The Ignition System

A distributorless ignition system.

The ignition system is one of the most overlooked elements when it comes to engine and car tuning. Most people think that once their car modifications are done, all they need to do is get the ignition timing right and turn the ignition. But it's much more complicated than that. For one, the spark must be strong enough to ignite the air/fuel mixture. That might sound obvious, but what's not so obvious is that air molecules act as an insulator, and when you modify your car to get more air into the engine, the spark from the stock ignition system might be too weak to effectively ignite the air/fuel mixture, particularly if you're using a forced induction system. In fact poor spark quality can have as negative an effect on engine power as poor ignition timing. In addition, an air/fuel ratio of 11 parts air to 1 part fuel, which is a fuel rich mixture, is most conducive to spark ignition. However, the air/fuel ratio for the proper burning of the fuel is 14,7 parts air to 1 part fuel. Thus, the air/fuel mixture is not ideal for a spark ignition system, particularly during cold start conditions where fuel vaporization is not as effective.

Once the air/fuel mixture is ignited, the rate at which the flame passes through the combustion chamber becomes important if you want to unleash the maximum power from your engine. If the flame travels too fast, it would place too much load on the pistons, conrods and bearings; if the flame travels too slowly, not enough force would be generated to create maximum power at the wheels. There are three things that influence the rate at which the air/fuel mixture burns and the flame passes through the combustion chamber:

• The quality of the air/fuel mixture mixture
• The movement or turbulence of the air/fuel mixture in the combustion chamber
• The design of the combustion chamber

Langer discussed the air/fuel ratio when he discussed the four strokes of the internal combustion engine; we discuss the movement of the fuel mixture in the combustion chamber and the design of the combustion chamber in our section on gas flowing and cylinder heads; but in this section we'll discuss the carignition system, effective ignition timing, spark strength and quality, and techniques for modifying the ignition system to improve engine performance. As always, we'll begin with some ignition system basics ...

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