Discussion
HughGabriel said:
Recently bought a Cerbie piston from ebay to use as a paperweight.
Does anyone know why the top of the piston is shaped like that and not smooth.
Hugh
This is to create an annular 'squish' region around the piston, with the Cerbera's extreme angle the turbulent forces are very high and preceeding each flame front is its sonic pressure wave. Colliding sonic pressure waves concentrate in this region, where reflecting pressure waves from the piston or combustion chamber walls can re-combine to increase localized high pressures and temperatures... this will of course produce a harsher noise but is not noticeable unless you put your ear on the block (I wouldnt advise it!) also can yield a power increase in many cases on an NA engine... Keeps the sonice pressures away from the walls and is angled to escape out through the exhaust valves at near-perfect efficiency.
Plus, also can adjust the compression ratio, increase or decrease depending on the alignment with the valves, I believe the red-rose spec engines have a 'less' of a squish region than standard - to bring up the compression ratio - but I also am aware that the cylinder liners are also more up to the job than standard.
Also the pistons shown here are the 'bad' variety, in my engine and other better spec'd cerbs, the pistons have very short skirts, this reduces the mass considerably and leads to a quicker revving engine, but this puts more load on the liners and increases the probability of piston slap... anyway, hope the above enlightened.
(TVR never used the same piston designs, they went through many changes, it would be nice to see a picture of a RR piston/rod assembly for comparison.)
>> Edited by SXS on Saturday 15th January 18:10
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