Jerry Hey wrote:
I spent about 5 hours trying to chop down the 2 inch 180 degree
sweep.
The plan was to cut a section out of the bend which would cause an
out
of round condition which I would repair by welding in material and
then
grinding to get back to round. It started out well and I soon had
the
two inch runner hugging the top of the engine. The problem came
when I
could not quite maneuver the tig torch far enough into the tube to
deposit material as far back as needed for fairing out the new
radius.
It would have been so easy to do with J & B weld (J & B whiskey
would have also come in handy) but the last step of welding the two
halves back together prevented that. I will spare you the details.
I
abandoned the effort as a no go.
So where to go from here. I see three possible solutions. One
is to
use a smaller diameter intake runner. The 1.5 o.d. runner has a 2.5
radius and would fit nicely. There would have to be a reducer with
an
internal taper to connect up soothly with my 2" o.d. throttle bodies
but that is not a big deal. The question how does that size runner
effect performance? I do like getting the fuel to the cool side.
The second possibility is to use the off the shelf 2 inch bends and
lean them over. As you said, I only need to lean them 20 degrees
to
get clearance. However, to lean them even 20 degrees, I have to
either
cut down or relocate the water pump. I have wanted to cut down the
water pump anyway just on esthetic principles. But this solution
may
not apply well to other installations especially those that need to
lay
down the runners a lot further.
The third possibility is the Russell Manifold. It is starting to
look
better all the time.
In looking for a solution, I would like to choose one that works
for
every application and not just mine.
To me, if the 1.5 inch runners will work, then that is the way to
go.
If not, then the Russell manifold would be the second choice.
I do want to ask about the possibility of a carbon fiber 180
degree
bend. I am thinking of something we can clamp the straight aluminum
legs into. Is this feasible?
Jerry
I agree with you on the Russell manifold and I am doing further work
on it.
Hopefully I can get the plenum box straight up and down. Hang on
more to come.
BTW To calculate the center line length of a 3 inch center line
radius bend
multiply the angle by .0524. For an example a 45 degree bend center
line
length would be 2.356 inches long.
BTW jerry cut down the length of the TB's as every little bit helps.
You don't need the hose barbs on the the prototype since the manifold
is under vacuum almost all of the time. All you need is 5/8 of an
inch
hose barb.
Paul Lamar
This is it. Uses a 6.5 by 4 by 4 Zero box with alternator flapper.
Bends 45, 180, 90, degree front tube.
Bends 20, 90 degree back tube.
Move the starter up as far as possible.
Adjust the length by moving the whole works closer or further
from the engine. You can also adjust the length by moving the
plenum forward. Moving it aft is not possible.
The neck bone is connected to the back bone and the back bone is
connected
to the hip bone etc., etc., etc., so don't make any other changes.
Everything fits under the stock cowl.
Current length is about 20 inches.
Paul Lamar
This is a breakthrough in intake manifolds. we have been fighting over
the
top for years. All made possible by the P-port. This will probably even
fit in a Lancair 360.
Thanks Russell.
Paul Lamar
It is beautiful but.....some things I still worry about. The plenum
box seems too small. Ram air blasting into that tiny box is going to be
extremely turbulent. Is this bad? I don't know. The rule I have heard
is the bigger the better when talking about intake plenums.
There must be a thousand articles posted on the internet about intake
tuning. To generalize, long, skinny runners are better for low end
torque and fat, short runners are better for max hp at high rpm.
Nobody discussed big, fat, long runners. All this kind of talk is so
vague it is impossible to apply. Is our aircraft operation "high
rpm?" Not according to Jim Mederer who a couple of years ago suggested
very small p ports and tiny runners for a 6000 rpm engine.
Here is another rule I read today: the intake runner diameter
should equal the port diameter. Does that mean our intake runners
should be 1.5" i.d. which is the size of my p port? My 1.5 port is
predicted to be able to flow adequately up to 8,500 rpm. Hmmmm. 1.5
i.d. runners would be a piece of cake to install on either side of the
engine.
It is almost pointless to talk about runner length. If the runners
cross over the engine they are going to be LONG.....and if they stay on
the hot side, they are going to be SHORT. And whatever length they
are, they are only tuned for a certain rpm. If you want to go faster
or slower, the intake is not going to be tuned to the job. How
critical is intake length? At the drags, it might make all the
difference but I doubt it is that critical for our medium rpm engines.
I believe Tracy uses a smaller intake runner, or at least he used to.
He uses little exhaust pipes too and a restrictive muffler hanging out
in the breeze. But he is gong 200 mph. I think this is good news.
Jerry
Well if you have room a larger plenum would be possible.
Mostly taller. IMHO you don't need it. Have you seen the plenum on a 3rd gen or
stock 3 rotor?
The runner length and size shown here is roughly what
the Lemans engine had. Are you going to go on what some piston engine
weenie says or are you going to go with what the Mazda engineers developed
for the 4 rotor to win Lemans ? :)
An aircraft engine is not like a car. The RPM range is less than
a 1000. Static to max speed. A car RPM range for a car is 1000 to 9000.
Write this down and paste it over your work bench. I am getting tired
of saying this. Don't make me send you the old messages on the subject. :)
Think of how much faster you will go than Tracy. If small pipes are the hot
tip why are you building P-ports? Allan Tolle went 238 MPH in the Sun 100
with P-ports and about the same size pipes. He also had the fastest time
to climb to 3000 feet beating all comers including jets.
Paul Lamar
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