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While I was not experiencing overheating early on in my flight testing, we got a really bad run of hot weather in Seattle, and I was getting elevated temperatures after initial takeoff and climb to pattern altitude and was pushing low 220's. Even trying slow lower power climbs it was not possible to reduce th temps to below 218, so I knew I had to deal with modifications to my cooling.
I started by replacing the supplied 1/4 by 20 100mm long rods with some longer ones and opening up about 6-7 tenths on in inch the radiator opening.
Secondly I created ducting to flow all the air coming in the lower ram to force it into the radiator.
The last was to wrap the muffler with exhaust wrap.
Between these cooling options I have been able to have virtually unlimited climbing in fairly warm weather without pushing over-temperature. I still get a bit higher fast cruise temperatures, but I don't have the wheel pants on, so when they are installed I should get a faster cruse with less power and that should help speeds, fuel burn and temps across the board.
Thanks Jonathan for the tip off. Mild Winter temps. here in South Australia at the moment. The highest I’ve seen on my similar project is 185F in climb, usually 170F when tootling around. No air ducting mods as you have described. Close to 40 hours now. John
What does your radiator intake look like?
Note little baffles, positioned each side and below, maximising air into the throat of the radiator.
I'll get my offset measurements; front opening and tapered rear, next time I'm at the hangar:
3" (75mm) opening at the front, like yours Loren, and 90mm to the underside of the radiator at it's rear most point. No cooling issues, whatsoever, at this stage. Still Winter here.
As an aside, with the Viking 130, I now gracefully lift off our main bitumen rwy (rather than physically rotate) and sedately climb at 4700 to 4900 rpm, saving the manic 5100 full throttle jump off the ground and nose high climb out for future eventualities. I'm practicing for that 'limo ride' with likely passengers, once I get my freedom ticket - still waiting!
is that a cookie rack?? lol thats awsome...
Are you talking about oil temps?
Evans Coolant temps.
What is the distance between the bottom of your fuselage and top of radiator?
Do you have a NACA duct on top of your cowl or did you open the gap between the spinner and cowl, or both?
How high can you climb from your normal cruise speed, at pattern altitude, before temperatures reach max?
No responses, so I guess I'll start.
We have 3" between bottom of fuselage and top of radiator. We do not have NACA duct, but have approx 3/4" opening around the spinner, but with more than 2" on the sides of spinner.
From a cruise altitude of around 1500 ft, and cruise speed of 60kts, we're lucky to climb 800ft before the coolant temperature reaches 220ºf. Without the cowl, the aircraft continues to climb without overheating.
To direct more air to the radiator, we also added inlet louvers under the fuselage and just above the radiator. These louvers didn't help, making me believe the radiator is already cooling as best it can.
I'm starting to suspect the cowl is trapping to much heat and we should add cooling louvers to both sides.
Hi Loren, I guess not many builders venture this far down into the Forum. I haven't been to my hangar yet to measure my radiator opening, sorry. Trawling my photos, I guess we have all done our Thermostat mod, as here:
This photo take at high idle on the ground after a flight:
John, this is great information. Thank you for sharing. I am a bit confused, though, with the graph on your flight test report. You discuss flying around 8400 ft, but the graph is only showing an altitude of around 2,400 ft. What am I missing. Any idea how high you can climb at around 65 kts before the engine reaches max temperature?