I thought it was a bit of a mystery that now that I am dumping heat from the oil/water heat exchanger to the coolant, the coolant temp is lower, even with the thermostat to the second radiator closed (yes, there are some small holes in the thermostat, but it's a tiny flow area - 0.02 sq. in.). It finally occurred to me that the second radiator, being very ineffectual as it was, was basically a bypass of the effective radiator in the cowl. Now that it is blocked by the thermostat, the increased flow through the effective radiator is lowering the coolant temp.
In effect, this says that the 460 cu. in of rad core volume is adequate for cooling my 20B, even when dumping some oil heat load into it. It's in the neighborhood of 2.3 cu. in. per hp out. Shows you what an effective scoop and diffuser can do.
Al
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Lehanover@aol.com
Sent: Tuesday, April 29, 2008 12:46 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Cooling sytem changes- Velocity 20B
In a message dated 4/29/2008 12:50:27 PM Pacific Daylight Time, ALVentures@cox.net writes:
I drilled three 5/32" holes in the thermostat to keep some flow going through not thinking that would provide any significant cooling, but I guess it does. First step is to replace the thermostat; then see if it might be appropriate to reduce the airflow into the in-cowl rad – in some way that reduces drag. But the nice thing is there is no urgency – and my flight regime is not limited.
I use a 180 degree thermostat with a single 1/8" hole to allow air to escape. On cold days the engine runs under 180 on yellow laps. That 1/8" hole is enough flow to cool the engine.
For best power, 160 degrees on the oil is as high as you need.
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