The key factors driving spark plug innovation include emissions legislation, engine design and longer service intervals. Still plugging away for just-auto, Matthew Beecham caught-up with Sandro Pino, European Application Engineering Manager, Powertrain – Ignition Products, Federal-Mogul Corp to find out how the sector is taking shape.
What are the factors pushing innovations in spark plugs?
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Today, the main factor influencing spark plug design is the significant trend to highly turbocharged downsized engines that increase the thermal, mechanical and electrical challenges for the plug.
Higher in-cylinder pressures create greater thermal and mechanical loads and increased voltage demands on the spark plug, requiring improved materials to be specified to achieve the required life and robustness. Advanced ceramics and sophisticated electrode alloys are used.
The spark plug is a vital element in the combustion system of a highly rated engine, rather than a commodity, and only the correct plug specification can give complete engine performance over the full design lifetime.
To what extent do direct injection gasoline engines affect the design and performance of spark plugs (e.g. increasing the thermal impact)?
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By GlobalDataThe effects of increased thermal impact and voltage demand put a lot more stress on the spark plug. The more severe in-cylinder conditions encountered in the latest generation engines have led to the standard use of new alloys for the electrodes with greater resistance to high temperature oxidation. The ground electrode, especially, needs to be able to withstand these greater thermal loads.
The increased pressures in the combustion chamber require the firing end design, in particular the ceramic core nose, to be more robust to withstand the high pressure waves associated with abnormal combustion. Otherwise breakage could occur, causing misfiring, requiring spark plug replacement or worse, leading to engine damage.
The increased voltage demand now specified on turbo direct injection engines, up to 42kV, in conjunction with tighter cylinder head packaging, has required the development of new ceramic materials to provide the necessary insulation.
I guess direct injection and the general downsizing of engines has led to smaller and light spark plugs?
Direct injection requires the location of the fuel injector in the combustion chamber, often already crowded in multi-valve engines, and improved engine efficiency dictates greater optimisation of the water-cooling jacket.
Both these factors have driven down the size of the spark plug. Over the last ten years the spark plug thread size has been reduced from M14 to M12 on the majority of new engines. At the same time, reach has increased from 19mm to 26.5mm in the majority of cases because greater competition for space means the spark plug must sit farther away from the combustion chamber.
With longer life spark plugs, what is the impact on the aftermarket?
The aftermarket is driven by number of conflicting trends. Over the last ten years the replacement interval has tended to increase up to 120,000 km for some engines in Europe. With the advent of turbo direct injection engines, the issues [above] mean that spark plugs face significantly greater challenges, such as electrode wear and we have seen service intervals drop back to 60,000 km in many cases.
These effects, plus the growth in popularity of diesels, mean that both the volume and value of aftermarket business has declined in recent years. But as the latest turbo GDI engines find their way into the aftermarket, we expect demand to increase once again.
Because of the higher loads in downsized engines, the latest spark plugs are designed as an integral part of the ignition system. This will change the nature of aftermarket supply, reducing the gap between OE and aftermarket products and making it harder for aftermarket spark plug providers to compete with the OE supplier.
Looking at the distribution channels in Europe, what are the big changes you are seeing at the moment? Is there anything in particular in the change or structure that is driving that? How do you see these channels developing?
The automotive aftermarket is changing as it fights to sustain margins and customer service, plus increase revenue, while reducing costs.
Vehicle manufacturers are reducing their margin expectations and developing all-make servicing programs, which is having a leveling effect in some markets. Buying groups, both independent and non, are leveraging preferential sourcing for their members and so becoming increasingly influential in market placement and brand strategy.
What’s happening to brand names in the market place? Is the power of brands increasing or diminishing with the changes? Anything in particular in the change or structure that is driving that?
The remainder of this interview is available on just-auto’s QUBE research service
