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Camshaft

The cam profile decides when and how far the valves open, which shapes the VE curve and sets where the engine makes power.

What it is

The camshaft opens and closes the valves. Its profile is described by duration (how long a valve stays open), lift (how far it opens), LSA (lobe separation angle), and the resulting overlap (the window where intake and exhaust valves are both open). The cam can be SOHC, OHV or DOHC — the V8 is OHV, the others DOHC.

Some real cams add VVT (variable valve timing), which shifts the profile on the fly. No shipped cam in Engone has VVT, but the principle is worth knowing.

Why it matters

The cam is the single biggest lever on the shape of the VE curve:

  • Mild cams (short duration, tight overlap) fill the cylinder well at low RPM → strong low-end torque, smooth idle.
  • Aggressive cams (long duration, lots of overlap) trade low-end for high-RPM breathing → big top end, but a lopey, unstable idle (the overlap makes idle airflow erratic).
  • VVT, on engines that have it, widens the usable band by moving the profile to suit RPM.

Two idle effects to know about:

  • A big cam raises your idle floor. The idle target can never go below the lowest speed the cam can hold stable (see Cold Idle).
  • Overlap leaves residual burnt gas at low RPM, which makes the idle lumpy and wants more spark advance (see Spark Fundamentals).

How to tune it

Choose the cam for the power band you want, then build around it. An aggressive cam needs a head and intake/exhaust that flow at high RPM, and its choppy idle will demand attention from idle control and the VE table at low load.

Watch out

A big cam's overlap makes idle VE erratic — that's the lopey idle. Expect to spend time stabilizing low-RPM fuelling and idle control on aggressive builds.

Rule of thumb

Cam choice = personality. Pick the RPM where you want peak power and choose the cam that breathes there; everything else follows.

In the game

Cam selection is the CAMSHAFT dropdown on the SETUP page. It reshapes the engine's real VE and the idle character. After a cam swap the VE table is stale and needs re-tuning.