Revising an older article for those wanting further specifics on the distributor vs DIS systems, their benefits and drawbacks, and what it means to your performance vehicle. We’ll be showing you how to convert to a distributorless ignition setup in our guide.
Many people have heard that a running a distributorless ignition setup is better than distributed and just blindly accept it. It is true but exactly why is it better? If you’re interested on why distributorless is better then this article will fill that void of knowledge. Before we get into the why one system is better we have to go over the basics of each system.
In a distributor system the igniter charges the coil and tells it when to release voltage in the form of a high tension current. This voltage is then sent through the coil wire to the distributor cap. From the distributor cap the voltage is transferred to the rotor. The rotor then distributes the high tension current bridges the gap between the rotor and the appropriate tower of the distributor cap.
From that tower of the distributor the high tension current makes its way through the spark plug wire to the spark plug jumping one final gap across the spark plug gap, where it finally grounds itself to the block ending one ignition pulse. This sequence is repeated for all cylinders.
A Distributorless Ignition System (DIS) comes in two forms, Wastespark and Direct fire. A direct fire ignition has one coil and igniter per cylinder. In the direct fire system the car’s computer tells the igniter to charge the coil and fire it, sending the high tension voltage from the coil to the spark plug wire, from the spark plug wire the voltage travels through the spark plug jumping the spark plug gap and grounding itself to the block.
A wastespark uses one igniter and one coil for 2 cylinders. The sequence of events is the same as Direct fire except it ignites not only the power stroke, but it ignites the exhaust stroke simultaneously.
DIS’s provide substantial reliability and performance gains over distributed systems. There’s no cap and rotor to wear out, a worn cap and rotor causes weak spark and leads to hesitation under acceleration. There is also one less gap for the charge to jump, between the cap and rotor, and less spark plug wire for the voltage to travel, this means less resistance, less resistance yields stronger spark at the plug.
Some direct fire systems place the igniter and coil pack directly on the spark plug completely eliminating the spark plug wire. In some instances a DIS system provides enough additional power that the plug gap can be increased, creating a more exposed spark igniting more fuel that could have been left unconsumed before.
DIS systems allow stronger spark and more precise ignition timing control which improves emissions and efficiency which will increase the overall power of the car. This is a primary benefit of knowing how to convert to distributorless ignition.
Some cars can benefit from a DIS more than others. We are going to use a 4 cylinder turbo Honda with small displacement B16a, (1.6 liter DOHC VTEC), for an example. The reason for this is the motor makes power at high rpm, 6500-8200, Due to the small displacement, and will encounter high cylinder pressures, with dense Air Fuel mixtures due to the turbo. Quick fact, the higher the cylinder pressure makes it harder to ignite a spark strong enough to bridge the plug gap.
This means the spark has to be extremely powerful in order to light such a dense air fuel mixture. That’s not too bad just use a stronger coil and igniter amplifier. But what happens when you have high cylinder pressure and high RPM, like a turbo B16a Honda engine? This situation provides inadequate coil charge time for reliable spark, which leads to hesitation. The remedy to this is our guide on how to convert to distributorless ignition (DIS).
In a distributor system one coil has to x amount of time to charge between ignition pulses.
In order to make more charge time, we just add another coil via DIS, now one coil will ignite cylinders 1 and 4 and the other coil will ignite cylinders 2 and 3. This is a waste spark system. We can make 4 times the charge time (not necessary) if we use 4 coils, direct fire, one per cylinder.
Make sure to tune in for Part 2 of our how to convert to distributorless ignition, where we show you how to wire in a universal ignitor.
- Pro Street Staff