Lycoming 1650 TIT upper limit recommendation

[Rick Junkin]

Can anyone point me to the Lycoming recommendation to limit TIT to 1650 rather than the published redline of 1750?

I remember reading this in a Lycoming publication, I think, but I can't find it again. I've searched here and also used an open Google search with no luck. Am I remembering this wrong? 

Thanks for any help.

Cheers,
Junkman

EDIT: 

Found it! It's in the TIO-540 Series Parallel Valve Cylinder Heads Operator’s Manual, Lycoming Part Number: 60297-23P. On page 3-4 it states "On turbocharged engines never exceed 1650°F turbine inlet temperature (TIT)." It continues on page 3-5 with instructions for leaning with reference to TIT that include the same 1650 upper limit.

https://www.lycoming.com/sites/default/files/attachments/60297-23P.pdf

[FoxMike]

My recollection is the same as yours but I have no reference.  The 1750df redline was reduced to 1650df and notice may have been through Mooney many years ago.  I cruise with the TIT at 1600df. Not having to repair the cracks in exhaust system is worth the extra fuel burned.

 

[Rick Junkin]

Found it! It's in the TIO-540 Series Parallel Valve Cylinder Heads Operator’s Manual, Lycoming Part Number: 60297-23P. On page 3-4 it states "On turbocharged engines never exceed 1650°F turbine inlet temperature (TIT)." It continues on page 3-5 with instructions for leaning with reference to TIT that include the same 1650 upper limit.

https://www.lycoming.com/sites/default/files/attachments/60297-23P.pdf

EDIT: Ok, I continued reading. On page 3-9, just to confuse the issue, the footnote for TIT for the AF1A/AF1B states a maximum of 1750 just like the POH. Every other parallel valve TIO-540 has a 1650 TIT maximum. I'll stick to 1585-1610 LOP.

[LANCECASPER]

The Lycoming rep back in the mid to late 90's was at a MAPA convention and spoke at a M20M owners session. He mentioned that as soon as cylinders started coming back to them in the early TLS days ('90-'92) they told Mooney to issue a Service Bulletin not to go above 1650 TIT. (They actually would have liked Mooney to go back to the FAA and revise the POH to show 1650.) Since the POH wasn't revised Lycoming still can't put anything in print re: the M20M that contradicts the POH

Mooney's ownership in the 90's (until '97) was the French consortium and they wanted the long range of the TLS to be stay where it was in all of the original marketing materials, which required the high TIT and lower fuel flow. Over this disagreement in the early 90's between Jacques Esculier (Mooney CEO at the time) and Lycoming, he swore never to put another Lycoming in a new Mooney model.

Those words have proven true since then, since all later models (Ovation, Encore, Eagle, Acclaim) have Continentals.

[kortopates]

Although it really wasn’t up to Jacques after he was gone. The fact is that the Continental 550’s are amazingly more efficient than the Lycoming that can only barely run LOP, with few exceptions. While the 550’s do LOP incredibly well. Not that i would, but pilots find they can run 100F LOP smoothly! That supports excellent range and endurance and is why almost all the others manufacturers use variants of the Continental 550’s for some time now. The notable exception is the Lyc TIO-540 350 HP used in the Malibu which is a good LOP performer but in a different class.


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[Rick Junkin]

43 minutes ago, kortopates said:

The fact is that the Continental 550’s are amazingly more efficient than the Lycoming that can only barely run LOP, with few exceptions.

It’s far from scientific, but from this poll it appears 50% of the responding Bravo owners are able to run LOP effectively at least some of the time. Could it be a result of more people tuning and working with their engine systems to make it work?

 

[kortopates]

Only what i would refer to as light LOP with a few notable exceptions.


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[Jetpilot86]

On 10/17/2024 at 1:39 PM, Rick Junkin said:

Can anyone point me to the Lycoming recommendation to limit TIT to 1650 rather than the published redline of 1750?

I remember reading this in a Lycoming publication, I think, but I can't find it again. I've searched here and also used an open Google search with no luck. Am I remembering this wrong? 

Thanks for any help.

Cheers,
Junkman

EDIT: 

Found it! It's in the TIO-540 Series Parallel Valve Cylinder Heads Operator’s Manual, Lycoming Part Number: 60297-23P. On page 3-4 it states "On turbocharged engines never exceed 1650°F turbine inlet temperature (TIT)." It continues on page 3-5 with instructions for leaning with reference to TIT that include the same 1650 upper limit.

https://www.lycoming.com/sites/default/files/attachments/60297-23P.pdf

I have a pdf of the Bulletin @LANCECASPER is talking about, somewhere.  It recommends, 1650 TIT limit, 65% power for maximum cruise, and 400 max CHT to get a longer TBO.  When I dig it up I'll post it here.

My common power setting is 30"/2200 running 10-30 LoP, depending on the cylinder, near the edge of the red box at that power setting.  I've got 2 CHT's flirting with 380 at that setting and a TIT of 1500-1525.  My Factory OH'd engine has around 130 SFOH on it, it came with a new/OH Turbo, and has the OEM Injectors on it, so I'm probably cheating....  I've not tried to see how lean I can run her, because I'm trying to see how fast I can go on the lean side and staying in the 380/1550 range, but I'm sure I could get in the 50 LoP range without much trouble at that power setting.

Edit:  Here it is: Leaning Lycoming Engines Doesn't mention the TIO-540 specifically, but does cover turbo's.

"Leaning the Turbocharge Lycoming Power Plant

• The cylinder head temperature (CHT) and turbine inlet temperature (TIT) gauges are required instruments for leaning with turbocharging by Lycoming. EGT probes on individual cylinders should not be used for leaning.
• During manual leaning, the maximum allowable TIT for a particular engine must not be exceeded. Check the POH/AFM or the Lycoming Operator’s Manual to determine these temperatures and fuel-flow limits.
• Maintaining engine temperature limits may require adjustments to fuel flow, cowl flaps or airspeed for cooling.
• All normal takeoffs, with turbocharged power plants, must be at full-rich mixture regardless of airport elevation.
• If manual leaning of the mixture is permitted at takeoff, climb power or high-performance cruise, it will be specified in the POH/ AFM and will list required ranges for fuel flow, power settings and temperature limitations.
• Leaning to best economy mixture:
  1. Set manifold pressure and RPM for the desired cruise power setting per the aircraft POH/AFM.
  2. Lean slowly in small steps, while monitoring instrumentation, to peak TIT or maximum allowable TIT, whichever occurs first.
• Leaning to best power mixture (before leaning to best power mixture, it is necessary to establish a TIT reference poin):
  1. Set manifold pressure and RPM for the highest cruise power setting where leaning to best economy is permitted per the aircraft POH/AFM.
  2. Lean slowly in small steps until peak TIT or maximum allowable TIT is reached. Record peak TIT as a reference point.
  3. Deduct 125˚ F. from this reference, and thus establish the TIT temperature for best power-mixture operation.
  4. Return the mixture to full-rich, and adjust manifold pressure and RPM for the desired cruise conditions.
  5. Lean mixture to the TIT temperature for best power/mixture operation established in step 3.
• During normal operation, maintain the following limits:
  • Engine power setting – rating listed in the Lycoming Operator’s Manual.
  • Cylinder head temperature – limit listed in the Lycoming Operator’s Manual.
  • Oil temperature – limit listed in the Lycoming Operator’s Manual.
  • Turbine inlet temperature – limit listed in the Lycoming Operator’s Manual.
• For maximum service life, maintain the following recommended limits for continuous operation:
  • Engine power setting – 65% of rated or less.
  • Cylinder head temperatures – 400˚ F. or below. c. Oil temperature – 165˚ F. – 220˚ F.
  • Turbine inlet temperature – maintain 100˚ F. on rich side of maximum allowable."

[Rick Junkin]

15 minutes ago, Jetpilot86 said:

My common power setting is 30"/2200 running 10-30 LoP, depending on the cylinder, near the edge of the red box at that power setting.  I've got 2 CHT's flirting with 380 at that setting and a TIT of 1500-1525.

My engine runs very differently from yours. Every time I see your TIT numbers I think your probe is reading about 100dF low, but we've been through all that.  You run at 30/2200, 10-30 LOP at 14.2gph and your TIT is only 1500-1525. I run at 30/2200, 35-40 LOP at 13.2gph and my TIT is 1585-1600. If I increase FF to 14.2gph I'm still LOP but my TIT is around 1625.

Makes me scratch my head. Alot. 

Glad to see you got your airplane back!

[Jetpilot86]

20 minutes ago, Rick Junkin said:

My engine runs very differently from yours. Every time I see your TIT numbers I think your probe is reading about 100dF low, but we've been through all that.  You run at 30/2200, 10-30 LOP at 14.2gph and your TIT is only 1500-1525. I run at 30/2200, 35-40 LOP at 13.2gph and my TIT is 1585-1600. If I increase FF to 14.2gph I'm still LOP but my TIT is around 1625.

Makes me scratch my head. Alot. 

Glad to see you got your airplane back!

Me too!

My only guess is that mine came with a new turbo and everything is still new at 130 SFOH.  I finally got #6 CHT at 370 at 30/2200, but #3 is now the problem child suddenly running 380-385 when it used to run 370-375.  That or maybe your high end overhaul is just a beast!

[Rick Junkin]

6 minutes ago, Jetpilot86 said:

Me too!

My only guess is that mine came with a new turbo and everything is still new at 130 SFOH.  I finally got #6 CHT at 370 at 30/2200, but #3 is now the problem child suddenly running 380-385 when it used to run 370-375.  That or maybe your high end overhaul is just a beast!

Ok, let's compare apples to apples.

At 30/2200 and 10,000' what is your peak TIT, and what is your FF at peak TIT?

I'll check mine on Sunday and we can compare notes.

[Jetpilot86]

10 minutes ago, Rick Junkin said:

Ok, let's compare apples to apples.

At 30/2200 and 10,000' what is your peak TIT, and what is your FF at peak TIT?

I'll check mine on Sunday and we can compare notes.

Hopefully, I'll remember to check when I fly her to GGG in a few weeks.  But that low, I'd be surprised if I broke 1525 while running my 10 LoP and right at 14gph.  My CHT's run warmer than I like, but not the turbo....