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Owner: Spark Plugs Guide
SPARK PLUGS - FAQ's
Deciding which type of spark plug is right for an engine is a subject we find our selves discussing with customers quite often. It’s a safe bet that a standard, un-modified engine will run just fine with a set of OE spark plugs. If however, you’ve spent time and money tuning a high performance engine, you should consider a high performance spark plug too.
What’s the best spark plug design?
Durability, maximum fuel economy and cost are among many factors taken into consideration by car manufacturers when selecting the best spark plugs to meet increasingly stringent emissions regulations. The economist should arguably stick to the factory spark plugs. If maximum performance is your goal then these factors will be less of a concern and you may well consider upgrading.
Performance after market spark plugs such as NGK Iridium IX (image 4 & 5) were designed with maximum performance in mind. Finer tips are used ensuring a stable, precise spark and highly conductive materials with increased melting points allow the plug to perform under the most extreme circumstances. Whilst this type of spark plug often has a shorter life expectancy, it’s often chosen for superior ignition qualities when compared with most OEM supplied spark plugs.
Which heat range should I use for my engine?
Each spark plug carries a ‘heat range’ which is usually indicated within the part number. One of the functions of a spark plug is to dissipate heat produced during the combustion process, most of which is transferred into the cylinder head. The heat range represents the plugs ability to do this.
A warm spark plug is designed to maintain a high temperature at the insulator nose to burn off carbon and oil deposits, where as a colder spark plug is designed to allow a faster transfer of heat to the cylinder head which prevents over heating and premature failure.
The heat range selection is a complex task with many factors taken into account by spark plug manufacturers such as NGK. Standard or lightly modified engines should generally stick to the heat range of the OE spark plugs, even if you decide to upgrade to an aftermarket brand.
Highly modified engines will usually need to use a spark plug at least 1 stage cooler than standard. If you are planning substantial engine modification we advise that you speak to the person mapping your car for best advice on which heat range to use.
How do if I tell if I need to change my spark plugs?
You can tell a lot about the performance of your engine by the condition of the spark plug it’s self. A spark plug working under ideal conditions will have a light brown or grey insulator. A small amount of carbon build up can be expected but regular checks will give a better indication over time. (Image 1)
If a spark plug over heats then pre-ignition may occur, causing reduced engine power and possibly piston damage. Note the white deposits and blistered surface. (Image 2)
Possible causes are:
• Over advanced ignition timing
• Too lean fuel mixture
• Blocked injectors
• Insufficient cooling
• Excessive deposits in combustion chamber
• Spark plug too warm
If the spark plug is fouling it’s usually too cold resulting in bad starting and poor acceleration. Note the heavy carbon build up on the insulator. (Image 3)
Possible causes are:
• Too rich fuel mixture
• Excessive use of choke
• Prolonged low speed driving or idle
• Blocked air filter
• Spark plug too cold
JP4mance Tuning Parts stock hundreds of spark plugs to meet all requirements. Give us a shout if your unsure, we're here to help!