Engine trouble

[shdw]

I'm wondering if there's a correlation to running 25ROP - that seems very hot to me. Most of the reading I've done lately points to running further ROP like 100-150, or LOP (assuming IO-XXX with decent injectors and 6pt EGT/CHTs).
I used to have a ppt from an engine management seminar that talks about the Red Fin area, plotting intra-cylinder temps and pressures at various mixture settings. At a range around peak there is the highest probability of doing badness to the engine.
Which engine, what power settings were you running, etc?

Yes the hottest point in the cylinders occurs at about 50 ROP on the EGT, conclusion, the EGT is useless. Going based of the CHT's, especially if you have individual CHTs for each cylinder, is far more accurate. You are also correct in your 100 ROP or 20-50 LOP as better EGT selections than 25-50 ROP. Each of these better selections will yield cooler CHT temperatures.

As for running LOP, it is highly recommended as long as you have the equipment to monitor it. As for having the equipment for it to work, you need metered fuel injectors. Many people will say GAMI is required, this is, IMO, and from my reading, is not true. Most newer injectors are metered well enough to run LOP without an issue, the more important aspect is individual CHT's to ensure you are not running any cylinder too hot (or too rich in LOP ops).

The belief that GAMI is required I believe stems from GAMI injectors being the original founders and pushers of LOP operations about 15 years ago. When their injectors were introduced 15 years ago, the competitions injectors were not nearly as accurate as they are today. GAMI's are still, IMO, the best on the market for metered injectors, but they are not as far ahead of the competition as they once were.

Any mechanic Guru's want to verify this? I have done a couple days of research, but I have no actual experience in testing/operations of various injector types.

 

[roundout]

I'm wondering if there's a correlation to running 25ROP - that seems very hot to me. Most of the reading I've done lately points to running further ROP like 100-150, or LOP (assuming IO-XXX with decent injectors and 6pt EGT/CHTs).
I used to have a ppt from an engine management seminar that talks about the Red Fin area, plotting intra-cylinder temps and pressures at various mixture settings. At a range around peak there is the highest probability of doing badness to the engine.
Which engine, what power settings were you running, etc?

It may or not be related to the OP's problem, but this is absolutely correct. 25 ROP is way too hot and so is 50. 100 or more ROP or 50 or more LOP, PERIOD.

 

[CoffeeIcePapers]

GAMI's are still, IMO, the best on the market for metered injectors, but they are not as far ahead of the competition as they once were.

I have no actual experience in testing/operations of various injector types.

How do have an opinion about something you have never used?

:dunno:

 

[SteveC]

How do have an opinion about something you have never used?

:dunno:

Reading about others experiences, maybe.

 

[shdw]

How do have an opinion about something you have never used?

:dunno:

I wasn't referring to A/C testing, notice I said, "of various injectors." I have used the technique in the arrow and some newer 172 SPs. I just have not sat in a lab and put various testers into a controlled test environment to see how it worked. Nor did I have an aircraft equip with individual CHTs or know what type of injectors were installed.

My leaning technique in any aircraft has been, pull it till it shakes and push it in till it stops. In some aircraft this has been well LOP. I know they didn't have GAMI's but I am unsure what types of injectors they had. That being said and as steve said, my opinions on this topic are from hours of research and discussions. One of the discussions was on this forum about 6 months ago when I started researching this topic, asking about leaning procedures.

Here is some of that research, a graph to show CHT and EGT comparisons:

Take a look at the second two lines on the graph and note on the right side it points out that this section of the graph is for CHT. Now note the three vertical, left being ROP, center being peak, and right being LOP. You will see the CHTs on this graph are at their highest on the left line, 50 ROP.

 

[mshunter]

Take a look at the second two lines on the graph and note on the right side it points out that this section of the graph is for CHT. Now note the three vertical, left being ROP, center being peak, and right being LOP. You will see the CHTs on this graph are at their highest on the left line, 50 ROP.

Doooooooooooodddeeee! I am sooooooo gonna get there first!

Looser buys the beers! (I'll wait till your 21 if I have to):beer:

 

[patthepilot]

50 ROP is the worst for CHTs, and cylinder pressures. As to the originator of this topic-is the bonanza NA or turbo? does it have a carbuerator? What was the OAT? 25 ROP is also a bad place to be. I run all the planes I fly LOP, sometimes 25 sometimes 150 - i really just set it to a point that sounds right, and tinker from there.

As to the GAMIs, the whole point of GAMIs is to fine tune your EGTs, to have all 6 peak at a real tight fuel flow. Some of the newer TCM injectors we've seen have been much better than their old ones, but still no better than GAMIs, while other new injectors that are supposedly fine tuned, or way off. If you call about GAMIs, and John-Paul tells you to do the GAMI lean test, and you find real tight fuel flows for peaks - no need to get GAMIs, you've got really good injectors. But if not, then a new set of injectors, GAMIs or otherwise would be needed for running LOP well.

I used to have a NA 1961 Cessna 172, with carbuerator, that I could run LOP and everyone always asked-how do you do it?! without injectors! Pretty simple too, but I'll stop my soap boxing.

 

[Mike H]

Considering none of us have any idea what is wrong, I'm not gonna "hope" it doesn't blow out my exhaust in imc. The point was if it's gonna die, let it die, trying to restart probably won't work anyways and if it does, there is a chance it could blow out your exhaust and you just broke your engine that was gonna come back to life. If it the engine wasn't going to restart then there is no point. The point being is that there is no reason to try to restart, let it die and then try it. There is a small chance of this happening, but it's not worth it, what you would gain is very little and what you could lose is a lot.

Let the engine die? In IMC? On purpose?

That what you're suggesting?

Brilliant plan there, chief :hugerolleyes:

 

[shdw]

Let the engine die? In IMC? On purpose?

That what you're suggesting?

Brilliant plan there, chief :hugerolleyes:

I have to agree. What if it is running rough because parts are loose/bent/defective, letting it stop could seize up the engine. This obviously isn't likely, but neither is blowing out your exhaust and I could care less about a useless 2,000 dollar pipe if it saves me a trip to my grave. As long as your system is fuel injected the exhaust is not necessary, it'll be one loud ride though.


MS, I'm 25 so we are set. I have a full bar too, screw beer, hard liquor is so much better.

 

[Douglas]

There seems to be a lot of speculation on CHT and EGT in this thread.

POH?, it's that easy.
------

 

[shdw]

There seems to be a lot of speculation on CHT and EGT in this thread.

POH?, it's that easy.
------

That really depends on the aircraft. Newer aircraft, ok, many older models have POH's that are 40+ years old with engines and systems that are less than 10 years old. These aircraft are better operated by their engines operating handbook and some additional outside research. Remember, the fight for LOP ops only started about 15 years ago and with much disapproval. Today many are realizing they can improve economy and engine life with LOP operations, especially with the newer systems.

IMO, POH's are great for aircraft procedures most of the time but when it comes to specific system operations and optimizing that system, additional research can be invaluable. Want a for instance? Many POH's will note cruise charts that never go over squared but if you rip out the engines operating manual it will give you a chart for what spread is safe for continuous over squared operations, I trust the engines manual in that case.

 

[roundout]

There seems to be a lot of speculation on CHT and EGT in this thread.

POH?, it's that easy.
------

Fly the POH power settings and you'll be overhauling your Conti at 600 hours. Fly it the right way and it will have compressions in the 70s at 1500 hours.

 

[patthepilot]

exactly! We pulled some jugs off last week that have run LOP for 1600 hours and they were spotless inside. SPOTLESS. That's how TCM voids warranty claims-people send them in and if they are clean, they were run LOP and they are denied. If they're gunky and dirty like the underside of an airplane filled 6 quarts too much, then they were run "according to the POH" and warranty claim approved.

 

[minitour]

Many POH's will note cruise charts that never go over squared...

That's cuz when you run over squared puppies die. Oh teh noez!

-mini

 

[jikky54]

The OAT was 50 degrees, It's an analog EGT. You turn a switch to six different positions and read off the same EGT guage. We took out all the plugs and cleaned them and ran it up and got a really bad mag drop on the left mag. We took the left mag off and the mechanic said the leads were burnt up. He replaced the leads and we're supposed to reinstall the magneto tomorrow. I'll post if it works.

 

[Douglas]

IMO, POH's are great for aircraft procedures most of the time but when it comes to specific system operations and optimizing that system, additional research can be invaluable. Want a for instance? Many POH's will note cruise charts that never go over squared but if you rip out the engines operating manual it will give you a chart for what spread is safe for continuous over squared operations, I trust the engines manual in that case.

I agree with what you are saying about power settings, but what point does that make here?
Are you saying that Continental has a different leaning procedure?

 

[shdw]

I agree with what you are saying about power settings, but what point does that make here?
Are you saying that Continental has a different leaning procedure?

I wasn't because I am unsure. Though depending on the aircraft and the age of that aircrafts POH it wouldn't surprise me if we could find 10 different procedures for leaning the same engine from various POH's. I don't have a continental engine manual handy to check, does anyone? It would be interesting to hear what their leaning procedure is.


OP: Yup that mag definitely wouldn't help. Is it a 6 point EGT or CHT? Does anyone know the probe location for a single versus a multi probe EGT? Does it change, I never knew the probe location and wonder if it would change the accuracy of the system with regards to that chart I posted before.

 

[roundout]

exactly! We pulled some jugs off last week that have run LOP for 1600 hours and they were spotless inside. SPOTLESS. That's how TCM voids warranty claims-people send them in and if they are clean, they were run LOP and they are denied. If they're gunky and dirty like the underside of an airplane filled 6 quarts too much, then they were run "according to the POH" and warranty claim approved.

THat's funny, because TCM approve running Lean of Peak. So do the POHs of the airplanes into which (at least) the IO-550 variants are installed. Don't know about the 520s or 470s.

 

[patthepilot]

THat's funny, because TCM approve running Lean of Peak. So do the POHs of the airplanes into which (at least) the IO-550 variants are installed. Don't know about the 520s or 470s.

Where had TCM approved LOP? Between any number of POHs, you can find anything from run 50 ROP to the absolute lowest you can run is 25LOP, no more, otherwise the engine will explode. And those are between different airplanes that have the same engine.

 

[shdw]

25LOP, no more, otherwise the engine will explode.

:rotfl: Yes I am sure it will just explode and you will all die...EVERYONE WILL DIEEEE IF YOU GO 26 LOP!!!! Sorry I couldn't help myself but I almost wet my pants reading that.

Here, IO550 about half way through the video: http://www.gami.com/articles/frugalflyer.php

The richest cylinder was 50 LOP, the others further. The second aircraft also with an IO550 goes to 50 LOP as well. So, conclusion, you aren't going to die if you go more than 25 LOP, your engine might if you go much past 50.


Though I am not a fan of many articles posted on avweb and take them with a grain of salt. Unless, of course, I can prove it with various other sources, this article is right on par with my other research: http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning_198162-1.html


I cannot find an open source manual from TCM but here is an article for you: http://www.lancairtalk.com/?p=9 On the 6th paragraph, towards the bottom, "TCM has responded...providing tuned injectors and approving LOP operation of their engines."