Interesting picture of piston coating loss
Discussion
Regular readers interested in the causes of bore and piston scoring will be aware there are some disagreements between experts about the source and might find the following interesting.
Our research and testing (which is extensive) applies a simple test to all our work and theories - which is to make sure the explanation has a connection to why it is OK on bank 1 but not on bank 2 and tries to identify a technical reason for the differences.
We believe it is connected to the change to plastic coated pistons and temperature differences in the two banks resulting in excess temperatures on the thrust face of bank 2 in some circumstances leading to premature wear or failure of the coating and the fact that Lokasil is too aggressive to last without a suitable coating between it and the piston.
We came across this piston this week that seems to support our position. It comes from bank 1 and it can be seen that the thrust face has the usual wear in patches through the coating but it is all still intact - lasting much longer than the typically do in bank 2.
However the other side (not the thrust side on bank 1 but the hotter side) shows how a huge piece has simply become detached or de-bonded from the piston - despite which - as it is not the thrust face - there is no other wear and no damage to the bore and the remaining plastic surface is still managing to keep the piston and cylinder bore apart without scoring due to the much lighter face load on the non thrust face.
It seems to me that this is yet another clue as to the different temperatures and thrust loads experienced on top and bottom of the piston which on bank 2 of course places the weaker and hotter side of the piston on the thrust face.
Baz
![](http://thumbsnap.com/sc/J6EBGVI3.jpg[/img]</a> <a href="http://thumbsnap.com/J6EBGVI3" Target="_blank">[img]http://thumbsnap.com/sc/J6EBGVI3.jpg[/img]</a> <a href="http://thumbsnap.com/XuLc18fZ" Target="_blank">[img]http://thumbsnap.com/sc/XuLc18fZ.jpg[/img]</a> <a href="http://thumbsnap.com/XuLc18fZ" Target="_blank">[img]http://thumbsnap.com/sc/XuLc18fZ.jpg)
Our research and testing (which is extensive) applies a simple test to all our work and theories - which is to make sure the explanation has a connection to why it is OK on bank 1 but not on bank 2 and tries to identify a technical reason for the differences.
We believe it is connected to the change to plastic coated pistons and temperature differences in the two banks resulting in excess temperatures on the thrust face of bank 2 in some circumstances leading to premature wear or failure of the coating and the fact that Lokasil is too aggressive to last without a suitable coating between it and the piston.
We came across this piston this week that seems to support our position. It comes from bank 1 and it can be seen that the thrust face has the usual wear in patches through the coating but it is all still intact - lasting much longer than the typically do in bank 2.
However the other side (not the thrust side on bank 1 but the hotter side) shows how a huge piece has simply become detached or de-bonded from the piston - despite which - as it is not the thrust face - there is no other wear and no damage to the bore and the remaining plastic surface is still managing to keep the piston and cylinder bore apart without scoring due to the much lighter face load on the non thrust face.
It seems to me that this is yet another clue as to the different temperatures and thrust loads experienced on top and bottom of the piston which on bank 2 of course places the weaker and hotter side of the piston on the thrust face.
Baz
Gassing Station | Porsche General | Top of Page | What's New | My Stuff