Marks on Mahle Nikasil Cylinder - Pics

[8bit-ash]

Hi all,

I bought a set of Pistons and cylinders from here earlier this year, they were supposed to have had less than 3000miles on them. My first concern when seeing them was that they look like they have been honed. Am I right in thinking you shouldn't be honing nikasils? Its also just been pointed out to me that most of the cylinders are scored...



What are peoples thoughts on these marks, are they something to be worried about? I can feel the marks with my finger.

[fetuhoe]

The coating is likely to have a thickness of between 50 and 100 microns (0.05 to 0.1mm).

A conventional hone is likley to damage the coating and shouldn't be used although flex hones can be used to de-glaze used but undamaged cylinders but are not much more effective than using Red Scotchbrite.

If the cylinders are marked enough to need honing then they should be replaced or replated as honing is unlikely to be successful.

Re-bored cylinders are often plated with thicker layers to recover the correct dimensions and then honed to size using very specialied diamond hones but without specific information it isn't possible to reach a conclusion.

I don't think I would take the risk.

[redrobin911]

Was going to comment that they looked past their best, I see Chris has and I'd take is opinion seriously. It is possible, depending on current bore diameter to have them bored out to the next size up and re-coated which is what I'd do, then match to next oversize piston.

[911hillclimber]

Chris, you have pm.

[smallspeed]

Could you rebore and just use them as “non nickasil “ barrels?

[8bit-ash]

Its just a shame i've spent over £1600 on them because they were being sold as like new. If there is a way to at least be able to use the pistons to then at least its not a total loss. I'd say that the honing thats already been done on two of them will have gone through the Nikasil.

[fetuhoe]

Could you rebore and just use them as “non nickasil “ barrels?

I thought that this was a 90mm Mahle 'Nikasil' Cylinder which means that there is no real way of boring the cylinder and then re-using as the surface would then just be an un-treated aluminium alloy.

If it is a Biral Cylinder 84mm cylinder then you could re-bore without to much trouble.

The original 90mm cylinders made by Mahle could be Alusil as these cylinders were generally fitted to a 2.7 with a CIS fuel system.

I believe that the MFI engine used a Mahle Nikasil.

If your cylinders are Alusil then they will a hypereutectic Aluminium Alloy and they were never coated but they did have a chemical etching treatment to remove a small amount of aluminium from the surface of the bore. The piston as Iron Plated with a very thin coating of in as a boundary lubricant and the Ring pack is specific to Alusil barrels.

If you re-bored and Alusil Cylinder you would have to chemically etch and buy the correct rings and the same would be true if they were honed.

If the cylinder is either Nikasil or Alusil you would bore by a minimum amount and then re-plate back to a standard size and then use suitable pistons and rings.

I think you need to determine the type of cylinder before you take further action.

If they are Nikasil you can check them with a magnet in the bore and if you feel a slight attraction they are most likely Nikasil.

If they were sold 'as new' I am not sure I would be very happy

[8bit-ash]

These are definitely Nikasil's. I'm going to speak to Serdi and Langcourt to see if either of them can do anything about the marks then re Nikasil.

[fetuhoe]

I am sure that either Langcourt or Poeton will re-plate them back to size.