>>Here's another
thought: A lot of it might depend on your intended usage. If you
want to go really high (over 20K) and have maximum performance you might want
to consider getting the extra power of the TSIO-550. But if you, like me,
might limit altitudes to less than 20K and are more cost and fuel economy
sensitive, then a lower tech solution might be in order. I flew for many
years behind a Lycoming O-540 that was turbonormalized (C-TR-182) and it worked
quite well. It didn't have an intercooler or automatic waste gate - the
waste gate was connected to the throttle linkage so there were no extra levers.
It was fed by a pressurized carburetor, so that doesn't apply with a
Continental. So the question is, what's wrong with using a standard
IO-550 with a turbo and manual waste gate? The Lycomings don't bother
with a sniffle valve, so there isn't any difference between turbo, fuel
injected, or naturally aspirated engines in that regard. At 18,000 feet
the use of an aftercooler has real, but marginal benefit, as the extra
aerodynamic drag and pressure loss negate most of the charge-cooling benefit.
Just a thought, suggesting a KISS methodology.
Gary<<
Gary,
Some comments.
I think new designed high compression engines with
compressors of any kind should use our present state of knowledge and incorporate
intercoolers - - good intercoolers.
The engine you are discussing had lower compression ratios.
As someone else said in this same thread of messages, unless you
really know what you are doing, you can screw up and have a very unhappy
installation.
Intercoolers have large benefits - - - even at sea
level. I do not think it is accurate to claim that
intercoolers only have “marginal benefit” below 18,000 feet.
Here is why I think they are important: At 18,000
feet, the compressor discharge temperature on a warm day can easily
exceed 200dF. Without an intercooler, 200dF air
goes straight to your cylinders.
With the TN IO-550, the induction air
temperature at 30” at 18,000 feet on a hot day will be less than
105dF. Typically 95 to 100. There is a large difference
in performance and detonation margins between 200+dF air and < 105dF air.
The O-540 “solution” does not really provide more
fuel economy. Rather, likely just the opposite.
The TN IO-550N engine that Tornado Alley delivers to Cirrus
will produce horsepower at 0.38 to 0.39 BHp/lb-fuel/hr
across an altitude and power range that spans anywhere from sea level to 29000
feet and do so at 200 Hp or at 310 Hp, or anywhere in between. [The
real world numbers for the Thielert diesel was about 0.36 to 0.37
BHP/lb-fuel/hr.] There is no other general aviation engine installed in any
fleet of aircraft that works anywhere near that well across that broad
range of operating requirements and environment.
90% of the hours flown with those engines are flown between
11,000 and 18,000 feet.
There is a reason why Cirrus has sold ~ 900+ turbonormalized
SR22 aircraft in the last 35 months, including 15 months of some of the worst
times in general aviation history.
The reason is - - the systems consistently exceed the
expectations of the owners.
During that period of time TAT continued to improve and
refine those systems. They are, today, about 15 lbs lighter than
they were in 2007. They run cooler. They are simpler to
maintain. That comes from a passion for continuous improvement.
And those systems are going to become still more efficient and
versatile when the electronic density controllers are installed.
Regards, George