Vance Atkinson Oil Cooler Solution
by Vance Atkinson
Here are a couple of oil cooling things I did over 20 years. Tried the usual stuff, and looked at an Apache twin, noticed they had the oil cooler on the back of the engine baffle, lots of planes do. So I did the same thing, only in reverse This worked well for 12 years of so until the vibration broke the ears off the cooler. I had a lot of RTV around the unit so it hung right in there until I finally changed it. Don't know if it would work on a Long EZ as the NACA inlet is where Nat started the cheek bulges outward. The EZ doesn't have quite the same set up. see the below drawing.
You will notice the exit ramp on the top of the cowl. That took a fair amount of engineering also ( doesn't it always?) anyway the drawing below is the result of the slot placement. It was developed separate before the oil cooler and I put them on before the cooler and left them there. the actual hole is quite small but works well and the airflow stays attached. Early iterations of this produced a decrease in speed due to the air rooster tailing into the prop and wrecking the props efficiency.
After the ears fell of the old cooler I went to the lower aft baffle and the
next size up cooler. I couldn't put this cooler where the old one was, as
it just wouldn't fit. I went for bigger size because in a long climb, and a full load in
the Texas summer heat would put the temps a 250 at the top of the climb and
take about 20 to 30 mins to come down at cruise altitude ( usually 12 to
14,000') and I got the cooler almost free. Below is a picture of it. I also made a
small dam between the oil sump and cooler...it sort of heads the incoming rush
of air to the cooler. Amazingly enough, cylinder head temps didn't change.
I typically run 300 to 330 cylinder temps ( bayonet on bottom of cylinder) in cruise at
170kts true flowing 6.8 gal per hour. We can go faster but of course burn more
fuel and when we go in a pack or group, everyone wants to save fuel so we
throttle back to the above speeds. Actually I run FULL throttle but come back
on the mixture. I run way lean of peak..