10-18-03 1.2 / 6.2 total
Started the day by
reducing the size of the air inlet to 19 1/8” wide, by 2.5” tall (48 sq
in). I also tied a bright colored
string to the cowl exit on the left side, so I could see where the air
went.
Test flight number
one showed 2500 fpm on my new VSI, at about 110 mph, and 5psi of boost. Unfortunately, the oil temp was
high. On climb to 4000 ft, the oil
reached 230F, and the water stayed at 180F. I remained level at 3500 ft for a few
minutes, at about 27” MAP, and the oil started coming down slowly. Water dropped pretty fast to 130F. Oil came down to 130 on low power
descent, and water remained at 130F.
Watching my cowl
exit string revealed that the air goes pretty much straight back from the
opening. On the ground, I could
feel the hot exit air, and it seemed to go just about 3 inches below the canopy
rail. My eventual plan is to blow
my exhaust out this exit hole. I think I’ll be able to exit the exhaust here, as
long as I direct it a bit outboard, and maybe downward some, and get a good
carbon monoxide sensor. I can’t get
too carried away with the downward stuff, because that would be pointing right
at the fuel tank.
From the temp tests,
it seems clear that I have far more excess water cooling, than oil cooling
capacity. After the flight, I went
ahead and opened the cowl inlet back up to it’s normal 80 sq in area to make the
oil temp happy, then covered over more of the radiator. It’s getting really small now. In fact, it’s half covered!
Second flight was a
quickie, and only went to about 3000 ft, at 2700 fpm,
and 100 mph. I realized after the
flight, that I didn’t completely block off the rear cowl opening on the bottom
when I put the cowl back on, but I don’t think this will make much
difference. Water stabilized at
160F, and oil went to 185F, and was probably still rising very slowly. Both temps dropped to 130F on
descent. Not sure what the next
test will be yet.
The rad core width
is 17.25, and the length as been changed.
Full length is 24.25”. The
length (not covered) on the first flight today was 17.75. The final length (not covered) was
12.625”. HALF the original
radiator. The core is 2.25” thick
if anyone is doing the math.
Here is a chart of
inlet, rad size, and temps for climb at around 100-100 mph. Outlet is fixed at
about 66 sq in, but will be close to 80 sq in due to larger cheeks on the new
cowl.
Inlet (sq in) |
Rad core (sq in area) | water temp F |
oil temp F | OAT
F
80 |
423 | <180 (t-stat) | 180 |
80
80 |
306 | <180 (t-stat) | 180 |
80
48 |
306 | 180 (no t-stat) |
230 | 75
80 |
218 | 160 (no-t-stat) |
185 | 70