Hard Chrome vs. Nikasil Bores?

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max2cam

max2cam

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I was looking at the RedMax Chainsaw website and they look like really nice high-quality saws.

But like my Jap-made Echo the RedMax has a chrome-lined cylinder. It seems like the Asian brands still use hard-chrome while the Euros have gone over to Nikasil. I wonder why the Asian saws stick to hard-chrome? The Nikasil seems to have advantages.

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"The Nikasil coating used in our cylinders is a nickel and silicon carbide matrix coating about 0.07mm (.0025-.003") thick. The nickel matrix is very hard, but it is comparatively ductile, whereas chrome is brittle. Dispersed through the nickel are particles of silicon carbide less than 4 microns in size. These extremely hard particles make up 4% of the coating and form a multitude of adhesion spots on which oil can collect. Beside providing a very long wearing surface for the piston and rings, the silicon carbide particles also contribute to longer engine life by ensuring good cylinder lubrication".

"This superior process was developed by the German firm Mahle, originally for use in the Mercedes Wankel rotary. Porsche uses Nikasil in their turbocharged 917 - 935 series of race cars. In racing two strokes both Morbidelli and Rotax have had great success with Nikasil and of course it is used in thousands of professional grade chainsaws. The major drawback to chrome plating is the fact that chrome can flake. It is also easily damaged by dirt inducted into the motor."

Reprinted from Graham Bell's book, "Two Stroke Performance Tuning"

http://www.brisonaircraft.com/cylinders.htm
 
I dont know this for fact but I have heard that asian companies still use chrome because of their limited material supplies (suppliers?) and because of cost. I'm sure nikasil is better but not too many years ago it seems like almost all saws had chrome bores and help up pretty well. Of course they werent exposed to the leaner fuel and oil ratios and the higher muffler and head temps.
 
Chrome & Nikasil

Chrome plating is basically that; chrome is stuck to steel through chemical or electro- plating. The idea here is that the chrome has wonderful slickness and resistance to abrasion and makes a cylinder bore better through reduced friction of the ring rubbing against it. It's an expensive process and the only things that I know of that use this are some two stroke engines in model airplanes and chainsaws.
It's also used to refurbish (build up) bores in many aircraft piston engines (Lycoming, Continental) but I have never seen this used in other 4 stroke engines. (These jugs cost $800 each and up new)

Nikasil is a process whereby silicon is impregnated into aluminium cylinder bores to surface harden them, increase their scuff resistance and slipperiness. It was first used in a number of German street and race cars, first street car I know of was the 1968 911 S and the first real use in liquid cooled was the 928 Porsche V8 in about 1978. Mercedes aluminium block V8 do use this system as do pretty much any aluminium block engines where the pistons run inside the block and not inside an iron liner.
A note, GM did something with this system in one of their periodic jokes, the 70's Vega with 4 cylinder aluminium engine. It turned out to be a complete disaster in this application and I don't to this day know of any US manufacturers that run pistons inside treated aluminium bores (I don't know if Saturn in the 1.9 does or not) (the Chrysler 2.7 V6 is one of the most advanced alum block US engines I know and even this uses embedded iron liners).

Now as for a comparison, Nikasil equipped street cars can run a long, long time. Bore probs are not known problem areas even on early 911 Porsche that use them, chrome also seems to be pretty nice as a bore material but can flake.
I guess it is what you can do; If the Japanese don't have the manufacturing desire to Nikasil their bores (this probably requires some REAL capital investment) then they chrome, I think either is a quality setup. Zenoah (RedMax) is a really good product....
 
BMW evidently had a lot of problems here in the U.S. with their Nikasil bores in the mid-'90s.  I think it was found to be a result of the high-sulfur fuel we were then using, but that (the fuel) was remedied in the late '90s.  I saw that somewhere...

Glock uses Tenifer on their slides/barrels, and it's almost as hard as diamond.  Maybe we could get them to cough it up for use on jugs/pistons, hahaha!

Glen
 
I have approx 13,000 rounds through my Glock 30 and it is still a very tight gun.....there maybe something to that there tenifer stuff.
 
There are alot of different types of coatings, When I raced sleds the motors were factory race rotax's , and from what I was told Porsche did the coating , I have never seen any other coating like it, it was so hard you could break 10 pistons and still the jug was fine, try that with some of the other snowmobile motors. I know it was very costly for the jugs and those motors were double the cost of the normal jugs.
I find the normal chainsaw jug very soft compared to what comes back to me from when I have a jug bored and recoated,
 
Old school

Ford ,Chevy,Harley D.and Honda all use iron liners .That's good enough for me.Nothing I know of holds oil film better than good old grade 40 or 50 grey iron.Gee,does it show I'm old school? :)
 
Old school is not bad. I am a bit that way with all the old saws I have.

On a different note, granted I am comparing apples to oranges but those old Ford ,Chevy, and Harley's did not run at 14,500 rpm.

Bill
 
You should also consider the other half of the friction surface... the rings. The ring material will determine the longevity of the cylinder wall as much as the wall material itself. You have ring facing materials of iron, stainless, chrome, and plasma-moly. Iron on iron is the old basic combination, with the fastest break-in period. Iron rings on chrome cylinder, and the cylinder will last longer as the softer ring will impregnate foreign material, sparing the cylinder. Chrome rings on chrome cylinder walls, and you need forever for break-in, so chrome rings are best paired with iron cylinders. Moly faced rings are the most popular compromise.
 
Interesting subject

I haven't done the math but I would say a Harley engine,at 5000 rpm,would have about the same surface feet per minute travel as an 044 ,at 14 thou.I was referring to the die cast,aluminum blocks and cylinders,with spun cast iron liners,in use today.Working in the auto industry,I get to see some of these new innovations,first hand.An interesting concept is the use of Teflon pads,on the skirts of pistons used on engines ,such as the Ford Aj 30 [Lincoln Ls] and the 3 liter Vulcan.Both engines use chrome rings,of course.While I am "old school",I look on,in amazement,as these engines are assembled with microns,as being the units of measurements[ a micron,is 1/1000 of a millimeter].I drifted a tad off the subject. :dizzy:
 
Composite cylinder coatings are light years ahead of chrome and cast iron bores.
Ford, chevy and harley are not exactly pinnacles of engine longetivitey :eek:. Honda uses Iron liners in some engines on a cost basis only and because the Japanese in general have a engineering philosphy that shuns high tech coatings.
 
I could perhaps go along with that ,with one exception.I can show you many small block Chevys with well over 100 thousand miles on them.In my drive way,is a 1977 Ford f-250,with 250,thousand,a little tired though.As far as Honda,I hate to admit,but they make a good engine.The statement about composite coatings,does have some merit,perhaps for 2 cycle engines,but I guess that's what we're talking about.
 
Al 100,000 miles is nothing and is really not exceptional in any way for a motor to go that far. As fro composite coatings being only relivant to two cycles. Thats not true at all. They benefit four cycles just as much or more than they do two cycles.

BTW keep in mind that there are many differant brands of coatings out there that genericly called nikisil. Nikisil is a tradmark of the Mahle company.
 
Yes,100 thousand is not the exception,now days.Nearly every auto engine,with just normal maintenance ,can attain that.This has not always been the case.During the 60's,and we were all[ teenagers] were driving mid 50's cars, 50 thou.,was about it,before a rebuild,or at least ,a valve job.A lot of the longevity of modern engines,is the fact of better oils etc.Another factor is better manufacturing methods.In my opinion,engines are better ,today,than ever,all makes.In the case of small engines,take the example of B and S ,Ic engines,iron cylinder,aluminum block,the best of two worlds.Cheap engine,yes,but effective.Kohler,all iron engines,will,no doubt out last them,but cost several times more.In the case of high quality air craft engines,I know little about.As I understand it,however,there is usage of iron and steel cylinders [4140,I think],that have coatings,therein.This would be,no doubt,the acme of excellence .In the case of coated cylinders on saw engines,of course I am going to use the example of McCulloch,and refer to the 10 series engine.Strictly speaking on terms of longevity,they will out last a lined cylinder.Now,I will be the first to admit they are not the most pleasant to operate.Noisy,vibrate badly,but cu. in,per cu in,cut just as well.Many are still in service today,as compared to those of lined aluminum engines,that gave up the ghost,years ago.
 
I'm not sure how they do it but the old Ford 300 straight 6 will easily get to around 400,000. I've seen several like that, didnt really smoke much either. Maybe they hid a Honda in there lol :)
 
I know this , port a chainsaw jug and you will see it is pretty soft, send that jug to the guy that does my big bores and his coating is real hard , I mean hard
 

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