Choosing the Right Ignition Coil

Buying a coil is easy, but buying the right coil can be complicated. We offer more than a dozen options, they’ll all bolt right up, and they more or less all look the same on the outside other than their color. That’s why we’ve put together this guide to help simplify the ordering process.

The same ignition system was used across Type 1, 2, and 3 air-cooled engines because they all share the same core internal design. Some of the peripheral components may change, but the system is largely the same across the board. For example, Type 3 engines use longer spark plugs wires, but they use the same coil and plugs.

The VW ignition system is a straightforward points-based setup matched to specific electrical tolerances. It consists of a mechanical points distributor, condenser, a 1.5 (6v) or 3 (12v) Ohm coil, standard-resistance plug wires, and spark plugs gapped at 0.028".

Compression ratios across the air-cooled family rose gradually over the years, from 6.1:1 in the early 1,200cc (36 HP) engines to a maximum of 7.3:1 in the later 1,600cc dual-port engines. The stock ignition system was designed around these modest compression ratios and a relatively narrow RPM range. It works well within those parameters, but has no headroom for performance modifications. Mechanical points also wear over time, causing timing to drift and performance to degrade between tune-ups.

So, if you’ve got a bone-stock car, it’s pretty simple. If you have a stock 6 volt electrical system found in 1966 and earlier VWs, you want a 1.5 Ohm coil. If you have a 1967 and later car with a 12v electrical system (or an earlier car with upgraded electrical) you want a 3 Ohm coil.

Anything beyond stock, things get a little more complicated.

While originally oil-filled, the Bosch coils available today are epoxy-filled, allowing them to be oriented in any way you see fit. A Bosch coil is a direct OEM replacement requiring no changes to any other component. It is compatible with your existing distributor, condenser, plug wires, and spark plugs. And if you have a 12v car, it can also be used with our JBugs drop-in electronic ignition kit without issue. If you prefer oil filled, go for the German-made Beru oil-filled coil or Pertronix brand oil-filled coil.

Any modification that raises compression or increases RPM demands more from the ignition system. Higher cylinder pressure creates a more dense fuel/air mixture, which is harder to ignite, and at high RPMs the coil has less time to charge between firings. A higher-output coil solves both problems: lower resistance means it charges faster (shorter saturation time) and delivers more current, not just more voltage, resulting in a stronger, more reliable spark and more complete combustion.

A higher-output coil must always be paired with electronic ignition. The increased current flow will rapidly burn a set of mechanical points. The Pertronix Ignitor replaces the points with a transistorized trigger that handles high current cleanly, eliminating wear and ensuring consistent timing at all RPMs.

3 Ohm (12v stock)

3 Ohm is the factory standard, so you can select any of the Pertronix 3 Ohm coil from the 12v options above. Use with the Pertronix Ignitor if you want the reliability of electronic ignition on an otherwise unmodified engine without changing spark output.

1.5 Ohm (6v stock)

Vehicles that came with a 6v electrical system (1966 and earlier) used a 1.5 Ohm resistance coil. Pertronix’s 1.5 Ohm coils are designed to work with stock 6v systems, so you can choose one from the 6v list above.

0.6 Ohm (45,000 volts)

Higher output for more serious performance builds with meaningfully raised compression ratios or engines that regularly operate at high RPMs. Delivers a hotter, higher-current spark with enough reserve voltage to handle increased cylinder pressure reliably. Remember though, the hotter spark will eat up your points much faster, so it’s essential that you use an electronic ignition suited for the low resistance, such as 91847A.

Stock plug gap can be increased by .003” - .005” without loss of performance according to Pertronix.

0.32 Ohm (45,000 volts)

Maximum output for high-compression, high-RPM race and competition engines. If you're running a big-bore stroker, aggressive cam, or a purpose-built race combination, this is the correct coil. It is overkill for a street engine. Remember though, the hotter spark will eat up your points much faster, so it’s essential that you use an electronic ignition suited for the low resistance, such as 71847A.

Stock plug gap can be increased by .003” - .005” without loss of performance according to Pertronix.

 
They key to good ignition performance is choosing a coil that suits your application. You have a stock 6v car? You need a 6v coil. Whichever you choose just depends on your preference for how it’s insulated (filled) and the brand you like. The same is true for stock 12v applications. It gets dicey once you get into the lower resistance coils. You must remember to use a compatible electronic ignition (or just get a Pertronix Ignitor distributor). While not absolutely essential, Pertronix does recommend using lower resistance Flame-thrower wires with the 0.32 Ohm coil to ensure no current is lost before it can reach the plug.