REFLECTOR:INTAKE COMBUSTION AIR

Sun, 14 Sep 2003 08:18:02 EDT

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I have an XL FG with Lycoming IO540, two oil coolers.

I have always had a bit of a cooling issue. Not so much that temps are high, 
but that they are uneven between cylinders. The center two (3&4) are 
significantly cooler than the end four. Thisa is sometimes 70 degrees or more.

After a lot of time trying to get diverters in the ducting to move a greater 
amount of air to the ends of the plenum, I took a hard look at how Lycoming 
has the air flow controlled between the cylinders and noted that they have 
baffles between the cylinders that force the cooling air to stay within the 
cylinder fins nearly to the bottom of the cylinder. On the other hand, the XL plenum 
stops half way down the front and rear cylinders, allowing the air to "escape" 
from the cylinder fins at this point.

I also took a look at a a long EZ and how that engine is baffled. I saw that 
the baffling has the air confined to the cylinders with just a small (2.5") 
opening for the air to exit the fins.

By coincidence just this week I decided to extend the ends of the plenum to 
near the bottom of the cylinders, cutting them off at the approximate length of 
the Lycoming  baffles.

How does it work? I don't know yet as I have just completed the job and have 
not had a chance to fly it yet.

The other heat issue I have is that the front oil cooler puts too much heat 
into the nose., and then into the cockpit. I have a piece of foam above the 
canard inside the hatch cover to block the heat from the nose and insulated it as 
well as I can by adding insulation around the body of the cooler and 
insulating the oil lines. I point out that I have a FG, thus no nose gear door to 
allow air into the nose. I have toyed with the idea of adding a small vent to 
bring in cool air to this area.

Any thoughts or ideas or concerns?

Bob Wood
N658SE
XL FG Bob II

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<HTML>I have an XL FG with Lycoming IO540, two oil coolers.<=
BR>
 
I have always had a bit of a cooling issue. Not so much that temps are high,=
 but that they are uneven between cylinders. The center two (3&amp;4) are si=
gnificantly cooler than the end four. Thisa is sometimes 70 degrees or more.=
 
 
After a lot of time trying to get diverters in the ducting to move a greater=
 amount of air to the ends of the plenum, I took a hard look at how Lycoming=
 has the air flow controlled between the cylinders and noted that they have=20=
baffles between the cylinders that force the cooling air to stay within the=20=
cylinder fins nearly to the bottom of the cylinder. On the other hand, the X=
L plenum stops half way down the front and rear cylinders, allowing the air=20=
to "escape" from the cylinder fins at this point. 
 
I also took a look at a a long EZ and how that engine is baffled. I saw that=
 the baffling has the air confined to the cylinders with just a small (2.5")=
 opening for the air to exit the fins. 
 
By coincidence just this week I decided to extend the ends of the plenum to=20=
near the bottom of the cylinders, cutting them off at the approximate length=
 of the Lycoming&nbsp; baffles. 
 
How does it work? I don't know yet as I have just completed the job and have=
 not had a chance to fly it yet. 
 
The other heat issue I have is that the front oil cooler puts too much heat=20=
into the nose., and then into the cockpit. I have a piece of foam above the=20=
canard inside the hatch cover to block the heat from the nose and insulated=20=
it as well as I can by adding insulation around the body of the cooler and i=
nsulating the oil lines. I point out that I have a FG, thus no nose gear doo=
r to allow air into the nose. I have toyed with the idea of adding a small v=
ent to bring in cool air to this area. 
 
Any thoughts or ideas or concerns? 
 
Bob Wood 
N658SE 
XL FG Bob II</HTML>

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