SPARK PLUGS

Q: What is U-groove technology?

A: U-groove spark plugs are a patented design invented by DENSO to improve spark plug ignitability and reduce quenching of the spark. The U-groove shape cut into the ground electrode allows the spark to expand and fill the gap created by the ‘U’ shape, enabling the spark plug to ignite leaner mixtures, leading to fewer misfires. The U-groove is located on the ground electrode to minimise wear and ensure the U-groove lasts the lifetime of the plug.

Q: What kind of heat range do DENSO’s Spark Plugs offer?

A: DENSO’s Spark Plug programme for the aftermarket offers the best heat range coverage of any brand, without compromising on quality or performance. Because fewer DENSO parts numbers can cover a wider heat range than competitor plugs, distributors are able to keep reduced stock levels.

Q: Why aren’t normal spark plugs suitable for LPG engines?

A: Liquified petroleum gas (LPG) is an increasingly popular ‘green’ car fuel supported by a ever-widening network of filling stations. More than 4 million passenger cars currently run on LPG worldwide. However the ignition requirements of LPG engines are significantly different to petrol engines. This is because gas combustion is different to petrol combustion in two ways. Firstly, it is much harder to generate a spark in an LPG/air mixture than in a petrol/air mixture.  A higher voltage is required to achieve ignition: typically spark voltages of 10-15Kvs are needed for petrol engines, whereas for LPG operation 25 -30Kvs may be required.  However, a higher applied spark voltage is much more likely to break down the insulation of the ignition coil, or result in misfiring and poor drivability. Secondly, LPG needs more advanced ignition timing than petrol, which places a greater thermal load on the Spark Plug. As a result of these combustion characteristics, not only does the spark plug have to deal with the higher temperature inside LPG engines, but spark plug corrosion also occurs more quickly.  The spark plugs used in LPG vehicles must therefore be specifically suitable for LPG engines.  If a conventional spark plug is fitted in a vehicle that runs on LPG, the spark plug may not spark, causing misfiring.  Voltage will also be generated in the ignition coil and if this is too high, irreparable damage will be caused to the ignition coil.  Faults may also arise in the LPG controller. The solution is to change from standard spark plugs to precious metal spark plugs with a different heat range. Spark plugs that feature superior, hard-wearing materials such as platinum and iridium offer increased performance by significantly reducing the surface of the electrode. The very best example of this technology is DENSO’s patented, ultra fine-wire Iridium Tough spark plugs, which feature the world’s smallest iridium centre electrode and a platinum-tipped ground electrode. In these plugs the voltage is concentrated onto the tiny surface of the 0.4 mm electrode tip.  This means that a much lower voltage is required in order to create the field strength needed to generate a spark.  The second benefit of having such a narrow electrode is that the mass of the electrode is also small, which reduces the cooling effect on the growing combustion.  This gives the growing combustion a better chance to spread, until complete combustion of the mixture occurs.  Iridium Tough spark plugs last three times longer than a normal nickel spark plug would in the LPG engine.

Q: What are the special design features of DENSO’s Iridium Spark Plug ranges?

A: DENSO’s Iridium Spark Plugs feature a 0.4 mm dia. Ultra-Fine Iridium Centre Electrode - the world’s finest iridium centre electrode - made from DENSO-patented iridium alloy for lower voltage and better ignitability. The iridium tip is joined with a highly reliable ‘360° Laser Welding’ process to withstand all kinds of driving conditions. The plugs also feature a taper cut ground electrode, which reduces flash suppression and improves ignitability, smoothing the fuel-air mixture for steady ignition. In addition a U-Groove ground electrode allows a large space for the flame kernel; producing a low spark voltage without increasing the gap, and delivering superb ignitability.

Q: Can you summarise the key points of DENSO’s different replacement spark plug ranges?

A:

Standard

Double Platinum (Longlife)

Twin Tip

Iridium Longlife, Iridium Tough, Iridium Power

Iridium Racing

Super Ignition (SIP)

Q: What are the factors influencing ignition system today?

A: Probably the biggest challenge for ignition coil development at present is that trends in engine design mean that more discharge energy is required in order to secure stable combustion. This trend is being driven by the increasing number of direct injection gasoline applications and emissions regulations? Direct injection gasoline applications demand, for example, 100mJ of energy compared to the 30mJ required by conventional engines.  Stratified gasoline direct injection (Gdi) also places special challenges on the ignition system. These systems can require more energy than a homogeneous system.  For this reason, DENSO ignition system developments are focusing on developing an even more robust structure that can deliver the required outputs across a long lifetime.

Q: What are the main trends and influences on ignition systems in the aftermarket at present?

A: Three of the most significant Spark Plug developments now reaching the aftermarket are:

Introduction of innovative new fine-wire, non-precious metal Spark Plugs: A new, world-first Spark Plug technology developed by DENSO was made available to the European aftermarket from 2010: Twin Tip (TT) Spark Plugs. This highly ignitable, durable TT Spark Plugs range offers up to 5% better fuel efficiency and reduced carbon dioxide (CO2) and hydrocarbon (HC) vehicle emissions compared with Standard Spark Plugs – as well as better acceleration and output. The technology offers extensive benefits for drivers, stockists and installers. TT Spark Plug technology is the outcome of two years of R&D work at DENSO’s Japan-Ceramic Engineering centre, aimed at meeting the twin challenges of environmental protection and technical performance. Founded on DENSO’s OE-tested, Super Ignition Plug (SIP) technology, TT plugs are the first ever fine-wired Spark Plugs to be produced without using precious metal - such as platinum or iridium - on the electrodes. Thanks to their nickel alloy centre and a ‘twin’ protruding ground electrode with a slimmer than normal 1.5mm diameter, TT plugs produce more powerful sparks, ensuring better combustion of the air and fuel mixture. Ignition efficiency achieved is close to DENSO’s premium Iridium ranges, even in cold conditions.

Rise in demand for Super Ignition Spark Plugs (SIPs): Due to the ever-tightening demands of world vehicle emission legislations, including Euro 5 and Euro 6, lean-burn petrol engines are becoming more common. But what we’ll see more of in particular are direct injection, turbo charged engines. Although this market is currently tiny – representing only around 1% of today’s new cars – around 50% of new concept engines set to reach the market in the next couple of years are likely to feature direct injection with turbo charge. These engines may run on an unprecedented lean fuel mixture up to five times leaner than we see today; an incredibly demanding operational environment, requiring a new generation of advanced ignition parts. Meeting that need, however, is a ground-breaking, super-advanced Iridium spark plug that’s already making waves with vehicle manufacturers around the world. Super Ignition Spark Plugs (SIPs), developed by 0.4mm Iridium Spark Plug pioneers DENSO in 2006, improve ignitability even in the demanding environment of lean-burn petrol engines. Featuring not one, but two ultra-fine, highly durable centre and ground electrodes, they produce a truly exceptional spark and performance. As well as lean-burn, this makes them ideal for two additional engine demands of the future: Exhaust Gas Recirculation (EGR), which requires extreme spark plug ignitability; and aggressive air intake compression ratios, which generate a high discharge voltage that would normally fracture ceramic plugs. In each case only Super Ignition Plugs can provide the appropriate ignition and combustion, thanks to their superior ignitability.

Rise in demand for precious metal spark plugs: The number of vehicles manufactured with, or converted to, Liquified Petroleum Gas (LPG) operation has increased in Europe in recent years; a system that creates particular demands on the ignition system. As a result of these combustion characteristics, not only does the spark plug have to deal with the higher temperature inside LPG engines, but spark plug corrosion also occurs more quickly.  The spark plugs used in LPG vehicles must therefore be specifically suitable for LPG engines. The solution is to change from standard spark plugs to fine-wire, precious metal spark plugs with a different heat range. DENSO’s advanced Iridium Tough spark plugs provide the optimal solution for gas operated engines, making conversion and servicing not only easier, but also more reliable. The range covers 99% of conversion-capable cars in Europe, making them the ideal replacement spark plug for every LPG operated (or convertible) European car on the road. Featuring the world’s smallest 0.4mm diameter Iridium centre electrode and a platinum tip at the ground electrode, DENSO Iridium Tough spark plugs deliver the highest possible performance and longevity for LPG engines, lasting approximately 60,000 km (36,000miles) – three times longer than standard nickel plugs.

Q: What are the main uses of Super Ignition Plugs (SIPs)?

A: Thanks to the ever-tightening demands of world vehicle emission legislations, including Euro 5 and Euro 6, lean-burn petrol engines are becoming more common. In particular we’ll see more, direct injection, turbo charged engines. Although this market is currently tiny – representing only around 1% of today’s new cars – around 50% of new concept engines set to reach the market in the next couple of years are likely to feature direct injection with turbo charge. These engines may run on an unprecedented lean fuel mixture up to five times leaner than we see today; an incredibly demanding operational environment, requiring a new generation of advanced ignition parts. Super Ignition Spark Plugs (SIPs), developed by DENSO in 2006, are set to meet that need. SIPs improve ignitability even in the demanding environment of lean-burn petrol engines.  Featuring not one, but two ultra-fine, highly durable centre and ground electrodes, they produce a truly exceptional spark and performance.  As well as lean-burn, this makes them ideal for two additional engine demands of the future: Exhaust Gas Recirculation (EGR), which requires extreme spark plug ignitability; and aggressive air intake compression ratios, which generate a high discharge voltage that would normally fracture ceramic plugs.   In each case only Super Ignition Plugs can provide the appropriate ignition and combustion, thanks to their superior ignitability.

Find out more
DENSO Europe B.V.’s Business Unit Aftermarket can be contacted on tel: +31 (0) 294 493 493.