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Turbocharged aircraft engines: facts and consequences

@spirit49 it took me some time to understand what your post said. Am I correct to interpret as follows?
1. When adding an intercooler to a turbocharged engine some STC owners have promoted a reduction in MP for unchanged output power, and this is a bad idea
2. Intercoolers have a big drawback which is that they restrain airflow and cause a pressure loss in an installation – the exact opposite of the purpose of a turbo, causing a cascade of bad things on the exhaust side.
Confirm?

I was aware of 2. This thread is making me learn how naively wrong it is to think “turbo = free boost”.

Given an existing installation and type certificate, all we can do is
1. minimize the decrease of MP caused by the intercooler ( for example by keeping the inner channels clean of oil and other deposits) and
2. maximize the cooling effect ( by making the setup airtight and eliminating bad aerodynamic details).

We could also try to get free boost via ram air. It seems that this is even more worthwhile on a turbo engine than on a normally aspirated one!

LSGG, LFEY, Switzerland

Im no expert, but my understanding on the Intercooler upgrade is that the “expected” performance increase is more or less nullified by the issues described earlier.

It seems that the STC owners only took the temp decrease into account, not the restriction in flow.

Imagine you send your aircraft in for an intercooler upgrade. You get it back and follow the MP-Temp reduction schedule. And you end up with an aircraft that is super lazy.

I can’t imagine many has really followed the MP reduction.

The biggest advantage is an increased detonation buffer.
With our previous posts on LOP/Magneto timing etc, this is a great advantage.

spirit49
LOIH

spirit49 wrote:

Intercooler upgrade is that the “expected” performance increase is more or less nullified by the issues described earlier.

Add to that the added cooling drag.

No free lunch here

FAA A&P/IA
LFPN

… and at least in aircraft where the CDT is the limiting factor, the ability to fly higher.

Disclaimer:

I understand nothing about aircraft engines, I can only report on own experience.

I have a TB21 and about 6 to 7 years ago I exchanged the standard sponge airfilter with a Challenger airfilter that has a higher throughput. To achieve the same speeds as before I now need less fuel burn.
I have no intercooler but my theory is that my turbo needs to run less hard as it gets more air to start with hence the compressed air delivered to the engine is less hot.

My book says the following:
FL 150 75% (2400/25) 62.2l/h for 172KTAS with no antennas.
To achieve the same I can set the fuel flow at about 57 to 58 l/h with antennas and not the cleanest airframe. With this setting I am at about 75 to 80 degrees rich of peak.

Maybe you already have a high performance airfilter and the above won‘t help you.

Regards
Placido

LSZH

All this stuff about these numerous turbo issues doesn’t go down too well on me to be honest. Somehow, it makes a well powered NA aircraft (such as 300+hp IO-550 powered C182, 33/35 Bonanza or an early SR22) sound like a good proposition, if the moderate altitude performance is considered sufficient. I can fly my SR22 pretty much however I want, and CHT never go above 360 in the climb (300 in cruise). Just fly it, fill it up with gas and change oil occasionally. No in-depth semi-scientific studies, troubleshooting / fixing up over seveal years and all the other convolutions described in this thread.

Last Edited by boscomantico at 23 Dec 09:36
Mainz (EDFZ) & Egelsbach (EDFE), Germany

boscomantico wrote:

hese numerous turbo issues

I don’t see a big problem with these Turbo’s.

It is more about knowing how they work, and how to operate them properly.

I remember when I first bought my P210, I got so many horror stories from people about the Turbo system.

Yes, mine wasnt set up properly, and needed some work. But as soon as I could figure out what was expected of it, and got it all dialled in, it has been no problem.
You will monitor it like any other aircraft system, and troubleshoot any indication that it is not behaving as described.

The Wastegate needs annual lubrication with Mousemilk(Very important). The Turbo controller needs to be freed of oil crude occasional.
The Turbo needs an inspection to see that there is no greater play in the turbine, and that there is no damages to the fans.

The Turbo controller needs to be adjusted so to deliver exactly Max MP on take off.

I would always buy another Turbo aircraft. I live near the Alps

Last Edited by spirit49 at 23 Dec 10:42
spirit49
LOIH

@Placido do you mean the K&N filter? I bought it too at the same time (via that guy on the Socata group) but discovered the STC was duff and they tested them only on the pre GT TB. I sent it back. The MP gain was tiny, a small fraction of 1".

Turbo experiences vary hugely according to whether you have good people to sort them, and to some extent luck. One TB21 guy was grounded 6 months while Air Touring was learning how to fix the waste gate… Most of the stuff doesn’t get posted.

Administrator
Shoreham EGKA, United Kingdom

Some turbo installations are better than others. The Bonanza Turbo Normalized versions are some of the best. I believe the Intercooler is already in its third iteration and yes, you can upgrade from one version to the next. I have helped my friend transition his bog standard A36 to a full blown A36TN with TKS, 02, Gross weight increase to 4000lbs, etc; it is transformational. Last week he flew to Fano Italy at FL180, 3:02 (with a bit of help from a tailwind). In about 1200 hours since the upgrade: zero engine/turbo problems.

EBKT

I would always buy another Turbo aircraft. I live near the Alps

Fair enough. I do like the altitude capabililties of turbo aircraft. Not just for flights over the mountains, but mostly to get above weather, into calm air. But particularly flyingfish’s odyssee towards obtaining a flyable aircraft would have completely put me off. That one sure is special, because it’s such an exotic (and never debugged ) aircraft type, but even in a P210, one really has to put a lot of consideration into all the apsects of the turbo operation, and sure enough, the amount of trouble and downtime will be higher than in an IO-550 powered aircraft. I just want t fly and have as little issues and downtime as possible.

Last Edited by boscomantico at 23 Dec 12:25
Mainz (EDFZ) & Egelsbach (EDFE), Germany
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