In a pressure vessel resulting in a 15kV spark for both plugs, the Pulstar discharge on the left is significantly brighter (lumens) than the ultra premium fine wire irdium electrode traditional spark plug on the right, visually demonstrating the difference between pulse plugs and spark plugs

In a pressure vessel resulting in a 15kV spark for both plugs, the Pulstar discharge on the left is significantly brighter (lumens) than the ultra premium fine wire irdium electrode traditional spark plug on the right, visually demonstrating the difference between pulse plugs and spark plugs

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US-based Enerpulse Inc develops ignition products through the application of pulse power technology. Matthew Beecham talked with Louis Camilli, founder and president of Enerpulse Inc, about why its so-called Pulstar 'pulse plug' is the only solution currently available that poses an opportunity for automakers to significantly improve the combustion process without a major, and very expensive, propulsion system change.

just-auto: What is the Pulstar pulse plug?

Louis Camilli: A pulse plug replaces a spark plug and essentially accomplishes the same task of initiating the combustion process in a spark ignited internal combustion engine. The pulse plug looks like a spark plug because it installs in the same hole in the engine and adapts to the same electrical fittings of the vehicle ignition system.  However, the resemblance is superficial.

Who invented it?

The original concept of placing a capacitor in the high-voltage circuit of an automotive ignition system to improve combustion efficiency dates to the early 1900’s. There have been many patents over the years, though none were commercially successful. The Pulstar pulse plug is the first successful patented high-power fuel ignition technology to reach the automotive marketplace. The original concept and design of the Pulstar pulse plug was the brainchild of Louis Camilli. Since its inception, 14 patents have been granted with 21 more in some stage of examination.

Did the ideas and technology originate from the automotive industry?

While the early 1900’s and later efforts to improve the effectiveness of the spark plug involved elements of the auto industry, the roots of Pulstar stem from work at Sandia National Laboratories (SNL) in their Ultra-High Power Electromagnetics department. SNL was the principal source of technology and products for President Regan’s Star Wars Initiative, a definite departure from the automotive channel.

What does it do, and how does it work?

The Pulstar design incorporates a high-voltage, current peaking capacitor wired in parallel to the high voltage circuit of a vehicle ignition system. This design provides for a very high-current (> 1000A) and high-power (>1MW) initial discharge of the plug to create a larger and more robust flame kernel in the fuel charge. Testing at Southwest Research Institute proves that Pulstar creates a larger the initial flame kernel which produces a more complete and efficient combustion process resulting in a more powerful and efficient engine.

Like any capacitor, the Pulstar capacitor stores energy over a relatively long period of time and discharges it in a relatively short period of time. In the case of Pulstar, time compression is on the order of 10,000X resulting in a peak discharge current for Pulstar of over 1000 amps as compared to a traditional spark plug discharge of less than .050 amps.  As you can see from the image [included in this article], in a pressure vessel resulting in a 15kV spark for both plugs, the Pulstar discharge on the left is significantly brighter (lumens) than the ultra premium fine wire irdium electrode traditional spark plug on the right, visually demonstrating the difference between pulse plugs and spark plugs.

Why is it useful?

Pulstar improves the combustion process extracting more work out of the fuel charge than traditional spark plugs. This leads to increased performance out of the engine and/or improved fuel economy dependant on the application of throttle.  Independent testing confirms fuel economy improvement up to 10% and improvement to torque of approximately 6%.

Why is it different and how is it significant?

All traditional spark plugs look alike and perform alike. Their differences are localised in the design, location, and materials used in the positive and negative electrodes. The electrical characteristics are unchanged from brand to brand and design to design. As such, spark plugs are design limited to less than 50 watts of peak discharge power.

While the pulse plug appears to duplicate a spark plug externally, the internal composition shows the patented Pulstar design required to incorporate the HV capacitor in parallel to the high voltage circuit of the ignition system.

This design provides for a very high-power initial spark to create a large and robust flame kernel, while at the same time having no effect on ignition timing or creating additional load on the ignition system.


What does it replace?

The Pulstar pulse plug replaces any and all spark plugs in spark ignited internal combustion engines: including automotive, power-sports, commercial, lawn and garden, and small engine. In a plug and play aftermarket scenario, the pulse plug consistently improves performance beyond factory delivered levels. At the automaker level it is a “whole new ball game”. Here there are enormous opportunities to re-calibrate fuel delivery, ignition timing and gearing to optimise combustion efficiency benefits of Pulstar on both existing and future powertrains. The ability to convert the Pulstar high-energy pulse ignition to measurably improve combustion efficiency qualifies it as a truly disruptive technology.

What does it threaten?

The Pulstar high-power technology threatens the use of current spark plug design employing low-power discharge.

Are there different versions of the plug for certain market segments?

In the automotive segment Pulstar offers five basics designs that apply to approximately 75% of the licensed for street vehicles and light duty trucks. This as compared to several hundred models from traditional spark plug manufacturers. Product design variables are in five areas:

  • thread diameter;
  • thread reach or length of thread;
  • seating provision to the cylinder head;
  • spark placement; and
  • seat range.

The automotive sector primarily uses a 14mm thread that, beginning in the 1950’s, utilised washer seat with a .375” reach, short projection into the combustion chamber, and a hot heat range. Today, however, automakers have segued to employing 12mm thread, washer seat, 21mm reach, projected spark placement and cooler heat range designs.

Pulstar will open other channels such as Powersports and Marine in mid to late 2011 which will require different Pulstar characteristics to accommodate the channel requirements.

What are the factors driving innovation in spark plug design today?

The primary factors driving automakers to improve combustion efficiency are governmental regulations on fuel economy and emissions combined with the high cost of fuel. In the automotive internal combustion power-plant design area, it appears all of the low hanging fruit has been harvested as improvements to fuel economy and emissions are focused on incorporating hybrid drive. Hybrid drive is a combination of a small spark ignited internal combustion engine coupled to a drive system that utilises large electric motors and a powerful battery pack.

In some cases, the hybrid drive propulsion uses both combustion and electric drive. In others the combustion engine is used to charge the batteries of the primary drive electric propulsion system. The emergence of this complex and expensive solution speaks to the inability of the automaker to extract significant gains in combustion efficiency from current combustion engine designs.

The Pulstar pulse plug is the only solution currently available that poses an opportunity for the automaker to significantly improve the combustion process without a major, and very expensive, propulsion system change. That said, the Pulstar plug is also poised to improve the performance of hybrid drive systems.

To what extent do direct injection gasoline engines affect the design and performance of spark plugs?

Direct injection or GDI (Gasoline Direct Injection) is becoming the fuel delivery system of choice for automakers. With the first commercial introduction in 1996 by Mitsubishi, nearly all automakers today offer at least one advanced powerplant equipped with these systems - with more platforms scheduled.

However, there are operating nuances with GDI that continue to prevent wholesale adoption of the process. One is that, in some engines, devastating knock occurs during lean operation with no warning.  A second is that not all combustion chamber designs are suitable for stratified charge lean operation using GDI. These are engineering issues that will be resolved over time and may be mitigated using the Pulstar high-power discharge ignition.

To date the only change to the design of spark plugs has been the migration to a cooler heat range with added thickness to the insulator projecting into the cylinder for added mechanical strength.

What effect has GDI and general downsizing of engine displacement had on spark plug design?

The over-reaching effect has been available physical space in the cylinder head into which the spark plug is installed. The cylinder with multiple valves has reduced the area between the valves forcing the automaker to reduce the size of the threaded portion of the spark plug from 14mm to 12mm and some engines are now employing spark plugs with 10mm threads. This physical constraint both reduces the size and weight of the spark plug, both not it’s function. The same can be said of the Pulstar plug. Engineering and insulator chemistry unique to Pulstar accommodates these new powertrains.

What impact to the aftermarket is there with longer life spark plugs such as those with iridium electrodes?

There is no question that there is a significant downturn in the volume of spark plugs sold in the aftermarket as a result of the introduction of these plugs. According to Frost and Sullivan, the volume is predicted to drop but revenues climb as these long life plugs retail for more than conventional spark plugs. The Pulstar pulse plugs are priced at the same level as premium spark plugs and not priced out of the market.

What is the future for spark plugs?

For over 100 years the spark plugs did not change in design or general characteristics. Minor improvements have reduced wear and improved their function but not their electrical output. Today commercial spark plugs still only discharge a peak current of .05A with electrical to plasma (energy) transfer efficiencies of less than 1%. Still good enough for the automakers to induce ignition but times have changed and, as stated earlier, all the low hanging fruit has been harvested.

This from the Engine Conference in Strausberg 2007:
“To this end, a resurgence of the spark ignition engine, with diverse technologies and fuels is expected over the coming years, as a new generation of spark ignition engines will be introduced to meet the CO2 challenge. Technologies such as downsizing are already under development and offer great potential for increased power density and improved thermal efficiency of the gasoline engine. Furthermore, combining technologies such as turbo charging, direct injection and new valve actuation technologies is providing opportunities for gasoline engines to reduce the gap in fuel efficiency and CO2 emissions compared to their Diesel counterparts. Apart from conventional concepts, new combustion processes such as Controlled Auto-Ignition (CAI) or Homogeneous Charge Compression Ignition (HCCI) could offer further potential to improve the efficiency and lower engine out emissions. Other avenues for efficiency improvements and CO2 reductions for spark ignition engines could come from different fuel types and technologies which have been explored over the years, such as gaseous fuels, flex-fuels and bio-fuels.”

As can be seen above, there is very little apparent attention and/or interest at the automaker for improved spark plugs. As a result, innovations will come from outside the automotive channel, just as Pulstar was developed. Of further interest is the mention of CAI and HCCI, which holds the future for the gasoline engine. In both cases, power and performance will increase along with significant reductions in emissions.

Enerpulse, Inc. the manufacturer of the Pulstar pulse plugs is on the leading technological edge with its joint development programme with Grail Engine Technologies. Using the Pulstar pulse plug Grail has enabled a form of HCCI called Forced Semi-homogeneous charged compression ignition.  The results show huge increases in performance with significant reductions in emissions.

In conclusion, the spark ignited engine and spark igniters will be in our future for a very long time.