KR> Dual ignition
Ford went to the trouble of putting dual plugs into their 2.4L, ultra-successful, Lima engine. Anyone know why?Peter
KR> Dual ignition
There is another reason (maybe not in most conventional aircraft magneto systems) also that used to be used by the automotive boys with dual points and a coil splitter. By setting the timing slightly out of phase and running both points simultaneously, the length of the effective spark can be increased. The phase shift was achieved by offsetting the point mounting dowells/holes by a few degrees on the distributor plate. A less elegant way is to alter the point gap to vary the dwell but with conventional coils there is a certain time needed for the coil to energise which limits the time the points can be open and the dwell extended. I have heard of one magneto in aircraft being retarded a little to make starting a little easier but not sure if this is common. John Martindale 29 Jane Circuit Toormina NSW 2452 Australia ph:61 2 6658 4767 m:0403 432179 email:john_martindale at bigpond.com web site: -Original Message- From: KRnet [mailto:krnet-bounces at list.krnet.org] On Behalf Of Flesner via KRnet Sent: Monday, 14 December 2015 2:36 PM To: KRnet Cc: Flesner Subject: Re: KR> Dual ignition At 10:48 PM 12/12/2015, you wrote: >Concerning Dual ignition: I also get 100 rpm more with both ignitions on. + The reason for an rpm increase is because two plugs firing in the cylinder gives a better flame front and thus a faster burn. snip - No virus found in this message. Checked by AVG - www.avg.com Version: 2016.0.7294 / Virus Database: 4489/11174 - Release Date: 12/14/15
KR> Dual ignition
probably customer demand. People have had dual plugs in airplanes so long, they think it is the best medicine, rather than thinking it through. But that's just a guess. On 12/14/2015 05:55 PM, peter via KRnet wrote: > Ford went to the trouble of putting dual plugs into their 2.4L, > ultra-successful, Lima engine. Anyone know why?Peter > ___ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options
KR> Dual ignition
Jeff, for smaller volume cylinders, it's a Ford vs Chevy argument about whether to use one or two plugs per cylinder and the debate will rage on long after we've passed. I prefer single plug where possible due to 1. flame front calculations, 2. fewer holes in the head for stronger structural integrity, and 3. lower overall cost and maintenance. Yes, beyond a certain volume, two plugs are absolutely required. Don't even get me started on the mag versus electronic ignition debate... David M. On 12/14/2015 09:24 AM, Jeff Scott via KRnet wrote: > Sorry for the blank emails. My email keeps changing itself to html > formatting... > - > > An engine with dual ignition is set up to have the flame front within the > cylinder coming from two points in the cylinder, typically top and bottom. > It really doesn't have anything to do with the cylinder volume itself, but > with efficiency and redundency. For instance, if one wanted to run a typical > aircraft engine designed for dual ignition on a single ignition, you would > advance the timing several degrees to compensate for the time it takes for > the flame front to propagate from a single plug vs dual plugs. > > Most aircraft engines have each magneto fire 2 top plugs and 2 bottom plugs. > However, some of the small Continentals have the magnetos split so one mag > fires all the top plugs and the other mag fires all the bottom plugs. > Engines configured in this manner typically have the mag that is firing the > bottom plugs advanced 3? ahead of the mag firing the top plugs. The bottom > seems to run a bit richer, so the flame front tends to propagate slower. > > As Larry described, most aircraft engines use an impulse coupler to retard > the timing back to near TDC for starting. This is to avoid kickback, whether > turning on the starter or hand propping. Most Lycomings only have an impulse > coupler on the left mag, so the mag switch grounds out right mag when > starting. Most Continentals use an impulse coupler on both mags. > Additionally, the impulse Coupler stops the magnet inside the magneto. The > snap you hear is the magnet and shaft releasing, which will also cause the > magneto to generate a hot spark for starting. The impulse coupler has a set > of counterweights on it that will cause the catch pawl on the coupler to > retract once the engine is turning more than 400 rpm. > > Most of the after market ignition systems for aircraft also use an electronic > scheme to sense that the engine isn't running and retard the ignition timing > back to TDC for starting. Retarding the timing for starting, while > desirable, isn't really necessary on the smaller Continentals like the A > series engines. Same is true for the VW and Corvairs in that the kickback is > light enough that it isn't going to be tearing up a starter drive or hurting > someone propping the engine. Many of the 1940s vintage aircraft with A-65 > Powerplants didn't have impulse couplers when they were new. > > -Jeff Scott > Los Alamos, NM > > > ___ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options
KR> Dual Ignition Systems, it Saved My Bacon
Yes, that is correct. I too have joined the elite group of knowing what a dead engine in flight sounds like. There is no sound and man is that one quiet cockpit when the engine ceases to sing. Yesterday as I was leaving the KR Gathering out of Mt. Vernon, Illinois, my engine hic-upped. I really did not think much of it thinking maybe an air bubble in the fuel line. Well I continued to climb and was at 2300' ASL when all of a sudden things got real quiet. I was not too far away from the airport so I executed a 180° and set up a glide to MVN runway 23 and announced that 6MJ had turned final. Next, flipped the toggle switch to my back up secondary ignition and hit the starter. The engine fired right up and we started climbing. Instead of continuing to land, I decided to keep climbing and circling. After three circles and altitude gained, I determined the problem was strictly electrical and not the engine. I tested the main ignition again and again the engine died but only for a half second as I immediately went back to secondary ignition. Probably not the wisest decision but I decided to head on to my first stop at Pontiac, Illinois which was 149 miles away. I was never out of gliding distance from an airport and made the leg there with no further problems. The haze was terrible and from 15 miles out I began calling my position to PNT traffic. I noticed there were several planes in the area and some calling taxi back on the runway. At five miles out I still could just barely see the airport. As I entered downwind for PNT runway 24, I noticed four planes in the holding area waiting for my arrival. On one mile final, I noticed there were at least two hundred folks sitting around the tarmac watching the runway. Needless to say, I made the worst landing I have ever made in my KR. I bounced two, maybe three times and then swerved back an forth on the runway. This was the one day out of the year they have their local fly-in and I dropped in right in the middle of it. Anyway, I pulled my cowl look for the problem and found that the condenser wire had broken at the coil. A pair of wire strippers and a wrench and two minutes later the problem was fixed. The only problem now was that I had drawn a crowd of pilots and spectators and the questions about the plane and engine started flying. An hour later, I managed to continue my journey which was eventless the rest of the way home. Moral of the story is: Redundancy will save your bacon. Don't fly without it. Mark Jones (N886MJ) Wales, WI USA E-mail me at flyk...@wi.rr.com Visit my KR-2S CorvAIRCRAFT web site at http://mywebpage.netscape.com/n886mj
KR> Dual Ignition Systems, it Saved My Bacon
vell done mark as you infer better to take off perhaps with both ignitions on up to a decent altitde and be prepared to switch onto secoundary at the slightest hiccup or keep both running all the time - p - Original Message - From: "Mark Jones" <flyk...@wi.rr.com> To: "Corvaircraft" <corvaircr...@mylist.net>; "KR Net" <kr...@mylist.net> Sent: Tuesday, September 13, 2005 3:09 AM Subject: KR> Dual Ignition Systems, it Saved My Bacon Yes, that is correct. I too have joined the elite group of knowing what a dead engine in flight sounds like. There is no sound and man is that one quiet cockpit when the engine ceases to sing. Yesterday as I was leaving the KR Gathering out of Mt. Vernon, Illinois, my engine hic-upped. I really did not think much of it thinking maybe an air bubble in the fuel line. Well I continued to climb and was at 2300' ASL when all of a sudden things got real quiet. I was not too far away from the airport so I executed a 180° and set up a glide to MVN runway 23 and announced that 6MJ had turned final. Next, flipped the toggle switch to my back up secondary ignition and hit the starter. The engine fired right up and we started climbing. Instead of continuing to land, I decided to keep climbing and circling. After three circles and altitude gained, I determined the problem was strictly electrical and not the engine. I tested the main ignition again and again the engine died but only for a half second as I immediately went back to secondary ignition. Probably not the wisest decision but I decided to head on to my first stop at Pontiac, Illinois which was 149 miles away. I was never out of gliding distance from an airport and made the leg there with no further problems. The haze was terrible and from 15 miles out I began calling my position to PNT traffic. I noticed there were several planes in the area and some calling taxi back on the runway. At five miles out I still could just barely see the airport. As I entered downwind for PNT runway 24, I noticed four planes in the holding area waiting for my arrival. On one mile final, I noticed there were at least two hundred folks sitting around the tarmac watching the runway. Needless to say, I made the worst landing I have ever made in my KR. I bounced two, maybe three times and then swerved back an forth on the runway. This was the one day out of the year they have their local fly-in and I dropped in right in the middle of it. Anyway, I pulled my cowl look for the problem and found that the condenser wire had broken at the coil. A pair of wire strippers and a wrench and two minutes later the problem was fixed. The only problem now was that I had drawn a crowd of pilots and spectators and the questions about the plane and engine started flying. An hour later, I managed to continue my journey which was eventless the rest of the way home. Moral of the story is: Redundancy will save your bacon. Don't fly without it. Mark Jones (N886MJ) Wales, WI USA E-mail me at flyk...@wi.rr.com Visit my KR-2S CorvAIRCRAFT web site at http://mywebpage.netscape.com/n886mj ___ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.10.21/96 - Release Date: 10/09/2005 -- I am using the free version of SPAMfighter for private users. It has removed 24377 spam emails to date. Paying users do not have this message in their emails. Try www.SPAMfighter.com for free now! -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.10.21/96 - Release Date: 10/09/2005
