High ignitability engine designs are becoming increasingly prevalent, especially due to EPA’s fuel efficiency requirements and emissions regulations on automotive manufacturers.
GDI fuel systems, turbocharging, coil on-plug and multi-strike ignition systems, unique combustion chamber designs, and high ignitability spark plugs are crucial enhancements that make up high ignitability engines.
In gasoline direct injection (GDI) systems, fuel is injected directly into the combustion chamber at high pressures – ranging as high as 3000 psi – to ensure better atomization of the fuel, leading to more efficient combustion.
Turbocharging increases air intake to allow more air (and fuel) to be combusted, which increases power output. Turbocharged engines often have higher compression ratios, which can improve power while challenging the ignition system.
Coil-on-plug ignition systems consist of an ignition coil for every spark plug, which allows for direct ignition. This eliminates the need for spark plug wires and uses all energy available to deliver the spark. In these systems, the powertrain control module (PCM) can precisely control the timing and duration of the spark, optimizing performance and efficiency.
Multi-strike ignition systems fire the spark plug multiple times per combustion cycle at low RPMs to ensure complete combustion. This reduces emissions as it promotes a more complete burn of the air fuel mixture.
Inside the combustion chamber of high ignitability engines, pistons may be specially designed to direct the fuel spray towards the spark plug and optimize the combustion process. The design of the combustion chamber and intake ports can create swirl and tumble-effects; this improves the mixing of air and fuel to have a better combustion. Therefore, following spark plug-torque specifications is critical to overall ignitability for some manufacturers’ engine designs.
Spark plugs with high ignitability tip designs have improved spark performance for a more complete combustion as well, leading to better fuel efficiency and lower emissions. High ignit- ability spark plug metal types include platinum, iridium, and ruthenium; these materials have high melting points and excellent conductivity. The tips are configured with single or dual fine electrodes; modern spark plugs often feature a fine-wire center electrode and some designs have a second fine wire on the ground strap which together creates a more intense voltage spark, therefore improving ignitability.
To accommodate the compact design of modern engines, these spark plugs are often longer and thinner in diameter to fit into tighter spaces without compromising performance. High ignit-ability spark plugs are also designed to dissipate heat efficiently, which prevents pre-ignition and fouling.
High ignitability spark plugs have longer life cycles than nickel center electrode plugs but may still need to be serviced under 100k miles due to today’s engine demands. Overall, when trouble shooting the computerized engine management of these various systems that makes up today’s high ignitability engine designs, it’s essential to use the following tools: a bidirection diagnostic scan tool, DVOM, and a multi-channel oscilloscope with various testing probes.
For more detailed information and troubleshooting high ignitability engines, reach out to the NGK Pro Training & Development Team at [email protected]
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