Pistons¶
They set the compression ratio and add to the rotating/reciprocating mass — and their strength caps RPM.
What it is¶
The pistons seal the combustion chamber and transmit pressure to the rods. For the build, they contribute three things: their shape sets part of the compression ratio, their weight adds to the reciprocating mass (and thus inertia), and their construction sets a maximum safe RPM.
Why it matters¶
- Compression ratio — piston crown geometry, together with the head, sets how much the charge is squeezed. Higher compression makes more power and efficiency but lowers the knock limit, demanding higher octane.
- Weight — heavier pistons add inertia (slower revving); lighter pistons free the engine to rev but are often the limiting factor on max RPM.
- Max RPM — like every component, the piston's limit feeds into the engine's redline.
How to tune it¶
Choose compression to match your fuel and aspiration. High compression suits naturally aspirated engines on good fuel; boosted engines usually run lower compression to leave knock headroom for the boost. Lighter pistons help a high-revving build but watch the RPM ceiling.
Watch out
Raising compression without raising octane (or pulling timing) pushes you toward knock. Compression and fuel must be chosen together.
In the game¶
Piston choice on the Setup page updates the displayed compression ratio and feeds the inertia and redline figures.