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Alain said:
When boosting engines beyond their design output, does Performance Engines take
into account the significant stresses imposed on the crankshaft (and other
stressed parts, for that matter)?
Walter
Atkinson said: Alain, I think you're on the right track.
There has been compelling evidence shown that the Lycoming crankshaft
problem is one of design, not manufacture.
I do not have any first hand knowledge of the Lycoming fiasco, therefore I
will default to Walter as I am confident he is correct. However, I will
point out there are a lot of factors that go into making a reliable engine
besides crankshaft ultimate strength. One important item is: How do you fly the
engine? As Water has correctly pointed out in the past...where do you
develop peak cylinder pressure. Is the engine well balanced? Are
other components such as pistons up to the task? I just returned Saturday
afternoon from a visit to Performance Engines relative to them building a 400 hp
TSIO 550 for my IV-P. I was very impressed with Ron Monson and Performance
Engines.
Back to the crankshaft....General Motors has a very sophisticated computer
finite element model program for designing crankshafts. They still TEST
engines. The only way to test engines is on a dyno or in our case in a
plane. In my mind, the necessary test time has been accomplished on the
TSIO 550 to make me comfortable with the engine I want. There are a lot of
these engine flying and the same engine is being raced at 600 to 700 hp.
The racing alone does not make a 400 hp version acceptable, however the
ultimate crank strength is pretty good. The one thing I am 100%
confident in is.....if I was to buy a "new" TSIO 550 engine, I would send it to
someone like Performance Engines to be "fixed". If you are not comfortable
with a higher hp engine, then go with a "high quality" built standard hp
version. Whatever you choose, I don't think you should need a top overhaul
in 800 hrs let alone in 400 hrs. I believe a good builder will warranty
his build unless you are calling the design shots or racing.
My direct answer to your question is.....the testing has been done and
will continue to be done by those who buy and fly these high hp engines.
On the other hand, just because the "Factory" says its OK does not necessarily
make it so. The Lycoming fiasco was do to standard engines going south.
But I also believe you have to be even more careful when venturing away
from the norm. Decide what interests you and talk to those that fly
them. If you want something totally unique, then you are the man....you
take the initial risk.
Craig Berland
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