Nikasil vs Iron Liners
Nikasil vs Iron Liners
(OP)
I know Nikasil is great for wear resistance, but is there any advantage, compared to cast iron liners, in cylinder cooling?
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RE: Nikasil vs Iron Liners
Regards
Pat
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RE: Nikasil vs Iron Liners
RE: Nikasil vs Iron Liners
Regards
Pat
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RE: Nikasil vs Iron Liners
Nikasil can be applied to iron or aluminum bores. It is used on iron bores because it gives better wear, reduced friction, and improved performance under marginal lubrication conditions. With aluminum bores a more precise fit can be achieved with an aluminum piston, due to similar CTE's.
Whether the bore is air-cooled or liquid-cooled, the thermal conduction across the liner wall thickness is probably more efficient in a monolithic aluminum structure, as opposed to an iron/aluminum composite structure.
However, I'm not brave enough to make unqualified statements backed by a promise to pose naked on the the steps of city hall like patprimmer does. There may be some extreme combination of engine operating pressures/temperatures and structural requirements that works better with the iron/aluminum combination.
Regards,
Terry
RE: Nikasil vs Iron Liners
Regards
Pat
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RE: Nikasil vs Iron Liners
RE: Nikasil vs Iron Liners
RE: Nikasil vs Iron Liners
Mike Halloran
Pembroke Pines, FL, USA
RE: Nikasil vs Iron Liners
That's a good point. But simply comparing dimensionally identical cylinders (one monolithic aluminum, one having an iron liner with finned aluminum sleeve, and one monolithic iron) does give a true picture of the situation. On one hand, aluminum has much better thermal conductivity than iron. But on the other hand, iron has a couple of things in its favor. Iron has a higher MoE than aluminum, it has better strength at elevated temperature, and iron has a much higher allowable operating temperature limit than aluminum (400+degF vs ~275degF). To get an honest comparison, we should compare each cylinder construction after it has been optimized for all operating variables.
Assuming an equally stiff cylinder structure, the iron liner wall can be much thinner than the aluminum liner wall. And if the lube conditions at the bore surface permit, the iron liner can be operated at higher temperatures than the aluminum liner. This would help thermal efficiency by reducing heat transfer from the combustion gas to the liner wall due to a smaller deltaT.
The big recip piston aircraft engines of the late '40s showed that air-cooled steel liners can be made to work quite well while achieving low weight and high reliability.
Interesting discussion.
Terry
RE: Nikasil vs Iron Liners
RE: Nikasil vs Iron Liners
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Nikasil vs Iron Liners