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In a recent engine rebuild of a standard BJ7 engine which was fitted with
four ring pistons, when I looked at replacement pistons they were pictured
with five rings, which did not seem good to me.
I fitted Omega pistons from Denis Welch. These have three rings with a
total width of 3.2mm compared with 9.8mm for the four rings. (For the oil
rings only the width contacting the cylinder bore is measured)
Since friction is in proportion to ring width (possibly due to the lower
pressure required to make thinner rings seat against the cylinder wall) this
represents a reduction in losses to heat and a power increase (small).
Another, much more expensive, option for consideration. I also have no
doubts about the quality of the pistons, whereas I am not sure about the
four or five ringed replacements. They seem very cheap to me.
Ian
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class=3DWordSection1><p class=3DMsoNormal>In a recent engine rebuild of =
a standard BJ7 engine which was fitted with four ring pistons, when I =
looked at replacement pistons they were pictured with five rings, which =
did not seem good to me.<o:p></o:p></p><p =
class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>I fitted =
Omega pistons from Denis Welch. These have three rings with a =
total width of 3.2mm compared with 9.8mm for the four rings. (For =
the oil rings only the width contacting the cylinder bore is =
measured)<o:p></o:p></p><p class=3DMsoNormal><o:p> </o:p></p><p =
class=3DMsoNormal>Since friction is in proportion to ring width =
(possibly due to the lower pressure required to make thinner rings seat =
against the cylinder wall) this represents a reduction in losses to heat =
and a power increase (small).<o:p></o:p></p><p =
class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>Another, =
much more expensive, option for consideration. I also have no =
doubts about the quality of the pistons, whereas I am not sure about the =
four or five ringed replacements. They seem very cheap to =
me.<o:p></o:p></p><p class=3DMsoNormal><o:p> </o:p></p><p =
class=3DMsoNormal>Ian<o:p></o:p></p></div></body></html>
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