Aspiration (Turbo / Supercharger / N/A)
Power-delivery shape. Centrifugal SC is usually the most PI-efficient for road; twin turbo on small engines is a trap.
What it does
Aspiration changes the *shape* of the power curve, not just the peak. Naturally aspirated revs cleanly and stays light, at the cost of peak power. Centrifugal supercharger is the most PI-efficient choice for most road builds — strong, predictable power, modest weight. Positive-displacement supercharger gives instant torque off the line (drift, drag launches, cross-country) at higher PI. Single turbo balances stock turbo cars. Twin turbo is for big engines and top-speed builds — putting it on a small displacement engine creates lag without enough peak gain.
Availability is engine-specific. Not every engine has every aspiration option, and the choice often appears alongside the engine swap decision. Pick aspiration after the engine, not before.
Options
PI-efficiency by discipline
| Option | Road | Dirt | Cross-country | Drift | Drag |
|---|---|---|---|---|---|
| Naturally aspirated | ○ | ○ | ○ | ○ | ✗ |
| Single turbo | ● | ● | ○ | ○ | ○ |
| Twin turbo | ○ | ✗ | ✗ | ○ | ● |
| Centrifugal supercharger | ● | ● | ● | ○ | ○ |
| Positive-displacement SC | ○ | ○ | ● | ● | ● |
Decision rules
- 1.Pick the engine first; aspiration after.
- 2.Centrifugal SC is the default for road builds unless the engine specifically suits a turbo.
- 3.Don't put twin turbos on engines under 2.5L — you get lag without a power payoff.
Build smells that point here
- Twin turbo on a sub-2.5L engineSwitch to centrifugal SC or single turbo — twin turbos lag without payoff on small engines.