LIGHT SPEED ENGINEERING™, LLC
Plasma CD Ignition     

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Products FAQs


last update:
December 03, 2011



FAQs



1.)
Why should I choose Plasma CDI over good old magnetos?
2.)
What is the difference between the Plasma II Plus and the Plasma III system?
3.)
Can I use one Plasma CDI and one mag?  How do they work together?
4.)
How does the Plasma CD system advance the timing?
5.) Will my engine temperatures change when I install a Plasma CDI?
6.)
What are the power requirements for the Plasma CD systems?
7.)
Back-up battery?
8.)
I have an older Lycoming engine with a small generator pulley, does that work with the Direct Crank Sensor system?    
9.)
My engine has a single drive dual magneto in place of two magnetos.  How can I adapt my engine to run with Plasma ignition?
10.)
How should I feed the wires through the firewall?
11.) Can the supplied coax cable be replaced with any other wire?
12.)
Which spark plug location do you recommend for a single Plasma CDI installation?
13.)
Can I use my key switch with the Plasma CD ignition system?
14.) Does the Plasma CDI work with my electronic tachometer?
15.) Are the Plasma CD ignition systems FAA approved?



1.) Why should I choose Plasma CDI over the good old magnetos?

  • Aside from the significant performance and efficiency gain, electronic ignitions are significantly more reliable and do not require regular overhauls, inspections, or repairs.

    In the excellent 1992 book "The Magneto Ignition System", author John Schwaner  says the following about magneto repair:

         "Since 1985, the National Transportation Safety Board has cited magnetos as a cause or factor in 92 accidents involving 22 fatalities and 21 serious injuries.  This is surprising in that only one magneto is required to operate the engine."
         "Magnetos are reliable and provide a redundant safety factor, but they have the potential of causing engine failure if they are not inspected and serviced.  When the magneto bearings fail  on one obsolete magneto model, the rotor seizes causing the gear teeth inside the engine to break.  The broken gear uncouples both magnetos causing instant engine shutdown.  Worn impulse-coupling rivets can cause engine failure when the impulse coupling engages in flight.  The adage "...if it's not broke don't fix it." translates to "...operate it until it fails and hope it doesn't take the engine (and us) when it does."
         "Low voltage and hard starting can be caused by shorted secondary turns within the magneto coil."
         "Any time the magneto is "fired" without the secondary circuit attached to spark plugs or ground, the full secondary voltage stresses the winding insulation.  Eventually the insulation breaks down and the windings short."
         "Shorting of a secondary winding may create an open circuit as the winding burns."

    In writing of impulse coupling failure, the author states, "The flyweight moves outward until the heal(sic) of the flyweight strikes the stop pin.  At first, the heal(sic) just grazes the stop pin causing a telltale mark on the flyweight.  Eventually, the heal(sic) strikes the stop pin with enough force that it pivots the flyweight outward where it engages the stop pin.  When this happens during engine cruise, there is enough force that the flyweight disintegrates into the accessory gear train.  Pieces of the impulse coupling then lodge into the engine gearing, breaking off gear teeth and decoupling both magnetos from the engine.  The engine quits."

    Other failure mechanisms have to do with arcing of the distributor block, oil or moisture in the magneto, especially on super-charged engines, heat failures of the capacitor, weak armature magnets, incorrect timing of the "E" gap, and incorrect impulse coupling lag-angle when faster or slower starters are installed which can cause kick-back.

2.) What is the difference between the Plasma II Plus and the Plasma III system?

  • All Plasma systems are high energy Capacitor Discharge type systems.  They are more accurate due to their faster voltage rise time and provide a hotter spark from a smaller and lighter coil when compared to the typical inductive type ignition system.  

    The Plasma II series is a single spark system which has a fixed spark duration at all rpm.
    The Plasma III has a dual output stage which provides a continuous spark for about 20 degrees of crankshaft rotation at all rpm.  Extensive flight testing with cockpit variable spark duration showed maximum performance gain with an un-interrupted 20 degree spark.   

3.) Can I use one Plasma CDI and one mag?  How do they work together?

  • Under high power conditions the Plasma CDI fires at about the same ignition timing as the mag.  Only when MP is reduced will the Plasma CDI advance its ignition timing accordingly.  While this is not as ideal as advancing the timing on both spark plugs, it is much better than not advancing the timing at all, as is the case with magnetos.

4.) How does the system advance the timing?

  • The Plasma CDI adjusts the timing based on manifold pressure (MAP) and rpm.  Most of the change is based on MAP, and only a few degrees of change are based on rpm.  

    Optimized timing means more advance at lower manifold pressures and less timing advance at high power.  During start, the systems fire at TDC, independent of manifold pressure.

    The ignition timing is at an optimum when the engine produces peak torque.  At peak torque the highest amount of energy is used for work and the least amount of energy is absorbed by the cylinder head (too much advance) or wasted in the exhaust (too much retard).

5.) Will my engine temperatures change when I install a Plasma CDI? 

  • As mentioned in question 3, optimizing the timing means less heat is lost into the cylinder head, piston, cylinder, and exhaust and more heat is used to make power.  This applies to all power settings including idle. At altitude you should see a 75F- 150F lower EGT when the Plasma CDI is used.

    Since heat is a byproduct of power, and since the spark characteristics and timing of the Plasma CDI increase max power, the associated heat can also be slightly higher at the new power output.

6.) What are the power requirements for the Plasma CD systems?

  •  The current versions of Plasma CDI systems need a minimum of 6.2 volts to start operation.  This is more than 2 volts less than the minimum voltage needed by the starter solenoid, thereby eliminating the possibility of kick-backs during starter operation.

    Plasma systems shipped before December 20 of 2004, need 8.5 volts to start operation.  This higher "on" voltage can cause a misfire if the starter current drain is high and/or the battery is weak and the voltage collapses below this threshold during cranking.  Systems shipped before 2005, can be upgraded to have the lower voltage capability.  

    Once the engine is running, all systems operate down to less than 5 volts, should you lose your charging system.

7.) Back-up battery?

  • All Dual systems are shipped with a Schottky diode to be used with a back-up battery.  A simple wiring diagram is also supplied.

Any aircraft with a starter has excess energy stored in the battery for starting.  In flight, this large capacity is not needed.  In case of an alternator failure, 17ah or more should be available.  If this is only used for the ignition (2ah at 13.8v), the airplane will probably run out of fuel before the battery does.  It should be standard procedure to land ASAP if there is a charging problem on an all-electric plane.  Also, one of the Plasma systems can be switched off to minimize current consumption since the power is nearly the same, especially when the interconnect feature is used.

8.) I have an older Lycoming engine with a small generator pulley, does that work with the Direct Crank sensor system?   

  • The larger pulley flywheel (8.5" ID) is required for the Direct Crank Sensor installation.  Aside from Lycoming, two other sources are Superior Air Parts: (972) 829-4600 and ECI in TX: (800) 324-2359.  The price is about $300.

9.) My engine has a single drive dual magneto instead of two magnetos.  How can I adapt my engine to run with Plasma ignition?

  • The Lycoming O-320-H2AD and IO-360-A3B6D engines (among others) typically have a single magneto drive fitted to a dual magneto.  

Most pilots with these engines replace the dual mag completely and use a dual Plasma CDI with Direct Crank Sensor or DCmini Sensor triggering.  This installation eliminates the failure points of a dual mag set-up, significantly reduces weight, and is less expensive than other options.

Hall Effect Modules are not used on engines with single drive dual magneto configurations. 

10.) How should I feed the wires through the firewall?

  • It is important that the sensor wires (connecting the Hall Effect Module, Direct Crank Sensor, or DCmini Sensor to the Plasma CD box) are routed through the firewall by themselves or only with other low-voltage "sensor" wires.  All "sensor" wires should be well separated from high power wires.

    The RG-400 primary ignition wires (connecting the ignition coils to the Plasma CD box) are high power wires and should only be by themselves or with other high power wires (starter cable, alternator cable...).

    For best reliability, do not splice or otherwise modify the supplied cables.

11.) Can the supplied coax cable be replaced with any other wire?

  • Light Speed Engineering supplies the highest quality wire, pre-assembled and tested for best reliability.  Substitutions or modifications are not recommended.  

12.) Which spark plug location do you recommend for a single Plasma CDI installation?

  • A single Plasma CD system keeps the entire combustion chamber clean so it does not matter much if the Plasma CDI is on the top or the bottom.  It is best if you use your first system on the top and the second on the bottom plugs.  Since even a single Plasma CDI will keep the spark plugs clean, the systems should not be crossed.  Use either all top or all bottom plugs for each system.

13.) Can I use my key switch with the Plasma CD ignition system?

  • Yes, all Plasma II Plus and Plasma III CDI systems can be operated with a standard aircraft key switch.  A "P"-Lead (wired to the output connector) is provided and should be connected to the key switch in the same way as the magneto "P"-Lead.  There is no current drain on your battery when power is supplied via the input connector and the key switch is in the off position.  A pull-able circuit breaker should still be installed in the positive power wire.

    The older Plasma II does not have this feature and must be turned on and off with a quality toggle switch.

14.) Does the Plasma CDI work with my electronic tachometer?

  • All Plasma CD Ignitions have a pulse output (on the input connector) for an electronic tachometer.  The pulse characteristics are shown in the manual and most tachometers will respond to that signal.  If you have two Plasma systems and you want to have a tach reading from either Plasma CDI, you need to run the signals through a selector switch.  

    If you are using Plasma III versions "A" or later (available after 12/05), you can connect the tach pulses from two systems together to one tach terminal.

    Plasma III and Plasma II Plus CD ignitions also have a built in tach which provides a voltage output for a millivolt meter on the output connector.  See the wiring diagrams for details.

15.) Are Plasma CD ignition systems FAA approved?

  • We do not have FAA approval for the Plasma CDI.  In order to install the ignition system on your certified aircraft, you will need to get a field approval or a STC.  Several have been applied for.  News regarding a field approval will be published here.

    On December 10th 2007, Helicopteres Guimbal received a Supplemental Type Certificate from EASA* for the Light Speed Engineering Plasma CDI as standard equipment on their new Helicopter, the Cabri G2.

    Reciprocal agreements between the FAA and EASA can facilitate further applications on certified aircraft in the future.

    * The European Aviation Safety Agency is the European equivalent of the FAA.

 

 

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