EGT temperatures

DEWATSON · #1 09-07-2007, 10:23 AM

I have a Lycoming IO 360 A1A and have flown behind it for many hours. I decided that I wanted to know CHT and EGT temperatures since the engine is injected. I installed four posistion CHT and EGT guages and cranked the engine. After running at about 1200 rpm for several minutes the CHTs settled at about 300 degrees farenheit. The EGTs were questionable...hence my question. They settled at 850 degrees for #1 and #3 and about 1250 degrees for #2 and #4. The CHTs were very close at 300 degrees but quite a difference with the EGTs. The airplane was obviously not flying. What should the EGT temperatures be in this particular situation? I pulled the injectors out and checked for obstructions, but they were as clean as could be.

JonJay · #2 09-07-2007, 10:34 AM

Are the probes in the same position on each stack i.e. distance from the flange?

DEWATSON · #3 09-07-2007, 10:54 AM

The probes are all about 1.5 inches from the flange.

DEWATSON · #4 09-07-2007, 02:20 PM

What should the EGT be in flight with the mixture full rich and what should the temperature not exceed when leaned?

Don at Airflow · #5 09-07-2007, 04:23 PM

EGT is a relative reading and varies with lots of different parameters. Probe calibration, compression ratio, ignition timing, exhaust back pressure (that?s the big one), fuel air ratio, and the position of the probe in the pipe all affect the reading you see on the gauge. On normal Lycoming engines with standard compression ratio and mags timed per the manual the ?typical? EGT you see at take off power (2700 and 29?MAP) is around 1350-1450 degrees F. Your reading may vary due to the above. This doesn?t matter, what does is the change in EGT from full rich to peak EGT. This should be around 200 degrees. Check it at 3000 ft, 2500RPM / 25? MAP. At the point at which the EGT peaks is a specific fuel air ratio. If you are 200 degrees less than this at full rich the fuel air ratio is correct for your engine. The actual temperature you read is just a number. DON?T TUNE INJECTOR NOZZLES BASED ON EGT TEMPERATURE.

Hope this helps.

Don

Bob Martin · #6 09-07-2007, 05:02 PM

David,
My JPI engine monitor said 2 to 4 inches away from the exhaust head.
Closer will give higher temps and lower probe life and farther away will give the opposite. Your install seems too close, what brand did you install and what did they recommend about probe placement?

For good general info on temperatures, check out:
AVWeb Pelicans Perch John Deakin's articles.
Look for #64 "Where Should I run my Engine".
Good reading.......his articles helped me finally cool my engine down on takeoff.
Good Luck.

DEWATSON · #7 09-10-2007, 07:17 AM

Thanks for the information fellows.........I did some testing over the weekend and found that 1250 to 1300 degrees is where all four cylinders stabilized running the engine on the ground for four minutes at 1800 rpm. I did some high speed taxi tests too. I was happy just to see that all four cylinders were within 50 degrees. CHTs never got over 300 degrees. I'll know more when I finally get to fly.

Also, the probes are two inches from the flange. Again...thanks so much for the replies.