Power Setting for Determining Peak TIT

[Tom 4536]

For a 231 w/Gamis, Merlyn, intercooler and JPI900, what power setting should be used for determining peak TIT. I’ve read full power and also 65% power.

Thank you.

[kortopates]

Peak TIT is a function of Power. So it’ll be higher at higher power settings. Peak TIT is determined by leaning; either with mixture or air (MAP). but to be kind to your engine:exhaust components you don’t want to be determining peak TIT at power settings above 65%.


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[Tom 4536]

3 minutes ago, kortopates said:

Peak TIT is a function of Power. Peak TIT is determined by leaning; either with mixture or air (MAP).


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Are you saying if I want to cruise at 80% HP at ROP I should find peak TIT at 80% power and if I want to cruise at 65% HP at ROP I should find peak TIT at 65%?

[A64Pilot]

13 minutes ago, Tom 4536 said:

Are you saying if I want to cruise at 80% HP at ROP I should find peak TIT at 80% power and if I want to cruise at 65% HP at ROP I should find peak TIT at 65%?

Yes, and if you are trying to cut fine lines even with power setting being identical peak will change from day to day. It’s sort of like true airspeed as in he way true airspeed will be within a range but changes slightly from day to day.

I don’t run a turbo so maybe I should bow out, help me understand please, but isn’t max allowable TIT usually the determining max and you either run lean or or rich of that number? TIT max allowable occurs before peak?

 

Edited May 30, 2022 by A64Pilot

[Tom 4536]

27 minutes ago, A64Pilot said:

TIT max allowable occurs before peak?

Not at 65%HP but it does at 80%HP. That is why I asked the question of people who run turbos.

[kortopates]

Running high power ROP, your much better off just keeping TIT in the low 1500’s; such as below 1540. This will be or should be nearly 1 GPH richer than your POH recommended FF for the power setting; after adjusting MAP lower per the amount of cooling provided by the after cooler (between 2 to 3”). Use the table provided by the aftercooler OEM.

Your cylinders will last a lot longer running at no more than 65% power and at that power setting you’ll be able run LOP pretty easily.
At 80% power you’ll have to be a minimum of 50F LOP on the richest cylinder (not just TIT) to guarantee ALL cylinders are at least 50F LOP, but you’ll still be above 1600F TIT which although is below redline limitation it too high from an exhaust/turbo longevity standpoint. Plus to get that deep LOP requires your ignition system to be in top shape.


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[carusoam]

While getting to know your engine…

You also get to know your instruments…

There is a small lag in the thermocouples depending how thick their armor is….

The EGT is pretty hot…. But, it may take a few seconds for it to register completely….

This delay makes one part of the brain want to lean slowly to get good data….

The other part of the brain wants to skip extended periods near peak, using the big pull technique…. To get safely on the LOP side before setting power….

PP thoughts only, not a TC’d pilot….

Best regards,

-a-

[Z W]

Peak TIT is just the highest TIT reading you can get by moving the mixture knob from rich to lean.  Peak TIT in the TSIO-360 is maximum efficiency for fuel burn and will result in the highest possible speeds at the lowest possible fuel burn.  I personally believe that's why the POH recommends it, as that was the ultimate design of the M20K model and I believe it's marketing sales pitch.

As an owner-operator some 40 years later, other concerns do arise.  If I run POH-recommended 75% power, being 28" MP and 2500 RPM, leaned to peak TIT, I get best efficiency and good speeds, but peak TIT will be somewhere around 1625 degrees, which is 25 below redline and within limits, but running the turbocharger system that hot is likely not best for its longevity.  Cylinder head temperatures are all fine and can be kept below 380 degrees by adjusting the cowl flaps.

My current practice on most trips is to instead run 26.5"-27" MP and 2500 RPM and then lean to peak TIT.  I lose about 5 knots, but on most days and altitudes, the TIT will peak somewhere below 1600.  Fuel flow is also reduced, and CHT's are easier to keep under 380.  Often you get to close the cowl flaps a little more, which makes the speed loss even less, more like 2-3 knots, compared to running the engine harder and hotter with them open.

Alternate practice for engine care is to remain at 28" and 2500 MP, and lean only to 1575 TIT, which will be well rich of peak.  You will be burning an extra 1 to 1.5 GPH of fuel, probably close to 13.5 GPH.  You may pick up about 5 knots.  This is high speed, low efficiency cruise and is fun if you're trying to set a ground speed record.  The extra fuel keeps your CHT's nice and cool also.

I have tried running lean of peak TIT lots of times at different power settings.  The idea is to boost your MP up to get the same speeds and performance while LOP, with lower temperatures.  My engine, at least, does not run as smoothly and does not seem to like it.  That's unscientific and I wish I had better data, because the plane will do it, but I feel the roughness in my feet.  It stays smooth at very low power settings where the engine temps are already good and fuel burn very low anyways, but when I push it hard, say at 28, 30, or 32" MP, I get the rough condition, so I just don't go there.  Your experience may vary.

Be careful reading posts about other engines and their power settings and LOP procedures.  The TSIO-360 series is kind of an odd duck in the Mooney lineup.  Great engine but a little complicated and it seems set up to run very differently than the earlier 4-cylinder Lycomings and the later, bigger engines they put in the Bravo and Acclaim.  I do have a TSIO-360-MB as opposed to your TSIO-360-LB, but if you have an intercooler and automatic wastegate, supposedly the engines run about the same.

[N201MKTurbo]

I know I don’t have a 231. The Lycoming intake system provides better airflow distribution than the Continental’s. I’ve been running LOP for almost 20 years and have never measured peak TIT. I don’t think it matters. I just pull the mixture till I’m sure I’m LOP by a power loss and then set my MP to my desired setting (using 27 these days, used to use 28.5 doesn’t seem to matter much) then richen the mixture until I get the FF I’m looking for or the cylinders get to 380, whichever comes first. I watch my TIT to fine tune the mixture, it changes faster than the CHTs. Since I rebuilt my engine, the CHTs have been coming down, quite a bit on  my last trip. When I first started flying this engine, it would hit 380 at about 1460 TIT at low altitude and even lower TIT at high altitude. Now I can run 1500 TIT at lower altitudes and 1475 at 15000. Before I rebuilt the engine I couldn’t get the CHTs to exceed 380 in cruise no matter what I did. I assume I’ll get back to that point eventually as the engine breaks in. 
 

On this last trip I accidentally set the mixture too rich after the climb to 15500. I looked down and the TIT was at 1550 and the CHTs were at 410, too hot for me, but the TAS was 180 KTS. Woo Hoo! Hopefully I will be able to cruise that fast sometime soon. 

Also, I imagine it is because of the Lycoming’s intake design, the engine never runs rough as you lean it. The power just drops off smoothly till it’s windmilling.

Edited June 1, 2022 by N201MKTurbo

[Shadrach]

3 hours ago, N201MKTurbo said:

I know I don’t have a 231. The Lycoming intake system provides better airflow distribution than the Continental’s. I’ve been running LOP for almost 20 years and have never measured peak TIT. I don’t think it matters. I just pull the mixture till I’m sure I’m LOP by a power loss and then set my MP to my desired setting (using 27 these days, used to use 28.5 doesn’t seem to matter much) then richen the mixture until I get the FF I’m looking for or the cylinders get to 380, whichever comes first. I watch my TIT to fine tune the mixture, it changes faster than the CHTs. Since I rebuilt my engine, the CHTs have been coming down, quite a bit on  my last trip. When I first started flying this engine, it would hit 380 at about 1460 TIT at low altitude and even lower TIT at high altitude. Now I can run 1500 TIT at lower altitudes and 1475 at 15000. Before I rebuilt the engine I couldn’t get the CHTs to exceed 380 in cruise no matter what I did. I assume I’ll get back to that point eventually as the engine breaks in. 
 

On this last trip I accidentally set the mixture too rich after the climb to 15500. I looked down and the TIT was at 1550 and the CHTs were at 410, too hot for me, but the TAS was 180 KTS. Woo Hoo! Hopefully I will be able to cruise that fast sometime soon. 

Also, I imagine it is because of the Lycoming’s intake design, the engine never runs rough as you lean it. The power just drops off smoothly till it’s windmilling.

It’s my understanding that the air distribution on most Continentals is actually pretty good. It’s more the migration of fuel from one intake port to the next that causes mixture problems in some Continental intake designs. I believe that GAMI injectors correct for this issue by graduating the injector volume from front to back..

[Shadrach]

2 hours ago, N201MKTurbo said:

I know I don’t have a 231. The Lycoming intake system provides better airflow distribution than the Continental’s. I’ve been running LOP for almost 20 years and have never measured peak TIT. I don’t think it matters. I just pull the mixture till I’m sure I’m LOP by a power loss and then set my MP to my desired setting (using 27 these days, used to use 28.5 doesn’t seem to matter much) then richen the mixture until I get the FF I’m looking for or the cylinders get to 380, whichever comes first. I watch my TIT to fine tune the mixture, it changes faster than the CHTs. Since I rebuilt my engine, the CHTs have been coming down, quite a bit on  my last trip. When I first started flying this engine, it would hit 380 at about 1460 TIT at low altitude and even lower TIT at high altitude. Now I can run 1500 TIT at lower altitudes and 1475 at 15000. Before I rebuilt the engine I couldn’t get the CHTs to exceed 380 in cruise no matter what I did. I assume I’ll get back to that point eventually as the engine breaks in. 
 

On this last trip I accidentally set the mixture too rich after the climb to 15500. I looked down and the TIT was at 1550 and the CHTs were at 410, too hot for me, but the TAS was 180 KTS. Woo Hoo! Hopefully I will be able to cruise that fast sometime soon. 

Also, I imagine it is because of the Lycoming’s intake design, the engine never runs rough as you lean it. The power just drops off smoothly till it’s windmilling.

What’s the ignition timing spec for the M20 turbos mod?

[N201MKTurbo]

19 minutes ago, Shadrach said:

What’s the ignition timing spec for the M20 turbos mod?

Humm. The STC says 20, the engine says 25. I find it works better LOP at 25. Sandman liked to run at peak EGT. If I was going to do that I would run 20.

[N201MKTurbo]

25 minutes ago, Shadrach said:

It’s my understanding that the air distribution on most Continentals is actually pretty good. It’s more the migration of fuel from one intake port to the next that causes mixture problems in some Continental intake designs. I believe that GAMI injectors correct for this issue by graduating the injector volume from from to back..

The LB is a lot worse than the MB. I remember a guy like 30 years ago who made intake restrictors for the rear cylinders out of beer can metal. He said he got them dead even with stock injectors. 

If you want to see how elegant the Lycoming 360 intake is, remove the servo and look in the hole, it is a thing of beauty. The four intake bells are in a perfect square pattern.

[Shadrach]

2 hours ago, N201MKTurbo said:

The LB is a lot worse than the MB. I remember a guy like 30 years ago who made intake restrictors for the rear cylinders out of beer can metal. He said he got them dead even with stock injectors. 

If you want to see how elegant the Lycoming 360 intake is, remove the servo and look in the hole, it is a thing of beauty. The four intake bells are in a perfect square pattern.

I have seen it enough times to not need to see it again!  It is indeed a very symmetrical system. Form seems to follow function in this case as all four engines (read cylinders) typically seem to run in tight formation