How to read EGT steam gauge?
Posted by UltimateAv8or@reddit | flying | View on Reddit | 54 comments
My family is buying a ‘72 Beechcraft Sundowner with all steam gauges. I did my PPL in a Piper Cherokee with steam gauges, and my Instrument through CFII in an SR20 with full glass cockpit, so I’m familiar with both. It has been a while since I’ve seen the EGT in a steam gauge form. I just want to make sure I’m reading it correctly in flight.
It says 25°F/DIV. Does this mean the large tick marks are increments of 100°, and the smaller ones are 25°? If so, how does it show ≈1400°? Because there aren’t enough tick marks for that temp. Or does it only kick in and start moving the needle at 1000°?
I’ve been looking through the POH and haven’t found anything regarding leaning for cruise, but my experience has usually been 100° rich of peak for best power. So I’m guessing if I lean that way, I would enrich the mixture 4 tick marks?
redditburner_5000@reddit
This is one of the most useless gauges in aviation.
Depending on where the probe resides, it tells you the EGT from a single cylinder -or- the EGT from two or three cylinders.
The information is useless because...
...in the case of reading a single cylinder, you only know what that cylinder is doing. The rest could be waaaay off or exactly the same. You have no idea.
...in the case of reading two or mor cylinders, you don't really know what any cylinder is doing.
In both cases, you only have a rough approximation of where your peak EGT is so can never really lean properly.
A multi-probe RGT, CHT, and FF should be a standard item in a privately owned plane. Especially one with a 400/500 series six-cylinder engine.
Cool-Acanthaceae8968@reddit
As a former aircraft mechanic I have to disagree.
As a pilot I ran thousands of trouble free hours on TCM IO-360, O-470, IO-470, and IO-520 as well as Lycoming IO-360 and IO-540 with single probe setups. Turns out that at the reduce power settings you cruise at, the mixture simply doesn’t matter.
I loved private pilots who had multi probe setups though. Usually good for several hours of labour troubleshooting and replacing bad probes… and then at customer insistence doing open heart surgery and yanking jugs because one or two probes started doing something different (could be for any number of reasons) and they got too nervous.
Even though the main cause of engine failure is dry tanks—usually from a pilot who is too distracted by engine analyzers and nextrad and iPad and 5 minute radio calls doing a verbal lateral traffic resolution advisory from a plane that’s 20 miles away.
redditburner_5000@reddit
Me too. But a multi probe is a game changer if you know how to use it. And they're cheap.
Below about 65%. I don't know many 320/360 powered planes that run that low though.
wingedRatite@reddit
no, that's not true. engine power output is monitored by EGT. reciprocating aircraft are flown by EGT. it's the only thing specifically noted on power charts, and they all align to it.
https://i.redd.it/z0fyifq2unde1.png
redditburner_5000@reddit
Okay
UltimateAv8or@reddit (OP)
I definitely understand your point, however I wouldn’t go as far as to say it’s useless. For example, the SR20s have temp probes in each cylinder. Plus we know that they aren’t going to be the same temp. It’s to help you know the best fuel mixture for a particular situation. Is it necessary? No. Is it helpful to a more precise level? Absolutely.
redditburner_5000@reddit
It's helpful to know that 50° lean on cyl4 is 25° rich on cyl2at a given setting. When you lean, you're looking for all cyls to be in a safe zone. A single probe can't do that.
jaylw314@reddit
Not as useful for carbureted motors, since you can't really do anything about those differences in fuel mixture anyways.
redditburner_5000@reddit
That's true, and if the mouse line is carbureted, then everything I said is not helpful.
flyingron@reddit
Absolute value of EGT is largely meaningless because it varies substanially based on where the probe sites in the stack. The EGT is used to find where things peak dn then you can enriched 50 degrees or so.
gimp2x@reddit
50deg ROP is not where you want to be
Head_Visit849@reddit
Why not?
gimp2x@reddit
Take the advanced pilot seminar on engine management, the cylinder pressures and heats at that close to ROP will lead to premature failure of components
Head_Visit849@reddit
75deg rich of peak better? I’m a cfi now but where I did my training we were taught 75deg rich of peak
PiperFM@reddit
75-100 rich is pretty safe
Cool-Acanthaceae8968@reddit
75 is fine. That’s how I ran my fleet over thousands of trouble free hours, engines on condition 500 past TBO, and no failures.
gimp2x@reddit
My last piston airplane I ran for 1500hrs trouble free, 150d ROP, or 75 LOP, but never in the middle of that range
Head_Visit849@reddit
Thx for the insight
UltimateAv8or@reddit (OP)
I’ve always been taught 100° rich of peak, that’s usually what the POH says.
gimp2x@reddit
I was turbo normalized, I’m sure diff engines have diff envelopes
DocDynasty@reddit
Very true that the absolute value of EGY has very little meaning. 50F rich of peak is smack in the middle of the danger zone at a lot of power settings for highest risk of engine damage in many engines. Savvy Aviation’s two webinars on leaning are must-watch content for a healthy engine.
flyingron@reddit
I have no clue what "many" engines you're talking about. Neither Lycoming nor Continental has a "danger zone" at 50 ROP.
DocDynasty@reddit
I strongly recommend you watch Mike Busch's (several) videos on this topic, but this one addresses the "50 degrees ROP" that's in a lot of old aircraft POH's.
https://www.youtube.com/watch?v=msYJxkHg0Co&t=182s
flyingron@reddit
If you're not running high power settings, Braly's red box, even when it was possibly existant, isn't a problem. Lycoming has subsequently debunked it (even though it originated with them). Continental states quite strongly, that if you're at the cruise settings, you can set the red knob anywhere from full rich to so lean that the engine is misfiring and you're not going to damage anything.
Cool-Acanthaceae8968@reddit
Yep. I believe it’s anything under 75% power.
Most engines don’t have multi probe EGTs and run carbs with massive differences in mixtures by the time they reach the cylinders. Things like exhaust valve burning is more likely from excessively rich mixtures causing valve sticking or leaky valves than running on peak.
UltimateAv8or@reddit (OP)
Yeah exactly. It’s mainly for aiding in leaning for fuel efficiency, and to make sure you don’t shock cool the engine.
Sailass@reddit
Mike B with Savvy did an excellent writeup on EGT and specifically touches on that style.
First page is where the meat of your question is
Cool-Acanthaceae8968@reddit
Mike Busch is the Bob Hoover of aviation.
UltimateAv8or@reddit (OP)
Awesome I’ll be sure to check it out. Thanks!
ShieldPilot@reddit
Remove it. Install a JPI with CHT and EGT probes for each cylinder. Take the Advanced Pilot online class.
MastuhWaffles@reddit
step 1
stare at it
step 2
dont use it
Tough-Choice@reddit
You are correct, the large tick marks are 100 degrees. The small ones are 25. The bottom of the scale is, yes, something around 1100 or more. When using an EGT gauge, the specific absolute value is not important, but rather you’re just looking at the EGT relative to peak EGT.
bhalter80@reddit
In addition you set it with a small screwdriver so that the * likes up with the pointer at peak egt at cruise. This will change with the seasons so it's not absolute which is why there are no absolute markings on the instrument face mm
It's the ultimate TLAR instrument
Full_Wind_1966@reddit
You'll love the sundowner. Kinda hard to land at first for me but it was primary training so I might have been the problem, not the plane
UltimateAv8or@reddit (OP)
That’s good to know! Funny enough, I actually have never heard of the sundowner before until recently. I find it interesting that it’s newer than the bonanza, yet the bonanza is much more popular. If I’m not mistaken, it’s Beechcraft’s answer to the Piper Cherokee (which I did my PPL in). Same engine (180HP), but bigger body with more room in the back. Definitely going to be a family plane!
Full_Wind_1966@reddit
Yep and with the 60 gallons, you'll be able to go pretty far with it too. I miss that plane
poisonandtheremedy@reddit
I Googled "Beechcraft Sundowner POH" and got this link. I then CTRL + F "EGT" and got to page 4-10 "How to Lean Using EGT Gauge" https://airhawks.org/wp-content/uploads/2023/06/Sundowner-C23-POH-1.pdf
I then Googled "Asterisk on EGT gauge" and the very first link was a guy with an old Mooney asking what the (*) was for on the EGT gauge. Answer was in that thread. You calibrate the gauge for peak EGT at the asterisk and it gives you an easy reference point to lean accordingly based on POH procedure.
The gauge itself tells you each tick mark is 25 degree increments.
Here's the Alcor website selling that style gauge and you can see in the description that with a 'special screwdriver' you adjust the gauge in flight to set peak EGT at the asterisk for easy future reference: https://alcoraero.com/product/indicator-2-1-4-egt/ and also see the install manual with "In-Flight Calibration" - https://alcoraero.com/wp-content/uploads/2021/05/EGTCHT-Idicator-Installation-Rev.I.pdf
There ya go :) About 4 minutes of Google-Fu.
UltimateAv8or@reddit (OP)
Thanks, I appreciate it! Yeah I was browsing through the POH that was in the aircraft itself, and I didn’t see anything in there. Maybe there was a separate one I didn’t see. If not I’ll definitely use this one from now on!
ThisZucchini1562@reddit
This gauge really doesn’t tell you the “actual” EGT, you just keep watching it until it peaks( stops increasing) you won’t know what that temp actually is. Then you should be able to move a bug to mark that spot and then you can enrichen the mixture to cool 125 degrees and that will give you your best power. It’s easy to use and in my opinion all you really need on a simple engine set up that you have on your new beech.
UltimateAv8or@reddit (OP)
Gotcha. Yeah I’ve gotten so used to the G1000 where it just tells you the exact temp, then you just go 100 degrees rich, and bobs your uncle!
FossilFuelBurner@reddit
How do you get 1400 out of 20 increments of 25 degrees?
Rockboy286@reddit
That’s his question, yea
FossilFuelBurner@reddit
Right, so I’m asking for the math that shows 25x20=1400
In case you haven’t figured it out yet, like OP. It doesn’t.
OP is overthinking this, you don’t appear to be thinking at all.
Rockboy286@reddit
“If so, how does it show ~1400F? Because there aren’t enough tick marks for that temp.”
OP seems to have figured out that it doesn’t reach 1400F well before he made this post, otherwise he wouldn’t have made it. His question is if the scale starts at 1000F in order to allow the gauge to show up to 1400F.
UltimateAv8or@reddit (OP)
I originally was wondering this, but the needle won’t start moving until around 1000°, give or take. Since the EGT’s will be above that for the time they’re running, it wouldn’t make sense to have temp markings below 1000°.
Lowlypaidintern@reddit
Apart from others said, the info may be in your engine owners manual. For my aircraft the engine (io-540) it says to run it at peak. The little asterisk. But like others say that is just a best guess because there's a lot of information missing.
PilotGuy85@reddit
The gauge is relative to where you set it with the screw at the bottom. It’s not showing you an actual temperature (that you can know, at least).
For it to be accurate, you need to get it to peak and then adjust it so the peak occurs on the little star. Then you can measure how many degrees rich or lean of peak you are.
MEINSHNAKE@reddit
Don’t worry about it, leaning is for losers. Throw a PT6 in that summofabitch.
QuinnKnivesDotCom@reddit
I Googled "Beechcraft Sundowner POH" and got this link. I then CTRL + F "EGT" and got to page 4-10 "How to Lean Using EGT Gauge" https://airhawks.org/wp-content/uploads/2023/06/Sundowner-C23-POH-1.pdf
I then Googled "Asterick on EGT gauge" and the very first link was a guy with an old Mooney asking what the (*) was for on the EGT gauge. Answer was in that thread. You calibrate the gauge for peak EGT at the asterisk and it gives you an easy reference point to lean accordingly based on POH procedure.
The gauge itself tells you each tick mark is 25 degree increments.
There ya go :)
Fun_Market1780@reddit
This one is showing 0 steam.
time_adc@reddit
Reach cruise altitude.
Lean mixture, watch the EGT gauge.
Keep leaning. Find where the needle stops at hottest EGT - now you know peak EGT, and have achieved "best efficiency".
Enrichen 100F (four tick marks). Now you have "best power".
DocDynasty@reddit
Congrats on your new Mouse! I love my Sierra (Musketeer, but the gear folds). Strongly recommend you get a digital engine monitor at some point rather than that mystery gadget. I like my JPI EDM-900, though there are plenty others. If you haven’t yet, join the Beech Aero Club, which is the type club for the Musketeer/Sport/Sundowner/Sierra line. Best $10 you’ll spend for years of owner/mechanic knowledge.
UltimateAv8or@reddit (OP)
Will do, thanks for the suggestions! Yeah there’s definitely room on the panel for a digital one. Hell, maybe at some point we’ll get a GN750 or some other garmin that will fit.
rFlyingTower@reddit
This is a copy of the original post body for posterity:
My family is buying a ‘72 Beechcraft Sundowner with all steam gauges. I did my PPL in a Piper Cherokee with steam gauges, and my Instrument through CFII in an SR20 with full glass cockpit, so I’m familiar with both. It has been a while since I’ve seen the EGT in a steam gauge form. I just want to make sure I’m reading it correctly in flight.
It says 25°F/DIV. Does this mean the large tick marks are increments of 100°, and the smaller ones are 25°? If so, how does it show ≈1400°? Because there aren’t enough tick marks for that temp. Or does it only kick in and start moving the needle at 1000°?
I’ve been looking through the POH and haven’t found anything regarding leaning for cruise, but my experience has usually been 100° rich of peak for best power. So I’m guessing if I lean that way, I would enrich the mixture 4 tick marks?
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