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  #11  
Old 02-01-2021, 05:52 PM
NinerBikes NinerBikes is offline
 
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Originally Posted by rvbuilder2002 View Post
Can you provide a reference to info that substantiates this?
Scott,

from July through October here in So CA, on any given day with temps in the high 70's to 90 F on the ground with the airport I take off out of, at 1004 MSL, it's very, very common for days to have a temperature inversion to 5500 to 6000 ft.

It's also common for me to see full throttle exhaust temps at or around 1450 F on initial climb out, to about 2500 ft, where I will then drop the nose from a 75 kt climb to level and about 5200 rpm, trimmed up level. Usually the exhaust temps will drop 100 to 125 F pretty quickly, once level, to 1320 -1350F

The other really important observation I need to make is watching my oil temps on hot days like this. A climb from airport at 1004 to 3000 ASL will usually have my oil temps right around 230F and edging into the yellow range. At that point I have to give up the 85 kt XC climb rate, throttle back to 5100 and fly level for a couple of minutes, before I attempt to climb shallow at 250 -300 fpm under light engine load. The inversion factor and the temp going up as I increase in altitude, magnifies the temperatures oil and exhaust run at.

It takes a long time to get to 6000 ft to get above the inversion and have the air temps start dropping as you go higher so that your exhaust and oil temps start dropping down again too. It was that way down here for probably 4 months with the inversions, during the forest fire season.

It's rarely a problem since late November, so far, through the winter months, the oil or exhaust temps being on the higher side. But July through October, absolutely. Seems to be common, at least on some 2012 RV-12 Legacy models. SN120212
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Last edited by NinerBikes : 02-01-2021 at 05:54 PM.
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  #12  
Old 02-02-2021, 11:46 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Originally Posted by NinerBikes View Post
Scott,

from July through October here in So CA, on any given day with temps in the high 70's to 90 F on the ground with the airport I take off out of, at 1004 MSL, it's very, very common for days to have a temperature inversion to 5500 to 6000 ft.

It's also common for me to see full throttle exhaust temps at or around 1450 F on initial climb out, to about 2500 ft, where I will then drop the nose from a 75 kt climb to level and about 5200 rpm, trimmed up level. Usually the exhaust temps will drop 100 to 125 F pretty quickly, once level, to 1320 -1350F

The other really important observation I need to make is watching my oil temps on hot days like this. A climb from airport at 1004 to 3000 ASL will usually have my oil temps right around 230F and edging into the yellow range. At that point I have to give up the 85 kt XC climb rate, throttle back to 5100 and fly level for a couple of minutes, before I attempt to climb shallow at 250 -300 fpm under light engine load. The inversion factor and the temp going up as I increase in altitude, magnifies the temperatures oil and exhaust run at.

It takes a long time to get to 6000 ft to get above the inversion and have the air temps start dropping as you go higher so that your exhaust and oil temps start dropping down again too. It was that way down here for probably 4 months with the inversions, during the forest fire season.

It's rarely a problem since late November, so far, through the winter months, the oil or exhaust temps being on the higher side. But July through October, absolutely. Seems to be common, at least on some 2012 RV-12 Legacy models. SN120212
Ok, but you said "I like seeing my EGT's no higher than 1400, 1300's, even 1200s is better."

What makes them "better" if they are in the 1200's"?
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  #13  
Old 02-02-2021, 02:47 PM
NinerBikes NinerBikes is offline
 
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d
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Originally Posted by rvbuilder2002 View Post
Ok, but you said "I like seeing my EGT's no higher than 1400, 1300's, even 1200s is better."

What makes them "better" if they are in the 1200's"?
Let me ask you the opposite? What makes them worse? I am all ears.


Keep in mind, I have a muffler sitting an inch away from my oil cooler, by Van's original design... what's an extra 200F worth when I am trying to cool oil, too? Am I better off, backing off out of the throttle, lowering my attitude, increasing my airspeed, and lowering my rpm, oil and exhaust temps or not, when trying to climb out, putting less load on the engine? I am surrounded by mountains here around Los Angeles, everywhere I fly. I live down in a 1000 ft elevation valley.


IMHO, if your carbs are jetted correctly, high exhaust temps can be caused by several things. Too low an octane fuel, too lean on the jetting, too advance ignition timing ( a non issue on a 912ULS) or increased load on the engine. We can control octane, and load on the engine. Once fuel is in the tank, all we can control is load on the engine, for that batch of fuel. Pitch of prop has an effect on that engine load.
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Last edited by NinerBikes : 02-02-2021 at 03:10 PM.
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  #14  
Old 02-02-2021, 02:54 PM
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Here's a good article on EGTs.

https://www.savvyanalysis.com/articl...myths-debunked
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  #15  
Old 02-02-2021, 03:08 PM
NinerBikes NinerBikes is offline
 
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I'm curious, Jon, what are the EGT's on your IS motor in the summer time, there in UT, at full throttle and Vy?
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  #16  
Old 02-02-2021, 04:19 PM
seagull seagull is offline
 
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How do these numbers look for prop pitch? Two blade Sensenich.
Obviously the GPM is a calculation but it is spot on when I measure remaining gallons in the tank. I fly at gross and typically 120 knots, my average (measured over many flights, in all weather) is 4.8 GPH.

climb WOT, 5070RPM, 750 fpm, 3500MSL, 76TAS, 27.2hg, 67f OAT, EGT 1203 / 1259, 5.0GPM

cruise 5370 RPM, 3600 MSL, 119TAS, 25.1hg, 120TAS, 64f OAT, EGT 1256 / 1309, 4.9GPM

cruise 5170 RPM, 3600 MSL, 115 TAS, 24.3hg, 63f OAT, EGT 1280 / 1327, 4.2GPM
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  #17  
Old 02-02-2021, 04:19 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by NinerBikes View Post
d

Let me ask you the opposite? What makes them worse? I am all ears.


Keep in mind, I have a muffler sitting an inch away from my oil cooler, by Van's original design... what's an extra 200F worth when I am trying to cool oil, too? Am I better off, backing off out of the throttle, lowering my attitude, increasing my airspeed, and lowering my rpm, oil and exhaust temps or not, when trying to climb out, putting less load on the engine? I am surrounded by mountains here around Los Angeles, everywhere I fly. I live down in a 1000 ft elevation valley.


IMHO, if your carbs are jetted correctly, high exhaust temps can be caused by several things. Too low an octane fuel, too lean on the jetting, too advance ignition timing ( a non issue on a 912ULS) or increased load on the engine. We can control octane, and load on the engine. Once fuel is in the tank, all we can control is load on the engine, for that batch of fuel. Pitch of prop has an effect on that engine load.
Lower EGT's can be an indicator of being excessively rich.
In reality, the Bing carbs are conservatively rich all of the time but particularly at mid range throttle.
That is why the iS (which typically has higher EGT's than the ULS) is able to be so much more fuel efficient and why EGT's in the 1200's are not particularly desirable or necessary.

BTW, lower EGT's has a very negligible effect on oil temp, and low EGT's caused by a rich mixture could be a negative influence on CHT/coolant temp.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #18  
Old 02-02-2021, 04:46 PM
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jrtens jrtens is offline
 
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Originally Posted by NinerBikes View Post
I'm curious, Jon, what are the EGT's on your IS motor in the summer time, there in UT, at full throttle and Vy?
1350 to 1400 in full power climb, then 1400 to 1450 in cruise with the power back to ECON (about 5150)
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Last edited by jrtens : 02-02-2021 at 04:51 PM.
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  #19  
Old 02-02-2021, 05:43 PM
seagull seagull is offline
 
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Quote:
Originally Posted by seagull View Post
How do these numbers look for prop pitch? Two blade Sensenich.
Obviously the GPM is a calculation but it is spot on when I measure remaining gallons in the tank. I fly at gross and typically 120 knots, my average (measured over many flights, in all weather) is 4.8 GPH.

climb WOT, 5070RPM, 750 fpm, 3500MSL, 76TAS, 27.2hg, 67f OAT, EGT 1203 / 1259, 5.0GPM

cruise 5370 RPM, 3600 MSL, 119TAS, 25.1hg, 120TAS, 64f OAT, EGT 1256 / 1309, 4.9GPM

cruise 5170 RPM, 3600 MSL, 115 TAS, 24.3hg, 63f OAT, EGT 1280 / 1327, 4.2GPM
Suggestions?
Should I start a new thread?
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  #20  
Old 02-03-2021, 12:18 AM
RFSchaller RFSchaller is offline
 
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Out here in PHX summers Iíll do anything to run cooler. I have had to return to the airport twice for excessive oil and CHT temps in summer. Each time the result of having to sit too long in the run up area watching the endless maerry-go-round of touch and goes.
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