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Home , Dual ignition, High energy ignition, Ignition coil, Ignition timing, Magneto

AIRCRAFT RESEARCH REPORT

TRIAVIATHON Ignition Dynamics I TROPHY

CAFE FOUNDATION BY BRIEN SEELEY AND THE CAFE BOARD

PRESIDENT Brien Seeley

VICE PRESIDENT Larry Ford

TREASURER Scott Nevin

SECRETARY Cris Hawkins

CHIEF TEST PILOT C.J. Stephens

TEST PILOT Otis Holt

DIRECTORS Otis Holt Jack Norris Bendix 1200 , Stephen BRIEN SEELEY Williams Ed Vetter This is the first of three would improve the perfor- shelf, bolt-on products. Al- Scott Nevin CAFE Foundation research mance of light aircraft while though their popularity is Jo Dempsey reports on aircraft ignition reducing their fuel consump- increasing, wider use of elec- Bill Bourns systems. Part I discusses ba- tion. One such innovation tronic ignition systems in Darrel sic operational and design was the use of electronically aircraft has been limited by Harris considerations while Part II advanced concerns regarding battery presents comparative flight when operating with reduced dependency, reliability and test results. Part III will pre- manifold pressure at very lean the safety of using ignition sent the results of ignition mixture settings. Some of the timing advanced beyond that system bench testing. A more aircraft that won the CAFE specified on certificated en- comprehensive version of 400 races employed this tech- gines. Claims of up to 20% each report will be available nique to significantly improve greater fuel economy and up at www.cafefoundation.org their MPG score. to 7% increase in In the last 10 years, high have been made for these sys- BACKGROUND energy electronic ignition tems.2,3 The CAFE systems for reciprocating air- Foundation performed exten- The CAFE 400 flight effi- craft engines, particularly in sive flight performance ciency races of the 1980's experimental aircraft, have testing of electronic ignition encouraged innovations that been developed into off-the systems during 2001. To properly evaluate the test results, a re- trodes to prevent stray arcing. Its coil COMPARATIVE AIRCRAFT view of basic spark ignition engine is capable of generating as much as FLIGHT EFFICIENCY, INC. operation is helpful. 30,000 volts.5 The CAFE Foundation: In the quest for better fuel econ- A Non Profit, All Volunteer, Tax-exempt omy, automotive engineers have Educational Foundation developed distributorless ignition sys- 4370 Raymonde Way In conventional aircraft magnetos, tems that allow the use of even higher Santa Rosa, CA. 95404. a high voltage arc crosses the spark energy sparks without unwanted arc- FAX 707.544.2734 plug electrode gap at the desired igni- ing. High energy sparks are better Aircraft Test Facility, Santa Rosa Airport tion timing point, typically at 25¡ able to ignite very lean mixtures. 707.545.CAFE (hangar, message) before the reaches top dead America Online: [email protected] center (25¡ BTDC). For the sake of COMBUSTION DYNAMICS simplicity and to avoid detonation, the 25¡ BTDC timing is held constant at Ideally, the rise and fall of IMPORTANT NOTICE all power settings and RPM's. pressure is timed by the ignition event Any reproduction, sale, republication, The peak voltage demanded from a so that as much of the pressure as pos- or other use of the whole or any part magneto by a properly gapped aircraft sible is used for the mechanical work of this report without the consent of seldom exceeds about of pushing the piston. The ignition the Experimental Aircraft Association 12,000 volts. The spark voltage and timing that accomplishes this is called duration depend upon several factors "maximum brake torque" (MBT) tim- and the CAFE Foundation is strictly as shown in the table below.4 ing. MBT timing must also account prohibited. Reprints of this report for the piston’s ever-changing me- may be obtained by writing to: Sport Makes Makes Aviation, EAA Aviation Center, 3000 An increase in: chanical leverage on the voltage duration during the expansion . For a Poberezny Road, Oshkosh, WI. Plug electrode gap increase decrease given engine at a given power setting, 54903-3086. Altitude, non-turbo decrease increase MBT timing causes the peak cylinder Mixture richness increase decrease pressure to occur slightly after top ACKNOWLEDGEMENTS dead center, often in the range of 11¡- Water vapor increase decrease 16¡ ATDC. Igniting the mixture too increase decrease This study was supported by grant early or too late causes a reduction in funding from the Experimental Air- Air temperature decrease increase power. Likewise, if the mixture burns craft Association and by FAA Gap airflow increase decrease too slowly, burns incompletely or ex- Research Grant Number 95-G-037. tinguishes prematurely, power loss The CAFE Foundation gratefully ac- Because the spark plug electrode will occur. Deviations from MBT knowledges the assistance of Klaus gap is a main determinant of the volt- timing of +/- 3¡ BTDC produce only Savier, Ben Ellison, Lyle Powell Jr., age required to ‘fire’ the spark plug, 1-2% reduction in torque, so that cycle magnetos typically use smaller gaps to cycle timing accuracy of 1¡ should Paul Loewen, Tim Davis, Steve Pen- (~0.018") than generally be adequate to sustain near ning, Wyman Shell, Wayne Reece, systems (~0.030"-0.040"). If the spark optimum torque.6 See Figure 1. Walt McPeck, Bob Pixton and Anne plug gap is set too wide, the higher The details of the propagation of Seeley, EAA Chapter 124, and the voltage discharge that this demands the flame front created at the spark Sonoma County Airport FAA Control from the magneto's coil may ulti- plug exert an important influence on Tower Staff. mately cause the coil to short fuel economy and power. The speed internally, overheat and fail. Gaps that and direction of the flame front's dis- SPONSORS are too small, although they increase persion are mainly influenced by gas Experimental Aircraft Association spark duration, are subject to fouling flow (swirl and turbulence), fuel/air Federal Aviation Administration and consequent misfiring. It is there- mass ratio, and the homogeneity, at- fore very important to set the proper omization and exhaust gas dilution of Engineered Software “PowerCadd” and WildTools electrode gap when servicing aircraft the mixture. Ideally, the fuel mixture Bourns & Son Signs spark plugs. burns smoothly and completely at the AeroLogic's Personal Simulation Works Use of larger magneto coils with proper rate and does not explode or DreeseCode Software-www.dreesecode.com higher voltage capability is limited by detonate. the tendency for stray arcing to occur within the magneto’s , espe- FUEL MIXTURE engine power all vary with changes in cially at high altitude where it takes this ratio. When flying at altitudes less voltage to initiate such a stray arc. Most reciprocating aircraft engines above about 5000 feet, appropriately The Bendix 1200 magneto, shown in are equipped with a mixture control to leaning the mixture improves power, the first photo, was introduced circa allow adjustment of the leanness or economy and engine vibration. 1965 as a modern “high altitude” mag- richness of the inducted fuel to air Gasoline powered engines typically neto. It uses an extra large high mass ratio (or weight ratio). The ex- operate with fuel/air mass ratios that voltage coil and has exceptionally haust gas temperature, speed of vary from a lean value of about 0.056 wide separation of its distributor elec- combustion, ideal ignition timing and to a rich value of about 0.083. For Figure 1. Maximum Brake Torque (MBT) Timing Effects Actually, the best economy mixture is that which delivers the lowest value in Torque pounds of fuel per horsepower per 100 3 hour for the engine as a whole, a term 50° defined as the engine's brake specific adv. fuel consumption, or b.s.f.c. Piston 30° 2.5 98 adv. engine b.s.f.c. values can range from 10° about 0.38 to 0.60 lb./hp/hr. and vary adv. 2 with mixture, manifold pressure, RPM 96 and ignition timing. The b.s.f.c. MBT serves as a yardstick for the fuel effi- timing 1.5 ciency of different engines and power 94 settings and is an important determi-

linder pressure, MPa nant of range, payload and cost of 1 y C operation. 92 x An engine’s best (i.e., lowest) 0.5 b.s.f.c. occurs at a particular MBT ig- Relative torque, percent of maximum x nition timing that will vary depending 90 x TDC upon the engine’s power setting. The 0 0 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 more the mixture is leaned from stoi- Crankshaft position, degrees chiometric, the more advanced will be its MBT ignition timing, because the Spark advance effects on cylinder pressure and torque. "X" signifies ignition point. leaner the mixture, the more slowly it takeoff at full power near sea level, As the mixture is leaned from this burns. fuel/air ratios are often enriched to as "best power mixture" point, power and Figure 2 indicates that, for the high as 0.11 so that excess fuel can airspeed steadily diminish, while CHT CAFE testbed aircraft, best MPG and maximum relative CAFE score occur serve as a coolant and help prevent rises slightly to peak at around 50¡ detonation. at an EGT that is over 100¡ LOP, ROP. The flight data in Figure 2 illus- where the peak CHT has fallen by Depending on the fuel's chemical trate these phenomena. composition, a fuel/air ratio of about about 50¡ F. This unusually lean mix- A fuel/air ratio of about 0.059 gives 0.065 to 0.067, produces a "stoichio- ture operation is made possible by metric mixture", meaning that it has an EGT about 50¡ "lean of peak" some modifications made to the test the chemically correct proportions of (LOP) and this has popularly been engine’s induction and exhaust sys- fuel and oxygen. A stoichiometric considered the mixture for best econ- tems. mixture will burn completely, oxidiz- omy or best miles per gallon.9 From Figure 2, the average peak ing all of the fuel molecules with little 1650 Figure 2. Fuel flow versus EGT, CHT, TAS, MPG, and CAFE Score F F or no residual oxygen. It produces the ° 380 ° highest or "peak" exhaust gas temper- 1600 Left Axes Lean misfire TAS ature (EGT) for a given manifold 12500 1550 roughness pressure and RPM and requires the EGT #1 least amount of ignition energy to ig- 360 nite. Fuel mixtures that are leaner or 1500 EGT #2 richer than stoichiometric will pro- EGT #3 1450 340 duce cooler EGT values. EGT #4 Flame speed varies dramatically Balanced 1400 mixture with the fuel/air mixture. As the mix- distribution 320 ture is leaned from the stoichiometric 1350 Right Axes ratio, it burns progressively more Exhaust Gas Temperature (EGT),

Cylinder Head Temperature (CHT), CHT #4 slowly. As the mixture is made richer 1300 300 195 MPG than stoichiometric, flame speed pro- 25 gressively increases, up to a fuel/air 190 24 CAFE 185 23 Score ratio of about 0.080, which is the 22 fastest burning mixture possible. As 180 21 175 20 the mixture is enriched beyond the 19 0.080 ratio, it will burn progressively 170 18 17 7 165 Best more slowly. 16 160 CAFE Score 15 True airspeed (TAS), mph

Maximum horsepower,, and thus CAFE Score** MPG maximum true airspeed, is produced 155 14 6 7 8 9 10 11 12 by mixtures that are about 100¡ F be- Fuel flow, gallons per hour low peak EGT on the fuel-rich side of ° 8 Mooney N6057Q: Lycoming IO-360A1B6X engine, dual Bendix 1200 magnetos @ 25 BTDC stoichiometric. Such mixtures are timing. 12,500' density altitude, wide open , 2550 RPM, hottest cylinder #4, 2455 lb called "100¡ F. rich of peak" (ROP). flying weight, wing Barograph #3. **Relative CAFE Score = TAS^1.3 x MPG EGT occurs at about 8.7 gph at 2550 thus reduce EGT and produce more LEAN MISFIRE RPM and at 12,500’ power. Likewise, if, during dual mag- altitude. Assuming that represents a neto operation, the ignition of a super Flame speeds of 75 cm/s at stoi- stoichiometric fuel/air ratio of 0.066, lean mixture succeeds at only one of chiometric mixtures slow by nearly and noting that the leanest fuel flow the cylinder's two spark plugs, slightly one third to only 52 cm/s at the lean for smooth operation is 7.0 gph, the advancing the ignition timing im- fuel/air ratio of 0.052. Diluting a stoi- test engine’s lean operational limit proves power. chiometric mixture by just 20% with with dual magnetos can be calculated recirculated exhaust gas reduces the to be a fuel/air weight ratio of: KNOCK flame speed to only 23 cm/s.12 With very lean mixtures, some (7.0/8.7) x 0.066 = 0.053 fuel to air If the ignition timing is too ad- combustion cycles may burn so slowly vanced, the ignition pressure wave that flame propagation is completed OPERATION crossing the can just prior to exhaust valve opening, induce the mixture at various other i.e. too late in the cycle to do much Aircraft engines must time their ig- points in the chamber to spontaneously work. In such a case, a large fraction nition so that the resulting flame front ignite. This produces undesirable ir- of the energy release occurs late in the smoothly propagates across their large regular burning with intense pressure combustion cycle when changes in diameter combustion chambers within fluctuations, very high combustion cylinder volume are more rapid, caus- a short time period. Initiating flame pressure peaks and loss of power. The ing greater variations in cycle to cycle fronts of finite speed from two sepa- hammering or pinging sound that re- pressure and end gas residuals. With rate spark plugs helps assure that all of sults is called ‘knock’ or ‘detonation’. even further leaning, there is further the fuel mixture will be consumed be- At high engine speeds, knock may not power loss as some cycles occur in fore the exhaust valve opens. Aircraft be audible. It can begin insidiously which the flame continues its slow engines typically have uneven mixture and progress as a vicious cycle of in- burn after the exhaust valve opens, composition with significant combus- creasing temperature and knock wasting energy and increasing EGT. tion chamber turbulence and swirl. intensity. This slight rise in EGT is a sign of Two spark plugs are better than one The sharp peaks in pressure and lean misfire and may indicate that for igniting mixtures of variable com- consequent high temperatures of only one of the two spark plugs has succeeded in igniting the charge. positions and flow velocities. In knocking can quickly produce struc- With further leaning, cycle to cycle addition, dual spark plugs provide re- tural engine damage and engine fluctuation in peak cylinder pressure dundancy and reduce the tendency for failure. A typical result of light knock becomes increasingly erratic. At some knock. For these reasons, aircraft en- is an erosion of the piston crown that point, this produces cycles in which gines typically use two separate spark looks as if it had been heavily sand- the flame extinguishes prior to exhaust plugs.10 blasted. A borescope examination Lycoming states that a conventional valve opening or fails to ignite at all, can sometimes detect such knock dam- causing EGT to plummet. At this ex- loses about 3% of its age. Knock is the foremost reason to treme degree of misfiring, engine power when one of its two magnetos avoid excessively advanced ignition roughness and vibration are unaccept- is turned off.11 EGT rises during sin- timing. able for continuous operation. gle magneto operation. These effects Susceptibility to knock is highest at Advancing the ignition timing at this are due to fuel burning after it leaves mixtures that are stoichiometric or point can sometimes restore smooth the cylinder. This late burning can be slightly richer than stoichiometric, operation, extending the lean misfire explained as follows: precisely where many pilots have been limit and increasing power. See Fig- During single magneto operation, taught to set the fuel mixture. Here, if ure 3, which shows the reduction in only one of the two spark plugs per one spark plug is fouled or misfiring, EGT from advanced ignition timing cylinder is firing and its flame front knock becomes even more likely. and the rise in EGT at the lean limit must therefore travel farther and Knock tendency is much reduced at for different ignition systems. thereby take longer to fully consume very lean, slow-burning mixture set- As the mixture is leaned, uneven the inducted mixture. Standard dual tings. High compression ratios and mixture distribution usually causes magneto ignition timing is predicated high inlet air temperatures increase some cylinders to reach their misfire on having both spark plugs initiate knock tendency. limit before others. The ability of the combustion, with each of their flame Ideally, ignition timing advance leanest cylinder to operate smoothly fronts having a shorter distance to should be controlled by knock sensor and without misfire sets the practical travel. When only one plug fires, in a closed control loop to continually limit on the leanness of the overall standard timing is too late, causing the operate just below the knock limit fuel/air mixture that the engine can mixture to continue burning after the where MBT timing and, thus, best use.13 The lean misfire limit is ex- exhaust valve opens. Optimally ad- power are usually to be found. Unfor- tended in engines with evenly vancing the ignition timing can tunately, knock sensing transducers balanced mixture distribution among provide more 'burn time', so that the work poorly in aircraft engines be- all cylinders and such engines can flame front from a single spark plug cause of the high noise and vibration therefore achieve lower b.s.f.c's. See can more fully consume the mixture levels that exist. Figure 2 showing the variations in in- before the exhaust valve opens, and dividual cylinder EGTs at lean Figure 3. EGT#4. Lean misfire limits of dual Bendix 1200 magnetos at brief CDI sparks in rapid succession to 25° BTDC versus EIS-1 electronic ignition at 41° BTDC. extend their effective spark duration. If these multiple sparks are delivered 1600 1600 Peak EGT from separate, alternately firing igni- SE 41° tion sources, the 'dead' interval BTDC between them can be diminished so as 1550 1550 to approximate a continuous long du- DE 41° ration spark of high energy. F F ° BTDC ° The diameter of the spark can be 1500 1500 thought of much the same as we ob- DM 25° serve that a lightning bolt can be either BTDC skinny or fat. The spark diameter de- 1450 DM--lean 1450 pends upon its amperage. The length misfire of the arc is ordinarily set by the spark limit plug gap, although mixture airflow 1400 1400 can stretch a spark into a curved loop of much greater length. See Figure 5, “C”. Larger gaps require higher igni- tion voltage to successfully ionize the 1350 1350 molecules between the electrodes. Exhaust gas temperature (EGT), Exhaust gas temperature (EGT), Sparks that are stretched by airflow into loop shapes require substantially 1300 DE--lean 1300 misfire higher energy to avoid being ‘snuffed limit out’. Because some degree of airflow, squish or mixture swirl is nearly al- 1250 1250 ways present, many engine designers 567891011 shelter the spark plug electrodes in a Fuel Flow, gallons per hour somewhat recessed location in the Mooney N6057Q in level flight at 15K density altlitude. Wide open throttle, combustion chamber to prevent such 2550 RPM, stable TAS, digital acquisition device recordings. Cowl flaps fully ‘snuffing’. Recent work suggests that opened. DM = dual magnetos. DE = dual electronic ignition. SE = single a high energy, stretched loop spark can electronic ignition with one magneto. succeed in igniting super lean mix- mixtures (the “EGT spread”). ing of one of the two spark plugs in tures.14 Max Conrad developed a simple the leanest cylinder was kept hidden The instantaneous power of the method for finding an engine’s practi- by the successful firing of the fellow spark can vary dramatically. The fi- cal lean misfire limit. On his famous spark plug in that cylinder as long as nite packet of energy stored in an long distance flights in his Piper Co- both magnetos were operating. Al- can be delivered as a high manche, his technique was to lean the though it delivered a maximum in power but very brief spark or, alterna- mixture until the engine ran roughly miles per gallon for his record flights, tively, as a lower power longer this technique is not recommended by duration spark. A reduction in spark and then enrich it just to the point aircraft engine manufacturers. power in order to provide longer spark where it would run smoothly on both duration can be achieved by reducing magnetos but show slight roughness SPARK PLUGS the gap between the electrodes. when operated on one magneto. Such Higher energy ignition systems afford roughness likely meant that the misfir- To assure that a self-sustaining in- enough energy to sustain good spark Figure 5. Relative spark kernel surface flammation process disperses rapidly duration even when using plug gaps area for magneto (A), high energy ignition away from the spark plug requires in- that are twice that of a magneto sys- (B) and high energy with gap airflow (C). creasing amounts of ignition energy as tem. the mixture is leaned beyond peak A fatter spark across a larger gap EGT. creates an initial inflammation zone of Distributorless electronic ignition much greater surface area than a systems using large inductive coils skinny spark in a short gap. See Fig- can deliver higher spark energy and ure 5, “A versus B”. The larger this spark duration than those of a magneto surface, the more likely it will ignite a system. This can be helpful in ignit- very lean mixture and the faster its ini- ing very lean mixtures. tial burning rate will be.15 Most capacitive-discharge ignition Conceptually, a large surfaced initial B (CDI) systems deliver a strong but spark kernel can better ‘reach out’ to A short duration spark lasting about 100 ignite the scarce fuel molecules nearby to 300 microseconds. Some multiple- and launch of the flame front. spark-discharge (MSD) ignition A long spark duration has a greater C systems use a sequence of several effect than high current in extending age gas temperature just outside a droplets. Droplets of less than 15 mi- cylinder's exhaust port and this re- cron diameter have been found to best flects the relative temperature of the follow the bending airflow path of in- gases that bathe the head of the ex- duction manifolds.19 Research has haust valve when the valve is open. shown that lean ignition is more sensi- Continuous operation at peak EGT tive to atomization quality than to thus imposes the maximum heat bur- ignition energy.20 den on the exhaust valve. The tiny emitter orifices of the Elli- A cylinder's EGT represents a son Throttle Body deliver a finely moving average from many combus- atomized fuel fog to the induction sys- tion cycles in that cylinder. Values tem. This fog distributes more evenly typically range from 1300-1650¡F for and ignites more readily than larger normally aspirated engines at cruise fuel droplets. This helped make possi- power. Mixtures that are “rich of ble the very lean mixture operation of peak” (i.e., ROP or richer than stoi- the test engine used for this report. REM37-BY plug with long-reach elec- chiometric) produce cooler EGTs The presence of excess oxygen in trodes. because unburned fuel acts as a lean mixtures promotes more com- plete combustion because more 16 coolant. Mixtures leaner than stoi- the lean misfire limit. The swirl, chiometric (LOP) produce cooler collisions occur between fuel and oxy- turbulence and mixing of lean fuel/air EGTs because there is less fuel to burn gen molecules. This means less mixtures can cause some regions in and the excess of air literally “puts the wasted fuel and an overall reduction in the combustion chamber to contain fire out”. See Figure 6. exhaust emissions. mixtures too lean to ignite at a given The 'EGT spread' is the difference In normally aspirated engines that instant. Thus, the bottom spark plug between the highest and lowest EGTs have a narrow EGT spread, operating of the combustion chamber may suc- among all of an engine’s cylinders at a at below 70% power with mixtures ceed in igniting the mixture nearby given mixture setting. See Figure 2. 150-200¡ F lean of peak EGT offers while its fellow top spark plug's arc At a fixed RPM and M.P., the EGT the following benefits: fails to do so. A longer duration spark spread observed across a range of lean may allow the top spark plug to suc- mixture settings reflects the evenness 1) much cooler exhaust valves. ceed in igniting its local mixture a few of the mixture distribution among all 2) reduced cooling drag. hundred microseconds later when the cylinders and can be used as a guide to 3) reduced emissions. swirl places a richer mixture near its modify the induction system to im- 4) less noise. electrodes. Longer reach spark plugs prove that distribution. Such 5) less coking of the chamber. that place the electrodes deeper into modifications should only use EGT 6) less oil contamination. the combustion chamber may also in- data obtained at wide open throttle set- 7) reduced spark plug fouling. crease the success of the plug in tings due to the highly variable 8) less risk of detonation. igniting locally lean mixtures. induction flows at part throttle. By accelerating the initial spread of The reduced power and airspeed of combustion, a larger, high energy MIXTURE DISTRIBUTION such operation are compensated by a spark kernel can allow use of slightly valuable increase in the distance be- less timing advance than that of a Regretably, uneven mixture distrib- tween fuel stops. See Figure 2. lower energy (magneto) spark.17 With ution plagues most aircraft engines fast-burning rich mixtures, this advan- where many cylinders share a com- CONCLUSIONS tage of higher spark energy has less mon manifold, and fuel is noticeable effect because the flame is poorly atomized. Large fuel droplets 1. The ideal ignition timing easy to ignite with even meager spark may distribute erratically through the (MBT timing) for a given engine energy and ignition energy applied af- induction manifold due to inertia and varies with power setting, altitude ter inflammation has occurred has collimated airflows. EGT spreads of and fuel mixture. only a modest impact on flame propa- about 100¡ F with and 2. As the mixture is leaned be- gation. over 200¡ F with are fairly yond peak EGT (LOP), it burns typical in such engines, especially at progressively more slowly and EXHAUST GAS TEMPERATURE (EGT) 18 part throttle. therefore requires a progressively In the automotive industry, exten- more advanced ignition point for Exhaust gas temperature (EGT) re- sive research has been devoted to maximum efficiency. flects the leanness or richness of the improving fuel atomization and vapor- fuel mixture. EGT is also an impor- ization by and induction 3. MPG and flight efficiency are tant diagnostic parameter. It rises tract modifications that use nozzles, maximized and cooling demand and significantly during magneto failure or heated manifolds, vibrating plates, ex- emissions are minimized by opera- during misfiring due to a fouled spark haust gas recirculation or other tion at lean (LOP) fuel/air mixtures. plug or other cause and it falls during methods. Results show that fully va- Such operation is usually not possi- knock or detonation. porized fuel may not ignite quite as ble (nor recommended by engine The EGT gauge measures the aver- readily as ideally atomized tiny fuel manufacturers) because of the un- Figure 6. EGT varies with altitude and power setting. 9. Ibid. #7. Page 42. 1600 1600 10. Ibid #6. page 445.

1550 1550 11. Ibid. #8. Page 63. F F ° ° 12. Ibid. #6. Page 849. 1500 1500 13. Lean Combustion in Spark-Ig- nited Internal Combustion Engines--A Review, Germane, Wood and Hess. 1450 1450 SAE paper 831694. page 199. 14. High-Energy Spark-Flow Cou- pling in an IC Engine for Ultra-Lean 1400 1400 and High EGR Mixtures. Michael A. V. Ward, Combustion Electromagnet- ics, Inc. SAE paper 2001-01-0548, March, 2001. 1350 1350 Exhaust gas temperature (EGT), DM EGT#4, 15K Exhaust gas temperature (EGT), 15. Ibid. #6. Page 436. 16. Ibid. #9. Page 433 and 440- 1300 DM EGT#4, 12.5K 1300 441. DM EGT#4, 8.5K 17 Ibid. #6. Page 436 and 445-446. 1250 1250 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 Fuel Flow, gallons per hour 18 Ibid. #8, Page 41.. Mooney N6057Q at 8.5K, 12.5K and 15K density altlitudes. wide open throttle, 19. Parametric Study of Fuel- 2550 RPM, digital acquisition device recordings. Cowl flaps fully opened. Droplet Flow in an Idealized Engine Magnetos @ 25° BTDC. DM = dual magnetos. Induction System, Robert S. Lo and Demitrius P. Lalas, SAE paper 770645, even mixture distribution that exists June 1977. in most conventional aircraft en- 2. Electronic Ignition For Aircraft, gines. Klaus Savier, Sport Aviation, February 20. A Study of Carburetion Effects 1995. on Power, Emissions, Lean Misfire 4. Magnetos require relatively Limit, and EGR Tolerance of a Single- 3. Unison Lasar product brochure, Cylinder Engine, J.A. Harrington, small spark plug electrode gaps to JP00767, EAA Oshkosh Convention, Engineering and Research Staff, Ford avoid arcing in their coil and dis- 1999. Motor Company. SAE paper 760754, tributor. Although this limits their October, 1976. Page 8. ignition power capability, magnetos 4. Measurement generate more than adequate spark Techniques and Correlations for Break- The CAFE Foundation wishes to energy for the ignition demands nor- down and Arc Voltages and Currents. thank Jeff Rose at Electroair for pro- Nick Pashley and Richard Stone, Uni- mally encountered in conventional viding the electronic ignition system versity of Oxford, and Graham for this study. His experience, advice aircraft engines. Roberts, BG Technology. SAE paper and guidance were indispensable in 2000-01-0245, March 2000. performing this work. 5. High energy electronic ignition Internet links: systems with long spark duration 5. Personal communication, Tim cafefoundation.org and variable ignition timing can of- Davis, Senior Engineer, Ignition Prod- [email protected] fer extended lean misfire limits and uct, Teledyne Continental Motors, LightSpeedEngineering.com better fuel economy. (Bendix magneto). P.O. Box 90, Mo- bile, Alabama. 36601. 1-251-438-3411 The CAFE Foundation is a non-profit, x 8301. all-volunteer educational foundation Ignition Dynamics II will present with no financial interest in Bendix CAFE Foundation flight perfor- 6. Internal Combustion Engine Fun- magneto, Electroair, Textron mance data comparing a standard damentals, John B. Heywood, Lycoming, Mooney Aircraft, Unison, magneto ignition to high energy elec- McGraw-Hill 1988. ISBN 0-07- LightSpeed Engineering, Ellison Fluid tronic ignition that uses variable 028637-X, page 374. Systems JPI, KS Avionics or any other advanced ignition timing. GAMA business entity. This study 7. Basic and Advanced Light Plane was supported by grant funding from BIBLIOGRAPHY Maintenance--EGT Systems, page 63. the Experimental Aircraft Association Kas Thomas, Belvoir Publications, and the Federal Aviation 1. Electroair ignition systems are Inc., 1989. ISBN: 0-9613139-8-6 Administration. marketed by Jeff Rose, 105 Gardner 8. Lycoming Flyer--Key Reprints, Street, Chattanooga, TN. 37411. (423) page 41. 1996. Textron Lycoming, 622-8825. 652 Oliver Street, Williamsport, PA. [email protected] 17701.