Take off EGT's too high?

[Jeev]

I have a LYC IO-360 with about 250 hrs since factory overhaul in my Mooney 20J. Since the install I have been mostly flying with DA's above 3000 but after moving the plane to Florida I have been departing from sea level airports.  My EGT's on my #3 & #4 cylinders are around 1380 to 1420.  CHT's are all under 360 in the climb and peak fuel flow is about 18GPH.  Climb performance seems not so good until I get above 3000ft.  My question is with those EGT's am I running too lean?  Induction leak? timing?  I usually climb using a target EGT of around 1275- 1300 but at sea level with the dense air I can't get the EGT's below 1380 until I get around 3000 ft.

 

I have it scheduled to go into my mechanic to look for induction leaks next week.  Any insight would be appreciated.

 

Thank you,

Jeev

[jetdriven]

Ff looks good, and the EGT number depends on probe placement and timing. If it peaks at 1510-1525 degees, then 1380 is not too high for a 20 degree engine. 25 degree engines are a little lower, I like 1300 or so.

[Lood]

I have the same engine and my sea level EGT is 1230 deg. As a rule of thumb, I don't like to have the EGT's go higher than 1250 deg in the climb.

I fly ROP and EGT's of around 1360 deg is what I normally see in the cruise. But EGT's are apparently not all that important?

[Bob_Belville]

Jeev,

 

EGT is most useful as a relative number. The absolute value depends upon probe placement and... . Also, EGT probes are subject to fairly rapid deterioration, I think replacement @ 300 hours is recommended but after a quick conversation with Ms. Google I can't confirm that number. And I do not know whether reading high is a failure/fatigue mode.

 

Are you climbing @ max rpm/MAP? IAS?

 

I would love to see CHTs @ 360 in climb in FL. But cooling with my E cowl is not as good as your J.

[Bob_Belville]

Worth (re)reading:

 

www.gami.com/articles/egt_myths.pdf

[Bob - S50]

What are the EGT's on #1 and 2?  If they are significantly different, it may be dirty injectors.

 

Do they all peak around the same temperature?  For takeoff I'd like to see EGT's about 200 to 300 degrees below peak.

 

Bob

[N201MKTurbo]

I would have your mechanic check your timing.

[N601RX]

I think I have read somewhere that EGT temps decrease at a rate of about  100 deg per inch.  JPI recommends probe placement of between 2-4 inches from engine if possible, so even if you stay in the recommend mounting range there is the possibility of 200 deg difference based on distance alone.

[Alan Fox]

What type of monitor are you running???

[Jeev]

What type of monitor are you running???

JPI 700 with fuel flow on a IO-360A3B6

My reference to EGT's in the 1275 range was on my engine i exchanged with the "D" Mag and I know that was set at 25deg timing and my current engine with two separate mags is at 20deg. Maybe I'm just being paranoid since I want to take

Good care of the expensive new engine. I'm still going to have my timing, mags & plugs checked out though. Any other suggestions?

Thanks

[FloridaMan]

Runaway EGTs may be an indication of one plug not firing. I had that issue when I had a coil go on a mag and it was operating intermittently. 

[Jeev]

Took it to the A&P and he found the injectors on 3 & 4 leaking a little and those are the two cylinders that we're running the highest EGT's. These are also the same two that were over torqued by Lycoming during the factory overhaul. For reference A little blue staining on the injectors is normal but not the amount I had. Threads were repaired last annual but he said it looks like the sealer wasn't given time to cure. I checked my plugs with a LOP inflight mag check and they were ok, they are champion massives with 200 hrs on them I decided to just swap them out for Tempest fine wires. During the inflight mag check I noticed quite a difference between each mag in EGT's, according to Mike Busch's web site that could indicate a difference in timing between the two so I suspect timing may be an issue as well. He is cleaning all the injectors, installing new plugs, checking the timing and fixing the injector leaks on 3&4. I should have it back tomorrow and will report back. Thanks for all the responses, hopefully this thread helps others diagnose issues.

[jetdriven]

The uneven EGT rise on a mag check may not be a problem if the left cylinders act as a pair and the uneven rise is repeated on the right two cylinders when checking the other mag. slick mags fire the two onside top plugs and the offside bottom plugs. This explains the different EGT rise inflight. The EGT rise differs depending on whether the top or bottom plug fires during the check. The 2000 rpm peak EGT mag check is a more accurate indicator of split mag timing.

[philiplane]

EGT's above 1300 dF on takeoff are an indication of improper max power fuel flow. This is a fuel servo adjustment, not a mixture control adjustment. This is the one place where EGT is NOT a relative number. 1200-1275 is the normal full throttle full rich full RPM range for most piston engines, turbo or normally aspirated. Any lower and the engine will bog from over fueling, any higher and the engine will overheat.

 

18 GPH is a little too low for that engine. It should be closer to 18.5 to 19 at full throttle, full rpm, at sea level.

 

Ignition timing has very little effect on EGT in this engine unless it is very far off. In which case it wouldn't run very good at all. It will run OK between 15 and 25 degrees BTC, but it is optimized for 20 degrees BTC. 

[Jeev]

Thanks guys, learning some good stuff here. I'll talk to my mechanic about adjusting the fuel servo.

[jetdriven]

The fuel flow on the Bendix RSA-5 installed on the M20J is not adjustable.  The only adjustments are idle mixture and idle speed.

[Guest]

Adjustable but not field adjustable. It will have to go to a fuel injection repair shop to have this corrected.

Clarence

[N601RX]

Make sure the mixture cable is adjusted to fully open the mixture arm.

[Jeev]

Thanks for the info guys will do

[Jeev]

Ok problem fixed. I suspected plugs and/or timing based on this thread and my engine monitor data and my mechanic also thought the injectors were dirty. Well I didn't want to do each thing and wait a week to fix test fly and repeat ext so I installed Tempest fine wires, had the injectors cleaned and timing checked. The timing was pretty far advanced at 34 deg! Mags were re timed, new plugs and cleaned and re sealed injectors. Flew it today and the power and climb rate is Back to what it should be and all EGT's at sea level full power are between 1260 and 1290, starts right up and idles much more smooth.

[Bob_Belville]

Ok problem fixed. I suspected plugs and/or timing based on this thread and my engine monitor data and my mechanic also thought the injectors were dirty. Well I didn't want to do each thing and wait a week to fix test fly and repeat ext so I installed Tempest fine wires, had the injectors cleaned and timing checked. The timing was pretty far advanced at 34 deg! Mags were re timed, new plugs and cleaned and re sealed injectors. Flew it today and the power and climb rate is Back to what it should be and all EGT's at sea level full power are between 1260 and 1290, starts right up and idles much more smooth.

Amazingly that it would run at all! 

[Jeev]

Amazingly that it would run at all! 

 

Yeah it was not performing like I am use to.. We are baffled on what could cause the timing to change so much?  Both mags were tight and I noticed a progressive decline in performance and rise in full rich EGT over the past 10 hrs before I had it checked out.  Any ideas?

[Super Dave]

Yeah it was not performing like I am use to.. We are baffled on what could cause the timing to change so much? Both mags were tight and I noticed a progressive decline in performance and rise in full rich EGT over the past 10 hrs before I had it checked out. Any ideas?

Strange. Advanced timing will raise CHTs, but typically lowers EGTs. Must be some weird stuff going on when timing gets that far advanced.

I'm curious about the sealant your mechanic used on the injectors. What is it and where does it go?

[Jeev]

Strange. Advanced timing will raise CHTs, but typically lowers EGTs. Must be some weird stuff going on when timing gets that far advanced.

I'm curious about the sealant your mechanic used on the injectors. What is it and where does it go?

 

Yeah who knows but it runs much better now, CHT's are up probably due to making more (rated) power but under 380DF in a hot climb out.  Not sure what type of sealant he just mentioned it and I figured it was normal practice. He said it went on the threads.

[N601RX]

How old are the mags?  When timing changes that much quickly its possible something is wearing internally in the mags.