Jeff,
Sorry, I forgot to mention that I'm using a water-to-oil heat exchanger. So, where the water temps go, the oil temps follow. The water-to-oil exchanger does not have a thermostat. So, installing a water thermostat brought both the water and oil temps to where I wanted. It had a "180" stamped on it, and it stabilizes at around 180* on the ground. I'm guessing that the reduced flow caused by the thermostat probably accounts for the slightly higher temps (195*).
If possible, cowl flaps would be preferrable as that would also reduce cooling drag.
Mark S.
On Mon, Dec 8, 2008 at 8:39 AM, Jeff Whaley <jwhaley@datacast.com> wrote:
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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