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Boxer engine cooling


motorbob

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Can someone explain how the cooling of this engine works. Is it strictly air cooled ?

 

No, it is an oil/air cooled engine. The cylinders themselves are air cooled, the heads however are oil cooled. There are in effect two oil circuits in the engine. The oil gets picked up from the front of the sump (finned for cooling) and pumped around the heads, concentrated around the exhaust port, then through the oil cooler and back to the rear of the sump. Here it is picked up and pumped through the bearings, from where it drains back to the front of the sump.

 

Here is a cutaway picture of the older, but essentially similar, R259 oilhead engine:

 

734638-BMWR1150RTzcengine.jpg

 

Andy.

 

(I may have got the front/rear sump bit reversed but the description is sound(ish)

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This is interesting.

 

My dealer told me the R1200 line has a different cooling layout than the previous lines. There are plenty of folks on the 'net who comment about how much cooler their 1200 series engines are compared to other engines, and I'll definately say my air-oil cooled 1200 is, comfort-wise, the coolest liter+ bike I've ever been on.

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GF's R65 is approaching "warmed up" when the little puddles in the tops of the heads (from being left out overnight in the rain) is starting to boil.

 

I can touch my R1200RT's valve cover at any time- it's been hot but never too hot. Amazing engine.

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Ya. I took a ride through Vegas and Death Valley. Vegas was traffic (about 15 MPH), at least 110 degrees ambient but with the cars and concrete, who knows. It felt like 130. Our feet were burning as if a hair dryer was blowing close to your skin. The bike temp. gauge only went up slightly, like two ticks. Death Valley at 117 was no problem. I'm very happy. My water cooled Goldwing wouldn't do as well (and the fan running would drain my battery at low speeds).

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I find also that that my 12RT appears to cool better than my 1150. The temperature doesn't increase nearly as fast as it did on the 1150.

 

Andrew

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This is interesting.

 

My dealer told me the R1200 line has a different cooling layout than the previous lines. There are plenty of folks on the 'net who comment about how much cooler their 1200 series engines are compared to other engines, and I'll definately say my air-oil cooled 1200 is, comfort-wise, the coolest liter+ bike I've ever been on.

They've improved the heat dissipation and regulation a bit, and I suspect recalibrate the temp display system to cause less 'overheating panic', but the basic oil cooling system is virtually identical, oilhead to hexhead.
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