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Pistons

They set the compression ratio and add to the rotating/reciprocating mass — and they are the part most damaged by detonation.

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 part of the engine's RPM tolerance.

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 how far it can go.
  • RPM ceiling — every part has a hidden RPM ceiling, and the weakest one decides where the engine breaks. Engone doesn't print it — you find the limit by pushing, so don't set your rev limiter past what you've tested.
  • Detonation damage — pistons are the part most damaged by knock. They take 2.5× the block's wear rate (see Damage & Wear).

How to tune it

Choose compression to match your fuel. High compression suits engines running good fuel with a well-managed timing table. 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.

On a boosted engine

Engone currently simulates naturally aspirated engines only. For background: a boosted engine packs far more air into the cylinder, so the tune changes — target lambda moves richer (to cool the charge and protect against knock), ignition advance comes down in the boosted cells, compression ratio is usually lowered, and higher octane matters more. See Boosted Engines (Background).

In the game

Piston choice is the PISTONS dropdown on the SETUP page. It updates the Compression Ratio in the specification summary and feeds Total Inertia.