RobertL18C wrote:
Also the typical 4 psi of the pressurisation means cabin altitude is comfortably below 8000 feet.
If your Malibu can only hold 4 psi diff pressure than it has most likely had a major accident damage that was poorly repaired or a damage in the pressurization system. Both is extremely dangerous and I’d suggest having it checked by a Malibu experienced A&P before the next takeoff!
A normal, well maintained Malibu should easily hold 5.5psi pressure diff. That gives you a very comfortable 5000ft cabin altitude at FL210 – the sweetspot altitude for the piston Malibu.
@malibuflyer was actually thinking of the 340, impressed at the Malibu having 5.5 – this may explain cylinder and exhaust system stress, as the PA-46 is comfortable at FL250
Is there any data to show the hypothesis, that cylinders in a Malibu (or P210) need to be replaced more often, than in non pressurized planes with similar engines?
From what I see in my very limited filter bubble, the friends with a Conti-550 Malibu do not feel to have more trouble with the engine than the ones who operate a very similar power plant in a Turbo-Cirrus. Obviously that is not data as it is a far to limited view and not systematically tracked – but I simply do not have the impression that Turbo-Cirrus Owners complain less about cylinders.
quatrelle wrote:
A friend in Germany had a hot section (on a -35) and a new compressor turbine vane ring done at the same time 2 years ago by P&W themselves (at the maintenance facility the aircraft was at), total bill was 20.000 Euro plus tax and he showed me this bill to prove it, as I didnt believe him.
Or about the same as the cost of 6 new cylinders on a Continental, which I from personal experience would plan for every 1000 hours.
Presumably that 20k figure includes other rectification of stuff discovered at the time, but that’s normal as well 
Out of interest do the Cylinders on the Lycoming 540 powered versions last longer?
denopa wrote:
7 years of ownership and I’m still finding out what it can do (playing with long range settings as my kids grow up eating into my fuel load for example, it’s incredibly quiet, peaceful and pleasant in the cabin at those settings, especially LOP), but I still have the same day-1 joy going for a short flight around the Isle of Wight or doing an airliner-style trip to the Continent.
Do I understand correct that you run the Lycoming version Lean of peak? If so can you provide some data what FL, RPM, MP do you use for this? What is fuel flow and CHT and TAS?
Malibuflyer wrote:
Is there any data to show the hypothesis, that cylinders in a Malibu (or P210) need to be replaced more often, than in non pressurized planes with similar engines?
How is the PA46 pressurized? I suppose bleed air from the turbos somehow?
On how long a turbo engine lasts (before cylinder replacement ect) for sure also has alot to do with how the engine is operated. And also how much power output the engine is asked to deliver in a certain application, cooling and so on. The PA46 application is very high power output. My TB21 TIO540 only outputs 250 HP in comparison. I fly it usually between FL180 and FL200. Temperatures are easy to keep in check in this altitude in cruise. Actually the engine just had an special engine check in relation to annual and everything looks great. Valves looks good, compressions are fine, oilconsumption is fine. I doubt it will need major work before at least reaching 1500 hours or more. On the other hand getting into a PA46 I think one has to realized that one is taking a step up in ability as well as price. I could live with cylinder replacement at 1000 hrs in a PA46.. The question of the PT6 jetprop/meridian version is just how close they compare in running costs. I found this PA46 cost comparison which does indicate the jetprop is close in price to a lycoming PA46 even including overhaul.
Another question on the PT6. Does is suffer in the same way with periods of inactity? Typically the piston engines suffer from internal corrosion especially if flown on only short trips before long periods of no use, where the engine (oil) does not warm enough to boil out water from the oil. What happens to the PT6 if left on ground for extended periods of time?
THY wrote:
I found this PA46 cost comparison which does indicate the jetprop is close in price to a lycoming PA46 even including overhaul.
This comparison assumes (amongst other things) that you only fly at cruise speed at cruise altitude. If your average leg is 1000NM, than this simplification might make sense. If you more often fly 200-400NM legs, it’s vastly off reality…
But the theme is directionally right (and has been mentioned before in this thread): As a long range workhorse a turbine Malibu can be operated at very similar cost (if not cheaper) than a piston one. The beauty of the SEP-Malibu is, that you can use it in the Levels over the Alps and for the 30 min Pizza-Hop economically.THY wrote:
And also how much power output the engine is asked to deliver in a certain application, cooling and so on. The PA46 application is very high power output. My TB21 TIO540 only outputs 250 HP in comparison.
I don’t think that absolute power output is the best comparison because an engine is designed for that power. I typically run my Malibu at 65-75% power – that is including the power needed for pressurization. My impression is that most Cirrus Owners do use similar power settings and therefore put the same strain on their engine.
Therefore my question was on actual data and not on beliefe of why a certain result could or could not be explained. One could also imagine good reasons to believe, that the engine in a pressurized plane should actually last longer…
Did check on the Continental TSIO-360, so not a strict read across, but operations that put several thousand hours a year on them, mainly at FL80-100, find them reliable and making TBO of 2000 hours. Some cylinder work, affecting 2 or 3 cylinders, is common at around 1200-1400 hours. The SOP is not LOP but to lean to a target fuel flow, which is around 65%.
They are investigating getting a revised TBO of 3000 hours based on a mid time TOH.
The power plant is also used on the Mooney 231.
The main reason the same or a similar engine lasts less long when it has a turbo, and even less in a pressurised aircraft is the altitudes they are flown at, and how they get there. So I am not surprised that a long-lasting engine with an added turbo (and slightly different compression) remains long-lasting if flown reasonably low, in the cruise it will have a little less cooling airmass than a NA engine, and the climb power will be higher, but only for a few minutes.
Put the same engine in a Mooney and fly at FL250 every flight and it won’t last quite as long.
There are of course aircraft installation factors that make a difference.
