I'll show you my Lokasils, if you show me your Nikasils

When your cylinder cracks, this is what falls off (catastrophic edge failure) If you look carefully you can see the colour/texture difference between pure metal and the Lokasil silcon/alloy matrix: Also here is a shiny new liner (Nikasil hybrid): Further to my thread of March 2009, I had a research trip out to AutoFarm last weekend and took these pics. http://911uk.com/viewtopic.php?t=42952 The water coooled Carrera's have NO liners. They have impregnated Lokasil, the hybrid cooled GT3 and Turbo (+ derivs GT2 etc) have aluminium sleeves coated with Nikasil. The Lokasil is a silicon hardening process for the aluminium castings. Porous cylindrical shells of silicon are aligned in the cast where the cylinder walls will be and when the molten aluminum is poured in it reacts with this LOCAlised SILicon matrix. The silicon "bleeds" into the local surrounding aluminium. The cooled cast is machined and acid etched to create smooth and hard cylinder walls. Because the Lokasil is part of the cast it cannot "slip". As the GT3, Turbo (GT2) are hybrid cooled (water cooled heads, air cooled bottom ends and cases), they have a different design so the air, oil and water stay separate. The case has a sealing liner coated with Nikasil. (NICkel-SILicon carbide). The incredibly hard Nikasil was first used by Porsche in 1970 for the 917 aircooled engines to allow smaller engineering tolerances, allowing greater pressures and bigger power. One problem the Lokasil engine design can have is catastrophic edge failure. The casting of the tube (cylinder wall) is squared off at the end. By this I mean the tube just ends perfectly straight. This means a very sharp right-angle edge with the associated point stresses and aerodynamic/hydrodynamic vortices. The edge can get fatigued and break off, this in itself is not ideal as piston sealing may be jeopardised, the real issue is where the broken cylinder wall fragments end up next in a fast moving engine. The debris will destroy the pistons, conn rods, crank shafts etc and complete engine destruction ensues. Fortunately it is pretty rare. A more common failure of the casting is not related to any liners or lokasil etc, it is the thin walls associated with cross-flowed water cooling and large bore. Apparently (according to Hartech) eventually ALL water cooled Porsche flat sixes will become ovalised over time (warped). Including Boxster. For both, the solution is a re-bore with liners. Hybrid Nikasil liners have with rounded/tapered edges to prevent the edge stress. (With thanks to AutoFarm) Sleep Well!

Is it possible to check for wear so that you know when to re-bore?

Well, other than engine out, you can pop a little endoscope camera down the spark plug holes AFAIK. What are you worried about? You have the bomb-proof GT1 block with Nikasils!

I'm not worried, just curious Besides I have other things to worry about - hedges in particular

I don't like the direction the Dong is going either.

Ah yes, the Dong. Spreads tend to be wide, but it still seems to get more and more difficult to take a long postion without significant volatility risk.

Never mind the vega, watch your gamma.

its all Greeks to me

Well, technically half or more don't have anything to do with Greek. Vega for a start.

Agreed. No more than Vanna or Vomma (Vanna Vomma - the ratio between cornering speed and queasiness in a Ford Transit). .."Dont blame it on the sunshine, don't blame it on the moonlight, don't blame it on the good times, blame it on the Black-Scholes."... H PS On reflection perhaps some thread drift here, apologies to 99.9% of the rest of the world who don't find any of this remotely amusing.

That includes me. :judge: Before we return to topic, I must just say my feet are so much more comfortable now I have a pair of those nice Black-Scholls inserts, particularly near expiration.

I can traslate :floor:

I tell you what, we'll pass until we get a Greek who can speak english as well!