Making progress, Jeff! Good work!
When I first flew with high oil temps the
water temps were elevated as well. When I solved my oil temp problem, the
coolant temps also dropped. So there is no question there is some “leakage”
of heat between the oil and coolant system – not too surprising as both circulate
in the block where all that hot metal is.
In the winter time, I ,like Mark, see
coolant and oil temps at cruise down in the lower 140F range – cooler than
I would like. But, in the summer they are in the 160-170F range (both oil
and water)
IF I flew a lot in the cold/hot weather, I
would probably put some time of hand operated baffle in the oil duct to divert
some of the air flow causing its temp to rise and the coolant would tend to
follow it up.
I have tried using a thermostat on two
occasions and almost fired my engine on the ground. I am not certain but
because I am plugs up, I think I may trap some air around the thermostat
stopping it from heating up and opening – even though I drilled some 1/8”
dia holes around the lip of the thermostat to get rid of any air. In any
case, I never tried flying with one because the engine got too hot just on the
ground. You engine is installed in the “normal” orientation
so should be able to operate with a thermostat.
Just remember the engine’s cooling
system was originally designed for relative low average power being produced
(as in touring down the free way at 2500 rpm) where as we are asking for “more
power! Scotty!” from take off to level off. High power = high heat
with low air speed = low air mass flow = High temp problems on take off.
If you optimize your engine cooling for cruise,
it’s likely you will have a cooling deficit during the take off
phase. If you optimize if for take off then you will likely have more
drag at cruise than necessarily.
While, I am not advocating it, I have
accepted the cooling deficit during take off in order to have my “high
speed” aircraft have minimum cooling drag at higher speeds. I typically
will hit 220F with the coolant and 200F with the oil for the 2-3 minutes it
takes me to get up to a comfortable altitude and power back a bit, once the
airspeed hits 120 mph IAS then my cooling deficit is overtaken and all it good.
At 8000 ft MSL my max possible power (WOT)
and rich air/fuel mixture will push my coolant and oil temps right up between
195 and 200F. So if I had any less cooling capacity (or any more power),
I would face a cooling problem, but as it is I am satisfied that my system is
very close to “optimum” at cruise.
Sounds to me like you are zeroing in on
what needs to be done.
Enjoy your success!!
Ed
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
On Behalf Of Jeff Whaley
Sent: Monday, December 08, 2008
9:40 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Update
... Three more flights, water ok, oil too cool
Mark,
I’m not sure
what the cruise temps are as we have been flying short, tight circuits only. I
think cruise temperatures need to be determined before doing too much else,
though re-installing the thermostat may happen.
What is the
relationship between the water and oil temp? I guess you have stock Mazda
thermostat 195F?
Most of the rotary
world has cheek radiators up front, with the oil cooler going in whatever space
is left. My oil cooler is up front on top of the PSRU with inlets/outlets on
both ends and the water radiator (19x5.5x5.5) is below/behind the oil pan
… two independent systems one working too well the other not well enough
… see attached photo.
Jeff
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
On Behalf Of Mark Steitle
Sent: Monday, December 08, 2008
8:53 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Update
... Three more flights, water ok, oil too cool
Climb out temps are of concern because they are the worst-case
scenario, but they are also short-lived. What are your oil
& water temps in cruise? Mine were good during the summer
months, but now that it colder weather is here, they have
dropped into the 130* range, which is much too cool. Saturday I installed
a thermostat and then flew it. Temps in cruise were 195* water, 193*
oil. I'll wait to see what happens when it starts warming
up next spring, but for now, the thermostat stays in. I
did notice that with the thermostat installed, coolant pressure went
up. Makes sense as I now have a significant flow-restrictor in the
system.
I would prefer to control temps with cowl flaps, as that would
result in less drag, but I'm still designing that system.
On Mon, Dec 8, 2008 at 7:23 AM, Jeff Whaley <jwhaley@datacast.com> wrote:
With thermostat removed, bypass plugged, new accessory
belts and alternator pulley installed, we retested the new rotary installation.
On first climb out water temperature reached only 195F,
compared to 230F on very first flight a week ago. With the water temperature
okay we did 2 touch and goes then shut everything down and checked under the
cowl … no broken belts, no leaks that's a relief.
On the subsequent climb outs the water temp was about
185F; on approach the water cooled to 150F. I guess with the approach momentum
you spend less time at full throttle on a touch and go. Some other numbers of
interest, 6300 rpm, 1100 fpm, outside air temp 30F, oil temp 110F.
So I would say that the water cooling system is still not
good enough (at 80F that 195 could go to 245F) on the other hand my oil is too
cool.
For present winter operations I'm wondering … put
the thermostat back in, which may help the oil … I don't like the cooling
to 150F on approach, or should I keep the systems separate? Plug the oil cooler
air intakes or outlets? Or should we first fly at cruise speeds for 10-15
minutes to see how things stabilize?
Jeff Whaley
(I call it an airplane now)
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