FREE TOOL · IGNITION
Spark plug heat range
Stage 2/3 builds raise combustion temps significantly. Stepping spark plugs one or two heat ranges colder than stock prevents pre-ignition. This tool maps the NGK ↔ Denso ↔ Brisk codes.
Heat range conventions
| Brand | Direction | Cold = ? |
|---|---|---|
| NGK | Higher number = colder | NGK 9-11 |
| Denso | Higher number = colder | Denso 27-31 |
| Brisk | Lower letter = colder | Brisk LR (L) |
| Bosch | Lower number = colder | Bosch 2-3 |
NGK 6 ≈ Denso 22 ≈ Bosch 6 (typical stock). Step ONE NGK colder for Stage 1+, TWO for Stage 2-3.