Danb

Turbine inlet temperature

44 posts in this topic

Thanks Don I will look into that here as I approach my next annual.  I agree, I never operate my engine above 400°, but at the power setting that I typically  run, which is 29/2400, I am finding that I have to keep my TI T at around 1500 to 1525, with cowl flaps closed, burning about 21 gallons an hour to keep the temps where I want them to be. I would love to be able to lean  it back to about 18 gallons per hour and have the CHTs stay in the 380s to low 390s. I will examine the Gami spread angle more closely. I appreciate the input.

Regards, Frank

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2 hours ago, Bravoman said:

Thanks Don I will look into that here as I approach my next annual.  I agree, I never operate my engine above 400°, but at the power setting that I typically  run, which is 29/2400, I am finding that I have to keep my TI T at around 1500 to 1525, with cowl flaps closed, burning about 21 gallons an hour to keep the temps where I want them to be. I would love to be able to lean  it back to about 18 gallons per hour and have the CHTs stay in the 380s to low 390s. I will examine the Gami spread angle more closely. I appreciate the input.

Regards, Frank

Frank, there is something wrong with either your engine of your instrumentation.  29/2400 should give you 18-18.5 gal/hr the first hour and 17.5-18 gal/hr thereafter with all CHTs significantly below 400°F.

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I am thinking that if I have any issue it has to do with my Gami  spread. The engine, which only has a little over 100 hours on it and is a factory reman runs like a top. I have noticed a large CHT difference( 40-50df) between the number one and number three cylinders , which could be evidence of what we are talking about.  I would be interested in hearing what others are experiencing in terms of fuel flow, and CHT's at the various power combos and TITs

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The numbers Don quote are what they should be. Make sure the baffling material on your engine does not let air get by the top rear. If you shine a flashlight in the front cowl opening you should see that there aren't any gaps at the top where air can get by. If the baffling is correct and the baffles are folding forward the air has no place to go except down over the cooling fins on the cylinders. It doesn't take much of an air leak on the baffling to make the back cylinders run hot. If the old baffling material becomes "lazy" it folds back and lets a lot of air over the top providing little or no cooling where it's needed most.

A top end overhaul with all new cylinders had just been done on the Mooney Encore below and no one ever bothered to suggest to the owner that part of the high temperatures was that the baffling was worn out and wasn't doing its job. I discovered it during a pre-buy. I bought the airplane but the first thing I did was order a new set of baffles from Guy Ginby.

N40FM Baffling.png

 

This picture of an Acclaim is a better example of what they should look like:

IMG_0767.thumb.JPG.28791b18149c55edeca33dc3a2315bb6.JPG

 

 

 

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1 hour ago, LANCECASPER said:

The numbers Don quote are what they should be. Make sure the baffling material on your engine does not let air get by the top rear. If you shine a flashlight in the front cowl opening you should see that there aren't any gaps at the top where air can get by. If the baffling is correct and the baffles are folding forward the air has no place to go except down over the cooling fins on the cylinders. It doesn't take much of an air leak on the baffling to make the back cylinders run hot. If the old baffling material becomes "lazy" it folds back and lets a lot of air over the top providing little or no cooling where it's needed most.

A top end overhaul with all new cylinders had just been done on the Mooney Encore below and no one ever bothered to suggest to the owner that part of the high temperatures was that the baffling was worn out and wasn't doing its job. I discovered it during a pre-buy. I bought the airplane but the first thing I did was order a new set of baffles from Guy Ginby.

N40FM Baffling.png

 

This picture of an Acclaim is a better example of what they should look like:

IMG_0767.thumb.JPG.28791b18149c55edeca33dc3a2315bb6.JPG

 

 

 

Lance, would you mind sharing the contact info for the gentleman from whom you ordered the baffling? Thanks so much, Frank.

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Thanks Lance. I just ordered one of his baffle and seals kits. Very much appreciate it!

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You're welcome. I recently put a set on my TLS - my old baffles weren't terrible but i knew I could get the temps down a little with better baffles and it has made a significant difference. I did it at the same time as fine wire spark plugs so I hard to tell which made a bigger impact but either way I'll take it.

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3 hours ago, LANCECASPER said:

You're welcome. I recently put a set on my TLS - my old baffles weren't terrible but i knew I could get the temps down a little with better baffles and it has made a significant difference. I did it at the same time as fine wire spark plugs so I hard to tell which made a bigger impact but either way I'll take it.

Lance, Which fine wires did you use, the champion or tempest? And do you know the particular part number for the plugs that you used? Thanks again. Frank

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Thanks again Lance!

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Lance that's the wires I recently installed also, coming home from West Palm and no workable tit probe the cyl temp went up to 406 at 31/2400 19gph no clue the TIT temp, I never had an issue with cyl temps I have to assume  the TIT was to high? I'm still have the original baffles12 yrs old, does gee bee make the baffling for our planes, wouldn't harm to replace it after winter.

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They make a set specifically for the M20M. Check yours first tho - they may be ok. I do anything to stay under 400, open the cowl flaps or adjust mixture. 406 CHT for one flight isn't going to be a big deal tho. Once you get your new probe you'll get a better idea where you are.

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On 1/9/2017 at 7:43 PM, donkaye said:

PITCH + POWER + CONFIGURATION = PERFORMANCE

As such, I originally leaned to peak at 29/2400, richened 100°, and use that number for all future leaning at 75% power.  Physics is physics.  In no event, however, do I lean to any number greater than 1625°.  I compare that number to the FF to make sure the setting is reasonable.  After an hour in flight, the TIT goes down and I relean the engine.  It's been that way for both engines I've had.  Some say the 1 gph difference is because the fuel warms up after an hour, but that doesn't make sense to me, so I'm not sure why the fuel required is less after an hour.  Physics is physics, so there must be a reason, but I don't know what it its.

 

This might be a dumb observation- and you've probably already thought of this, but in the event you haven't- I'd start by investigating the most simple possible answer... if the tit/egts are moving, and you're noticing a 1gph shift in FF... maybe the mixture knob is vibrating out over time?  Is the tension on the vernier loose?

or am I reading the issue wrong?

like you- I wouldn't expect that heat would take an hour to warm up the fuel (doesn't make sense to me, either)... most of the engine compartment and lines will reach their high temp much earlier than an hour into the flight.  If anything, the fuel would be cooler (until it gets to the firewall)... as you'd be at cooler ambient temps up in the FL's; assuming you're "exercising that clamshell."  Just a few thoughts.

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18 hours ago, M016576 said:

... maybe the mixture knob is vibrating out over time?  Is the tension on the vernier loose?

Had it happen to me on a J ... Good suggestion @M016576 !

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19 hours ago, M016576 said:

This might be a dumb observation- and you've probably already thought of this, but in the event you haven't- I'd start by investigating the most simple possible answer... if the tit/egts are moving, and you're noticing a 1gph shift in FF... maybe the mixture knob is vibrating out over time?  Is the tension on the vernier loose?

or am I reading the issue wrong?

like you- I wouldn't expect that heat would take an hour to warm up the fuel (doesn't make sense to me, either)... most of the engine compartment and lines will reach their high temp much earlier than an hour into the flight.  If anything, the fuel would be cooler (until it gets to the firewall)... as you'd be at cooler ambient temps up in the FL's; assuming you're "exercising that clamshell."  Just a few thoughts.

Not likely, since the mixture control on the Bravo is Vernier.

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@donkaye Check this out - the friction lock was loose enough (and worn) that just the normal vibration was enough to cause the vernier knob to slowly rotate and do exactly what @M016576 was suggesting. This was the fix while we waited for the new assembly to arrive.

IMG_2510.JPG

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DVA - just noticed on your profile that you own 9153Z. I bought that airplane from Mooney back in '96 and flew it until '00. Great airplane! Brings back good memories!

N9153Z.jpg

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Just now, LANCECASPER said:

DVA - just noticed on your profile that you own 9153Z. I bought that airplane from Mooney back in '96 and flew it until '00. Great airplane!

PM me, I have a few questions that you if you don’t mind.

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