Danb

Turbine inlet temperature

44 posts in this topic

I flew a cross country from Delaware to sunny Florida, after my plane got stuck on the ice I was on my way quite cold.

Upon reaching cruising altitude I could not get the tit above 1530, it's started to go down realizing something was screwy I then leaned to gal per hour, as most know I'm not the brightest bulb in the box re: mechanical.,DVA help.

My numbers were, I also have pix of the G1000, but I'm giving the results.

at 8000 ft, EGT1524, TIT 1530 Cyl #4 362 , also number four temp jumped around 360-370? 31/2400 I leaned by gph 18 gph

at 14,000, Not knowing what to lean to for sure I went to 32/2400 that setting was in the manual so I went there for a reference, at 14,000 EGT 1520 TIT 1576 CYL 4. 380 stopped fluctuateing GPH 18.0 TAS 192.. not knowing for sure I assumed the probe was messed up and leaned via GPH

I won't get back to KILG for a few days. I generally fly 31/2400, what GPH should I lean to until I get it checked out?  

Basically it stops increasing around 1570-1580, if a Bravo guy would give me what I should try on the way home, figure I'll fly between 8000-16,000 depending on wx and icing. I think the temp reading is currently unreliable.

Thanx Dan

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It don't know what everyone else is doing?

i  usually run 21 to 22 gallons an hour on the upper end of the power curve , and around 19 gallons at I'm thinking 29 mp & 2400rpm

 

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When was the last time your TIT probe was changed out?

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Thermocouples are very reliable... if they are bouncing, then you have a bad connection in the wiring harness (CHT fluctuating).. as for the TIT probe.. check it is properly anchored, and connectors are clean/solid... (I had them bounce.. but not read so low).  (pilot side, you can see it with just the upper cowl removed. )

the MP/prop/ fuel rates are on the pilot's glare shield & POH. 

From the POH:

32/2400 is 16-16.5... but I would assume your TIT probe is out of place but can measure peak.. so when it peaks you are at the max. 

18Gph is rich.. but if the CHT's aren't complaining then you aren't too hot.  I wouldn't have a problem with 15.5 at 21/2400.  but you can run rich as long as the CHT's are not going high.. it is just fuel. 

 

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14 minutes ago, PaulM said:

Thermocouples are very reliable... if they are bouncing, then you have a bad connection in the wiring harness (CHT fluctuating).. as for the TIT probe.. check it is properly anchored, and connectors are clean/solid... (I had them bounce.. but not read so low).  (pilot side, you can see it with just the upper cowl removed. )

the MP/prop/ fuel rates are on the pilot's glare shield & POH. 

From the POH:

32/2400 is 16-16.5... but I would assume your TIT probe is out of place but can measure peak.. so when it peaks you are at the max. 

18Gph is rich.. but if the CHT's aren't complaining then you aren't too hot.  I wouldn't have a problem with 15.5 at 21/2400.  but you can run rich as long as the CHT's are not going high.. it is just fuel. 

 

Careful with the POH which said you could go to 1750 TIT. That extra 100 degrees has proven disastrous to probes and exhaust systems.

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1 hour ago, LANCECASPER said:

When was the last time your TIT probe was changed out?

Never, plane is a 2005. 

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30 minutes ago, LANCECASPER said:

Careful with the POH which said you could go to 1750 TIT. That extra 100 degrees has proven disastrous to probes and exhaust systems.

I've never gone there..I know heat/cold kills engines, but I've always leaned to the tit probe. 1600 degrees, I know there's folks that don't like 1600, but that's whats been done since new. 31/2400 1600TIT, 14,000 ft., 18 gph, cyc temp 360-380 are my typical numbers. Since my new tempest fine wires I've been messing around with lop it's been especially smooth since switching from champ fines to temp fines.

Lance I just read the TIT probe post  it seems like a $400 part will be on order when I get back.

Thanx DB

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Numbers sound great. I'd be tempted to try the A002C-30 probe from KS Avionics.

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I lean by TIT and FF.  On the way back from Wilmar last November my TIT probe went out, so I leaned by FF only.  29/2400 = 18.5 gph the first hour changing to 18 from then on at same TIT.  If TIT is working that should give about 1600 TIT.  At 31/2400 (81% power) 19 gph 100° ROP.  Numbers quoted above by PaulM waaaay to lean if operating ROP.

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43 minutes ago, donkaye said:

I lean by TIT and FF.  On the way back from Wilmar last November my TIT probe went out, so I leaned by FF only.  29/2400 = 18.5 gph the first hour changing to 18 from then on at same TIT.  If TIT is working that should give about 1600 TIT.  At 31/2400 (81% power) 19 gph 100° ROP.  Numbers quoted above by PaulM waaaay to lean if operating ROP.

Don

I'm curious, would you normally lean to peak and then go rich to 100ROP or are you setting to 1600 knowing that this is 100ROP?  In other words, do you typically see a peak of 1700?  Do you ever see red line before reaching peak?

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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.

 

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20 minutes ago, 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.

 

I suspect this may be the result of the cold temperature compensation circuit in the instrument. (I spend too much time staring at temperature instrument behavior in my shop).  It takes some time for the engine analyzer temperature to stabilize (power supply, display, etc) and each cold junction (splice or pin) causes a slight error if they are not at the same temperature as the compensation circuit.  So, what you may see is a circuit that is not perfectly compensated for some time.  When you relean, the thermocouple circuit is stabilized and technically more accurate.  I suspect that if you checked peak, it may also have drifted a few degrees, so you may only be at 100 ROP one of the two times...

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When my probe is working properly and fly say 30-2400 then go to TIT 1600, is this procedure incorrect?

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2 hours ago, Danb said:

When my probe is working properly and fly say 30-2400 then go to TIT 1600, is this procedure incorrect?

No.  Sounds good to me.

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12 hours ago, donkaye said:

After an hour in flight, the TIT goes down and I relean the engine.

Don,

  Is your TIT gauge the original Alcor dial, or do you have a JPI digital system?

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52 minutes ago, PaulM said:

 

Don,

  Is your TIT gauge the original Alcor dial, or do you have a JPI digital system?

Don has a G1000, but i think the original gauge on the M20M was a Sigmatek with an Alcor probe.

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1 hour ago, PaulM said:

 

Don,

  Is your TIT gauge the original Alcor dial, or do you have a JPI digital system?

Neither.  I have the MVP 50 EI Engine Monitor, and use their probe.

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25 minutes ago, LANCECASPER said:

Don has a G1000, but i think the original gauge on the M20M was a Sigmatek with an Alcor probe.

I don't have a G1000 airplane.  My panel consists of products I choose, not the OEM.  I have a G500 and associated Garmin products.

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Sorry my mistake, I meant Dan has a G1000 not Don.

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14 hours ago, 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.

 

I was about to ask to - why you expect less fuel burn after an hour of flight.  I still don't understand now that I read this.  I also agree with your remark - why would the fuel warm up in flight.  If anything, I expect it to cool off since it is colder at altitude than on the ground.

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Since Don has a MVP50 it isn't the temperature compensation circuit.   The G1000 uses a K thermocouple for the reference junction. 

I would go with the fuel getting colder and therefore more dense..  That enriches the mixture, which would lower the TIT and allow further leaning..   I will check on the next long flight if I see differences.  The flow meter expects a standard density of fuel.  Jets measure in lbs for this reason and their meters are mass flow devices.  

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5 hours ago, PaulM said:

Since Don has a MVP50 it isn't the temperature compensation circuit.   The G1000 uses a K thermocouple for the reference junction. 

I would go with the fuel getting colder and therefore more dense..  That enriches the mixture, which would lower the TIT and allow further leaning..   I will check on the next long flight if I see differences.  The flow meter expects a standard density of fuel.  Jets measure in lbs for this reason and their meters are mass flow devices.  

The K type probes require compensation of the cold junction.  If there are multiple junctions ( splices, connectors, etc) at various temperatures (cabin, cowl, instrument panel, instrument), especially if they are different metals, they will generate false voltages which shift the accuracy.  Ideally, you would have two junctions, the hot junction at the TIT and the cold junction at the processor. That is hard to achieve in practice.  It takes time for the circuit board temps and connector temps to stabilize and these can make the voltage shift.  Not saying this is it, but it can happen.  The fuel density is certainly a valid theory as well.

Don,

How much does your temperature shift from 1600 over an hour?  I guess that would give us a measure of degrees per gallon....

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14 hours ago, takair said:

The K type probes require compensation of the cold junction.  If there are multiple junctions ( splices, connectors, etc) at various temperatures (cabin, cowl, instrument panel, instrument), especially if they are different metals, they will generate false voltages which shift the accuracy.  Ideally, you would have two junctions, the hot junction at the TIT and the cold junction at the processor. That is hard to achieve in practice.

Back about 25 years ago I designed multichannel A/D systems for 4-20mA & TC work  for general scientific datalogging.  We used a platinum RTD at the reference junction, the issue isn't really cross board drift.  the TC voltage differential is from where you switch from the common materials (copper) to the dissimilar metals (K, J etc)   Therefore that is the back shell where the K wire is terminated into the copper pins.  I would have expected the probe at the back shell to have been an RTD.. but the maint manual says that it is a K TC.. which implies that the GEA 71 has another internal reference (probably a silicon chip near the A/D), and actually has the Yellow/Red K type wire internally to just measure the refrerence point.        Inline splices all depend on the temperature gradient across the splice, critical for precision work but not significant with 1500F.   The airplane installations that I have seen all have one splice between the airframe wiring and the probe. If the connectors are the proper metal, then it won't be an issue. 
 

I am leery of the temperature compensation in the older analog modules.. often the EGT gauges wouldn't be compensated and that is why they are just calibrated to a peak, but I assume all of the modern digital systems get the compensation correct and are accurate to a couple of degrees. 

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On 1/9/2017 at 9:43 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.

 

I agree that  the TIT comes down after a while at the same setting thereby allowing additional leaning. It would certainly be interesting to know the reason for that! 

Also, at least for me, at 29/2400 with cowl flaps closed leaning to 1625 would be too aggressive and would result in CHTs in excess of 400df. However, I am not sure if you were saying that is your TIT  limit at 29/2400 or if that was your limit generally at any setting.

regards, Frank

Edited by Bravoman

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2 hours ago, Bravoman said:

I agree that  the TIT comes down after a while at the same setting thereby allowing additional leaning. It would certainly be interesting to know the reason for that! 

Also, at least for me, at 29/2400 with cowl flaps closed leaning to 1625 would be too aggressive and would result in CHTs in excess of 400df. However, I am not sure if you were saying that is your TIT  limit at 29/2400 or if that was your limit generally at any setting.

regards, Frank

I noticed an approximate  50°F decrease in CHTs on all cylinders compared to that shown on my previous JPI 700 after I installed my MVP 50.  I talked to EI about that and they assure me their probes are accurate.  I have my MVP 50 set up to give me highest CHT and EGT at a glance, although I can look at all of them individually if I want to.  That maximum CHT doesn't go anywhere near 400°C if the engine is set up properly.

I did have some problems over a year ago that required me to have Top Gun investigate.  First I ran a GAMI lean test and found that my fuel distribution was not within .5 gallons max distribution.  I sent the data to GAMI and they replaced the required fuel injectors.  My distribution is now below .5 gallons.  I had some issues with "leaking" spark plugs due to the way the GAMI installation differs from the original injectors.  I also replaced all spark plugs.  All the above fixed my problems and CHTs are all below 370° at 75% power.  The maximum power I ever run when flying into a large headwind is 31/2400.  I never set the TIT above 1625° and CHTs are all considerably below 400°F, a temperature above which your engine should never be operated.

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