Sooo, my 2 year quest for an Inconel exhaust for the Continental TSIOL 550 in my Extra 400 has finally succeeded!
Thanks to all of you here who pointed me to the possible sources. A UK shop called Goodfabs solved the problem.
They delivered nice work with good in-house QA that made them decide to redo the job after the first attempt.
A UK-based mechanic with good E400 experience checked the parts and gave them a thumbs up.
Before calling this a success, I intend to do 3 gradually more demanding test flights to see how the Inconel parts survive in the real world.
Meanwhile I am exploring the idea of taking advantage of the increased heat resistance to remove the annoying TIT limitation:
According to the POH, the maximum allowable TIT is 1750F.
I have been taught by my late instructor to use 1650 F instead and indeed the melting exhaust risers suggest this was good advice which I have shared with others.
But this has prevented me from running LOP and caused higher than book fuel flows in cruise.
Now that the exhaust line can keep up, I am looking at setting max TIT at 1700F which would allow LOP operations as well as operating the engine closer to peak EGT under ROP. Before you shoot me down for the latter, consider I would only lean at 75% or less ROP and it would still be >100F ROP.
I expect the hottest EGT to reach 1620 F under the new settings, up from 1560 previously (fire-breathing turbo!)
Keeping in mind that the liquid cooling keeps CHTs well below 250F (TWO fifty) – would you think I am looking for trouble with the EGT increase?
This TSIOL 550 is definitely a weird animal, and I am now convinced that it has huge performance potential to be carefully explored…
What do you think?
The TIT limit is for the turbo, you can briefly exceed it on the way to LOP, just don’t keep it there permanently. Once LOP, the temps will drop rapidly, both TIT and CHT. EGT is not a limiting factor, only used for ‘navigating’ to peak and beyond. We routinely fly at about 85% power, well LOP on a turbonomalised IO550.
Also on my previous turbocharged aircraft, the TIT instrument needed to be calibrated every 100 hours or so using an Alcor test set with probe heater. Calibration was against an eutectic metal of known melting temperature.
A thermocouple instrument can be calibrated with a voltage source. What type of thermocouple is used? Most likely J or K.
This, and PT100, is my day job right now 
I’d be worried about the rest of the turbo system at those temps, like the blades, but I’m a coward.
@denopa – indeed, I am worried about the turbo (but if the factory say max continuous 1750F, then it must have an Inconel impeller unlike the other turbos rated at 1650 F?) Also worried that EGTs around 1600-1620 would damage valves?
@Peter these are K types – and I would be very grateful if you could teach me how to test the probe with a voltage source!
@dirkdj – your idea of running LOP high power is still on my mind but I am concerned about blowing up something. Would appreciate more detail and in particular for how long you have done this and whether you noticed any negatives?
And thanks to all three of you :-)
Flyingfish, I collected John Deakin’s articles for you about piston turbos:
Pelican_s_Perch_31_Those_Fire_Breathing_Turbos_28Part_1_29_AVweb_pdf
Pelican_s_Perch_32_Those_Fire_Breathing_Turbos_28Part_2_29_AVweb_pdf
Pelican_s_Perch_33_Those_Fire_Breathing_Turbos_28Part_3_29_AVweb_pdf
Pelican_s_Perch_34_Those_Fire_Breathing_Turbos_28Part_4_29_AVweb_pdf
Pelican_s_Perch_35_Those_Fire_Breathing_Turbos_28Part_5_29_AVweb_pdf
Pelican_s_Perch_36_Those_Fire_Breathing_Turbos_28Part_6_and_FINAL_29_AVweb_pdf
Guys you are amazing!
Peter: I will test my probes next week, thank you.
dirkdj: I just checked Savvy files from the EDM 930:
Here some typical data
ROP climb (per POH climb power) at 120 KIAS and 1’000 fpm from sea level to FL200. ISA + 10.
Engine settings during the climb:
37.5 inches , 2500 RPM, FF 125 LPH (33 GPH),
TIT 1550 F (yes, 1550). EGTs typically 80-100 F lower than TIT.
CHT start at 220 and creeps to 265 F. Simultaneously, coolant goes to 215 F.
I intend to try your high power LOP idea, please correct me if you see something you don’t like in the following plan !
Phase 1 LOP in cruise with max continuous settings
1. Climb as usual (ROP) to cruise. Keep climb power, set autopilot and wait for speed to stabilize. Note CHT
2. Make a big mixture pull to where TIT will be 1650 or less. from experience this is enough to make the engine run slightly rough.
3. Readjust mixture to get TIT back to 1700 – I expect this to run reasonably smooth.
4. At this point, watch CHT
After finding good settings, go full rich again and move to
Phase 2 LOP in cruise starting from 75% ROP settings
1. set 75% ROP power (32.5 /2400) and repeat 2 to 4
Phase 3 LOP in climb with max continuous settings
1. Climb as usual (ROP) to 4’000 ft. Set autopilot to a safe climb rate (600 ft/min) and let it fly the aircraft. Expect 140 KIAS…
2. Make a big mixture pull to where TIT will be 1650 or less. from experience this is enough to make the engine run slightly rough.
3. Readjust mixture to get TIT back to 1700 – I expect this to run reasonably smooth. At this point, watch CHT
4. At this point, watch CHT
Very curious to compare smoothness (my primary OK criterion) and then performance vs FF
The idea is to go high power but well LOP, maybe 90°F LOP, otherwise, your ICP will be very high. The main effect of leaning LOP is to reduce the speed of the flamefront, putting the peak pressure later in the cycle, reducing internal combustion pressure because you are already in the downgoing cycle of the cylinder and less temperature will build up.
Temperatures of EGT are unimportant except for navigating either side of Peak EGT.
I would first start with the GAMI check, in cruise, let the EDM note the CHT, EGT and TIT for every liter of fuel flow, the IAS you can note yourself, starting at a point well ROP and continuing until well LOP or until rough. Do this at 65% or maybe 70% power, not more until you know how it will react. Flying high-power LOP is not a good idea if the engine is not smooth. Allow about one to two minutes before leaning the mixture to the next step, write down the IAS just before the next leaning step.
With the data from the above operation, it may be that one or more Gamijectors may need to be exchanged before proceeding further up the power curve.
Ouch – this is exactly what I feared: I don’t think my engine can do 90 F LOP smoothly.
I have recently replaced both mags and harness and have not done much GAMI testing since.
Annual is planned in February. I will make a thorough intake/exhaust leak check and then the GAMI tests you suggest and report back.
Thank you again for your advice. Much appreciated
