Why Properly Gapping Your Spark Plugs Is So Necessary

Spark plug gapping may sound like one in every of those old-timey chores, like setting breaker points in a distributor or lubricating the frame, but having the correct spark plugs and ensuring they’re properly gapped is a vital a part of engine operation. Before we dive too deep, let’s start with some basics about spark plugs: They supply ignition for the air-fuel mixture in most internal combustion engines. (You diesel people can sit this one out; we’ll discuss glow plugs one other time.) 

At the highest of a spark plug, you could have the terminal nut. That is where the spark plug wire, or the person coil in a coil-on-plug system, connects to the spark plug. Current travels through the plug to the middle electrode on the underside after which jumps to the bottom electrode — that curved, half-horseshoe-looking a part of the plug. That current is what we’d like to manage with the gap. High-quality-tuning the gap between the bottom electrode and the middle electrode is what persons are referring to after they say “gapping” a spark plug. Set the appropriate gap, and you possibly can potentially avoid issues comparable to misfires, fouling, quicker plug wear, bad fuel mileage, and reduced horsepower, all of which might all stem from the spark plug gap being too wide or too narrow. The trick is to be like Goldilocks and find that gap that is good.

There are two primary categories of plugs: cold and warm. “Cold” is relative, in fact. For those who were holding a “cold” plug in your hand because it sparked, the nearly 930 degrees Fahrenheit would feel pretty warm. Cold plugs have shorter center electrodes and a shorter porcelain insulator, while hot plugs have longer center electrodes and porcelain insulator. You fastidious, maintenance-focused folks probably already know all of the signs that you simply need recent spark plugs in modern vehicle scenarios, but in the event you’re modifying your vehicle or working on something vintage, you would possibly need to alter which type of spark plug you employ — hot or cold.

Turbocharged and supercharged engines are likely to run warmer, as do high-rpm engines, and with their hot operating temps, cold plugs will typically be the appropriate selection. Engines running low rpms, comparable to those in lawnmowers and ATVs, can use nice and toasty hot plugs to assist burn away deposits and keep the chambers clean. With a “hot plug,” the insulator (the white porcelain part) will probably be longer than in a “cold plug.” For the reason that insulator, well, insulates, the more of it there’s, the higher it’s at retaining heat. Hot plugs push more heat to the combustion chamber and are higher at burning away deposits, something cold plugs can struggle to do.

The particular gap set to your spark plugs depends upon a variety of aspects, including compression ratio, optimal spark advance, quality of the gasoline you employ, the elevation at which the automobile is often driven, and any mods you’ll have done, like adding forced induction. 

As of late, unmodified cars rarely need fussy fine-tuning of spark plug gaps. But, in the event you’re within the habit of checking and re-checking every tolerance in your automobile, otherwise you’re tuning the engine in your weekend drag automobile after diagnosing regardless of the heck was causing plug wear, gapping will be done with some low-tech tools. The kind of spark plug gap tool you would like depends largely on the kind of plugs you could have. The coin-style or ramp-gauge tools are effective for old-school copper plugs, but not for plugs comprised of platinum, iridium, or ruthenium. Coin tools have gradual measurement ramps and little bottle-opener-style sections for prying gaps wider, but precious metal plugs need something more accurate and fewer prone to damage the plug.

Feeler gauges are what you wish for platinum and iridium plugs. When using feeler gauges, never try and use the gauges to pry the gap larger — the gauge will just bend. For the convenience of a coin tool and the precision of a feeler gauge, get a wire loop tool. It’s shaped like a coin, but has various thicknesses of wire loops protruding so you possibly can get that exact gap you wish. But, if you want to gap the plug to some odd size, that wire tool might leave you hanging since it only has room for a small variety of loops. 

To set your spark plug’s gap tighter, you possibly can gently tap the bottom electrode against something hard, heavy, and immovable, comparable to a vise. To loosen the gap, use either the prying section of your gapping tool or a pair of pliers. You will know the gap is correct when your measuring tool needs an honest tug to drag it out. Consider it like an excellent handshake. You don’t need the loose and unsightly “limp fish,” nor do you wish the tight “phalange cruncher.”