Ignition Coil Breakdown and Testing

Coil-on-Plug Breakdown

A coil-on-plug is designed to perform the functions of the ignition coil (creating the spark energy) and the spark plug wire set (containing and delivering the high voltage energy to the spark plug). To ensure proper function, BWD and Intermotor Coil-on-Plug Assemblies feature premium-quality components.

Coil-on-Plug Ignition Coil from Standard Motor Products

Designed using advanced thermoplastics to ensure proper connection and resist fractures caused by heat and thermal cycling

Coil Connector for Coil-on-Plug Ignition Coil from Standard Motor Products

High-temp boot prevents highvoltage leaks, while stainless steel spring with internal ferrite noise suppressor prevents radio frequency interference (RFI)

Spring Assembly for Coil-on-Plug Ignition Coil from Standard Motor Products

High-impact material bonds extremely well to epoxy to ensure longer life in all operating conditions

Coil-on-Plug Coil Housing for Coil-on-Plug Ignition Coil from Standard Motor Products

Internal neodymium permanent magnet surrounded by grainoriented magnetic-laminated steel maximizes high-voltage output at all speeds

Coil-on-Plug Core for Coil-on-Plug Ignition Coil from Standard Motor Products

Primary (25 gauge) and Secondary (43 gauge) copper wire ensure high-voltage availability for peak performance while reinforced bobbins prevent voltage flashover for extended service life

Coil-on-Plug Bobbins with Winding for Coil-on-Plug Ignition Coil from Standard Motor Products

Manufactured using high-voltage resistant thermoplastics to prevent premature coil failure

Coil-on-Plug Isolator for Coil-on-Plug Ignition Coil from Standard Motor Products

To ensure proper function, BWD® and Intermotor® Coil-on-Plug Assemblies feature premium-quality components.

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Coil-on-Plug Testing

We performed an extensive engineering analysis of OE DG500 and DG508 to BWD®. The engineers measured winding resistance, inductance and output voltage, spark, energy, waveform peak voltage and ringing, as well as a complete physical and sectioned comparison to OE.


  Primary Secondary Output Voltage Spark Energy
  Resistance Inductance Resistance Inductance 50pf 60 Hz 60 Hz
Part no. (mohms) (mH) (kohms) (H) (Peak kV) (mV-S) (mJ)
BWD® E261 492 1.53 5.36 9.59 25.2 3.70 29.6
BWD® E262 489 1.49 5.28 9.47 25.2 3.74 29.9
Average BWD® 491 1.51 5.32 9.53 25.2 3.72 29.8
OE DG500 515 1.63 5.55 8.61 24.4 3.72 29.8
OE DG508 511 1.58 5.50 8.19 24.2 3.69 29.5
Average OE 513 1.61 5.53 8.40 24.3 3.71 29.7
Coil-on-Plug Testing

The Findings

BWD Ignition Coils look, fit and perform like the original they replace with 100% end of the line production testing. The Standard coils also provide an improved secondary winding design (additional winding bays) that helps prevent internal arcing and high-voltage breakdown.

  • The BWD coils tested 3.7% higher than OE in output voltage.
  • The BWD coils were equal to OE in spark energy.
  • In waveform testing, BWD coils’ peak output voltage was about 1000 volts higher than OE.
  • The Standard coils had a longer spark duration than the OE, resulting in more energy supplied to the spark plugs.

The BWD coils match or exceed the OE coils in all categories and are an excellent replacement exceeding the OE performance.

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Blue Streak Outperforms the OE

All products manufactured at our IATF 16949 and ISO 9001-certified facility in Poland undergo extensive measurement and life testing, in addition to a full range of environmental analysis that includes thermal shocks, thermal cycling, and vibration tests, just to name a few. To see what goes into our coil testing, take a look at this competitor comparison between our E255 and the OE:

OE Comparison Analysis

Blue Streak Outperforms the OE

Testing Takeaways

  • The two OE coils tested short circuited after 68 hours and 140 hours, respectively
  • The two BWD® coils tested passed the 300-hour life test as well as 100 thermal cycles, a 24-hour life test, and 10 thermal shocks
  • Compared to the OE, BWD® coils have 9% higher spark energy and 18% higher secondary voltage, which leads to better combustion of fuel mixture and reduced exhaust gas discharge

"As testing shows, we’ve designed our BWD Ignition Coils for superior performance and durability under the harshest conditions."

Tomasz Michalik

Technical Director - SMP Bialystok, Poland