The Volvo Parts, Accessories &
Performance Specialists Since 1963

Spark Blowout or is it My Birthday?

2011-01-05 - IPD Staff

Somehow in this day of skepticism and disbelief we have allowed a sneaky little myth to arise and take hold of a position in the ranks of car enthusiast vernacular: Spark Blowout.

I’m not sure what this is supposed to mean but I hear it all the time. I think the people who use it are talking about the air flow from a turbo blowing out the ignition spark like it was a birthday candle. If that is the case, it’s not quite accurate but I can see where the misnomer came from.

First, electricity cannot be ‘blown out’ in an engine because at the moment of combustion the air and fuel in the cylinder isn’t moving very quickly when compared to when it enters the cylinder via the intake valve. Once the valve closes and the piston heads up toward top dead center the air/fuel mixture is forced into a tightly closed, highly compressed area and there’s not much blowing happening. Shortly thereafter the spark plug passes the spark across its electrodes and Kablam, combustion. The term most likely arose from the experience of higher than stock turbo pressures attributing to ignition misfire. This is in fact reality but not from a ‘blow out’ spark event.

The result of ignition misfire is from the higher combustion pressure due to the higher turbo pressure, which packs more molecules of fuel and air into the same space making the ionization voltage of the spark plug rise to a level that the coil, wires, cap, rotor cannot support. Recall that ionization voltage is the initial voltage necessary to start the spark jump across the spark plug terminals. Once the gap is jumped and electricity begins to flow the voltage needed is now lower and this voltage is referred to as burn voltage. So, how to combat ignition misfires due to high cylinder pressure. First make sure your cars ignition system is in good shape. Replace the cap, rotor, plugs, and plug wires if they are old or worn out. Consider replacing the spark plug wires with performance wires and the stock coil with a high output coil like the Ipd MSD coil kit. You’ll find that these performance upgrades will make the difference between a high performance car and a reliable high performance car.