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). Some cams add VVT (variable valve timing), which shifts the profile on the fly.
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 widens the usable band by moving the profile to suit RPM, getting some of both.
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 on the Setup page reshapes the derived VE curve and the idle character. VVT, where available, broadens the curve.