SNIP:
...........I turbo normalize plus (make moderate gains in power
at S/L
through use
of the turbo then 'normalize' that amount of power for benefit at
altitude). I achieve that by use of the throttle.
I have a fixed waste 'gate' (exhaust bypass really) because it
was the
easiest way for me to get a big wastegate. I believe an
aircraft style
wastegate is an excellent choice, but a LARGE automotive style
can work
equally well and is more available and less expensive.
David Leonard
Turbo Rotary RV-6 N4VY
N4VY.RotaryRoster.net
<http://N4VY.RotaryRoster.net>
www.RotaryRoster.net <http://www.RotaryRoster.net>
leonardiniraq.blogspot.com
<http://leonardiniraq.blogspot.com>
David,
Again I apologize for my ignorance, but can you explain exactly
what you
mean by "fixed wastegate"? If I understand the term "fixed
wastegate", its basically a wastegate that is always open a
little to
allow a constant leak? That would also allow a constant
percentage of
the exhaust to flow into the turbine side of the turbo. If that is
correct, Why use a "wastegate" at all? Why not just have a small
port before the turbine that leaks exhaust around the turbo and
back
into the exhaust pipe? I guess a set up like that would
require some
sort of trial and error getting the % of exhaust bypass
correct. Maybe
some type of restrictor in the bypass port? But you would
have much
control of the turbo that way!! Is that why you use a "fixed
wastegate"? So you can adjust the amount of bypass? How does that
differ from the normal wastegate operation? I thought a wastegate
cycled from open to closed based on its duty cycle. That's
different
from the fixed wastegate isn't it?? Damn I'm confused!!!!!
Also what
do you mean by, "then 'normalize' that amount of power for
benefit at
altitude). I achieve that by use of the throttle." I didn't
follow
that part at all.
Don
Don, you are right that it is not a wastgate proper, but a bypass
port.. it used to be a wastegate until if removed the flapper valve.
Why? Because it was creating more back pressure than necessary for the
boost I needed - even with the flapper in the full open position.
Nothing fancy, I just hacked it off with a dremmel. That opened up the
exhaust flow quite a bit.
There is still enough exhaust energy to get me about 10 psi boost (about
50 MAP) at sea level but I never use more than 5 psi. (that is the plus
part). at 10000' I still have over 30"MAP available (that is the
normalization part). Just like anyone else, I just control my MAP by
using my throttle - there is nothing else to control except mixture
etc..
Not the most optimal set up, but not bad either. Cheap, easy and
effective. The opening does not have to be exact. The preferred method
would be to use a much larger turbine housing and an operative
wastegate, but that is difficult, expensive, and most of all - won't fit
in my installation.
--
David Leonard
Turbo Rotary RV-6 N4VY
N4VY.RotaryRoster.net
<http://N4VY.RotaryRoster.net>
www.RotaryRoster.net <http://www.RotaryRoster.net>
leonardiniraq.blogspot.com
<http://leonardiniraq.blogspot.com>
Thanks David, that clarifies things quite a bit for me. I really
appreciate the info. This is a subject that I thought I understood
until I actually contemplated building it and started thinking it
through. I quickly realized that there is a lot more to it. Your
spreadsheet has been very helpful for zeroing in a several different
turbos that will work. Which turbos are you actually running in your
plane? Is it oil or water cooler or both?
Thanks again!!
Don Mitchell
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