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A Plug On Spark Plugs

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On: Tue, Sep 27, 2011 at 3:01PM | By: Peter C Sessler

A Plug On Spark Plugs

A spark plug is one of the three indispensable items an engine must have in order to run. The other two are air/fuel and compression. Of these, the easiest to change or modify is the spark plug. You’ll often see ads in some automotive catalogs about some super-duper type of spark plug that will give you more horsepower and better mileage. Most of these don’t work and are a waste of money.

Spark plugs by themselves really don’t do very much—they have no moving parts. Their function is to provide a gap for a burst of electricity to jump over to ignite the fuel mixture in the combustion chamber.

If you’ve ever looked closely at the tip of a new spark plug, you’ll notice that it has sharp edges. Eventually, over time, these edges erode and the tip itself gets smaller and smaller. The result is that more and more electrical energy is needed to jump the gap and, thus, ignite the air/fuel mixture. Today’s ignition systems have quite a bit of reserve energy left, so they can supply the additional voltage needed. However, a time will come where it can no longer deliver enough voltage and so the engine misfires. This means there’s incomplete combustion and the engine is making less power than it should—and using a lot more gasoline.

The simple installation of new plug brings the ignition system back to its original specifications, and, once again, all is well. Typically, new spark plugs will result in a one- to two-percent increase in power, over a set of worn spark plugs. Installing racing spark plugs or some of those funky plugs advertised in some catalogs won’t give you any more power— in fact, they can make the engine run worse.

A common misconception is that increasing the amount of energy available to jump the plug gap will result in better combustion; unfortunately, it doesn’t work that way. You can’t force extra electricity to jump the gap. The only time that extra capacity will come to play is when the spark plug tip starts to erode.

Interestingly, some makers of aftermarket ignition systems have used another tack. Normally, the spark plug gets one big jolt of energy to ignite the fuel mixture. But what if we can send a series of these jolts to the spark plug instead of just the one? That’s what makers, such as MSD, have done with their multi-spark systems. The series of short-duration sparks insure better combustion and they do make the engine produce more power.

Back to spark plugs—what about resistor spark plugs? Will switching to non-resistor plugs increase power in any way? A resistor is simply another gap within the spark plug that the electrical energy has to jump before it reaches the spark plug tip. By doing so, electrical interference that can be picked up by the car’s radio (and all the on-board computers) is eliminated. It takes only about 1,000 volts to pass through the resistor and most cars today have systems that put out 20-30,000 volts. In short, there’s no need to install non-resistor plugs.

A set of regular type plugs should last 30,000 miles or so. At that point, tip erosion will start affecting the combustion process. You can either remove them, file the tip flat, set the gap and reinstall them, or you can just install a fresh set. Platinum plugs, which cost a bit more, erode much more slowly so they last considerably longer. Many new cars come with these plugs and the manufacturers state that they’ll last 100,000 miles. Still, I’d remove them every so often to see how they’re wearing.

Bad ignition wires can also cause problems with the ignition process. Ignition wires, over time, deteriorate and hinder the flow of electrical energy to the spark plug, causing misfires even though the plugs may be new. When that happens, the wires must be changed (or you can change them at regular intervals).

Keeping your ignition system in tip-top shape isn’t difficult to do and your engine will be grateful to you!


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