Can the block be honed?
05-19-2013, 01:28 AM
#16
Rennlist Member
Alusil as a hypereutectic aluminium-silicon alloy contains approximately 78% aluminium and 17% silicon. This alloy was created in 1927 by Schweizer & Fehrenbach of Baden-Baden Germany and further developed by Kolbenschmidt.
To do an oversize bore, you have to cut the cylinder walls and then there is a FINISHING PROCESS, which does include stones and paste and the last part is with felt pads and the paste. Kolbenschmidt, still work with companies today, including Audi and more...
You might find the whole process, cut - stones - felts and paste etc online; I have a copy at home but I'm traveling. We use Duffin Engine Service in San Antonio.
Mercedes Benz Alusil Cylinder Conditioning - YouTube
Our new block that we built for the track car. Clean block, remove head studs, finishing pass, cut/hone/finish to desired piston clearance +/- 600. Send your new piston with it so the shop can measure on the skirt.
two others done by Duffin for friends, one o-ringed
To do an oversize bore, you have to cut the cylinder walls and then there is a FINISHING PROCESS, which does include stones and paste and the last part is with felt pads and the paste. Kolbenschmidt, still work with companies today, including Audi and more...
You might find the whole process, cut - stones - felts and paste etc online; I have a copy at home but I'm traveling. We use Duffin Engine Service in San Antonio.
Mercedes Benz Alusil Cylinder Conditioning - YouTube
Our new block that we built for the track car. Clean block, remove head studs, finishing pass, cut/hone/finish to desired piston clearance +/- 600. Send your new piston with it so the shop can measure on the skirt.
two others done by Duffin for friends, one o-ringed
Thanks for posting Bret
Regards
Ed
05-19-2013, 03:33 PM
#17
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05-20-2013, 09:09 PM
#18
Karl Poeltl of Racer's Edge nikasil's every one of his engines.
Also (directed at all, not you), FWIW, the technical term for what is done to the aluminum is "etching." The acid in the compound etches away the aluminum, leaving the hard silicon proud. The process also conveniently leaves features where oil can collect to better seal the cylinder, analogous to what cross hatching does. If you want to look up what is done, use the term "etch," not "hone," to get a better picture.
Also (directed at all, not you), FWIW, the technical term for what is done to the aluminum is "etching." The acid in the compound etches away the aluminum, leaving the hard silicon proud. The process also conveniently leaves features where oil can collect to better seal the cylinder, analogous to what cross hatching does. If you want to look up what is done, use the term "etch," not "hone," to get a better picture.
Last edited by BC; 05-21-2013 at 05:12 PM.
05-20-2013, 10:59 PM
#19
Race Car
Abrasion is not selective. Chemistry is.
05-21-2013, 07:00 AM
#20
Drifting
05-21-2013, 08:21 AM
#21
Drifting
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You might not understand Harry's point, but what he posted is correct as from the factory. They are originally etched, using a solution that will attack/etch the aluminum but leave the silicon untouched, but most if not all aftermarket machine shops will try to simulate this process with Sunnen felt pads, and AN-30 paste. From the internet:
Excessive bore scoring or galling does indeed lead one to conclude that a faulty tribological process has been at work.
Alusil is not a primary area of my expertise but the main points as I understand them are as follows.
1) After reboring and honing to size the critical thing in bore preparation is the correct polishing operation with Sunnen felt pads and AN-30 silicon paste to expose hard silicon crystals above the aluminium base. This process closely duplicates the aluminium etching process originally used at the factory to remove aluminium from between the silicon crystals to leave them standing proud.
2) Pistons must be tin or ferro coated to prevent aluminium/aluminium contact which is not a good wear interface in this application. The piston skirts will be a golden or dark colour rather than the normal silver aluminium colour if this has been done.
3) Piston rings must be barrel shaped on the outer faces to prevent sharp upper or lower edges from ripping the exposed silicon crystals out of the aluminium matrix. Most ferrous ring materials will be suitable including chrome plated as long as the barrel shaped outer faces are present.
Conventional rings for iron bores are usually taper faced or parallel faced to assist in oil scraping and compression sealing. These shapes will not work with Alusil.
Excessive bore scoring or galling does indeed lead one to conclude that a faulty tribological process has been at work.
Alusil is not a primary area of my expertise but the main points as I understand them are as follows.
1) After reboring and honing to size the critical thing in bore preparation is the correct polishing operation with Sunnen felt pads and AN-30 silicon paste to expose hard silicon crystals above the aluminium base. This process closely duplicates the aluminium etching process originally used at the factory to remove aluminium from between the silicon crystals to leave them standing proud.
2) Pistons must be tin or ferro coated to prevent aluminium/aluminium contact which is not a good wear interface in this application. The piston skirts will be a golden or dark colour rather than the normal silver aluminium colour if this has been done.
3) Piston rings must be barrel shaped on the outer faces to prevent sharp upper or lower edges from ripping the exposed silicon crystals out of the aluminium matrix. Most ferrous ring materials will be suitable including chrome plated as long as the barrel shaped outer faces are present.
Conventional rings for iron bores are usually taper faced or parallel faced to assist in oil scraping and compression sealing. These shapes will not work with Alusil.
Last edited by URG8RB8; 05-21-2013 at 08:30 AM. Reason: Added Article
05-21-2013, 08:48 AM
#23
Drifting
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By the way, Sunnen AN-30 paste is NOT an abrasive paste, it is an acetic paste which selectively etches away the aluminum. Please see attached MSDS.
05-21-2013, 11:41 AM
#25
Three Wheelin'
Duffin Machine does an excellent job on the Alusil blocks. It is a common everyday operation for them. Do not use a shop that is not familiar with the process . BTDT and have the t-shirt, actually a couple of sleeve candidates.
05-21-2013, 12:00 PM
#26
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Thanks everyone for the advice and great information! I'm sending it to Lindsey racing to get honed. One more question. I noticed on Lindsey's site that they can drill and tap for the late-style tensioner. Is this suggested?
Regards,
Rob
Regards,
Rob
05-21-2013, 02:53 PM
#27
Makes it easier to keep the belt adjusted since it's spring loaded rather than locking a cam roller in place.
Maybe someone can add more.......
Maybe someone can add more.......
05-21-2013, 04:05 PM
#29
Race Car
FWIW, I'm not competent enough to be removing material from the bores, either. I'm not trying to be snarky, but see cruise's response, and you'll see why it is important to understand the difference. People who don't understand the process may think they can just take a ball hone, and fire away. This is an abrasive step, and will remove the aluminum and the silicon. The only way to selectively remove one element from an alloy is with chemistry. Abrasion will remove the entirety of one surface.
05-21-2013, 04:24 PM
#30
Drifting
I've had my nikasiled 968 engine out for 2 track days so far. I know it's not a long term test by any means, but it's fast, not blowing smoke, and not leaving bits and pieces on the race track.