highflyer wrote:
The butterfly flap is locked in the open position by rust and debris. It is not possible to move. Furthermore there are fine cracks in the flap. I need to exchange the wastegate since the part is supposedly
not repairable. I strongly suspect a maintenance error. To prove my guess, I would like to know if there are any special maintenance instructions regarding the wastegate such as lubrication with mouse milk.
Mouse milk cannot avoid butterfly cracks. It just dissolves soot from the butterfly shaft and bearing surfaces hence smoothing wastegate operation.
Wastegates live in a tough environment and their life is not unlimited.
Check your PMs. I had a quick look in my private collection and among a vast quantity of Cessna manuals I see some 182 turbo stuff, but not sure if it is applicable to your year, etc.
I have a problem with the automatic wastegate (Lycoming TIO 540) now causing power loss. The butterfly flap is locked in the open position by rust and debris. It is not possible to move. Furthermore there are fine cracks in the flap. I need to exchange the wastegate since the part is supposedly
not repairable. I strongly suspect a maintenance error. To prove my guess, I would like to know if there are any special maintenance instructions regarding the wastegate such as lubrication with mouse milk. Does anyone have the maintenance manual for a Cessna T182T?
Can someone please post the maintenance instructions for the wastgate?
It don’t think it would lower the inlet temperature in any significant way. The temperature rise is almost entirely from compression, and the pressure difference between the manifold and ambient is the same, bleed air or not.
Of course, because of some air bleeding of to the cabin pressurisation, the turbocharger would have to work harder and get a bit hotter because a higher mass of hot exhaust is passing through it, but that is only a small source of extra heat.
Michael wrote:
Flyingfish wrote:
Would it make sense to add a valve that shuts off the bleed air until pressurization is switched on? The valve would have a default spring loaded position of “open” and be closed by energizing a solenoid, so as to be fail safe.
Since it’s probable that 99% of your take-off operations will be at DAs less than say 6000’, and most turbo’d acft can easily exceed the max MP all the way to critical altitude, (usually around 15000’, ISA) , then there would be nothing to gain .It’s above 12000’ where you would want/need the adtl MP for the engine, but that’s exactly when you need it for the passengers !
So unless you’re willing to suck O² in the flight levels, I can see no case for blocking bleed air.
Michael, thanks for your reply. I think this misses my point though:
We know that the turbo has enough power to deliver full take-off MP while simultaneously pressurizing the cabin with bleed air.
In my aircraft the turbo can actually do so all the way to the certified ceiling of FL 250.
My concern was that, in generating this MP, the turbo heats up the charge air. By avoiding the workload of supplying bleed air to pressurize the cabin, I was hoping to obtain lower inlet air temp, i.e. more engine power.
I have meanwhile done some testing which proves that my idea is not useful: on a hot day, I watched the inlet air temperature during the takeoff roll (at full MP).
It was below 130F, which is quite acceptable, so there would be no major benefit in trying to lower it. Case closed…
Flyingfish wrote:
Would it make sense to add a valve that shuts off the bleed air until pressurization is switched on? The valve would have a default spring loaded position of “open” and be closed by energizing a solenoid, so as to be fail safe.
Since it’s probable that 99% of your take-off operations will be at DAs less than say 6000’, and most turbo’d acft can easily exceed the max MP all the way to critical altitude, (usually around 15000’, ISA) , then there would be nothing to gain .
It’s above 12000’ where you would want/need the adtl MP for the engine, but that’s exactly when you need it for the passengers !
So unless you’re willing to suck O² in the flight levels, I can see no case for blocking bleed air.
@terbang thank you for the PIREP. Meanwhile I am convinced that it is reasonable to use max continuous power in the climb as long as all parameters remain in check. This summer I was able to make use of my additional probes and made the following observations. These are obviously only valid for the TSIOL550 C as installed in teh Extra 400 – it would be useful if PA46 operators would chime in.
(All data at MTOW of 2000 Kg, 2500 RPM, 37.5 inches and fuel flow between 125 and 130 liters per hour full rich)
On an ISA day, it is OK to climb straight to FL200 at 1000 ft per min.
On an ISA + 10C day, expect Inlet Air Temperature (IAT) to become limiting at FL 100, reduce MP and climb rate as needed , typically 800 ft/min until FL150 then 700 ft/min to FL200.
On an ISA + 20C day, IAT becomes limiting at FL100 and must thereafter be managed constantly to stay below 130 F. MP goes down and climb rate follows to provide sufficient airflow to the coolant radiator.
Airspeed (Indicated) must be kept above 110 knots for the coolant radiator to work well. Anything above 120 KIAS is unnecessary and can be traded for additional climb rate (I have dialed-in 1’200 ft/min occasionally when flying light and cold weather).
IAT must be kept below 130 F if more than 2 minutes of climb remains due. 140 F must be seen as a red line.
The IAT limits are based upon feedback from a F1 motorist who has also aero engine design experience. He is advising me as to how to optimize the setup.
I am very happy with the climb performance (and generally with the the performance) – I love passing FL 150 with 1’000 ft per min and 150 KTAS.
I find it extremely disturbing that this aircraft (and most other turbocharged ones) do not come with an IAT probe as standard. I believe that a LOT of the engine issues in this specific aircraft are caused by IAT exceeding 140F.
One question to the turbo gurus here:
the Extra 400 has a cabin pressurization system that uses turbocharged (bleed) air “stolen” downstream of the intercooler.
The bleed air duct diameter is about 14% of the duct that feeds the engine. So this is a substantial loss of pressure.
Obviously no-one needs pressurized air at take-off and I’d rather dedicate all of the turbo’s work for the engine intake.
Would it make sense to add a valve that shuts off the bleed air until pressurization is switched on? The valve would have a default spring loaded position of “open” and be closed by energizing a solenoid, so as to be fail safe.
Can someone point me to a high temp lubricant that is available in Europe? It seems Mouse Milk is hazmat.
There is an existing thread I wanted to add to but I really can’t find it at the moment. Maybe Peter knows and can move the post. [done]
Our TSIO360MB is at TBO + 20% and we decided it’s time to say goodbye. It’s in perfect shape, but we do longer over-water flights from time to time and we like doing that with a proven engine. As we currently don’t have any plans for a longer trip it appeared a good time to us.
The old engine has close to 2200 hours,TBO is 1800 and we bought it at a little over 1300. None of the six cylinders is original. The previous owner of the aircraft had replaced cylinders several times for reasons not really obvious. We changed two, each time directly before we crossed the Atlantic, maybe he was in a similar position. Both times I didn’t like the look of the exhaust valve. If it had been in a different situation I would have kept them and borescoped them again after ten or 15 hours. Only one of the six cylinders reached TBO, we had to replace it before we went to South America a year ago.
I couldn’t find anything in the records that indicates that the previous owner ever had any turbo related problems, neither did he tell me anything, we’re still in good contact. We never had any turbo problems what so ever.
The only engine related down-time we had was due to a broken alternator. It resulted in a canceled trip to Spain.
We climb at max RPM and full throttle to what ever cruise level we want to fly at. For longer legs that usually is 180 or 190 unless weather dictates something else. We usually cruise at 65% at 2200RPM. We keep the cylinder heads cool, always below 380F. Our aircraft is capable of doing so in climb even on hot days. A Mooney has an acceptable climb rate at 110KIAS, in fact it’s not much worse than at 90.
The only special treatment I give the engine is to put a little mouse milk (or similar) on the waste gate each time the cowling comes off (usually for an oil change and during annual inspection).
