> A new engine can be quite tight and needs a little running before the
> operating temperatures will come down. For ground runs you might
> find it advantageous to run it with the top and bottom cowlings
> removed for a while.
That certainly helps, but of course the ultimate goal is to being able
to run it in flight configuration. I know that a new engine runs a bit
hotter, but on the other hand, the current environment temperatures are
much lower than what I hope to be able to cope with.
> By the way have you configured the oil cooler
> directly behind the radiator -- if so, lowering the oil cooler in
> the duct can help a great deal.
Well, the oil temperature is the only temperature that never went into
the upper half of the green arc. In fact, it is difficult to get it into
the normal operating range before the coolant gets into the red zone. It
is the coolant temperature that makes a challenge.
> Also, don't run the engine below 2000 rpm unless you have to,
Ok, got that part, today I did all test around 2000 - 2200 rpm.
I had to draw the conclusion that my cooling setup, optimised for low
drag in flight, was not working well enough on the ground. I had the
radiators setup as a "stand alone" bay, with a small opening followed by
a diffuser. Theoretically this should give minimal cooling drag, and
plenty of cooling... while flying. Some testing revealed that there was
not much airflow during idle on the ground though.
So I literally took the saw and sawed off the radiator opening,
diffuser, and left the bare radiator extending under the cowl. The lower
cowling by itself is formed as a nice ramp, so the idea was that this
would produce more air flow.
Further testing confirmed this. With an engine already slightly warm
---From the previous test, an ambiant temperature that had increased by 10
degrees Celcius compared to this morning's test, I still got 23 minutes
until the boiling point. Quite an improvement!
So, I'm working now on cleaning up the mess, constructing a new
diffuser, and using the lower cowling as a ramp.
> I recommend once you have everything sorted out, carb balance etc -
> dynamically balance the propeller.
Yes, I'm going to do that. Thanks for confirming the idea that this
might be worthwile!
> Kingairs I flew as part of my job (when I worked) were always
> cracking exhaust stubs until the company bought a balancer and
> started a prop balancing programme. I borrowed the balancer from
> work and balanced my Airmaster.....made it run really smooth.
This sounds really encouraging!
Frans
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