| water cooled power
There are a multitude of reasons behind the surplus power of the watercooled engines.
Firstly, water cooled motors are designed specifically for racing. This means they have a comparitively large transfer area. The more oxygen you can pump into the cylinder, the more power you make. Thus you can see a full blown 6-port bizeta producing upwards of 18hp. (they have 6-transfers)
Secondly, the exhaust port size, shape and hight determine outright power, and the power characteristics of the engine. Most water cooled engines have very large exhaust ports. The 5-port polini and 6-port bizeta have three exhaust ports if you include the small auxillary exhaust ports set to the sides and high of the main exhaust port. These increase power throughout the rev range, and due to the hight of the ports, when combined with exhaust tuning, allow W/C engines to rev harder than their A/C counterparts (16000-18000 rpm).
Thirdly, the crank case and crank shaft itself are full circle items designed to increase crankcase compression and flow more efficiently than those in air-cooled motors. Once again, more air=more power. The crankshaft in italian engines are steel and are massively strong, allowing far more revs. The cases are stiffer to put up with the stresses 16+hp demands.
Hope that goes some way to explaining the basics. If you want more detail on anything, feel free to contact me. Cheers
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Trying to get more people to pocket bike events held around Tasmania
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