Calculate ignition coil dwell time, primary current saturation, and stored energy for optimal spark performance.
Input Parameters
Results
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Saturation Current
A
--
Required Dwell
ms
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Stored Energy
mJ
--
Max Available Dwell
ms
Note: Typical COP coils: 3-7 mH, 0.4-0.8 ohm primary. Dwell too short = weak spark. Dwell too long = coil overheating. Modern ECUs adjust dwell with battery voltage.
Reference
Time Constant τ = L / R
Saturation Current I_sat = V_batt / R_primary
Dwell Time = −τ × ln(1 − 0.9×I_sat/I_sat)
Stored Energy = 0.5 × L × I²
Max Dwell = 60000 / (RPM × 2) [4-cyl]