Mailing List Message #65316
From: Matt Boiteau <>
Subject: Re: [FlyRotary] Re: Update on Glasair Cooling in Phase #1
Date: Sun, 10 Nov 2019 20:57:00 -0500
To: David COOK <>
237F oil is hot with that being your inlet temperature. Like you said, need to increase the inlet duct size to 4". I tried getting away with a 2.5" inlet (even 3D printed molds to get the right bell shapes, etc), but quickly found out that didn't work and went with 4". 

My oil rad is only ~200sq" though compared to your ~250sq". I'll need to upgrade when summer comes back, but so far on climb I'll get 215F inlet / 235F oil pan, and leveling off at 2000rpm prop will drop down to 190F inlet / 205F oil pan. Have custom oil pan that holds gallons.

- Matt Boiteau

On 2019-11-03 4:53:20 PM, Stephen Izett <> wrote:

Sorry Matt, I just realised I hadn’t mentioned the actual oil temps.
Highest in climb were 114C (237F) settling back to 110C this is 10C higher than previous flight?? OAT was up 4C ~7F
I would have expected a symbiotic relationship between oil and water temps. Lower coolant yielding lower oil temps.
This is troubling me, Prior to this flight I noticed oil level down on the stick. Its always been very consistently full with no signs of leaks etc. (Standard Renesis pan)
It’s running Mobile 1 and measuring the oil entering the engine after cooler and filter.


> On 3 Nov 2019, at 11:35 pm, Matt Boiteau wrote:
> Coolant looks great. Are you running a t-stat?
> What are the oil temps when you say "high"? Synthetic? Weight? Oil pan or inlet temp location?
> This is my opinion, with synthetic 20W50 at oil pain temps, I'd be okay during the climb with 240F and hopefully after some air speed it drops down under 220F.
> I do agree you might have to open up to 100mm (4 inch) for oil cooler.
> - Matt Boiteau
>> On 2019-11-03 8:31:47 AM, Stephen Izett wrote:
>> Hi there people
>> Over the past month I have updated the cooling system of the Glasair Super II RG in order to continue our phase 1 testing.
>> The previous setup had 540in3 two pass behind the ~20in2 unmodified right cheek inlet.
>> We hadn’t included the left cheek as it was so difficult to get the air across to the right hand side diffuser.
>> The Oil is 250in3 behind a 8in2 under spinner inlet.
>> Initial testing was marginal with OAT below 20C (68F)
>> So having established that cooling was rather marginal above 68F I went for the planned upgrade path which included
>> installing a secondary bike radiator of 130in3 plumbed into the heater circuit behind the ~15in2 left cheek inlet.
>> The diffuser was designed to hopefully be more efficient in a climb configuration.
>> So the total radiators frontal area has been increased by 50% while the air in has increased 75%.
>> The unknown is that being in the heater circuit we don't know the total flow through the secondary rad compared with the primary rad.
>> Testing on the ground yield an approx 15-20C drop in coolant after 30mins of 1800rpm idle.
>> Flight Testing Results the next day: OAT 21C (70F)
>> Coolant Temps max’d on climb at 93C (200F) down 15C on highest Flight 3 climb temp with a 4C higher OAT.
>> Coolant Temps dropped to 83C (181F) as speed got to 147 KIAS (Cruise is published as 192 KIAS but we haven’t expanded the envelope to date)
>> I’m very pleased with this result.
>> Oil Temps are high. I would much prefer them below 80C (176F)
>> I’ll be interested to see what oil temp does as speed rises, but my hunch is it needs more air (increase air to oil cooler from a diameter of 77mm to 100mm)
>> Slow Speed Tests:
>> Vs Clean Stall is at 67 KIAS row 2011 (Glasair claims 70 Knots at Gross)
>> Vso Full Flap Stall is at 57 KIAS row 2062 & 2083 (Glasair claims 59 Knots at Gross)
>> Cheers
>> Steve Izett
>> Perth Western Australia
>> --
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