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Air Cooled Engine Question

Posted: Sat Oct 05, 2019 10:58 am
by hpetrino
I've always wondered about this. In a liquid cooled engine typically the temperature is controlled by either a thermostat or, in a thermosyphon system, the temperature of the coolant increasing or decreasing the flow. The results are the engine typically runs at a pretty consistent temperature once it's warmed up and when everything is working as intended.

So, in an air-cooled engine all I can see is a system that lowers the temperature of the engine relative to the ambient temperature. It seems to me that an air cooled engine will run much hotter in 100 deg. F. weather than it will in 10 deg. F. weather. It seems these engines operate in a much broader temperature range.

Is this true? Or am I missing something that actually regulates the operating temperature?

Re: Air Cooled Engine Question

Posted: Sat Oct 05, 2019 11:16 am
by Ruxstel24
I have a few miles of H-D and other air cooled bikes in my experiences...
Yes, air cooled engine cylinder and head temperatures can be higher, but they are designed for that with tolerances, oil splash and coolers. Oil greatly helps cool the cylinders and pistons. I run SAE 70 in my shovelhead...
The fins dissipate the heat and airflow is critical.
Sitting still in the heat is not a good thing for a shovelhead, newer aluminum engines handle it better, but they’re still really designed to be moving.
Many types that are designed to not be in the wind, will have a fan to move the air...
We were sitting in a long line on a poker run years ago...After about 20min and still waiting for cards, my buddy says. “You just put 500 miles on your engine in 20 minutes”!! :(

Re: Air Cooled Engine Question

Posted: Sun Oct 06, 2019 9:08 am
by Davey1916
Many air cooled engines actually have a sort of jacket around the fins so that the air from a fan at the front of the engine forces the air past all the fins.
Very cool to see, but problematic when in dirty muddy conditions or when fins start to break off.

Re: Air Cooled Engine Question

Posted: Sun Oct 06, 2019 10:28 am
by hpetrino
Interesting. Thanks for the replies!

Re: Air Cooled Engine Question

Posted: Sun Oct 06, 2019 11:47 pm
by Davey1916
There is an air cooled model t somewhere, I remember seeing photos of it. Just can't for the life of me find the photos

Re: Air Cooled Engine Question

Posted: Mon Oct 07, 2019 8:52 am
by Charlie B in N.J.
I've seen a number of air cooled collector cars and what's mentioned above is true. They are designed for air cooling. You will sometimes see thermostat controlled slats on the radiator to control temperature. Something like some diesel engine vehicles have today. As to very high outside temps I can't say beyond they worked so the design was OK.

Re: Air Cooled Engine Question

Posted: Tue Oct 08, 2019 1:35 am
by Mark Gregush
Battery and Model T coil.