dougknight
Well Known Member
We finally got a little cold winter weather here in the northwest...well cold for us anyway in the mid Willamette valley of Oregon. Teen's at night, 20's & 30's during the day (F) with 2 inches of snow on the ground. Sorry for you guy's in the midwest doing the minus 0* F thing. actually they are saying + 5* F tonight with freezing fog for the next two day's for us , O joy!
So, I decided to take the plane out and circulate the oil and warm it up for a bit. It was mid afternoon the sun was out and it must have been in the mid 30's (F) after being in the mid 20's overnight. Not sure what it was in the hanger where the plane is kept but had to be right around the freezing mark. T Hanger is not heated nor insulated but it is enclosed. I keep the engine on a heated dehydrator 24/7 when not in use which may give it another 10 degrees or so (home made with a 60 watt light bulb in a 5 gal bucket)
Did my normal run-up and mag checks as usual and saw nothing abnormal. Entered the runway and took-off. At about 1000 feet I pulled power back to 2000 rpm and started to lean a little to save some fuel, turn the sterio on and enjoy the sights when the engine stumbled quicker than I anticipated. I'm carburated and lean to roughness then richen to smooth as per lycoming manual. I glanced at my EGT gauge and it was up over 1450* F. I usually see it around 1050 before leaning and maybe up to 1250 after leaning even on a hot 90* summer day!! What the heck Is going on!! I have never seen it this high!!
I pointed it back to the runway, landed and de-cowled (top cowel only) and looked for any obvious indications and found none. I did two more take-off and landings within gliding distance back to the airport so as to gather more information. I figured 1400 wasn't critical. It was unusual, however still safe if I stayed within gliding distance back to the airport should I need to shut the engine down.
Long story short I found that EGT'S on both #1 & #3 peaked aound 200-250* higher than normal even on a hot summer day. CHT'S on both #1 & #3 were running 50-75* higher than normal (375*-425*). CHT'S on all four are usually within 25-50* F of each other in the 325*-350* F range.
EGT'S on both #2 & #4 stayed in the normal range of what I normaly see, 1000-1050 before leaning and 1150-1250 after leaning. CHT'S on #2 & #4 normal in the 325*- 350* range.
I have an idea or two to persue and check once the weather cooperates and warms up enough to work in the unheated hanger (that faces north away from the sun) but I thought I would throw this info out in the meantime and see what ideas others on the forum might provide as to why one side of the engine might see a spike upwards in operating temperature when the ambient temp actually goes down!!
specs are:
RV9A
Areosport re-built O-320 in 2006
475 hrs TT airframe and engine
carburator
STEAM GAUGES! vans EGT and CHT with four position rotary switch
slick mags, left side impulse only
timing=25* BTC
any ideas appreciated.
thanks in advance
doug
So, I decided to take the plane out and circulate the oil and warm it up for a bit. It was mid afternoon the sun was out and it must have been in the mid 30's (F) after being in the mid 20's overnight. Not sure what it was in the hanger where the plane is kept but had to be right around the freezing mark. T Hanger is not heated nor insulated but it is enclosed. I keep the engine on a heated dehydrator 24/7 when not in use which may give it another 10 degrees or so (home made with a 60 watt light bulb in a 5 gal bucket)
Did my normal run-up and mag checks as usual and saw nothing abnormal. Entered the runway and took-off. At about 1000 feet I pulled power back to 2000 rpm and started to lean a little to save some fuel, turn the sterio on and enjoy the sights when the engine stumbled quicker than I anticipated. I'm carburated and lean to roughness then richen to smooth as per lycoming manual. I glanced at my EGT gauge and it was up over 1450* F. I usually see it around 1050 before leaning and maybe up to 1250 after leaning even on a hot 90* summer day!! What the heck Is going on!! I have never seen it this high!!
I pointed it back to the runway, landed and de-cowled (top cowel only) and looked for any obvious indications and found none. I did two more take-off and landings within gliding distance back to the airport so as to gather more information. I figured 1400 wasn't critical. It was unusual, however still safe if I stayed within gliding distance back to the airport should I need to shut the engine down.
Long story short I found that EGT'S on both #1 & #3 peaked aound 200-250* higher than normal even on a hot summer day. CHT'S on both #1 & #3 were running 50-75* higher than normal (375*-425*). CHT'S on all four are usually within 25-50* F of each other in the 325*-350* F range.
EGT'S on both #2 & #4 stayed in the normal range of what I normaly see, 1000-1050 before leaning and 1150-1250 after leaning. CHT'S on #2 & #4 normal in the 325*- 350* range.
I have an idea or two to persue and check once the weather cooperates and warms up enough to work in the unheated hanger (that faces north away from the sun) but I thought I would throw this info out in the meantime and see what ideas others on the forum might provide as to why one side of the engine might see a spike upwards in operating temperature when the ambient temp actually goes down!!
specs are:
RV9A
Areosport re-built O-320 in 2006
475 hrs TT airframe and engine
carburator
STEAM GAUGES! vans EGT and CHT with four position rotary switch
slick mags, left side impulse only
timing=25* BTC
any ideas appreciated.
thanks in advance
doug