---------------------------------------------------------- RV-List Digest Archive --- Total Messages Posted Mon 12/03/12: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:34 PM - Engine combustion troubleshooting concepts (Ralph E. Capen) 2. 04:22 PM - Re: Engine combustion troubleshooting concepts (Shannon Miller) ________________________________ Message 1 _____________________________________ Time: 02:34:25 PM PST US From: "Ralph E. Capen" Subject: RV-List: Engine combustion troubleshooting concepts Re-breaking in my engine after prop-strike by hangar door induced by tornado. Considering the engine already had 160+ hours on it - I know how it was running for a while. I have one cylinder running not like the others. Before I tell what is happening, I want to make sure I understand/remember the basic concepts. EGT-only elevated - CHT reduced...unburned fuel going out exhaust and burning on the way out - plug not firing EGT-only elevated - ...unburned fuel going out exhaust and burning on the way out - plug not firing completely CHT-only elevated...not enough cooling air EGT and CHT elevated...lean mixture - air leak Refresh my memory here. ________________________________ Message 2 _____________________________________ Time: 04:22:37 PM PST US Subject: Re: RV-List: Engine combustion troubleshooting concepts From: Shannon Miller I'm no expert, but I can share my own understanding. See below. On Mon, Dec 3, 2012 at 2:33 PM, Ralph E. Capen wrote: > Re-breaking in my engine after prop-strike by hangar door induced by > tornado. > > Considering the engine already had 160+ hours on it - I know how it was > running for a while. > > I have one cylinder running not like the others. Before I tell what is > happening, I want to make sure I understand/remember the basic concepts. > > EGT-only elevated - CHT reduced...unburned fuel going out exhaust and > burning on the way out - plug not firing > Right. Possibly some sort of spark plug problem. Could be a fouled plug or disconnected/broken plug wire. Consider a mag check (even if you're only seeing this in flight -- just do it at a safe altitude and within gliding distance to a safe landing spot) to identify the plug/wire; if the engine quits, pull the throttle to idle before switching off the bad mag to avoid backfiring. > EGT-only elevated - ...unburned fuel going out exhaust and burning on the > way out - plug not firing completely > Agreed. Same possible causes as above. > CHT-only elevated...not enough cooling air > Or insufficient fuel flow, power too high for the air flow, mixture too lean, or RPM too low for the power setting. Possible in-flight solutions: lower nose to increase airspeed, open cowl flaps if you have them, enrichen the mixture (confirm that you're rich of peak by noting a decrease in EGT's as you enrichen the mixture), reduce power (MP), increase prop RPM. Now if it's just one cylinder, I would guess it's either some sort of baffling issue or fuel flow issue to that cylinder. > EGT and CHT elevated...lean mixture - air leak > Agree, or possible magneto/ignition problem if it's all cylinders -- a mag check would identify which mag/ignition source. If it's just one cylinder, it could be a partially clogged fuel injector: go full rich mixture and momentarily turn on the boost pump -- it might dislodge the clog! > Refresh my memory here. I assume you're talking only "somewhat" elevated EGT and CHT values, and not values which are "sky high" which could indicate detonation or pre-ignition and ultimate catastrophic engine failure! That's all I can offer. No warranty, but I hope it helps! --Shannon ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rv-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RV-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/rv-list Browse Digests http://www.matronics.com/digest/rv-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.