honda250sx
02-01-2009, 12:07 AM
I hear alot of guys talking plugs lately. It seems some guys even go as far as to "recommend" a different plug. That can be quite dangerous for your engine. Lets take a look at what spark plugs are all about.
Numbers and Letters:
Manufacturers work hard to select the right spark plug for each engine application. Plugs have significant impact on engine performance and fuel economy, and using the wrong one can cause poor running quality or engine damage. Each of the digits on a spark plug dictates its specifications or characteristics. A common spark plug is B8ES. The "B" designates 14mm thread x1.25 pitch, 20.8mm hex. The "8" is the heat range. The "E" is thread reach of 19mm. The "S" designates a super copper core center electrode. A spark plug can only cover a certain operating tempature range. Heat ranges vary by about 75 degrees. When selecting the correct plug for an engine, manufacturers choose one that works safely at the hottest temperature it could face under high RPM and heavy load. The plug must withstand the maximum temperature and be resistant to fouling at cold startup and idle.
Hot and Cold:
The length of the center electrode and insulator nose dictates whether a spark plug is a "hot" or "cold" burning plug. For example, a hot plug will have a longer insulator nose and a short center electrode. The long insulator nose transfers heat more slowly to the shell of the spark plug and then to the cylinder head. Cold plugs have short insulator and a long center electrode. Electrodes with copper also dissipate heat quicker than standard steel electrodes. As a rule of thumb, the hotter an engine runs, the colder the spark plug should be. Hot engines include modified or high performance engines! A spark plug starts to burn off fouling deposits at about 800 degrees farenheit. If too many deposits accumulate on the ceramic core, electricity from the ignition system will follow the path of least resistance into the core and ground to the inside of the shell rather than arc across the gap. Short ground electrodes take longer to reach the deposit burn off temperature, which makes them prone to fouling, but they are less likely to break as result of cylinder head vibration. Fouling caused by a rich fuel mixture CANNOT BE FIXED WITH A HOTTER PLUG! Prevent this problem with CORRECT JETTING.
Can You use a different plug than specified?
When possible ALWAYS use the spark plug that the manufacturer specs for your machine. There are cases when a different plug can work in a pinch to get you home. If your recreational vehicle calls for a B9ES for example, it's okay to use a different heat range plug such as a B8ES as a temporary fix. But because this plug is hotter than your stock plug, take it easy to avoid pre-ignition. In cases where special materials such as copper, gold, and platinum are used to dissipate heat more quickly or prolong life, a plug variance is acceptable for a short time. Some spark plug characteristics cannot be used as a temporary replacement. A reach that is too long could cause a collision between the bottom of the plug and the top of the piston at top dead center, which may cause damage. Plugs that have the wrong threads won't thread into the head and non-resistor plugs shouldn't be used in an application that calls for a resistor plug, otherwise the ignition system might suffer damage. Charts from spark plug manufacturers are a good reference to help determine which plugs can be used in a pinch. Cross-references between spark plug brands are available from the spark plug makers and are a good way to find replacements.
:welcome:
Numbers and Letters:
Manufacturers work hard to select the right spark plug for each engine application. Plugs have significant impact on engine performance and fuel economy, and using the wrong one can cause poor running quality or engine damage. Each of the digits on a spark plug dictates its specifications or characteristics. A common spark plug is B8ES. The "B" designates 14mm thread x1.25 pitch, 20.8mm hex. The "8" is the heat range. The "E" is thread reach of 19mm. The "S" designates a super copper core center electrode. A spark plug can only cover a certain operating tempature range. Heat ranges vary by about 75 degrees. When selecting the correct plug for an engine, manufacturers choose one that works safely at the hottest temperature it could face under high RPM and heavy load. The plug must withstand the maximum temperature and be resistant to fouling at cold startup and idle.
Hot and Cold:
The length of the center electrode and insulator nose dictates whether a spark plug is a "hot" or "cold" burning plug. For example, a hot plug will have a longer insulator nose and a short center electrode. The long insulator nose transfers heat more slowly to the shell of the spark plug and then to the cylinder head. Cold plugs have short insulator and a long center electrode. Electrodes with copper also dissipate heat quicker than standard steel electrodes. As a rule of thumb, the hotter an engine runs, the colder the spark plug should be. Hot engines include modified or high performance engines! A spark plug starts to burn off fouling deposits at about 800 degrees farenheit. If too many deposits accumulate on the ceramic core, electricity from the ignition system will follow the path of least resistance into the core and ground to the inside of the shell rather than arc across the gap. Short ground electrodes take longer to reach the deposit burn off temperature, which makes them prone to fouling, but they are less likely to break as result of cylinder head vibration. Fouling caused by a rich fuel mixture CANNOT BE FIXED WITH A HOTTER PLUG! Prevent this problem with CORRECT JETTING.
Can You use a different plug than specified?
When possible ALWAYS use the spark plug that the manufacturer specs for your machine. There are cases when a different plug can work in a pinch to get you home. If your recreational vehicle calls for a B9ES for example, it's okay to use a different heat range plug such as a B8ES as a temporary fix. But because this plug is hotter than your stock plug, take it easy to avoid pre-ignition. In cases where special materials such as copper, gold, and platinum are used to dissipate heat more quickly or prolong life, a plug variance is acceptable for a short time. Some spark plug characteristics cannot be used as a temporary replacement. A reach that is too long could cause a collision between the bottom of the plug and the top of the piston at top dead center, which may cause damage. Plugs that have the wrong threads won't thread into the head and non-resistor plugs shouldn't be used in an application that calls for a resistor plug, otherwise the ignition system might suffer damage. Charts from spark plug manufacturers are a good reference to help determine which plugs can be used in a pinch. Cross-references between spark plug brands are available from the spark plug makers and are a good way to find replacements.
:welcome: