Killed LOP my engine?

[NicoN]

Recently 4 cylinders of our TSIo360GB were changed. One year before 2 cylinders were changed.All due to defective exhaust valves.  Now, at about 1000h all cylinders are exchanged.

2015 the compression test was perfect. I did not see  newer compression tests. Only something from 2016 were 2 cylinders had no compression and 4 were  close to limits.

In 2014 an EDM was installed, thereafter the owners started flying LOP. I have no EDM-data. ONly since end of 2017 and 2018.

Knwonig this history, LOP must be very harmful to the engine.

What went wrong ?

[KLRDMD]

8 minutes ago, NicoN said:

Recently 4 cylinders of our TSIo360GB were changed. One year before 2 cylinders were changed.All due to defective exhaust valves.  Now, at about 1000h all cylinders are exchanged. 2015 the compression test was perfect. I did not see  newer compression tests. Only something from 2016 were 2 cylinders had no compression and 4 were  close to limits. In 2014 an EDM was installed, thereafter the owners started flying LOP. I have no EDM-data. ONly since end of 2017 and 2018. Knwonig this history, LOP must be very harmful to the engine. What went wrong ?

Maybe it was the 1000 hours of ROP versus the 100 hours LOP that killed the engine. Known data on LOP versus ROP supports LOP being much kinder to the engine. Maybe it was the -GB engine that's known to run very hot and kill cylinders. Since it was -GB, when was the last overhaul ? I'm guessing decades ago. Defective exhaust values is a manufacturing issue, not LOP versus ROP issue.

[kmyfm20s]

I would question whether the owner was truly running the engine LOP properly and the quality of the cylinder rebuild. Just because you have an engine monitor and say you run LOP doesn’t mean you are. Turbo charged engines are even more technique sensitive.

[231LV]

28 minutes ago, NicoN said:

Recently 4 cylinders of our TSIo360GB were changed. One year before 2 cylinders were changed.All due to defective exhaust valves.  Now, at about 1000h all cylinders are exchanged.

2015 the compression test was perfect. I did not see  newer compression tests. Only something from 2016 were 2 cylinders had no compression and 4 were  close to limits.

In 2014 an EDM was installed, thereafter the owners started flying LOP. I have no EDM-data. ONly since end of 2017 and 2018.

Knwonig this history, LOP must be very harmful to the engine.

What went wrong ?

LOP yields LOWER cylinder heat temps. ROP yields higher temps. Heat kills engines....you choose which is better for the engine

[kortopates]

All very good responses above!

As a professional that has reviewed a great amount of data on turbo engines I can also add what I see owners doing incorrectly that leads to harmful operations. With a normally aspirated engine flying at altitude most people can't hurt their engine since the max WOT power at altitude will quickly drop off to where it doesn't at all matter where you leave the mixture. You may not get the most efficiency but you can't hurt the engine once you get up there to where you are operating at less than 60-65% power. But with turbo's where we can operate at 100% power up into the flight levels engine management becomes much more critical; especially for those operating their engines aggressively at 70 and above % power. Its much safer and better to learn how to operate LOP at say 60% power than say 75% power but not everyone does so. 

The most common issue I see is that pilot owner believes he's operating LOP when in actually perhaps a couple of cylinders are LOP while half or more are on the ROP side squarely in what we refer to as the Red box at too high of a power setting. This happens because the pilot is trying to use a proxy for determining LOP before doing their due diligence to verify every cylinder is at least far enough LOP for % power setting being used. Gami publishes excellent conservative guidance on both how much ROP or LOP your cylinders need to be based on percent power. This will have you flying richer, if ROP, than the poor guidance given in the POH and give you very safe LOP targets as well. Its what I recommend to all of our Savvy clients when they have questions or clearly are operating outside of the boundaries. The most common misused proxy with the turbo's is using TIT. TIT can be a useful proxy, but one can't rely on say, leaning till 15 Lean of peak TIT at 65% power and expect every cylinder is at least 15F LOP. Till you do your homework to actually do the data analysis and find out where each cylinder really is you may be surprised to learn that only 1 or 2 cylinders are 15 LOP and the rest are at peak or ROP.  You may learn that you need to be 30F or more lean of peak TIT to get all the cylinders to at least 15F LOP, which is why proper leaning for LOP is done from the last to peak or richest cylinder. Mike Busch is famous for recommending CHT as a proxy, but Mike knows his engine intimately well and operates his engine very conservatively in below 65% range where he doesn't need to be concerned about the red box is running LOP for max efficiency.  None of this is too say that the cause for the OP's cylinder issues are due to engine miss-management since all the above issues are just as applicable, but if the turbo engine isn't being managed properly its much easier to abuse turbo's than the NA engines.     

For completeness the recommended mixture settings from Gami are:

In addition to the CHT caveats I  also recommend not exceeding a TIT of 1600F even if your max TIT is 1750F to maximize turbo and exhaust component longevity. Your exhaust system will thank you for it.

[Mike A]

Everyone should watch these because there is a lot of bad information going around and items that dont necessarily apply to the -360s

 

 

Edited February 10, 2019 by Mike A

[carusoam]

Engine instrumentation has done a world of good of dispelling operations rumors....

Data from the engine monitor has also given insight on differences of how the pilot thought he was operating the engine...

In the case of multiple pilots flying the same plane it is good to know what everyone thinks is a good LOP operation...

At high altitudes where CHT cooling is challenging... turbos allow for some pretty high power setting... either ROP or LOP....

 

When it comes to cylinder usage... This is very often a challenge for turbo operators...

When it comes to exhaust valve issues... This is very often a cylinder manufacturer issue...

 

So was the engine really killed?

Or is it four cylinders that need exhaust valve work?

Or is it six cylinders that gave their lives providing for some really high speed aviation at altitude? 

 

PP thoughts for consideration... not a mechanic?

Best regards,

-a-

[gsxrpilot]

1. Get an engine monitor.
2. Learn how to read it.
3. Load the data into SavvyAnalysis and share the link here.
4. I fly behind a TSIO360MB... I fly LOP regularly everywhere between 12K ft and FL270 but never over 65% power. I'm over 1500 hours on the original cylinders.

[67 m20F chump]

CMI cylinders are crap.  Roll the dice and take your chances.  

[philiplane]

Running LOP will extend the life of the engine by reducing cylinder pressures, temperatures, help keep the exhaust valves & seats clean, and keep the oil clean.

[N201MKTurbo]

43 minutes ago, philiplane said:

Running LOP will extend the life of the engine by reducing cylinder pressures, temperatures, help keep the exhaust valves & seats clean, and keep the oil clean.

Yes, but the EGTs and TITs  run hotter. You have to keep them in check. I have melted my exhaust system.

[PT20J]

2 minutes ago, N201MKTurbo said:

Yes, but the EGTs and TITs  run hotter. You have to keep them in check. I have melted my exhaust system.

What melted at what EGT?

[N201MKTurbo]

Just now, PT20J said:

What melted at what EGT?

The exhaust pipe just upstream from the collector. 

Mind you I have a Farley unique system.

i was playing around with LOP climbs...... Don’t do it....

[jetdriven]

3 hours ago, 67 m20F chump said:

CMI cylinders are crap.  Roll the dice and take your chances.  

It still seems that 800 to 1000 hours is the life limit of a factory continental cylinder. The valves seats are not concentric to the valve stem, so the valves wobble in the guides and then they burn the valves and then that’s it

[xcrmckenna]

Sent from my iPhone using Tapatalk

[NicoN]

Okay, thank you. Of course I know not much about the previous owners. But it seems, that at least one or 2 are known as hot cowboys and may be they flew very fast with high power.

Hope with engine monitor and 3 disciplined pilots we can extend the life of the cylinders.

We typically fly 65% LOP or less

[67 m20F chump]

Invest in a dental camera so you can look at the exhaust valve at annual.  You can google exhaust valve pics to get an idea of what to look for.  

I don’t know what shops are available where you are but finding a place that can install new valve and guides is good to know and will cut your down time when it happens to you.  

Lots of information about this on beechtalk.   I had one overhauled cylinder put on my first Beechcraft.  On my 2nd airplane I just put on new cylinders when I had issues.  The 2nd plane I planned on running the engine past TBO and the difference between overhauled and new was $400 or so.  The money was paying to put them on.

If you know the history of your cylinders you may be better off overhauling them.  If you don’t know if they are first run I wouldn’t gamble on it.  New ones are not that much more.

Edited February 12, 2019 by 67 m20F chump

[Bolter]

4 hours ago, NicoN said:

Okay, thank you. Of course I know not much about the previous owners. But it seems, that at least one or 2 are known as hot cowboys and may be they flew very fast with high power.

Hope with engine monitor and 3 disciplined pilots we can extend the life of the cylinders.

We typically fly 65% LOP or less

The multiple users add variability.  It is good that you are all disciplined and cooperative.  

I think it is essential with 3 owner-operators that you are all agreed on a standard operating procedure (SOP) for the engine.  This means talking about it on the ground and sharing data and assembling a written SOP (a simple bullet list).  Then you should go flying together and share the experience of ROP or LOP at several conditions, like practice IFR.  2 pilots watch the engine monitor, the other flies the plane and radios.  You may need an explicit rule, such as from @kortopates 's list that starts with " when pilot workload permits", that states clearly to remain ROP until the pilot can commit the time to operate LOP with full attention to detail.  

tschuss, -dan

[thinwing]

On 2/9/2019 at 7:55 PM, jetdriven said:

It still seems that 800 to 1000 hours is the life limit of a factory continental cylinder. The valves seats are not concentric to the valve stem, so the valves wobble in the guides and then they burn the valves and then that’s it

Unfortunately that’s what I’ve gotten out of continental cylinders...