---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 09/11/14: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:28 AM - Re: Speaking of battery issues... (GLEN MATEJCEK) 2. 10:24 AM - Re: Electronic Ignition Competitive Comparison (Ralph Finch) 3. 11:31 AM - Two wires (Janet Amtmann) 4. 05:08 PM - Re: Two power signals, one wire (Eric M. Jones) ________________________________ Message 1 _____________________________________ Time: 04:28:46 AM PST US Subject: AeroElectric-List: Re: Speaking of battery issues... From: GLEN MATEJCEK > > Thanks, Bob; Schauer is now in the house... now all I need is to get a > couple more batteries. That, and find / make the time to finish the > plane... > > At 03:03 AM 8/27/2014, you wrote: > >Hi Bob- > > > >Were you ever able to glean anything from the > >Battery Tender Jr I sent you some time back? > > > >Tnx- > > Yes, it was the second BT I picked out of the box. It > charges at a very low rate and oscillates between > charging and fully charged indications on the front > panel LED. > > Your original suspicions were correct . . . eess kaput! > > > Bob . . . > > ________________________________ Message 2 _____________________________________ Time: 10:24:26 AM PST US From: Ralph Finch Subject: Re: AeroElectric-List: Electronic Ignition Competitive Comparison LSE claims their spark energy is "> 120 mJ" for all their ignition systems. http://www.lightspeedengineering.com/Products/IgnitionSpecs.htm On Tue, Sep 9, 2014 at 4:18 PM, Justin Jones wrote: > With much talk about the EFII system by Robert Paisley here lately, I > thought I would share the results of a test between the EFII system, a > Slick Magneto, the Pmag 114, and the Lightspeed Plasma II+ systems. > > http://www.flyefii.com/ignition/ignition_comparison.htm > > > Bob, I am interested in your thoughts on this test. > > Thanks > Justin > ------------------------------ > > At the EFII facility at Cable Airport in Upland, California we gathered u p > the most popular choices for ignition systems on Lycoming engines to do > some comparison testing. The results were very interesting and brought up > some important differences between the systems tested. > > The systems tested were: > *Lightspeed Plasma II+* > *P-mag 114* > *Slick Magneto* > *EFII* > > There are other ignitions available for Lycoming engines. Those listed > above appear to be the most popular choices in today's market for > experimental aircraft. > > ------------------------------ > *IGNITION 101* > ------------------------------ > *Energy Storage* > In general, ignition systems are categorized first by how they store > energy to do their job. Their job of course is to produce sufficient > voltage and current to generate a spark across the gap of the spark plug, > and to create this spark at some nominal point during the rotation of the > engine. > > Most vehicle ignition systems fall into one of two categories depending > upon how they produce and store energy. > > *Capacitive Discharge* - The first category of ignition is "capacitive > discharge" or "CD". CD ignitions store energy in a capacitor and then > discharge the stored energy through the primary winding of an ignition co il > which in turn has a secondary winding connected to the spark plug. In CD > ignitions, the storage capacitor is typically charged through a DC-DC > converter circuit which takes the available charging bus voltage (commonl y > around 13.8V) and converts it up to around 400V. Charging the capacitor a t > 400V allows for much greater energy storage than if the capacitor was > charged at bus voltage. The ignition coil in a CD ignition is used as a > step up transformer. When the 400V charge in the capacitor is dumped > through the ignition coil, the voltage is stepped up to several thousand > volts by the coil. This provides the required spark voltage to jump the g ap > of the spark plug. These days, CD ignitions are found primarily on small > vehicles such as scooters, dirt bikes, and other small engines which > typically have a minimal electrical system. Common characteristics of CD > ignitions are a relatively low spark energy and relatively short spark > duration. > > *Inductive Discharge* - The second general category of ignition systems > is "inductive discharge" or simply "inductive" ignitions. Again, this > refers to how the ignition stores energy to do its job. In an inductive > ignition, the energy is stored directly within the ignition coil in the > form of a magnetic field. When current is passed through the primary > winding of the coil, energy is stored in the magnetic field. When the > charging current is shut off, the magnetic field collapses very quickly a nd > the energy is discharged through the secondary winding of the coil which is > connected to the spark plug. There are a few sub categories of inductive > ignitions. Magnetos were one of the earliest forms of inductive ignitions .. > Magnetos store energy in a magnetic field by passing a current through th e > primary winding of the ignition coil like all inductive ignitions. Howeve r, > they generate their own electrical power with an internal generator and d o > not rely upon the vehicle electrical system. > > Cars made before the 1980s typically used a points triggered, slow > charging type of inductive ignition in conjunction with a distributor. > These ignitions were powered by the vehicle electrical system and had > relatively low energy. > > Modern cars all use high energy inductive ignitions. High energy inductiv e > ignitions use an ignition coil that has a very low resistance primary > winding, typically in the 0.5 to 0.7 ohm range. The low resistance coil c an > charge very rapidly to a high energy level. This type system works very > well with larger engines that have a capable electrical system that > includes a battery and alternator. With the high energy inductive ignitio n, > the coil can draw a fairly high current during the time it is charging, b ut > this charge time is very short and the average current draw is low. Commo n > traits of a high energy inductive ignition are high spark energy and long > spark duration. > > ------------------------------ > *Spark Timing* - The next topic of interest when it comes to ignition > systems is spark timing. A good hot spark is only half of the story when it > comes to making an engine run well. The second part of the equation is > making the spark at the right time. Ideal spark timing is not a simple > thing. It varies with engine rpm, engine load, fuel type and octane, engi ne > compression ratio, and other factors. Spark timing is handled differently > by different ignitions. > > The most basic spark timing scheme is fixed timing. This means that the > spark timing is always the same. The engine designers choose a worst case > timing situation that won't cause engine damage regardless of how all the > operational variables stack up and they fix the spark timing at that poin t. > The fixed timing we find with aircraft magnetos is a prime example of thi s > method. The problem with this scheme is that the spark timing is never > correct for any given condition. You end up sacrificing horsepower, > efficiency, and starting characteristics when you're stuck with fixed > timing. > > Before engine computers, cars used a mechanical means of producing a > timing curve. Commonly, this included a vacuum advance mechanism to adjus t > the curve for engine load. With today's computer controlled ignition > systems, a complex spark timing curve can be generated by the engine > computer to optimize horsepower and efficiency, as well as starting > behavior. Aftermarket electronic ignitions typically have a base timing > curve that advances with rpm up to some maximum value and then retards th e > ignition timing to some degree as engine load increases. > ------------------------------ > *BACK TO THE IGNITIONS THAT WERE TESTED* > Here is a list of the basic traits of each of the ignition systems in our > test: > > *Lightspeed Plasma II+* - Capacitive discharge, electronically controlled > timing curve with load compensation. > *P-Mag 114* - Magneto inductive, electronically controlled timing curve > with load compensation. > *Slick Magneto* - Magneto inductive, fixed timing, points triggered. > *EFII* - High energy inductive, electronically controlled timing curve > with load compensation. > > We measured the spark energy, spark duration, and system current draw of > each of these systems. Below are graphs of the data that resulted. The > ignitions were run under load. This means that the instrumented spark plu g > was mounted in a pressurized chamber of inert gas to simulate the > electrical load that the spark gap sees when it is inside the combustion > chamber of a running engine at high rpm and high horsepower. > > *System current draw at 2750 rpm: P-Mag =C2=BB none; Slick Mag =C2=BB none; > Plasma II+ =C2=BB 1.5 amps; EFII =C2=BB 1.2 amps* > > > There are some interesting items in the data: > > Notice the increasing energy of the magneto as rpm increases. One drawbac k > of the magneto ignition is very low spark energy at cranking rpms. Impuls e > couplings are commonly used on starting mags to momentarily speed them up > in an effort to get a little more energy during cranking. This helps, but > the energy is still very low during cranking. > > You might expect the P-Mag to have increasing energy with rpm also, but > they have chosen to limit the charge time of the coil such that the energ y > does not increase as rpm goes up. > > Another interesting item is the very short spark duration of the Plasma > II+ ignition. This is a characteristic inherent to CD type ignitions. If > the air fuel ratio is optimal, this may not be much of an issue. However, > if you are looking for maximum power, you will be seeking an air fuel rat io > on the rich side. Short spark duration ignitions will tend to misfire > before long spark duration ignitions as you continue to add fuel. If you > are a lean-of-peak guy, you have a similar situation where a short spark > duration ignition will start to misfire before a long duration ignition a s > you take away fuel. These characteristics tend to favor long spark durati on > ignitions for best economy as well as for best power. This is a primary > reason cars all have inductive ignitions. The long spark duration of the > EFII ignition means that the spark is lit for more than 36 degrees of > engine rotation at 2750 rpm. This gives lots of opportunity for a non > optimal mixture to light. > > If you click on the thumbnail below, you can view a nice photo of Mannan > Thomason's EFIS display in his RV-8. His Dual EFII ignition is helping to > deliver 155 knots true at 6.0 gallons per hour - that's 178mph at 29.7 > miles per gallon! - not too shabby! > > > ------------------------------ > *EFII Flies Above the Rest* > Why does our system seem to come out on top? It's not because we're cleve r > with our data. There are really two reasons. First, we are a technology > driven company. We value function over form. Clever packaging or glossy > marketing are not what we focus on. Our priorities are performance and > reliability. Second, we have been designing and manufacturing performance > ignitions since the 1980s. We went through our ignition design learning > curves a long time ago. This allows us to design the correct product for a > given application without the teething pains that others seem to go > through. > > The data in this article highlights only some of the differences between > our system and others. Our Tefzel wire harness, OEM style connectors, and > billet crank trigger are also significant in a thorough comparison. The e nd > result of our experience and our sound design philosophy is a product wit h > unmatched quality and performance. > *This is why you too, should fly with EFII.* > ------------------------------ > > > ------------------------------ > *TECHIE STUFF* > Just in case you were wondering how to measure spark energy and duration, > here is a little extra info. > > It helps to have a nice oscilloscope that can do some fancy math for you. > Otherwise, data can be exported to a computer for computation. Fortunatel y, > we have an oscilloscope that is up to the task. Below, you can see a scre en > shot of the scope with the spark waveforms shown. This particular > measurement was of the spark output of the EFII ignition. > > > There are four traces displayed on the scope image. Trace #1 is the spark > current. This measurement is made by returning the spark current through a > 100 ohm resistor that serves as a current shunt. The spark current > generates a signal across the shunt resistor that is a few volts in > amplitude and can easily be measured by the scope. Trace #2 is the spark > voltage. The voltage was measured with a 1000:1 probe. The portion of thi s > signal that lies between the vertical cursor lines in the image shows whe n > there is a spark present in the gap of the spark plug. Notice in trace #1 , > this is also the period where there is current flowing. Trace#3 is a math > channel that is generated by the oscilloscope. This trace is defined as > (trace#1 x trace#2) or spark current times spark voltage. Current times > voltage is power. Trace #3 is a representation of the instantaneous power > (in Watts) of the spark event. Trace #4 is another math channel. In this > case trace #4 has been defined as the integral over time of trace #3. Thi s > can also be explained as the area under the curve of trace #3. > Mathematically, this gives you the spark power (in Watts) times the spark > time (in seconds) which is spark energy (in Joules). Watts times Seconds > equals Joules. In this case, the energy is much less than one Joule, so w e > express it in milli Joules, or thousandths of a Joule. Trace #4 shows the > accumulation of energy during the spark event. Notice that the #4 curve > stops rising when the spark current stops. This is because there is no > additional energy being delivered across the spark gap. Also notice the t wo > small "x" marks on the #4 curve. This is an amplitude measurement functio n > of the scope. The amplitude measured in this case is displayed at the top > middle of the screen. You can see it reads 44.4 mU. The scope doesn't kno w > what units we are acutally measuring, so it has labeled the value > generically as 44.4 milli Units. In this case, milli Units means milli > Joules. You may notice that in this measurement, the EFII ignition is > putting out 44.4 milli Joules of energy - which is a lot! The graphs abov e > show that our ignition puts out 36 milli Joules. Spark energy readings ca n > vary quite a bit with variations in temperature and humidity. We tried to > be fair to all the systems measured and take data on the same day when we > collected the info for the graphs. The scope screen shot was made on a > different day with high humidity and the reading showed much higher. We > want to emphasize, that we did in fact make every effort possible to > evaluate all the systems fairly and under the same conditions. The data i n > the graphs is a result of this. > > There is a little more to the energy measurement process, such as having a > pressure vessel for the spark plug to fire into to simulate the load on t he > spark gap that is present in a running engine. There is also the > requirement to trigger the different systems properly with crank signals in > the case of the LSE and EFII systems and to properly spin the input shaft s > in the case of the P-Mag and Slick Mag. We used an electronically generat ed > crank trigger signal for the EFII system. To trigger the LSE system, we > mounted a flywheel in our engine lathe and spun it with the crank trigger > assembly mounted on the tool post of the lathe. The P-Mag and Slick Mag > were also spun using the engine lathe. Below you can see the magneto moun t > rig on the lathe. > > > This setup above was used to test the Slick Mag and P-mag. You can see th e > spark pressure chamber in the image. There is an old Bendix mag in the > picture. We would have added the data to the graphs from this mag, but it > didn't perform very well at all. This one is overdue for overhaul. The > Slick Mag we tested was brand new as was the P-Mag. > > Below, you can see the EFII system under test. In case you are trying to > read the numbers on the power supply next to the scope, it reads 1.1 amps > and 13.8 volts. This was at 2500 rpm. > > ________________________________ Message 3 _____________________________________ Time: 11:31:28 AM PST US Subject: AeroElectric-List: Two wires From: Janet Amtmann Well said, Eric! Jurgen Amtmann Do not archive ________________________________ Message 4 _____________________________________ Time: 05:08:28 PM PST US Subject: AeroElectric-List: Re: Two power signals, one wire From: "Eric M. Jones" It turns out Magnecraft actually still sells relays that allow lots of funny-business to be done with one wire and a ground. http://www.serelays.com/library/archive/104_Section5.pdf Imagine a single push button in the cockpit that drives a small remote-end motor that has a cam that pushes a bunch of microswitches. The only problem is knowing how long to push the button...enter the stepping relay. One push one step. Stepping relays were used for telephone dialing. n-pulses on the dial and the stepping relay will step n-times. Imagine how cool it would be to have a rotary telephone dial on your panel! It could handle all your switching needs. Stepping relays were also used in old pinball machines. The ball hits the bumper, and the stepping relay indexes the lights to new locations. Enjoy. Send me a picture if you put a telephone dial on your panel. The gold ones might go along with your Jules Verne Nautilus motif interior. -------- Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge, MA 01550 (508) 764-2072 emjones(at)charter.net Read this topic online here: http://forums.matronics.com/viewtopic.php?p=430406#430406 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.