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The
cycle of a typical internal combustion engine is called
the four-stroke cycle. The piston rises and compresses the
fuel air mixture before the spark ignites it. This increases
the pressure and heat of the mixture near to its auto-ignition
point. This will enable the mixture to burn at its fastest
and consequently the fuels energy will be most efficiently
harnessed. However if the compression ratio is increased
too much then detonation
could occur. |
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| To
raise the compression ratio material could be either skimmed
off the top of the block or off the top of the cylinder head,
see below. However the limiting factors with this modification
are that the valves become increasingly close to the pistons,
as well as increasing the shrouding
factor. Also the head blots may need modifying. Another
disadvantage is that if ever the head needed skimming
this may not be possible as the clearance between the valves
and the pistons may already be at a minimum, meaning a new
head is required. |
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| A
better way of reducing the compression ratio is to install
high compression pistons. The top profile of these pistons
increases the compression ratio without the associated shrouding
factors of the previous method. The block will not have to
be skimmed and their will still be generous clearance between
the valves and pistons, meaning that in future the head can
be skimmed if needed. This method of increasing the compression
ratio could be cheaper in the long term. |
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