alpha26

What material are the cylinder walls on M156 engine ? Niscali ?

Thank you

bhamg

The original brochures which I still have state that the cylinder bores are sprayed with twin-wire-arc-spray coating - TWAS - process, creating a very hard (twice as hard as steel), low friction surface.

Ingenieur

One brochure 'plasma sprayed to a mirrored finish'
Another 'micropore'
Same one twin-wire arc sprayed coating

Some sort of metallic vapor deposition process

Ingenieur

The cylinder bores themselves are also unique. The M156 is world's first production engine to feature cylinder bores with twin-wire-arc-spray (TWAS) coating. TWAS is a new process that creates a very low friction surface, which is twice as hard as conventional steel. The application involves using water at high pressure to roughen the cylinder walls. Afterwards, high voltage is run through two metal wires, which begin to melt. An atomized gas is then used to spray the metal particles from the meted wires on to the cylinder walls. Afterwards, the cylinders are honed.

Ingenieur

Good article
http://m.americanmachinist.com/uncat...gine-cylinders

Ingenieur

Page 21
http://www.n2m-moveo.com/PDF/TRIBOLO...hel_BORDES.pdf

bhamg

Good find. This is why I've asked several times here - can one hone these cylinder walls w/o compromising the longevity of the bores - or does it just not need to be done during say, a piston replacement? I presume the surface is not silicon-etched prior to TWAS.

alpha26

Thanks guys for reply !!!

Ingenieur

The treatment layer is pretty thin I would guess (it may be in the document)
Fractions of a 1000th

Are the factory bores prep'ed or raw?
Honed, cross hatched, scruffed, whatever

I would say any machining may be out of the question
Shop manual would say for sure
As would who ever does the rebuilds for AMG's remfged program for replacement engines after a headbolt lets loose lol
My Bosch book may have some detailsbut it's at work

whoover

The layer is .1 to .15 mm or 4 to 6 mils. Not a lot to hone.

http://technicity.daimler.com/en/nan...omment-page-1/

whoover

The whole point of the technology is to produce a mirror-like surface to reduce friction. No scuffing!

http://www.motorauthority.com/news/1...on-engine-tech

Ingenieur

Looks polished almost

http://i1.ytimg.com/vi/ri_LFckaT7g/sddefault.jpg

whoover

More than almost polished.

bhamg

Duplicate.

bhamg

That is amazing! No wonder I've never heard honing mentioned when M156 pistons are replaced.