In this interview, Matthew Beecham talked with Shin Nishioka, spark plug engineer, Denso Europe BV, business unit aftermarket about the company's ignition system products. 

just-auto: Could we start by asking if you could summarise the factors influencing the design of an ignition system? 

Shin Nishioka: Trends in engine design mean that more and more discharge energy is required these days in order to secure stable combustion. This is probably the biggest challenge for ignition coil development at present. 

just-auto: Are you also seeing more use of electronics in the ignition coil itself?  How does that trend in Europe compare to the situation in Japan?  

Shin Nishioka: The majority of ignition coils in both Europe and Japan today are already controlled by the electronic control unit. 

just-auto: There is also a clear trend toward increasing energy requirements.  To what extent is that trend for more energy requirements being driven by more direct injection gasoline applications and emissions regulations? 

Shin Nishioka: Direct injection gasoline applications demand, for example, 100mJ of energy compared to the 30mJ required by conventional engines.  This is clearly an important consideration in the development and specification of the ignition system. 

just-auto: What are the special challenges on the ignition system posed by stratified GDi?  And what is Denso's solution? 

Shin Nishioka: Stratified gasoline direct injection 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. 

just-auto: In terms of ignition system design and technical specifications, do you see any regional differences say between Europe and North America? 

Shin Nishioka: No, they are the same overall. 

just-auto: Turning to trends in the ignition system aftermarket, what do you see happening there?  

Shin Nishioka: There are a great many trends and influences on ignition systems in the aftermarket at present, but three of the most significant spark plug developments now reaching the aftermarket are as follows: 

  1. Introduction of innovative new fine-wire, non-precious metal spark plugs: A new, world-first spark plug technology developed by Denso is being made available to the European aftermarket from September [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 and hydrocarbon vehicle emissions compared with standard spark plugs - as well as better acceleration and output.   The technology offers a number of benefits for drivers, stockists and installers, including:
  • TT plugs are a first in the market and a real chance for distributors and garages to differentiate themselves from competitors
  • With only seven part references offering enough applications to cover 80% of the top selling European cars, stock-holding is dramatically reduced
  • The range offers more profit potential than standard spark plugs.

TT spark plug technology is the outcome of two years of R&D work at Denso's ceramic engineering centre in Japan, 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.  

  1. Rise in demand for super ignition spark plugs: 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.  Set to meet 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, developed by 0.4mm iridium spark plug pioneers Denso in 2006, improve ignitability even in the demanding environment of lean-burn petrol engines.  Featuring two ultra-fine, durable centre and ground electrodes, they produce exceptional spark and performance.  As well as lean-burn, this makes them ideal for two additional engine demands of the future: exhaust gas recirculation, 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.   
  1. Rise in demand for precious metal spark plugs:  The number of vehicles manufactured with, or converted to, 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.  Fit a conventional spark plug in a vehicle that runs on LPG, and a variety of problems may arise.  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 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 (36,000 miles) - three times longer than standard nickel plugs. 

just-auto: As distributorless or direct ignition systems enter the replacement cycle, is there likely to be greater demand for coils and engine control units? 

Shin Nishioka: We anticipate that there will be very little additional demand for coils and engine control units as disributorless or direct ignition systems enter the replacement cycle. 

just-auto: In terms of tomorrow's ignition system designs, what could we expect? 

Shin Nishioka: The main focus is on achieving high energy outputs.  This really is the biggest ignition systems focus for product engineers.