I have heard that some turbo owners say that if you fly say a TB21 at the same power settings as you fly a TB20, you won’t get cracked cylinders etc.
Is this correct?
My view is that – for a mission profile involving any sort of altitude – a turbo engine must last less long simply because it is running at 100% power for the whole climb, whereas the non-turbo engine loses power the moment you get off the ground.
I expect that the top end components (in general) will see reduced life from being run longer at higher power settings. The bottom end (in general) may not see any impact because unless oil temperature is too high, or unless the bearing design load is exceeded, oil films will remain intact.
You really have to evalutate every component individually to determine the effect, unless you consider the entire engine limited by the most affected component in the engine. This then leads to the understanding of why engine ‘overhaul’ at a given time in service does not necessarily mean renewing every wearing compnent in the engine.
I wouldn’t think load makes that much difference if the engine is properly designed for it (you might be running it at 100 % of what is allowed, but who knows what is that to the engine). Presumably you have the same filters so the wear from abrasion should be comparable. And the same use profile so the corrosion should be comparable. Same lubricant. There could be a significant difference in temperatures but one could say that just shows a poor design (should have designed it with better cooling). If it’s a setting you can use continuously, it’s meant to withstand it. I would also think that generally speaking lower speed and higher torque is better for longevity and reliability than the opposite. Meaning an engine with forced induction could have an advantage as it would be able to deliver the same power with lower engine speed.
I personally think temperature is the key to long life. I know people who knowingly (somewhat) abuse turbocharged engines and accept the higher maintenance costs simply to get more out of them.
If you operate it at the same power setting, how could it be running at 100 % for the whole climb?
Martin wrote:
I personally think temperature is the key to long life. I know people who knowingly (somewhat) abuse turbocharged engines and accept the higher maintenance costs simply to get more out of them.
I agree. When i ran the Piper Mirage I had no engine problems at all due to three main reasons. Very careful on CHT and TIT temperatures. Very regular oil changes. I flew very regularly.
This was flying at FL250 where the turbo and engine is working very hard.
@JasonC
How Many hours did you fly the mirage ? What total time did it have when you sold it ?
I still don’t understand why a turbo normalised engine needs to have a lower CR than a non turbo engine of the same type and same max HP etc.
Is it because the turbo warms the air up so reduces the detonation margin? The TB21 has no intercooler AFAIK.
About 500 hours to 1100h TT. Beyond the point where many people have top ends, exhausts or turbos replaced.
In a thread somewhere about IO540 vs TIO540, I read recently achimba stating that his benign turbo installation was responsible for significant higher maintenance, in terms of turbo OH, cylinders, exhaust…
For my part, just had a short experience with a rented Arrow IV turbo, which had loads of oil on the belly.. The mecanics used to say it was normal and not a problem as long as level was regularly topped off… And in my young years, I believed him :-)
(In other words, don’t have any experience with turbos.)
Thanks Jason.
1100hrs is still a way to go to overhaul.
From the videos I saw with Dick Collins, who used to fly a P210, not known for engine reliability, it seems that extremely careful management, allowed him to fly his aircraft with little trouble (after hard times at the beginning, but it had to be linked with original conception)
