>
> Hey Marv, Ken,  et al,
>
> Cooling is firstly a function of the heat exchanger's ability to reject
> the heat transfered from the engine,  and a function of the specific
> heat of the coolant mediums.
>
I must make a confession here. I have strayed from the tried and tested GM
A/C cores. I actually tried pairs of 2 different sizes and was unable to
make them fit exactly as I wanted. I've read Tracy's report that due to the
density of the heat exchanger, it is not as important to position them
aligned with the air flow. I have no data to dispute this, but I just wanted
to have them aligned with the flow anyways. I have the RV-7 cowl for the
IO-360, which is slightly wider in this area, and yet I still could not fit
them the way I wanted them.
So, I got to thinking about the A/C performance of my Ford truck & my
neighbors Chevy truck. We often alternate whose truck we would take on
fishing trips, so I have spent many hours in both. Both trucks were new
(bought within the same week) and yet we both agreed that my A/C was far
better (we didn't agree on much else). Being as I've always been a Ford
Powerstroke man, I decided to try these.
The ford cores mounted perfectly where I wanted them, aligned with the
cooling flow, with a very simple light weight mount. They were actually
easier to weld on than the GM cores (different grade of alum?) I'm far
happier with them than I would have been with the GM cores.
The GM cores had a total volume of 623 cu" while the Ford cores have an
area of 575 cu". The Ford cores are .5" thicker, but 1.5" narrower and ...
damn, I forgot how many grams lighter, but it was enough. I reasoned that
even with proper ducting, how much of this extra width will get proper
airflow when you consider the area of the inlet. I won't be sharing any of
this cooling air flow with any other heat exchangers. The oil will have a
large NACA duct off the belly, the intercooler will have a small NACA duct
off the side and combustion air will be fed from the top. With all of the
airflow from the front inlets going through these rads, aligned with the
airflow, I hope to get as sufficient cooling as the GM cores, but with a
lighter installation.
I realize that this may skew the EWP test results one way or the other. If
I don't have sufficient cooling to begin with, I will change these and
retest before I give up on the EWP.

I thought I should share this, in case anyone has any concerns over the
validity of these tests.

S. Todd Bartrim
Turbo 13B rotary powered
RV-9endurance (FWF)
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm