Intake Manifold¶
Runner length and plenum volume tune intake pressure waves (Helmholtz resonance), shaping where in the rev range the engine makes torque.
What it is¶
The intake manifold routes air to the cylinders, and its geometry isn't just plumbing — it tunes pressure waves. The key dimensions are runner length and diameter, and plenum volume. Through Helmholtz resonance, the intake tract reinforces cylinder filling at particular RPMs.
Why it matters¶
The manifold shapes the torque curve via resonance tuning:
- Long, narrow runners resonate at low RPM → strong low-end and mid-range torque, ideal for a street engine.
- Short, wide runners resonate high → top-end power at the cost of low-end.
- Plenum volume buffers and distributes flow, affecting throttle response and where the curve peaks.
All of this feeds the VE curve: the manifold can add a noticeable bump of VE right where its runners resonate.
How to tune it¶
Pick runner length for the band you want filled. Match it to the cam and head: long runners suit a mild, torquey build; short runners suit a high-RPM cam and head.
Rule of thumb
Long runners for low-end grunt, short runners for top-end rush. The manifold and the cam should target the same RPM band, or they'll fight.
In the game¶
Intake selection on the Setup page shifts the VE curve's shape — watch where the torque peak moves as you change runner geometry.