Treating a turbo (TN) engine like a non-turbo engine, to make it last longer?

huv wrote:

Any details of that? Apart from the engine break-in, is there any harm in “babying” the engine if the oil and cylinder temps are within recommended margins?

Ask Deakin and his crew [Braly] they have the data.

Also, believe me, the heat and pressure (same thing) generated in a turbo’d engine is far greater than an NA engine (duh!) and if you inspected dozens of them all year ’round like I do, you would have absolutely no doubt about it.

Michael wrote:

if you inspected dozens of them all year ’round like I do

Does that mean that you agree with Peter that the high exhaust temps of the turbo’ed engines cause more exhaust pipe failures?

huv wrote:

Does that mean that you agree with Peter that the high exhaust temps of the turbo’ed engines cause more exhaust pipe failures?

Absolutely . There is no doubt whatsoever that turbo charged engine exhaust systems have a shorter life expectancy and require far more maintenace thanan NA exhaust system.

Exactement! I had two Cirrus SR22s before I got the TBM, one T and one NA model. The NA (by far the best piston aeroplane I ever had) was much cheaper to operate, must have been almost 30 percent cheaper.

The only problematic item for me is the exhaust. It requires regular repair, more so than on a NA engine. It’s not that expensive though, you just need a good welder and a good eye to catch the problems early. However, the added capability of a turbo engine is so significant that I would never consider giving it up. As the thread title says — you can choose how much power you demand from your engine. Being able to do a >800fpm climb at FL180 is priceless.

Another major thing for me is noise. I do not have to cruise at max RPM at my typical levels (ca. FL150), I can reduce the RPM and compensate by adding more MP. Makes a huge difference in comfort.

chrisparker wrote:

The GAMI/TAT course teaches that an RPM reduction after t/o slightly increases the internal cylinder pressure

That’s because we’re dealing with primitive engines. Speed influences where the piston will be as the combustion event progresses (higher speed means it will be “hit”, in layman’s terms, further down the stroke). So relatively high power settings are not desirable when the engine runs slowly. Even cars don’t like it.

huv wrote:

is there any penalty for running the TIT close to the limits?

It depends on how often you fancy overhauling/ replacing turbochargers. I know someone who runs them hot simply because the fuel saving is worth it.

Peter wrote:

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.

Let’s take an example at FL100. In standard conditions, OAT is -5°C, pressure 700mbar. Normalize it to 1 atm, assuming an average compressor efficiency and no intercooler, the intake air temperature will be around +35°C. What you’d get at sea-level on a hot day, no big deal.
Now on a hot day, a front or something. I read on some POHs a hot day as 30°C above STD. OAT=+25°C @ FL100, same pressures, intake air will be 75°C-ish.
In a modern engine, the ECU would delay the ignition timing to suppress knocking. But we don’t have that luxury in our dinosaurs, so the CR is reduced to keep the peak in-cylinder pressure and TIT within acceptable limits.

Concerning exhaust manifolds, a turbine is acting as a dam for exhaust gases. That’s why a turbo engine has higher pumping losses than a NA. So the part upstream of the turbine has a tough life at ~TIT and high pressure, while the part downstream is a lot colder and more or less ambient pressure. Appropriate materials for the respective segment could be different too.

Arne wrote:

In a modern engine, the ECU would delay the ignition timing to suppress knocking.

Leading to unpredictable power loss on any given day, and the inability to predict aircraft performance when full power is needed. Not a very good solution for an aircraft. A better solution is an intercooler, or higher octane fuel. These also provide for larger cylinders, which reduces complexity and weight – particularly in the case of good fuel, which reduces design complexity and weight without a bulky, drag inducing additional part.

Its bad enough when my turbocharged, intercooled (and heavy) 275 HP car goes into knock sensor mode, loses substantial power and foils my plan to use full power to slot into some hole in traffic. I need two more AKI points, not available at the pump in my area. I wouldn’t look forward to the same issues when flying my planes.

Silvaire wrote:

Leading to unpredictable power loss on any given day, and the inability to predict aircraft performance when full power is needed.

An ECU adjusting timing is not your biggest problem in an airplane context. Under these conditions, the filling efficiency goes down and hence the engine power goes down. If strictly normalizing, your engine cannot put out full power.

Silvaire wrote:

Its bad enough when my turbocharged, intercooled (and heavy) 275 HP car goes into knock sensor mode, loses substantial power and foils my plan to use full power to slot into some hole in traffic.

You are demanding too much too fast from your car, there is no way a reactive system would ever have time to react to such a load case in any car, the only way would be feed forward.