Controller92 Posted January 24, 2023 Report Share Posted January 24, 2023 I'm looking at picking up a Mooney 231 and I have heard that the turbo on that bird has a nasty reputation. Does anyone have any experience with how to fly these birds to keep the engine in good shape? Best practices, maybe? Quote Link to comment Share on other sites More sharing options...
carusoam Posted January 24, 2023 Report Share Posted January 24, 2023 No nasty reputations when it comes to Mooney turbos and turbo normalizers… Plenty of maintenance things to be aware of… Plenty of opportunities to save money on parts, and accidentally cause other issues… There are some ‘time limited’ parts to be aware of… when it comes to buying a pre-flown bird… the time is related to how it was flown… and it’s maintenance history… Let’s start with a few details… What does it have for hardware? Does it have a fancy pressure controller? Often called a Merlin… Does it have an intercooler? Often called an aftercooler… sometimes a TurboPlus. Does it have good records in the logs? Fastest Mooneys are flying in the flight levels lately… Go Turbo! To read about great discussions flying the M20K LOP… find @jlunseth… He has written a bunch of his experience flying his M20K with great detail… If you don’t fly a turbo Mooney already… by the time you are done reading… you will want a pair of TNs, manifold pressure controllers and a matching pair of intercoolers… and the latest engine instrumentation… Since you only asked about the turbo itself… you also kinda left out the other things related to it… If the plane belonged to Captain Hamfist…. Who was known for flying the plane only in Full Flaming Dragon Mode… Expect to be looking for the wear status on things from cylinders to exhaust systems…. High temps are the enemy… If the plane belonged to a conscientious MSers that most often cruised using LOP, kept his CHTs below 380°F most often… and liked to keep his TIT on the cool side of 1650°F… on hours long flights… lots of hours every years, and plenty of oil changes go with that…. One of these would be a better place to start…. PP thoughts only, not a mechanic… Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Mike A Posted January 24, 2023 Report Share Posted January 24, 2023 I have a 231 and absolutely love it. I keep this thread as a separate bookmark from general Mooneyspace and find that i refer to it often. You won’t regret getting a 231. 1 Quote Link to comment Share on other sites More sharing options...
FlyWalt Posted January 24, 2023 Report Share Posted January 24, 2023 "Real Turbocharger Pilots" do not need a wastegate and intercooler. :-) 4 Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted January 24, 2023 Report Share Posted January 24, 2023 My plane has the same turbo as a 231. it seems pretty robust. Just don't overheat it and it will outlast your engine. Quote Link to comment Share on other sites More sharing options...
jlunseth Posted January 24, 2023 Report Share Posted January 24, 2023 We get questions on MS about how to operate the 231 engine quite often and there is a wealth of information from past threads if you search for it. If you do and have any further questions let me know. I can tell you several mistakes never to make. Never lean for takeoff regardless of altitude and never lean in the climb. If you do, you can generate temps that will kill the engine or damage the turbo in a single flight. That is a method of operation for normally aspirated aircraft that does not apply to turbos. Turbos should be full rich full power for takeoff and climb. If you do make the mistake of leaning for takeoff and climb and see the temps rising, put in full rich full power. Does your new-to-you aircraft have the Merlin wastegate and/or an intercooler? The intercooler in particular makes a major difference in what power settings you use. Max for the non-intercooled engine is 40", max for the intercooled engine is 36-37" and full rich at that power setting. The wastegate does not affect power settings but it does change the Critical Altitude quite a bit (the altitude at which the engine can no longer make full power). It goes from 15,500 for the factory engine to about 22,500. These numbers vary quite a bit with day OATs. You should not use any cruise power setting that is at 70% HP or greater where the fuel flow is in the 12's, that is 12 point something GPH. You should not use the "at peak" settings that are in the manual. If you want to cruise in rich of peak mode and 70% or better HP the fuel flow needs to be at least 13.3 and if the CHT's are going over 400 put in more fuel flow. I cruise LOP most of the time, there are plenty of posts with my method for doing that if you are interested. The engine has to be set up properly or it won't work. 1 Quote Link to comment Share on other sites More sharing options...
kortopates Posted January 24, 2023 Report Share Posted January 24, 2023 3 hours ago, FlyWalt said: "Real Turbocharger Pilots" do not need a wastegate and intercooler. :-) Just envious of them! Quote Link to comment Share on other sites More sharing options...
PeteMc Posted January 24, 2023 Report Share Posted January 24, 2023 (edited) You may also want to take a look at another discussion here: Turbocharger cool down time Hopefully it will not muddy the waters with some of the original old wives tales that came from the original 231's fixed wastegate turbos. Bottom line is that GAMI and others did some pretty good research to show that unless you come into the pattern at full power and only taxi a few hundred feet and shut down, there's no issues with the turbo cooldown. It will cool down as you reduce power nearing the airport, in the pattern and especially as you pull power on short final and the roll-out. Your turbo will probably heat back up a bit during the taxi and when you pull up to parking. But the temps will still be down low enough to shut down. If the plane you are looking at does not have a Merlyn Variable Wastegate (really an upper deck controller) then you might seriously want to look at installing one. With the fixed wastegate (a bolt) you're using un-needed boost down low and for takeoff and eventually you start to loose boost around 12K when the turbo could give you more if it had a variable wastegate. Edited January 24, 2023 by PeteMc 1 Quote Link to comment Share on other sites More sharing options...
jlunseth Posted January 24, 2023 Report Share Posted January 24, 2023 The Merlin also substantially reduces bootstrapping, or so they say. I have the Merlin so I experience some bootstrapping but not much, more a matter of turbo lag and my not having the patience always, to wait for the turbo to settle. Both the Merlin and the intercooler are very worthwhile if you don't have them, notwithstanding that real pilots don't need them. Quote Link to comment Share on other sites More sharing options...
PeteMc Posted January 25, 2023 Report Share Posted January 25, 2023 4 hours ago, jlunseth said: more a matter of turbo lag and my not having the patience always I found that even though you may be able to climb faster, if you keep the climb in the 500~750ft/min, the Merlyn is quite happy and can keep up. And a factoid I just learned that many of you may also not know.... I was having a turbo discussion with my mechanic recently and he happened to ask if I knew my turbo was glowing BRIGHT RED while in flight! Guess first time he saw it years ago was when he was ferrying a twin at night with a TSIO360 and could see it glowing through the vents in the cowling. Gotta say... That would scare the cr*p out of me if I hadn't been told they all glow red. Quote Link to comment Share on other sites More sharing options...
jlunseth Posted January 25, 2023 Report Share Posted January 25, 2023 (edited) I was aware of that. The TIT is in the vicinity of 1600. The turbo is also significantly warmed by the act of compressing the intake air. Iron and steel start to glow red at 900-1000 dF so you don’t even need to be pushing the turbo hard to get red. I make my climb at 500 fpm. It will climb a little faster, but I fly with such a variety of passengers for Angel Flight. I have found that no one’s ears are harmed by a 500 rpm climb or descent. In addition, there are circumstances - a high, hot climb out west in the middle of the summer - where you need the cooling effect of the higher airspeed at 500. It will climb at 7 -800 pretty consistently if temps don’t start heating up. It will climb for periods of a few minutes in cold winter air at between 1-1500 rpm. Edited January 25, 2023 by jlunseth 1 Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted January 25, 2023 Report Share Posted January 25, 2023 Just take the cowl off and have someone run the engine up at full power at night while you watch it. It will be a “holy $#!t” moment. Quote Link to comment Share on other sites More sharing options...
carusoam Posted January 26, 2023 Report Share Posted January 26, 2023 Some steels will start to turn red just over 500°F… and you can feel the IR heating as you walk near it… Good gloves if you intend to touch any parts of it while hot… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted January 26, 2023 Report Share Posted January 26, 2023 On 1/24/2023 at 8:56 AM, FlyWalt said: "Real Turbocharger Pilots" do not need a wastegate and intercooler. :-) Every turbine I’ve flown has a bleed valve, which is a wastegate. Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted January 26, 2023 Report Share Posted January 26, 2023 On 1/24/2023 at 9:25 PM, N201MKTurbo said: Just take the cowl off and have someone run the engine up at full power at night while you watch it. It will be a “holy $#!t” moment. One whole hour of my IA on line renewal class was on turbo’s, the first pic is an automobile engine of course, but look at the turbine exhaust pipe, no glowing as the turbo has removed that much heat. Second pic is of I believe a 421 in flight looking through the cowling vent. I’m surprised aircraft turbo exhaust systems aren’t plasma coated Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted January 26, 2023 Report Share Posted January 26, 2023 Reference that class, according to Hartzell I think the 400 series turbo’s don’t need cool down, and neither do turbo normalized aircraft, but the 600 series do. 400 has an aluminum center section? Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted January 26, 2023 Report Share Posted January 26, 2023 16 minutes ago, A64Pilot said: One whole hour of my IA on line renewal class was on turbo’s, the first pic is an automobile engine of course, but look at the turbine exhaust pipe, no glowing as the turbo has removed that much heat. Second pic is of I believe a 421 in flight looking through the cowling vent. I’m surprised aircraft turbo exhaust systems aren’t plasma coated The first image illustrates the EGT vs TIT issue. You can see that it is a bit brighter at the collector then near the cylinders. Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted January 26, 2023 Report Share Posted January 26, 2023 2 hours ago, N201MKTurbo said: The first image illustrates the EGT vs TIT issue. You can see that it is a bit brighter at the collector then near the cylinders. You also see it’s very bright right at the exhaust collector, looks brightest right at the inlet of the turbo, not sure why. When you consider the minuscule amount of time the gasses spend in the tubing as well as the flow rate it’s not hard to think that EGT and TIT should be nearly identical. An engine turning 2400 RPM, each cylinder has an exhaust stroke 1200 times each minute, so 20 times a second, then each cylinder is 90 cu in, so even if we discount air expansion due to heat and compression from boost it’s still 1800 cu in per second of gas flow or 12.5 cu ft every second. That’s for a four cylinder Lycoming, individual cylinders total is different for the Conti but as the engine displacement is the same so should the total be. I suck at math so verify it. Plus all probes are to some extent averaging devices, but as they have mass and get hit 20 times per second I don’t know how much cooler they are than the actual EGT, whereas the turbine inlet as it gets gas from all cylinders is a much more continuous supply of heat, less intermittent. It may be that the difference is more of the way temp is measured as opposed to an actual temp difference? On edit, plus depending on valve timing the fuel could be still burning in the exhaust. You do see flames in a Radial engine exhaust at night. On drag bikes years ago I dialed in more valve overlap than stock, that meant that air and fuel were blown into the exhaust and burned which made the turbo develop full boost sooner. The bike was at low boost leaving the line of course, the quicker you could build full boost, the quicker the 1/4 mile. Quote Link to comment Share on other sites More sharing options...
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