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Hi Steve:
The photo from May 8 was of previous setup and that BLUE HOSE (Twist-Tite) is what departed my engine 3 years ago … that heat box was installed during winter
months … attached is a photo of right-side, present-day setup. The Cabin heat will now be scavenged off the radiator outlet plenum –look below the oil cooler. My Fluidyne oil coolers (DB-30416?) are only 2/3 size of your DB-30618. I’m not sure why the Mazda
oil cooler will not aid in oil temperature control as it seems to be doing so at present. During ground runs the Mazda cooler is cold while the Fluidyne is warm … during both flights so far, the oil temperature was stable at 160F while the water temperature
rose to 210F; after shutdown the temperature of both oil coolers was the same as discerned by touch, so at some point the Mazda thermostat must have opened. I wish I could drive over and talk to you in-person as it’s hard to get all these details down in
writing … I like having extra oil cooling as excessive oil temperature can damage the oil seals; excessive water temperature is not good but the lesser of two evils.
The 13B is odd in that the two fluid temperatures seem to be very disconnected. I’ve managed to get control over the oil but not the water so far; however,
from previous readings I believe even if the water jacket temperature was cooler that it would not necessarily mean a reduction in oil cooling capacity could be achieved - I have never experienced that luxury.
Jeff
Wag-Aero 2+2, 1988 13B NA, RD-1C, EC2
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From:
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Steven W. Boese <flyrotary@lancaironline.net>
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Subject:
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Re: [FlyRotary] Re: Return to Flight - 2
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Date:
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Tue, 19 May 2015 16:20:58 +0000
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To:
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Rotary motors in aircraft <flyrotary@lancaironline.net>
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Jeff, I was looking at the photo in your May 8th message concerning PSRU oil return. The blue Push-Lok hose is shown connecting the oil pump outlet to the bottom of the Fluidyne oil cooler on the
right side. Most of the air outlet of this oil cooler appears to be captured into a hose presumably for cabin heat. Is this the case for the Mazda oil cooler now in this location?
The thermostat in the Mazda oil cooler is unlikely to be very effective at maintaining a minimum returned oil temperature with the coolers in series, no matter which order the coolers are plumbed.
I realize that your main concern presently is coolant temperature control, but in the end, everything affects everything else.
Steve Boese
RV6A, 1986 13B NA, RD1A, EC2
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From: Jeff Whaley
Sent: Tuesday, May 19, 2015 8:11 AM
To: 'Steven W. Boese'
Subject: RE: [FlyRotary] Re: Return to Flight - 2
Hi Steve, a long time ago I had only one Fluidyne oil cooler and it wasn’t enough, so ended up with two in series – one wasn’t enough yet two is almost too
much. I swapped the right Fluidyne for the Mazda to get temperature control. I would never have guessed about the high pressures you pointed out. Also don’t know if it makes any difference which cooler is first but actually the Mazda oil cooler is connected
first to engine outlet and oil returns through the Fluidyne … hard to see from pictures submitted.
Jeff
Jeff,
When checking for wasted inlet area, consider checking the necessity of having the Mazda oil cooler. From a previous photo, it appears that the oil flows from the pump
to the Fluidyne cooler and then through the Mazda cooler. The Fluidyne oil cooler may be of sufficient capacity to handle the oil cooling by itself. I replaced the stock RX7 cooler with a Fluidyne DB 30618 cooler of similar dimensions and the improvement
in oil cooling was dramatic. The three RX7 coolers that I tested all behaved identically in that at RPM above 2600, the pressure at the inlet to the cooler was about 150 psi and independent of RPM. It didn't matter whether the oil temperature was 160 or
230 degrees. This means that at an RPM of 5200, half of the oil is being dumped directly back into the oil pan and not going through the cooler. With the Fluidyne cooler, all of the oil is passing through it, the back pressure is only a few psi, the oil
temperature at its outlet is less than 200 degrees in climb with an OAT of 90 degrees, and less than 1" H2O pressure across its core is sufficient to keep the oil temperature at the cooler outlet less than 190 in cruise.
It is possible that the Mazda oil cooler in your system is acting purely as a constriction to the oil flow and its internal thermostat isn't doing much. The Fluidyne cooler may
be operating at 150 psi or more most of the time and is doing nearly all of the oil heat dissipation.
If you haven't done this already, it may be very instructive to check the oil pressure and temperature between your Fluidyne and Mazda oil coolers.
RV6A, 1986 13B NA, RD1A, EC2
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