EGT and LOP

[Browncbr1]

i have what seems to be a good, smooth running io-360. I recently had an JPI 830 installed and just getting to learn it. Today was the first time I tried the lean find function for LOP. I was really surprised to see the huge difference between hottest and coolest egt. But, it was still running smooth.

I thought maybe something was wrong because of the big difference, so I went back to rich of peak until all EGTs were around 1350 ROP. Next time I preflight, I'll take the cheeks off to make sure the egt probes are all the same distance from the flange. But, meanwhile, how big of a difference is normal? I don't have gamijectors, but the motor seems to run smooth no matter the mixture. I just loses power when going too lean. I was told not to run egt higher than 1400 in cruise or I could burn up exhaust valves. Any advice ?

[Cruiser]

Hmmm, 1400 max in cruise? Not a lot of options with that limit.  What have you been running EGT in the past?

[Browncbr1]

The original gauge was all that was in there before the JPI. It doesn't quantify temps. I'm not sure about the 1400, as this is just what another pilot said. In the past, I had leaned the original gauge to 25 or so LOP. I tried doing the same thing with the JPI, but by the time the richest cylinder peaked, the difference was really large. Maybe 150 or more cooler.. But still running smooth.

[Marauder]

The original gauge was all that was in there before the JPI. It doesn't quantify temps. I'm not sure about the 1400, as this is just what another pilot said. In the past, I had leaned the original gauge to 25 or so LOP. I tried doing the same thing with the JPI, but by the time the richest cylinder peaked, the difference was really large. Maybe 150 or more cooler.. But still running smooth.

Have you run the Gami test?

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[Browncbr1]

Have you run the Gami test?

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No, but That was on my list to research and figure out tomorrow, so I could do that next time I fly.

[ArtVandelay]

Forget the 1400 limit, here is what mine look like:

I have GAMI injectors FWIW

[Shadrach]

It's not uncommon for folks to get hung up on EGT numbers, unfortunately its the wrong way to look at leaning. I'm curious to know who told you not to run over 1400? There is nothing in your POH nor is there any physical or scientific reason to follow that advice.

Use the search function and read up. There is plenty of info available on leaning

I'll tell you this to get you thinking the right way. EGT raw numbers don't really matter when leaning in cruise; how far apart they peak is what matters.

Example:

Let's say you lean through peak at 5000ft on all cylinders and this is what you get:

Cyl#1 peaks at 1356 @10.3gph

Cyl#2 peaks at 1430 @10.2gph

Cyl#3 peaks at 1447 @10.2gph

Cyl#4 peaks at 1462 @10.1gph

The EGT numbers are separated by 106 degrees (which means nada), but they peak withing .2 GPM of one another (this is important). That's a well conforming engine. Each cylinder is producing close to the same amount of power as the engine is leaned through the spectrum of useable fuel air ratios.

[carusoam]

Ross gives the best description on what is going on in an engine...

TJ demonstrates the best FF I've seen in a while! (How LOP was that 7.8gph)

Best regards,

-a-

[MooneyBob]

.

[NotarPilot]

EGT doesn't mean much. Like others have said, ignore any 1400F limit. The thing you need to be worried about is CHTs. Keep the CHTs below 380 and you should be good. Treat 380-400 as a yellow area of operation and 400 as your redline (Yes, this is well below the factory 480F) limit but this will help with engine longevity.

Deakins and Busch have written some great articles about this and Mike Busch had some excellent webinars on the subjects of Running LOP, The EGT Myth, All About Cylinders, and Engine Monitors, which are all available on the EAA website. All very good webinars to listen to if you're serious about engine management and longevity. Good luck and PM me if you have any questions.

Steve

[Shadrach]

Teejay gets special points for having "Miami Vice Wiki" saved in his favorites bar!

[ArtVandelay]

Ross gives the best description on what is going on in an engine...

TJ demonstrates the best FF I've seen in a while! (How LOP was that 7.8gph)

Best regards,

-a-

It was FT at 9500', about 30 deg LOP, you'll notice I leaned twice, the 2nd time was an hour into the flight, as I was leaning after leveling off ATC called and asked about my routing and interrupted me and I forgot to go back and finish

Despite running LOP, I did a in flight mag check just last week and this is what I saw:

I have about 115 hrs on the plugs since annual, had to have them cleaned and regapped (notice the EGT drop on #3), I don't see it on runup, Busch is right, in flight mag checks is a better stress of your ignition system.

[Browncbr1]

Thanks for the help guys. I'm going to reread the Busch articles on avweb. It's been too long. It seems that I recall my FF difference being quite large.

[pinerunner]

When I first got my UBG-16 I got a little hung up over EGT differences. Looking at data like in this post made me feel better about the numbers I was seeing. Also reading Deakins and Busch as others have mentioned helped me understand better.  Don't worry too much about differences in exhaust gas temperature. If you could see what the temperatures were at the beginning of the power stroke, right over your nice aluminum piston, you'd really freak. But that's how its made to work; it just doesn't get enough time to dump all that heat into the piston and melt a hole in the top. When you think about it you should worry if the EGT goes too low. Where did the extra heat go?

 

The Busch vids show some great diagnostic tricks to help you get the most out of your engine monitor. 

[Browncbr1]

do you have a link to the mike busch videos?  I couldn't find them on youtube...

 

 

I refreshed myself on all the busch articles and am now clear that i need to find my gami spread.. and keep an just keep my eye on CHT  

[DonMuncy]

google savvy aviation webinar

[Browncbr1]

thanks guys... i've familiarized myself and will try to report back my gami spread soon

[Browncbr1]

i pulled data from my edm... one thing i noticed is that full rich, full power, I'm just getting 16.5FF, but I haven't set the K factor yet.  I read the programming manual and it says to check the number on the transducer...   Even though this is the case, I may be a bit on the low side of FF because my EGTs are getting into the mid 1300's on some occasions... I noted they should be between 1200-1300... and these have been really hot days, which I would think would reduce EGTs as there is more fuel per parts oxygen...  Normally, all EGTs are around 1300 on take off, but saw a few take offs with higher EGT... Perhaps I didn't push the mixture as far in as it could have gone because I saw on those slightly higher EGT takeoffs, the FF was recorded as 16.3 ...  Do you guys agree that my FF may need to be cranked up a little bit?

[KSMooniac]

If your K factor is correct, then yes, your FF is low if taking off anywhere near SL.  I typically get 18.0-18.5 in my J.

 

You should read everything Deakin has published on Avweb under the Pelican's Perch column.  I believe the articles are still there...at least read all of this engine management columns, but all of them are entertaining and educational. 

 

The ultimate place to learn is www.advancedpilot.com, though.  Yes, you'll have to pay, but it is far-and-away the best method to learn this material efficiently.  They've done all of the hard work of tying decades of research and experience into a professional format that makes it easy to learn.  You won't be sorry taking their course, either electronically or live in person.  I learned more in the weekend seminar than I did in many semester-long engineering courses FWIW.

[Browncbr1]

thanks for the feedback   We are about 1000msl here, but DA has been around 3000 lately... 

[Shadrach]

That FF is still a bit on the low side for that DA, but probably not too far off.

 

My EGTs are all in the mid to high 1100s at full rich.

[DonMuncy]

I don't claim any real expertise here, but it is my understanding that numbers, as applied to EGTs, are meaningless. The early EGT gauges had no numbers on them. The relative EGTs have value.

With a particular engine, exhaust system and probe placements, I suspect you could develop some history to compare EGT readings to prior experience, but to say someone else should have and EGT of X, is probably not valid.

[PTK]

The EGT absolute values don't mean much. They're good for troubleshooting and that's it.

Don't look at EGT too much because you'll get depressed.

A large portion of the energy in your expensive avgas goes our the exhaust heating the air!

Concentrate on CHT. That's what you need to control for engine longevity.

[carusoam]

Some logic on why...

EGTs cool off rapidly as the gasses expand going down the exhaust pipes.

At best, for comparability it would require all EGT instruments to be located in exact positions.

Best regards,

-a-

[Shadrach]

I was referring to his FF being a bit on the low side (now clarified)  EGT values when leaning are meaningless. However, it's all we have when full rich, it's one marker of whether the engine is getting enough fuel.  The Bendix RSA fuel system is not adjustable, so it's likely his instrument needs to be calibrated.