Ive always wondered.... why dont they put the fan in front of the radiator? It feels like a fan is a lot better at cooling things off when it blows at it rather than trying to suck the heat away. Am I not right??
When I was working on telecom server systems, validating their designs.... the fans were always on the exhaust side of the air flow. I asked why, and the answer was that the fan motor adds heat to the airflow it is providing, so it's not going to cool quite as much if it is pressurizing the equipment, rather than putting lowering the pressure, drawing the air through the system.
Seemed like a pretty weak argument to me; a 12V fan, even pulling 4 amps is still only producing 50 W or so of heat. Compared to a 100+ HP engine, that's lost in the rounding error. Googling the conversion
, 1 HP = ~750 Watts.... 100 HP would then be equal to 75 KW.... trying to shed an additional 50 W doesn't strike me as a big deal.
If you really want to make the radiator work more efficiently, you need to increase the pressure differential, so the air flows through it more strongly. Mr. Britten figured out that if you put the radiator just ahead of the back wheel, the partial vacuum caused by the body of the bike moving through the air would produce a differential twice as big as what is present in the 'normal' position in front of the engine.
Having the rad so close to the exhaust headers is a pretty poor choice as well..... if the bike is sitting still the superheated air wafting up from the pipes will be drawn through the rad, making it much less efficient than it could be......