the intercooler counters; hotter charge means less margin.
How to tune it¶
Set the boost target to match the engine's safe limit at each operating point, keeping the high-load/high-boost cells within knock and octane margins. Build the target curve to follow how the turbo actually spools rather than demanding boost the hardware can't yet make.
Watch out
More boost without matching fuel, timing, and cooling changes is the classic way to detonate an engine. Tune the fuel and timing of the boosted cells as you raise boost, not after.
In the game¶
Boost target and behavior are managed on forced-induction builds; watch MAP climb to target as the turbo spools, and IAT respond to the intercooler.