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What CHT's and EGT's is normal Range

design4p

Active Member
Hi,

I'm in the process of test flying and my CHT's are in the region of 155 degrees Celsius (310 degrees Fahrenheit) and my EGT's in the region of 680 degrees Celsius (1200 degrees Fahrenheit).

I have the standard RV14A setup Lycoming 390 engine with all Garmin avionics, G3X, Garmin Sensors etc.

It would be good to know the expected range of temperatures as these appear quite low.

Regards John
 
Sorry

Not enough data to say, but generally those numbers are great. You owners manual from lycoming has your CHT params. EGT, used to troubleshoot and in leaning, so really no wrong # ..... depends on many factors. Enjoy your 14.
 
The CHTs are fine for cruise. Lower airspeed tells the tale in climb, resulting in higher CHT and oil temperature.

There is no "correct" EGT number. EGT on a non-turbo Lycoming is a reference, not a warning. It indicates mixture via the relationship between peak EGT and the EGT indicated under the given conditions. Best power is found about 65C (150F) on the rich side of peak EGT. Lycoming recommended economy cruise is peak EGT, a setting which offers fuel savings with limited or no airspeed loss. For maximum economy without regard for the airspeed loss, you may go as far as you wish on the lean side of peak, as long as it remains smooth.

Your cruise CHT is so low I'd recommend you try leaning to peak EGT at full throttle above 9500 ft.
 
SNIP

Your cruise CHT is so low I'd recommend you try leaning to peak EGT at full throttle above 9500 ft.

+1. Your EGTs suggest you are flying around at full rich. Not good for your wallet or your engine (plug fouling, stuck exhaust valve, etc.).

If you CHTs remain that low at leaner mixtures it suggests you have excess cooling - so excess engine cooling air drag.

Mike Busch has a video discussing the “Sweet Spot” for CHTs, above 350 but below 400 (Lycoming engines). He explains why cooler CHTs is not always better.

https://www.eaa.org/Videos/Webinars/Engines-and-Firewall-Forward/6178810783001

Carl
 
+1. Your EGTs suggest you are flying around at full rich. Not good for your wallet or your engine (plug fouling, stuck exhaust valve, etc.).

If you CHTs remain that low at leaner mixtures it suggests you have excess cooling - so excess engine cooling air drag.

Mike Busch has a video discussing the “Sweet Spot” for CHTs, above 350 but below 400 (Lycoming engines). He explains why cooler CHTs is not always better.

https://www.eaa.org/Videos/Webinars/Engines-and-Firewall-Forward/6178810783001

Carl

Also on YouTube here if you don't have a membership. Although I am betting you do. :) I highly recommend a membership if you don't.
 
+1. Your EGTs suggest you are flying around at full rich. Not good for your wallet or your engine (plug fouling, stuck exhaust valve, etc.).

Not correct as far as I understand. Absolute values mean almost nothing for EGT. They are highly dependent upon probe placement, for example. It could just be that the OP’s probes are a ways down the exhaust. As Dan mentions above, they are important really only in relative terms to where a particular cylinder’s EGT peaks.
 
Interesting video with Mike Busch, thanks.
My RV 14 is at 70 hrs and in cruise depending on OAT is often around 300 CHT so quite low relative to Mikes’ 350 to 400.
What have others done to increase CHT’s?
 
Interesting video with Mike Busch, thanks.
My RV 14 is at 70 hrs and in cruise depending on OAT is often around 300 CHT so quite low relative to Mikes’ 350 to 400.
What have others done to increase CHT’s?

What kind of ignition do you have? Put an EI on there that advances the timing and it will jump up for sure!
 
Oil Temp

Most of the aviation oil companies have stated oil temp need to be at least 180º for an hour to boil off moisture in the oil. Many thinking low oil temps are beneficial, when 180º is a floor.
 
+1. Your EGTs suggest you are flying around at full rich. Not good for your wallet or your engine (plug fouling, stuck exhaust valve, etc.).

If you CHTs remain that low at leaner mixtures it suggests you have excess cooling - so excess engine cooling air drag.

Mike Busch has a video discussing the “Sweet Spot” for CHTs, above 350 but below 400 (Lycoming engines). He explains why cooler CHTs is not always better.

https://www.eaa.org/Videos/Webinars/Engines-and-Firewall-Forward/6178810783001

Carl

Mikes logic is that sticking valves are caused by lead deposits on the valve stem. This flies completely in the face of the standard remediation method for sticking valves, which is too remove deposits from the valve guide. If Mike were correct about deposits on the stem reducing the clearance, cleaning out the valve guides would not resolve the sticking valve problem and would instead require that the valve stem be cleaned of deposit build up. Given that the standard fix, which seems to work universally, is to remove deposits from the guides without touching the valve stem, It seems extremely unlikely that he is correct in his hypothesis. He covers a lot of correct science about lead deposits, but I believe he misplaces it in identifying the root cause of sticking valves, which a long history has been shown to be due to build up in the guides.

Lycoming further supports this logic, as they recommend cleaning out the guides, NOT cleaning off the valve stem, if the stem to guide clearance is reduced below specs. If this were an ineffective approach to the problem and instead required valve stem cleaning, I am confident that we would have figured it out by now.

Larry
 
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