During high engine load, adequate engine cooling is necessary to prevent
irregularly highly machine temperatures and spark knock that are issues
affecting high power from being achieved. However, excessive cooling during low
engine load or cooling locations that do not require cooling relatively
exacerbates fuel consumption. Therefore, optimization of the engine cooling
system is needed to achieve higher performance of motorcycle engines.
First of all, in water-cooled engines, conventional water cooling system adjusts
the cooling amount via flow channel switching with a thermostat, which is opened
in high water temperature. However, with the bypass channel, water may bypass
the radiator but still continues to circulate, thereby leading to loss arising
from heat transfer from the cylinders. Moreover, use of a thermostat allows
water to flow through the radiator even during low engine loads under high water
temperature operation, thereby resulting in further heat transfer from the
cylinders. In order to solve this issue, we consider that an electromagnetic
valve installed in a single path cooling circuit without bypass channel blocks
water circulation and creates zero flow without depending on engine operation
condition. As a result, we achieved early engine warming, loss reduction, and
fuel consumption improvement.
Next, with respect to the optimization of cooling distribution, we found it
desirable to concentrate cooling near the spark knock spots and hot spots and to
warm the cylinder block for loss reduction simultaneously. As a specific method,
water inflow from the cylinder head instead of from the cylinder block can
reduce knock strength.