Lets back up for a minute and consider putting the oil cooler in there the
long way. It has almost been working for Tracy with less than an ideal
air intake duct. Tracy's would work better if it had a NACA intake duct
on the top of the RV4 cowling IMHO.

An air outlet, either on the side of the cowling or on the top with an
exit flap for takeoff and climb could be used. This could make maximum
use of the stock RX7 oil cooler. The interior part of the intake duct
should be curved to encourage uniform air flow through the cooler. Perry
is also doing something similar.

I will make a drawing later today. Mike Wills is also considering
placing the oil cooler in this position but I am not sure if he is
planning on using the stock Mazda RX7 oil cooler. Mike?

Paul Lamar

Mike Wills wrote:

  I discovered a while ago that the stock cooler wouldnt work in a
transverse config. I'm using an Earls cooler part number 66010. Its about
1/3 larger in core area than the stock Mazda piece but will still fit
horizontally above the upper rear tubes of my engine mount.

  I question whether a NACA type inlet would really work on top of the
cowl. Pressure distribution plots Ive seen for most aircraft show this to
be a low pressure area - particularly at high AoA (climb). Seems it would
be better to take in air from underneath. It looks to me that a top exit
should be OK as long as its not too far back. I plan to use cowl flaps
there as you suggest. The plot I saw for the RV6 shows low pressure back to
within about a foot of the base of the canopy. Transitions to high pressure
from that point back to the canopy. Thats my opinion but I'd like to hear
from anyone who has a different viewpoint.

Mike Wills

You may well be right Mike. Do you have a scanner. Can you scan that 
pressure plot on the RV4? Are you going to use the stock air intakes
or are you going to place a water rad intake below the spinner?

Same question for Ken.

Paul Lamar
 
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