I definately do NOT want to start another thread discussing why HD should or should not introduce a water-cooled bike... But in those threads, it's always stated that water-cooled motors can produce more power. I'm just wondering why that is? What makes them able to produce more power? Are we talking same displacment makes more power, or is it that the displacement can be larger because there are no cooling fins on liquid motors?? I'm not real good when it comes to mechanical engineering, although I can hold my own as a shade-tree mechanic.

 

Just as guess, but, at some point, and engine can become hot enough that it locks up. Everything expands due to the heat, so, there is no room for anything to move any more. The more you push the motor, the hotter it gets, and the closer you get to locking it up.

When you cool the motor, you keep it away from expanding to the point of locking up, for a longer period of time, so you can push it harder.

 

A liquid cooled runs cooler so it can spin more rpm's thus can make more power.

 

Ok, that makes sense... So if our air-cooled HD's were to turn 9000 RPM, they would essentially melt, right? Whereas a liquid-cooled motor may be able to handle 9000 RPM and still remain relatively cool..??..

 

Yup. Everything that causes a motor to generate power also generates heat. Liquid cooling keeps the heat in check much better than air cooling so you can be much more aggressive with thinks like ignition timing, compression, cam timing, rpm, etc.

 

Liquid cooling allows better control of the engine temperature thus reducing the variables that affect tuning.

 

Yup, which can boost HP and be able to control the temp more which in turn produces less emissions in the air than an air cooled engine. Look at off road bikes, ever since they became water cooled, the power outputs have increased. Thats why the H2O engine will be here someday sooner than most people here want to admit to.

 

I do believe that the cooler the engine, the less emissions there are. Therefore, they can bump the motors and still meet Big Brother's standards if they use liquid to cool the motor.

 

Exactly.

and a few other posters explained it in more detail too.

 

I'm sure it's not just the water cooling, it's all the other mechanical operation of the engine as well I'm sure. Like overhead cams, weight, to name a few. But then we would be moving away from what we love about the twin, the low end torque, low end rumble. We would all be riding GW's..