What dwell time is
Before a coil can fire a spark, it needs time to build up energy. The Dwell Time table in NSP sets that charging period for each ignition pulse, in milliseconds. You'll also see it called charge time; they mean the same thing. It lives in the Ignition System setup.
Where the numbers come from
Dwell is specific to the coil, not the engine. The right values come from the coil's manufacturer or supplier, so get that data before you start. Don't copy a table from another car unless it runs the exact same coils.
| If dwell is | What happens |
|---|---|
| Too high | The coil and ignition system can overheat and be damaged |
| Too low | A weak spark, which can show up as misfires, especially under boost or at high RPM |
Our advice
- Use the coil supplier's figures as your starting point, and don't raise them to chase a misfire until you've ruled out plugs, gaps and wiring.
- After a run, carefully feel the coils. Unusually hot coils are a warning sign that dwell is too high.
- Remember that battery voltage affects how quickly a coil charges, so check your table across the voltage range your car sees.
Not sure what your coils need?
Send us the part number and we'll help you find the right figures before you risk a set of coils.
