---------------------------------------------------------- RV-List Digest Archive --- Total Messages Posted Tue 12/04/12: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:48 AM - Re: Engine combustion troubleshooting concepts (Ralph E. Capen) 2. 06:11 AM - Re: Engine combustion troubleshooting concepts (Kelly McMullen) 3. 06:25 AM - Re: Engine combustion troubleshooting concepts (Ralph E. Capen) ________________________________ Message 1 _____________________________________ Time: 04:48:26 AM PST US From: "Ralph E. Capen" Subject: Re: RV-List: Engine combustion troubleshooting concepts Thanks. This was only one cylinder, the EGT only went up (enough to catch my attention - not red-line). I have already pulled both plugs - the lower one was wet which may not mean anything. Neither of them looked abnormal - cleaned and reinstalled. -----Original Message----- From: Shannon Miller Sent: Dec 3, 2012 7:21 PM Subject: Re: RV-List: Engine combustion troubleshooting concepts 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 ________________________________ Message 2 _____________________________________ Time: 06:11:37 AM PST US From: Kelly McMullen Subject: Re: RV-List: Engine combustion troubleshooting concepts Only two items will cause a single cylinder EGT to rise significantly. Either one plug stopped firing, or an induction leak developed. Single spark instead of two plugs firing will cause 50-150 degree EGT rise. So will a loose intake tube or gasket. On 12/4/2012 5:47 AM, Ralph E. Capen wrote: > > Thanks. > > This was only one cylinder, the EGT only went up (enough to catch my attention - not red-line). > > I have already pulled both plugs - the lower one was wet which may not mean anything. Neither of them looked abnormal - cleaned and reinstalled. > > > -----Original Message----- > > From: Shannon Miller > > Sent: Dec 3, 2012 7:21 PM > > To: "rv-list@matronics.com" > > Subject: Re: RV-List: Engine combustion troubleshooting concepts > > > 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 > > ----- No virus found in this message. Checked by AVG - www.avg.com ________________________________ Message 3 _____________________________________ Time: 06:25:07 AM PST US From: "Ralph E. Capen" Subject: Re: RV-List: Engine combustion troubleshooting concepts Thanks - I'll keep looking for an induction leak. Already contemplating moving my MAP sensor port from that cylinder to the one in front of it. -----Original Message----- >From: Kelly McMullen >Sent: Dec 4, 2012 9:10 AM >To: rv-list@matronics.com >Subject: Re: RV-List: Engine combustion troubleshooting concepts > > >Only two items will cause a single cylinder EGT to rise significantly. >Either one plug stopped firing, or an induction leak developed. Single >spark instead of two plugs firing will cause 50-150 degree EGT rise. So >will a loose intake tube or gasket. > >On 12/4/2012 5:47 AM, Ralph E. Capen wrote: >> >> Thanks. >> >> This was only one cylinder, the EGT only went up (enough to catch my attention - not red-line). >> >> I have already pulled both plugs - the lower one was wet which may not mean anything. Neither of them looked abnormal - cleaned and reinstalled. >> >> >> -----Original Message----- >> >> From: Shannon Miller >> >> Sent: Dec 3, 2012 7:21 PM >> >> To: "rv-list@matronics.com" >> >> Subject: Re: RV-List: Engine combustion troubleshooting concepts >> >> >> >> 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 >> >> >> >> >> >> >> >> >> > > >----- >No virus found in this message. >Checked by AVG - www.avg.com > > ------------------------------------------------------------------------------------- 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.