---------------------------------------------------------- JabiruEngine-List Digest Archive --- Total Messages Posted Thu 08/25/11: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:47 AM - Some ignition timing observations (Lynn Matteson) 2. 11:29 AM - Re: Some ignition timing observations (Naftali Horowitz) 3. 01:29 PM - Re: Some ignition timing observations (Martin Hone) ________________________________ Message 1 _____________________________________ Time: 07:47:29 AM PST US From: Lynn Matteson Subject: JabiruEngine-List: Some ignition timing observations During some recent testing of a MAP sensor in my ignition system, I observed that the ignition timing (a panel gauge shows the exact ignition timing) was stuck on 34 degrees BTDC. I shut the MAP sensor down via a switch that I had been advised to install should such a condition occur....this IS experimental, after all. When I first started to run tests, the sensor was doing its job of setting the timing according to conditions, then it started to misbehave and I shut the sensor down, knowing that it was not right. A couple of days later I decided to see what happened if I switched the sensor back on. I did, and the panel gauge read 34 degrees BTDC timing, and the EGT's started to go down dramatically. I kept an eye on the CHT's and they didn't change much, staying right around the 300 degree mark (my CHT probes are located in a 50-75 degree F hotter location than the under-the-plugs location) I didn't make any notes about how times, temps, how temps changed, etc., because the EGT drop had my attention. This test tells me that if the ignition event is started earlier...before the standard 25 degrees BTDC...the fuel is no longer burning when the exhaust valve opens, there is no longer any fuel burning while the exhaust cycle is taking place, so the EGT's are reduced. In this instance, I saw the EGT's go from the 1340's to about the 1260's. After that day I removed the sensor and sent it to the factory for evaluation, so I haven't been able to repeat the test. It stands to reason that if the ignition event is started earlier, more heat should take place within the cylinder head and not in the exhaust pipe, so CHT's should rise. When the unit is returned to me, I'll repeat the test, taking better notes next time. Of course the timing won't be stuck at 34 any longer, so I'll have to fly it to an elevation, and set the throttle such that the timing WILL be at 34 degrees. After that, I'll try other timing settings, and be on the lookout for rising CHT readings. Lynn Matteson Kitfox IV Speedster, taildragger Jabiru 2200, #2062 Prince prop 64 x 30, P-tip Electroair direct-fire ignition system Rotec TBI-40 injection (sleeved to 36mm) Status: flying with "Ramcharger" intake manifold...1162 hrs (since 3-27-2006) ________________________________ Message 2 _____________________________________ Time: 11:29:39 AM PST US From: Naftali Horowitz Subject: RE: JabiruEngine-List: Some ignition timing observations Beware of detonation turning into preignition. > From: lynnmatt@jps.net > Subject: JabiruEngine-List: Some ignition timing observations > Date: Thu=2C 25 Aug 2011 10:43:02 -0400 > To: jabiruengines@yahoogroups.com=3B jabiruengine-list@matronics.com > > > During some recent testing of a MAP sensor in my ignition system=2C I > observed that the ignition timing (a panel gauge shows the exact > ignition timing) was stuck on 34 degrees BTDC. I shut the MAP sensor > down via a switch that I had been advised to install should such a > condition occur....this IS experimental=2C after all. > > When I first started to run tests=2C the sensor was doing its job of > setting the timing according to conditions=2C then it started to > misbehave and I shut the sensor down=2C knowing that it was not right. > A couple of days later I decided to see what happened if I switched > the sensor back on. I did=2C and the panel gauge read 34 degrees BTDC > timing=2C and the EGT's started to go down dramatically. I kept an eye > on the CHT's and they didn't change much=2C staying right around the > 300 degree mark (my CHT probes are located in a 50-75 degree F hotter > location than the under-the-plugs location) I didn't make any notes > about how times=2C temps=2C how temps changed=2C etc.=2C because the EGT drop > had my attention. This test tells me that if the ignition event is > started earlier...before the standard 25 degrees BTDC...the fuel is > no longer burning when the exhaust valve opens=2C there is no longer > any fuel burning while the exhaust cycle is taking place=2C so the > EGT's are reduced. In this instance=2C I saw the EGT's go from the > 1340's to about the 1260's. After that day I removed the sensor and > sent it to the factory for evaluation=2C so I haven't been able to > repeat the test. It stands to reason that if the ignition event is > started earlier=2C more heat should take place within the cylinder head > and not in the exhaust pipe=2C so CHT's should rise. When the unit is > returned to me=2C I'll repeat the test=2C taking better notes next time. > Of course the timing won't be stuck at 34 any longer=2C so I'll have to > fly it to an elevation=2C and set the throttle such that the timing > WILL be at 34 degrees. After that=2C I'll try other timing settings=2C > and be on the lookout for rising CHT readings. > > > Lynn Matteson > Kitfox IV Speedster=2C taildragger > Jabiru 2200=2C #2062 > Prince prop 64 x 30=2C P-tip > Electroair direct-fire ignition system > Rotec TBI-40 injection (sleeved to 36mm) > Status: flying with "Ramcharger" intake manifold...1162 hrs (since > 3-27-2006) > > > > > =========== =========== =========== =========== > > > ________________________________ Message 3 _____________________________________ Time: 01:29:40 PM PST US Subject: Re: JabiruEngine-List: Some ignition timing observations From: Martin Hone I don't see any evidence based on what Lynn has posted of either detonation or pre-ignition. Although both are detrimental to an engine's longevity, they are separate conditions. Over advanced timing and poor quality fuel will assist in detonation, but poor cylinder head design and insufficient squish is the main reason. Cheers Martin On Fri, Aug 26, 2011 at 4:25 AM, Naftali Horowitz wrote: > Beware of detonation turning into preignition. > > > From: lynnmatt@jps.net > > Subject: JabiruEngine-List: Some ignition timing observations > > Date: Thu, 25 Aug 2011 10:43:02 -0400 > > To: jabiruengines@yahoogroups.com; jabiruengine-list@matronics.com > > > > > > > > During some recent testing of a MAP sensor in my ignition system, I > > observed that the ignition timing (a panel gauge shows the exact > > ignition timing) was stuck on 34 degrees BTDC. I shut the MAP sensor > > down via a switch that I had been advised to install should such a > > condition occur....this IS experimental, after all. > > > > When I first started to run tests, the sensor was doing its job of > > setting the timing according to conditions, then it started to > > misbehave and I shut the sensor down, knowing that it was not right. > > A couple of days later I decided to see what happened if I switched > > the sensor back on. I did, and the panel gauge read 34 degrees BTDC > > timing, and the EGT's started to go down dramatically. I kept an eye > > on the CHT's and they didn't change much, staying right around the > > 300 degree mark (my CHT probes are located in a 50-75 degree F hotter > > location than the under-the-plugs location) I didn't make any notes > > about how times, temps, how temps changed, etc., because the EGT drop > > had my attention. This test tells me that if the ignition event is > > started earlier...before the standard 25 degrees BTDC...the fuel is > > no longer burning when the exhaust valve opens, there is no longer > > any fuel burning while the exhaust cycle is taking place, so the > > EGT's are reduced. In this instance, I saw the EGT's go from the > > 1340's to about the 1260's. After that day I removed the sensor and > > sent it to the factory for evaluation, so I haven't been able to > > repeat the test. It stands to reason that if the ignition event is > > started earlier, more heat should take place within the cylinder head > > and not in the exhaust pipe, so CHT's should rise. When the unit is > > returned to me, I'll repeat the test, taking better notes next time. > > Of course the timing won't be stuck at 34 any longer, so I'll have to > > fly it to an elevation, and set the throttle such that the timing > > WILL be at 34 degrees. After that, I'll try other timing settings, > > and be on the lookout for rising CHT readings. > > > > > > Lynn Matteson > > Kitfox IV Speedster, taildragger > > Jabiru 2200, #2062 > > Prince prop 64 x 30, P-tip > > Electroair direct-fire ignition system > > Rotec TBI-40 injection (sleeved to 36mm) > > Status: flying with "Ramcharger" intake manifold...1162 hrs (since > > 3-27-2006) > > > > > > > > > >============== > > > > > > > > * > > * > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message jabiruengine-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/JabiruEngine-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/jabiruengine-list Browse Digests http://www.matronics.com/digest/jabiruengine-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.