Hi Lynn,

I have a couple of comments/questions about the current configuration of
Andy and Darryl's cooling system. These are relevant in that I believe their
installation is significantly different from most designs utilized by the
members of this list.

1. On Race 33, they use updraft intercoolers that exhaust air from blisters
on top of the cowling. Thus the exhaust air from the intercoolers does not
contribute to increased backpressure under the engine which may interfere
with flow through the cylinder head cooling fins. On the other hand, the
blisters may add to the overall cooling drag of the installation through
increased frontal area in the high-velocity, high drag region of the
propwash.

2. The 2 cowl inlet openings are considerably larger than on a stock Legacy.
This will also increase cooling drag.

3. In 2002, I know that Andy and Darryl were spraying a significant amount
of liquid into the top of the plenum to keep the cylinders cool. Do you know
if they are still using air and liquid to cool the engine?

Based on the above comments, I would suggest that their installation likely
has MORE drag than a stock installation rather than less. I suspect their
excess cooling margin is derived more from larger inlets and potentially
larger TOTAL outlet area, the benefits of liquid spray evaporative cooling,
higher indicated air speeds, and, possibly larger/more efficient
intercoolers.

I'm not denying the success of Andy and Darryl's race effort. They have done
a tremendous job and have achieved great success in a short period of time.
But maybe the keys to their success are not lower cooling drag, but rather,
a very high performance engine coupled to an already very low-drag airframe
piloted by one of the best race pilots ever to fly at Reno.

From the data presented at Ada on engine cooling, it is the dogged attention
to detail design that pays the dividends when it comes to keeping our
engines cool. The only real benefit to a plenum, besides looking totally
cool, is that you have eliminated possible leakage paths for the incoming
air. The downside is that you have a reduced volume in which to decelerate
the high-velocity low-pressure air into a more useful, lower drag,
low-velocity high-pressure air source.

Best Regards,
Mike Hutchins