---------------------------------------------------------- Commander-List Digest Archive --- Total Messages Posted Wed 05/02/07: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:42 AM - Engine RPM fluctuation (Ray Mansfield) 2. 07:33 AM - Re: Engine RPM fluctuation (mike floyd) 3. 10:01 AM - Re: Engine RPM fluctuation (nico css) 4. 10:40 AM - Re: Engine RPM fluctuation (Robert Feldtman) 5. 01:54 PM - Re: Engine RPM fluctuation (N395V) 6. 03:59 PM - Re: Re: Engine RPM fluctuation () ________________________________ Message 1 _____________________________________ Time: 06:42:14 AM PST US From: "Ray Mansfield" Subject: Commander-List: Engine RPM fluctuation Hello, Have been having a strange and undiagnosed problem with my right engine. I fly a 680 FLP with the Mr. RPM conversion to IO-720 engines. Recently, primarily on takeoff and climb the left ending has been randomly dropping 50, 100, and sometimes 300-400 RPM numerous times, then returning to normal takeoff or climb RPM (2,650 Takeoff, 2,500 Climb). Manifold pressure goes up slightly in such instances. Have seen it happen during high speed, full power taxi runs, then sometimes it won't happen at all. Have had the, prop governors bench tested with everything shown to be working fine, fuel filter cleaned, new cylinders recently put on were borescoped and appeared OK. The manual turbo mechanism was checked and nothing was out of adjustment or loose. Currently the magneto (dual magneto in one unit) was removed. There was a small amount of oil on the bottom contacts, and the upper contact had carbon on them. The magneto was sent off for inspection and overhaul...it was near recommended overhaul time. Anyone ever seen this happen to them. We've talked to prop guys,...the props were recently overhauled. No one seems to have a concrete idea as to what's going on. We are not even sure the oil in the magneto contact is the problem, but will find out later this week if that's it. We thought the problem was solved after a good number of runs on the runway and one flight of 1.5 hrs with no problems. The next flight the same thing happened again. Anyone have any problems with water getting in a magneto...none was found in our magneto. Thanks. The amount of knowledge on this website is tremendous. Folks here have helped me before. Thanks. Ray Mansfield ________________________________ Message 2 _____________________________________ Time: 07:33:08 AM PST US From: "mike floyd" Subject: RE: Commander-List: Engine RPM fluctuation Ray, Look at the upper deck reference lines they supply turbo boost pressure to the fuel inj nozzles. Look for holes in them and the short hoses from them to the nozzle shroud. I have seen them get plugged when they are repaired and it restricts the airflow to a nozzle. Also look the "P" leads over vey closely looking for the shield portion to be touching the center conductor. Mike _________________________________________________________________ Interest Rates NEAR 39yr LOWS! $430,000 Mortgage for $1,299/mo - Calculate new payment ________________________________ Message 3 _____________________________________ Time: 10:01:30 AM PST US From: "nico css" Subject: RE: Commander-List: Engine RPM fluctuation Hi Ray, I hope this helps. It's not rocket science, but just checking a box for you might be worth sharing this. If the manifold pressure goes up when the RPM goes down, isn't that an indication that the engine is developing power and that something external to the power plant itself is consuming power, such as when one reduces RPM by setting a coarser pitch? Wouldn't the MP go down and the RPM remain constant (at that power setting) if a fuel blockage occurs? Does the RPM variation disappear in cruise? Nico _____ From: owner-commander-list-server@matronics.com [mailto:owner-commander-list-server@matronics.com] On Behalf Of Ray Mansfield Sent: Wednesday, May 02, 2007 6:41 AM Subject: Commander-List: Engine RPM fluctuation Hello, Have been having a strange and undiagnosed problem with my right engine. I fly a 680 FLP with the Mr. RPM conversion to IO-720 engines. Recently, primarily on takeoff and climb the left ending has been randomly dropping 50, 100, and sometimes 300-400 RPM numerous times, then returning to normal takeoff or climb RPM (2,650 Takeoff, 2,500 Climb). Manifold pressure goes up slightly in such instances. Have seen it happen during high speed, full power taxi runs, then sometimes it won't happen at all. Have had the, prop governors bench tested with everything shown to be working fine, fuel filter cleaned, new cylinders recently put on were borescoped and appeared OK. The manual turbo mechanism was checked and nothing was out of adjustment or loose. Currently the magneto (dual magneto in one unit) was removed. There was a small amount of oil on the bottom contacts, and the upper contact had carbon on them. The magneto was sent off for inspection and overhaul...it was near recommended overhaul time. Anyone ever seen this happen to them. We've talked to prop guys,...the props were recently overhauled. No one seems to have a concrete idea as to what's going on. We are not even sure the oil in the magneto contact is the problem, but will find out later this week if that's it. We thought the problem was solved after a good number of runs on the runway and one flight of 1.5 hrs with no problems. The next flight the same thing happened again. Anyone have any problems with water getting in a magneto...none was found in our magneto. Thanks. The amount of knowledge on this website is tremendous. Folks here have helped me before. Thanks. Ray Mansfield ________________________________ Message 4 _____________________________________ Time: 10:40:55 AM PST US From: "Robert Feldtman" Subject: Re: Commander-List: Engine RPM fluctuation I had to have my prop governor re-worked last year on the IO 540 in my AC500B. Works fine now. I'd say if you have >1-2% RPM fluctuation you need it fixed, certainly any more than 50RPM change. 300 is way too much. The little centrifugal force thingy that spins around and changes a valve position etc needed reworking - had id done in Dallas. Works fine now. qualify that - I am NOT a mechanic. - just a surgeon. bobf On 5/2/07, Ray Mansfield wrote: > > Hello, > > Have been having a strange and undiagnosed problem with my right > engine. I fly a 680 FLP with the Mr. RPM conversion to IO-720 engines. > Recently, primarily on takeoff and climb the left ending has been randomly > dropping 50, 100, and sometimes 300-400 RPM numerous times, then returning > to normal takeoff or climb RPM (2,650 Takeoff, 2,500 Climb). Manifold > pressure goes up slightly in such instances. Have seen it happen during high > speed, full power taxi runs, then sometimes it won't happen at all. > > Have had the, prop governors bench tested with everything shown to be > working fine, fuel filter cleaned, new cylinders recently put on were > borescoped and appeared OK. The manual turbo mechanism was checked and > nothing was out of adjustment or loose. Currently the magneto (dual magneto > in one unit) was removed. There was a small amount of oil on the bottom > contacts, and the upper contact had carbon on them. The magneto was sent > off for inspection and overhaul...it was near recommended overhaul time. > > Anyone ever seen this happen to them. We've talked to prop > guys,...the props were recently overhauled. No one seems to have a concrete > idea as to what's going on. We are not even sure the oil in the magneto > contact is the problem, but will find out later this week if that's it. We > thought the problem was solved after a good number of runs on the runway and > one flight of 1.5 hrs with no problems. The next flight the same thing > happened again. > > Anyone have any problems with water getting in a magneto...none was > found in our magneto. > > Thanks. The amount of knowledge on this website is tremendous. Folks > here have helped me before. Thanks. > > Ray Mansfield > > > * > > * > > ________________________________ Message 5 _____________________________________ Time: 01:54:47 PM PST US Subject: Commander-List: Re: Engine RPM fluctuation From: "N395V" I think it is a magneto, plug wire, or plug problem. -------- Milt 2003 F1 Rocket 2006 Radial Rocket website http://www.excaliburaviation.com Read this topic online here: http://forums.matronics.com/viewtopic.php?p=110492#110492 ________________________________ Message 6 _____________________________________ Time: 03:59:29 PM PST US From: Subject: Re: Commander-List: Re: Engine RPM fluctuation --Question ----Is your engine--Carburetor ed or Fuel Injected ? If you have a carburetor, the throttle shaft bearings wear out and get loose. At high power setting as on takeoff, this allows the fuel mixture to go lean and reduced power, just when you need all the power the engine can produce. What takes place, is the loose bearings allows air to be drawn into the carb Ventura ABOVE the fuel level in the main nozzle, resulting in the lean mixture. You can easily check for the loose throttle shaft bearings by moving the throttle arm up and down and checking for any slop in the shaft. You can do this without dissemble any thing, just reach in there and move the throttle arm up and down and see if you have any loose- nesss. Hoe this is of some help for your problem. HAPPY LANDINGS, and KEEP e,m FLYING, arm N395V wrote: > > I think it is a magneto, plug wire, or plug problem. > > -------- > Milt > 2003 F1 Rocket > 2006 Radial Rocket > website http://www.excaliburaviation.com > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=110492#110492 > > > > > > > > > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message commander-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Commander-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/commander-list Browse Digests http://www.matronics.com/digest/commander-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.