Queston about honing a cylinder

[timw128]

Hello,

Not to hijack this thread, but still on the topic of honing. Should you hone cylinders the are chrome or Nakasil plated?

Jeff

ABSOLUTELY NOT!... if you had a piston seizure, or scuff, wipe the Nik plating down with muriatic acid and mild Scotch Brite pad. Wash with warm water/Tide

solution, blow dry, inspect bore for any Nikasil wear through. If so, you need to send out for re-plate. Millennium Technologies is the best source and they

charge about $200/cyl. Nik plated cylinders use an entirely different piston ring than a steel bore. They also have the proprietary equipment to diamond hone

the cyl bore to a precise dimension, and they don't chatter and chip the plating.

We prefer the steel bore with a specific honing process and ring metallurgy in our Mercury V6 race outboards. Controlling the bore finish=horsepower.

http://www.millennium-tech.net/serviceInfo.php?id=7

Hope this helps.

tim

 

[bertsmobile1]

learn something new every day.
So they plate nickasil onto the bore ?
Would be interesting to know how that is actually done as once dissolved the nickel, aluminium, silicon & iron should all separate out and having different valiencies should not plate as an alloy.
Are you sure it is plated onto the bore or is it sprayed onto the core before the barrel is cast around it then diamond honed after the core is removed ?

 

[motoman]

Interesting, but a long reach into AC tractor engines with such Porsche technology....:laughing:

 

[timw128]

learn something new every day.
So they plate nickasil onto the bore ?
Would be interesting to know how that is actually done as once dissolved the nickel, aluminium, silicon & iron should all separate out and having different valiencies should not plate as an alloy.
Are you sure it is plated onto the bore or is it sprayed onto the core before the barrel is cast around it then diamond honed after the core is removed ?

'So they plate nickasil onto the bore ?'..... YES

NSC (Nickel Silicon Carbide) is plated to the cast aluminum cylinder bore- after the bore has been machine established at approx. .006"-.010" over to accommodate standard

plating thickness of .003"-.005" (can be applied to .035" thkns). (Ref: http://www.f1moto.com.au/view/nikasil-plating/51) Diamond honing is implemented to achieve final bore/piston fit.

'Nikasil' is a trademarked electrodeposited lipophilic nickel matrix silicon carbide plating. It was developed by Mahle GmbH around 1966. Mahle piston alloys are recognized as the best

in the world, and are found in hi-perf apps such as Porsche engines, among others.

Steel/Iron liners can also be plated accordingly. There are pros and cons to both a Nikasil cylinder wall and a 'steel', as we call them, cylinder wall. There are trade offs between

thermal transformations and cylinder sealing. It's a complex study in the realm of internal combustion engine design and, perhaps, too complicated of a treatise for discussion

here.

Hope this helps.

tim

 

[timw128]

Interesting, but a long reach into AC tractor engines with such Porsche technology....:laughing:

TRUE THAT! :thumbsup:

 

[fabricgator]

I am going to chime in with a little bit of (possibly incomplete) information that I am aware of (or believe to be true and pertinent)

You must cross hatch or hone your cylinders when you replace the piston rings. I was told (informally) that two fold, the newly roughened surface aids in the new rings being seated to the cylinder mating surface. [side bar] If you just replace the brake pads without resurfacing (or glaze breaking) the rotors, the pads will not seat on the rotors and you will only have partial contact, thus less braking ability] So in that sense, if you just install new rings on a glazed and polished cylinder bore, there is not any microscopic rough surface to aid in the wear and break in of the new rings. You may have been better off leaving the old rings in there as they have already been shaped and polished to the current cylinder profile.

Basically, your break in period, is a period of all the parts being worn and polished to perfect the microscopic fit of all the components to one another. If you were to monitor everything that is going on, you would note that compression increases over time of correctly breaking in period, and temperature will slowly decrease as the parts polish and friction decreases.

Remember it is called cross hatching, so while you are spinning the hone, you need to be always moving in and out of the bore. Don't just put a hone stone in there and rotate it quickly without aggressively moving in and out of the bore. Slow to moderate rotation and a balanced in/out movement all the while lubricating to remove particle matter. Think wet sanding a paint surface with fine grit sandpaper. You use the water to keep the cutting surface of the sandpaper from clogging with the dust...

Also, the cross hatching will hold more lubricating oil for the break in period, and assist in carrying the wear metals away (well, this is true in crankcase engines with oil bath and I can imagine somewhat similar in two stroke also)

Which inspires another comment for discussion, in two stroke, use additional oil in fuel for initial break in?
And we are air cooled, I know with aircraft engines, we do not run them much on the ground, (especially with the cowling removed) they need to be flown a certain way that puts the most cooling air across the cylinder fins for cooling (shallow climbs), and shallow descents (powered) descents to avoid shock cooling the cylinders.
If you overheat the cylinders during that break in period of high friction, you run the risk of galling the pistons.

So maybe, we should start a freshly honed cylinder with new rings, run it for an initial period (in tall grass like someone previously posted) but for a limited period and then let it cool off. Then an little longer run with a heavier load, but keeping in mind not to run it too long and getting too hot.

I was told one time to drive it like I stole it, and other said to baby it during break in. I know with aircraft engines during breaking, it is common practice to continually change the power settings so as to not "groove" the engine to being used to just running at one particular power setting...

I apologize for being so long in the finger. I like to learn and teach what I have learned. If I openly run my keyboard, maybe someone will point out where I am thinking wrong...

 

[jp1961]

Is there any definitive way to determine if the cylinder was either chrome or Nikasil plated? I'm assuming (maybe wrongly)a chrome plated cylinder doesn't actually look like a chrome bumper, as a bumper isn't shiney until it gets buffed to a high luster.

Jeff

 

[timw128]

Is there any definitive way to determine if the cylinder was either chrome or Nikasil plated? I'm assuming (maybe wrongly)a chrome plated cylinder doesn't actually look like a chrome bumper, as a bumper isn't shiney until it gets buffed to a high luster.

Jeff

Jeff, generally speaking, on a Nik plated cylinder you'll notice a small degree of casting porosity- little pockets or voids left behind from off gassing during the casting process.

They do not fill in with the plating operation, hence they can be seen. And actually, they'll retain lubricant. These voids do not affect cylinder sealing in any way.

Every engineering dept. has a tolerant point as to how much voiding is acceptable. On the other hand, a steel/iron liner will appear perfectly smooth- especially after

extended use and the cross hatching has worn smooth. Cylinders in an internal combustion engine do not wear uniformly, due to crank pin forces creating a variable load path

through the con rod, transferring the angular force normal to wrist pin center line. Hence uneven bore wear, to different degrees. For that reason, you may still observe

some cross hatch in the bore at different locations.

There are many more complex dynamics involved than this, though.

Hope this helps.

tim

 

[bertsmobile1]

Jeff, generally speaking, on a Nik plated cylinder you'll notice a small degree of casting porosity- little pockets or voids left behind from off gassing during the casting process.
They do not fill in with the plating operation, hence they can be seen. And actually, they'll retain lubricant. These voids do not affect cylinder sealing in any way.
Every engineering dept. has a tolerant point as to how much voiding is acceptable. On the other hand, a steel/iron liner will appear perfectly smooth- especially after
extended use and the cross hatching has worn smooth. Cylinders in an internal combustion engine do not wear uniformly, due to crank pin forces creating a variable load path
through the con rod, transferring the angular force normal to wrist pin center line. Hence uneven bore wear, to different degrees. For that reason, you may still observe
some cross hatch in the bore at different locations.
There are many more complex dynamics involved than this, though.
Hope this helps.

tim

Arrrrh,
the old two countries divided by a common language strikes again.
Nikasil was the registered trade name for a series of Nickel, Aluminium, Silicon alloyed cast irons dating back to the late 1800's
I can see where the new name come from because they form nickel-silicon carbides which makes them hard as hell. They also form Nickel-Aluminium -Silicides which does the same as the Aluminium Silicides in the 13% Si controlled expansion alloys used for pistons.
Nikasil was developed for cannon barrels so it is high temperature tollerant , high pressure stable , not reactive, abrasion resistant . Thus the fledging auto industry has a perfect alloy for brake drums when they developed the internal expanding brake.
It was also used for cylinder sleeves in wet sleeves aero engines ,motorcycle brake drums with intergral sprockets , excavator teeth , dozer blade tips and latter disc brake rotors.

That out of the way, I seriously doubt there would be any casting voids in a modern pressure die cast cylinder as the aluminium is degassed with chlorine prior to pouring or you end up with the infamous "growing castings" which kept cast iron being used for pistons right up till the 1940's and the whole point in pressure die casting is to force feed the solidifing casting to prevent the formation of shrinkage voids.
You could however etch the machined bore with hydro flouric acid which will dissolve some of the exposed silicon without touching the aluminium thus maintaining the overall bore dimensions prior to plating.
If you are involved in the process you can check because a casting void will have a very smooth rounded almost glass looking surface where as the etched holes will have a flat sided hole with sharp edges.

 

[bertsmobile1]

Is there any definitive way to determine if the cylinder was either chrome or Nikasil plated? I'm assuming (maybe wrongly)a chrome plated cylinder doesn't actually look like a chrome bumper, as a bumper isn't shiney until it gets buffed to a high luster.

Jeff

so what do you think the piston rings do ?
Chrome bores are shinny and slightly blue in appearence
Steel bores will also be shinny but slightly green in appearence.
cast iron will be shinny and grey looking