About that Jab cooling. Europa does not have a firewall forward so I
have been bad and not commented on cooling this engine.
I have found that putting a dam above the cylinder tends to work for the
cylinders forward of the dam, but consider you have reduced the size of
the plenum effectively as the air behind the dam becomes quite stagnant,
may starve the aft cylinders of air.
The object is to get high pressure air to pool above the cylinders and
allow it to pass through the fins in an orderly manner to absorb the
heat. If the air rushes through the slot, the air won't pick up enough
heat to help cool the cylinders. Since the heads are square-ish you
have the problem of having horizontal air flow over the heads as well as
vertical. Also what about the bottom of the heads and cylinders?
Quite some time ago Graham noted that the engine almost needs a set of
horns focusing air down over those square heads. From that idea and his
work, I put simple metal air guides down through the cylinders as guides
as suggested in the NACA cooling of air cooled engines work done pre and
post WWII.
I sent Rick picks of some of my Jab solutions we perfected in the shop.
We are quite pleased that at least we have made the Jabs flyable.
Prop pitch, carb tuning, intake manifold leaks, inlet size and more
importantly, the mechanical or aerodynamic draw of the cowl exit is
essential to get air through those poor overworked fins. The poor guys
at Lightning Aircraft opened a huge hole in the bottom with a large
flange, but it slows the plane because of the cooling drag. Much fine
tuning was required. But it does cool. Sonex has also had modest
success with their extensive mods.
Pay attention to your prop. The torque curve of the Jab falls off
beyond 2750 and that is where the heat starts to build. Pete at Jabiru
USA likes to run his engines at 2900 which needs a 62 inch prop and a
bit of carb tuning, but it gives Pete descent cooling. In the Jabiru
aircraft, with its large suction hole in the bottom, it does allow it to
cool at steady cruise. I prefer the larger diameter 64 inch, but have a
bit of an issue above 2750 RPM.
We need to get away from the two existing cowls and probably work a 5
inch diameter type inlet (just look at the new Zenith huge holes) and
control the air carefully over the square heads. As Rick and others
have found, the oil coolers need to be more like a certified type (I
suggest the 8 bar) and of course sealed well with a guided exit. Guide
the air over the fins and don't overcool those front cylinders in cruise
or on descent.
I know I should do an article about some of the solutions that we have
confirmed work, but there is just not enough hours in the day.
Keep plugging away guys, you're on the right track.
Just my two cents....
Regards,
Bud Yerly
Custom Flight Creations, Inc.
www.customflightcreations.com<http://www.customflightcreations.com/>
(813) 653-4989
----- Original Message -----
From: jimpuglise@comcast.net<mailto:jimpuglise@comcast.net>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Monday, July 16, 2012 6:08 PM
Subject: Re: Europa-List: N120ej trails and tribulations
Rick-
INTERESTING! Couple of thoughts. Before you modify your inlet
openings, try putting some vanes in the plenums hung off the top. I
have not done that, but it will be my next step if I still have cooling
problems. My thought was that they would be about 1.5 inches deep and
run from the front to just forward of 5 and 6. If that doesn't do it,
you could put some deflectors on the vane to deflect more air toward the
heads. The vane worked so well in my cobra head that I think it may
help here too. The air coming into the plenums must be very turbulent
as is. My plenums are back on the plane and now on to the oil cooler.
I may have told you that I split my shark's tooth along the sides and
made the opening about 1/2 inch higher. Both that, and my cooler is
11.5 inches wide, so I have some hope for it. Also, did you add the
holes and plenum on either side of the shark's tooth to cool the oil pan
directly? I have it on mine and oil temps have been OK. I built it
this way, so I can't say that made the difference, but I remember
reading somewhere that cooling the pan directly helps. John probably
told you too that he worked around the problem by mounting the cooler
directly in the cowl. When he takes the lower cowl off, he needs to un
hook the cooler from the hockey puck. We need to open a photo sharing
site somewhere. My pictures are 5 GB each, so e-mailing them does not
work well. Any thoughts?
Jim Puglise
-------------------------------------------------------------------------
-----
From: "AirEupora" <AirEupora@sbcglobal.net>
To: europa-list@matronics.com
Sent: Monday, July 16, 2012 11:15:59 AM
Subject: Europa-List: N120ej trails and tribulations
<AirEupora@sbcglobal.net>
After some very short flights I have finally gotten N120EJ up for a 46
minutes flight last week. I=C3=A2=82=AC=84=A2m still having some
heating problems, but am getting closer to solving them. Bud Yerly, Jim
McCormick, John Lawton, Jim Puglise have been a big help. I knew when I
bought the Jabiru that I'd have heating problems, but for the 10K that I
save by buying the Jabiru I figured I could do a lot of modifications to
the cowl and engine if need be.
One area is the plenum chambers for both sides. I have the type with
the spark plug wiring and CHT wiring running inside. The first
modification was to the plenum chamber. There is not a lot of
information out there for installing the baffles in the plenum. Bud
recommends not using any, but I had installed some. I had to cut these
out completely and my dealer, Jim McCormick, said I had installed them
wrong. I then installed three dams =C3=82=C2=BD=C3=A2=82=AC=EF=BD
across both front cylinders and mid cylinders plus a
1=C3=A2=82=AC=EF=BD dam over 5 & 6. I have since cut these down
to 1/8" on the front two cylinders on both mid cylinders. I have 1/2"
on the two rear cylinders. These are vertical to the air flow. Not
sure why, but that=C3=A2=82=AC=84=A2s what Jim McCormick
recommended. I have also installed the inter baffles that Jabiru stated
that I did not need. I have also wrapped a piece of aluminum around 5
and 6 to get more air moving across the fin area.
I have four inch openings on the Canadian Cowl that I'm using. I
found out after I installed them that John Lawton had gone to five inch
openings. I have modified the shark tooth or NACA duct for the oil
cooler. Trying to figure out a method of using this NACA duct and
keeping the oil cooler attached to the engine had been a real challenge.
I think I have modified this one piece five to six times. I have what
is called an 8 bar oil cooler. It is about the closest thing to
aviation type oil cooler. The last modification was wrapping the oil
cooler with duct tape and waxing it so I could make a fiberglass mold.
Once I had the mold made I placed it in the lower cowling and designed
it to be glued into place so air could not escape around it, but had to
go through it. I built a duct behind the oil cooler as recommended by a
good friend and that has help a lot. I noticed after doing all this
work that my cowling had dropped =C3=82=C2=BC=C3=A2=82=AC=EF=BD
I flew it this way and the oil temps !
came down and stayed down. I then went back and figured out what was
causing the drop in the cowling and fixed that, but that caused the oil
cooler opening to move away from the oil cooler about
=C3=82=C2=BC=C3=A2=82=AC=EF=BD on the bottom. I flew it that way
and sure enough the temp came up.
One area that I might work on is making a cowl flap for the oil cooler
duct. Not sure how to do it right now. It will have to be part of the
airframe and not the cowl. More on that later, if and when I do it.
I=C3=A2=82=AC=84=A2m planning on putting a raised ring around
the openings for the air intakes. Right now this is a flat area and I
have been reading some data that shows that I can increase the flow into
the plenum chamber by doing this. There is a dam on 1 & 2. I have made
a ramp so that the air will flow up and over these dams. The temps on 1
& 2 are good right now, but the ramps may cause them to run hot.
One thing that has helped a lot is the black box viewer on the MGL
Odyessey II. It gives me the data in one second packets. The air temp,
altitude, RPM, manifold pressure, oil temps, oil pressure,
CHT=C3=A2=82=AC=84=A2s, EGT=C3=A2=82=AC=84=A2s, etc. It is
a great tool.
Well, it time to go back to work on the Europa/Jabiru.
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