found some interesting stuff on why frm is used, why forged aluminum pistons tear it up, and how the nsx and s2000 get away with using them
from http://nsx.vtec.net/weekly15.html
Despite increases in horsepower and displacement, engine weight was reduced by 2.4 kilograms. To achieve both light weight and durability, the block is made of aluminum alloy. The cylinders on the new 3.2-liter V-6 are now made using an advanced metallurgical technique called Fiber Reinforced Metal (FRM), in which an alumina-carbon fiber is cast into the traditional aluminum alloy for enhanced rigidity. This process not only allows displacement to be increased without increasing bore centers, it also provides outstanding cooling characteristics. I'm thinking this means the block is actually stronger even with a larger bore- maybe this is why many who have their blocks resleeved have problems- removing the FRM weakens the block overall, and reduces cooling capacity
The NSX's block has cylinder bore surfaces consisting of an 0.5-mm-thick layer with fibers of carbon and alumina (aluminum oxide, or Al2O2) in the aluminum alloy. In production, the cylinder block's aluminum alloy is poured around cylinder cores composed of these two fibers. The cores absorb the molten aluminum during the casting. After casting, the cylinders are bored to a slightly smaller diameter than the cores, leaving a tough, wear resistant, composite cylinder wall integral with the block but reinforced by the fibers. The process allows larger bores within the same external block dimensions and bore spacing, and makes open-deck block construction possible. In turn, this is appropriate for the new NSX engine's higher performance level. And with the elimination of iron cylinder liners, the reduction in engine weight by 2.4 kilograms was made possible.
In engines with steel cylinders, conventional aluminum pistons are normally used. Because aluminum-on-aluminum is not a satisfactory combination for durability with a piston sliding in a cylinder, the NSX's aluminum pistons are given an iron coating. so that's how they do it! this is also why the forged pistons screw up our cylinder walls
The last alternative is a fiber-reinforced metal (FRM) cylinder sleeve, which is used by the Honda NSX 3.2-litre. Its cost and power / space efficiency are both half way between cast-iron liner and Nikasil. A fiber-based material in the form of cylinder sleeve is first inserted into the die of the block. Melted liquid aluminium is poured into the die and integrates with the fiber sleeve. Then the cylinder wall is machined to the desire bore dimension, leaving only 0.5 mm thickness to the fiber sleeve which covers the cylinder wall. It generates lower friction than an iron liner, thus improves revs and power. Moreover, the fiber sleeve reinforces the block, allowing the distance between adjacent bores to be reduced yet maintain mechanical strength.
something else on this page leads me to beleive an even better solution to iron liners on the pistons would be nikasil
Instead of a cast iron liner, Nikasil treatment coats a layer of Nickel-silicon carbide to the inner surface of aluminium cylinders. Since the Nikasil layer generates even less friction than cast iron liner, revability and power are both enhanced. Moreover, it is only a few hundreds of a millimetre thick, therefore the spacing between adjacent bores can be reduced considerably, making the engine smaller and lighter
from http://www.autofieldguide.com/articles/069902.html (sidebar near the bottom)
The optional 3.2-L engine is somewhat more interesting from a materials standpoint. The cylinders are made with a process called "Fiber Reinforced Metal" (FDM). In production, there are cylinder cores consisting of carbon fibers in an alumina (Al2O3) matrix. The cylinder block's aluminum alloy is poured around these cores. The cores absorb the molten aluminum. Then the IDs of the cores are bored so that there is a 0.5-mm thick layer of the material remaining, which provides a tough, wear-resistant cylinder wall. If cast iron liners were used in this engine, it would weigh 2.4 kg more. The pistons in the 3.2-L engine are given an iron coating. some additional agreement that the pistons are iron coated
from http://dwolsten.tripod.com/articles/nsx3.htm --just to make us feel good, FRM was in the H22 first!--
The type C32B engine is an enlarged version of the C30A with its bore increased from 90 to 93 mm, retaining the original 78-mm stroke. This was done by adopting fiber-reinforced metal (FRM) cast in an aluminum block, instead of the type C30A's iron liners. This material combination was originally applied to the Prelude's 2.2-L inline four-cylinder block which had started out as a 2.0-L unit. the way that was written makes me think honda felt that FRM was necessary for block integrity
well I hope this helps everyone out, and maybe will reshape the resleeving with forged pistons debate. something is definately nessacary as aluminum on aluminum isn't good. maybe we can find a piston manufacturer to do iron or nikasil piston coatings for our cars.
maybe this should be FAQ'ed, just trying to make sure everyone gets their $6 worth
That's an excellent collection of material. Unfortunately, if you do a search for FRM in the forced induction forum, you can see all of these points have been brought up previously and most of these links have been covered as well.
Thanks for bringing it together, though. It's nice to see someone doing some research and I agree, this should be FAQ'd.
__________________ DirtyLude
Mark Higgins
Toronto Prelude Club www.hondaprelude.to
i didn't realize it was coverd there, I've done a couple searches before and didn't find any totally satisfactory info, so i did a search on google.
i was kind of against resleeving before, now there is no question, i'd never do that to my motor.
it seems boring out this engine is a no-no as well as resleeving unless it is converted to closed deck.
vir2L, I'm saying that the pistons need to have iron or nikasil coatings. regular forged pistons will tear your cylinder walls up
Artifex, i remember reading that post awhile back, but noone conclusively answered how the NSX and S2K did it. Don't know about those caramic coatings, but nikasil might just be the best bet, with iron a close second (probably beacuse it's more available) cosworth did it on their engines for awhile, if you can find a co that makes pistons for one of their iron-coated piston motors, that also makes honda pistons, they could probably get them to do something up for you. we should combine these threads and FAQ.
Nikasil coated cylinder walls are good, but it's difficult to get it done properly. There's only a few places that do it in the US and those due it with a brush process which isn't the best. Nikasil can flake as well. I've seen it on the nikasil coated motorcycle engines. It would be nice to try it out if I was going for an all out NA race motor.
__________________ DirtyLude
Mark Higgins
Toronto Prelude Club www.hondaprelude.to
I'm actually glad this subject came up again. Those are some good references alphajesse.
I had a strong suspicion that the s2k and the nsx used iron coatings, but after reading your references, now I am sure.
If I read you correctly, you propose that Iron would be the best coating for the pistons. I considered this also, but I came to a different conclusion. Basically, we have three choices :[list=1][*]Iron[*]Nikasil[*]Ceramic Compound[/list=1]
There may be more options that these, but I couldn't find any information when I did a web search.
Iron is an okay choice in my mind. The reason it's not my first choice is because (a) it is heavier than the other two and (b) it lacks some cool bonus properties both Nikasil and ceramic/nickel have. Both Nikasil and ceramic/nickel are heat reflective, and have superior lubrication behavior. Given the choice, I think the Ceramic/nickel option is the best.
I am not convinced that the Ceramic/nickel will "flake" off. No one who posted in the last thread was able to say conclusively that they have seen it chip on a modern compound from a reputable company. If it does chip, I am willing to bet that we are talking like 150k+ miles before we get to that point anyways. FI motors have other concerns when you put those kinds of miles on anyways (since I was proposing this stuff as an alternative to resleeving for boost).
One more thing. In the past, I had heard references to "swain" coating a part, but I never knew what that meant. I always thought it referred to a coating process. Now I realize that it means getting the object coated at Swain Tech. I have heard a lot of good things about Swain, and Swain also seems to offer non-ceramic coatings that are wear-resistant (need more info on those).
Since alphajesse has reminded me, I am going to send a note off to Swain asking them directly about how many miles their coatings are good for. I will see what they say.
If anyone can show me a case where a modern ceramic/nickel compound flaked off, I will gladly shut up.
That's kinda funny. Why don't you ask the maker of the Tornado Air system whether it actually gives you 20 extra horsepower and twice the gas mileage as well. http://www.tornadoair.com Swain does have a guarentee against flaking/cracking so they address the issue.
Nikasil, I have seen it flake off the top of motorcycle cylinder walls that come stock with nikasil coating. For serious racing engines nikasil is used exclusively unless the regulations for that series rules against it. I'd really like to see someone go for nikasil plating and see what happens. It would be real sweet if someone had access to an engine dyno with the ability to motor the engine and check friction losses. I've never seen a before after test with iron to nikasil sleeves or FRM to nikasil sleeves in this case. About 46% of the engine friction is due to pistons/rings.
Ceramic coating is a thermal barrier and has nothing to do with the FRM / forged piston discussion. The ceramic coating goes on the top of the piston and does nothing for the skirts. There are skirt coatings, but these are usually with Molybdenum or Teflon. This is not an alternative to sleeving and has no bearing on this conversation. Unless you think these skirt coatings may help, but they are only skirt coatings and don't cover the ring lands.
Your only options are Nikasil coating the cylinder walls, and iron plating the pistons.
__________________ DirtyLude
Mark Higgins
Toronto Prelude Club www.hondaprelude.to
dirty lude, every solution i offered considered coating the pistons not the cylinder walls- if i got those recoated, i might as well resleeve. i was thinking the sides of the pistons could be nikasil coated, but having iron-wrapped piston skirts is how the s2k and the NSX mange to have both at once. let's find someone who makes aftermarket s2k or 3.2L NSX pistons!
I don't know of any company that nikasil coats pistons. You might be able to find someone out there that will do it for you, but the low friction benefit of the nikasil is mostly lost since you will still have the piston rings rubbing against the bare aluminum, or in our case FRM. Not to say that it won't work, but I've never heard of a nikasil plated piston before.
Good luck.
__________________ DirtyLude
Mark Higgins
Toronto Prelude Club www.hondaprelude.to
Originally posted by DirtyLude That's kinda funny. Why don't you ask the maker of the Tornado Air system whether it actually gives you 20 extra horsepower and twice the gas mileage as well. http://www.tornadoair.com
Because there are 100 people who have already said through personal experience that Tornado sucks, so I find that pretty convincing. I haven't found even 1 person to say **** about the longevity of ceramic, so hence the manufacturer is my next best alternative.
Quote:
Nikasil, I have seen it flake off the top of motorcycle cylinder walls that come stock with nikasil coating. For serious racing engines nikasil is used exclusively unless the regulations for that series rules against it. I'd really like to see someone go for nikasil plating and see what happens. It would be real sweet if someone had access to an engine dyno with the ability to motor the engine and check friction losses. I've never seen a before after test with iron to nikasil sleeves or FRM to nikasil sleeves in this case. About 46% of the engine friction is due to pistons/rings.
If you have seen it flake off, then that's a bit of a problem for most of us . I agree that Nikasil would be cool, but coolness for 20k miles doesn't help me much.
Quote:
Ceramic coating is a thermal barrier and has nothing to do with the FRM / forged piston discussion. The ceramic coating goes on the top of the piston and does nothing for the skirts. There are skirt coatings, but these are usually with Molybdenum or Teflon. This is not an alternative to sleeving and has no bearing on this conversation. Unless you think these skirt coatings may help, but they are only skirt coatings and don't cover the ring lands.
The company I posted in the other thread, Maxpower , will put their ceramic on the piston skirts. Swain seems to stick to just Moly/Teflon as you say.
After looking further, you are right. No company I can find will cover the ring lands, so that is a dealbreaker right there . I wonder why. Do you know of a technical reason it isn't done?
Quote:
Your only options are Nikasil coating the cylinder walls, and iron plating the pistons.
So it seems that Iron plating the piston is still a viable alternative to sleeving then.
One last idea : Would it be possible to coat the bore in Moly or Teflon? Presumably, this would be similar to choosing Nikasil, except with more reliable results (given your Nikasil experiences above). My original goal was to avoid sending away the block for sleeving, but it looks like that is getting harder and harder to avoid. It seems to me like Aluminum/Teflon is better than Iron/FRM from a frictional loss point of view.
I know this thread is old, but I wanted to add one more thing that I think is relevant here.
I asked Swain why they don't coat the piston ring lands, but will coat every other part. Richard from Swain replied with this message :
I must have missed your message because I see it here and it does not appear
that I have responded. Sorry for the delay. The most critical step in
prepping the substrate, in this case a piston, for coating is an abrasive
blast. To avoid blasting in the grooves, the grooves would have to be
masked. Masking in there is extremely difficult, if possible at all to do.
If you did not bother masking and went across the entire ring area, you not
be able to get a uniform coating in relation to the top, bottom and depth of the
groove in relation to the OD of the ring land. Also, there will be some
areas in the groove that would be roughened up from the blast, but not
accessible enough for coating so it would leave you with rough aluminum.
Finally, there is little functional gain so it just does not justify the risk, effort
and cost of coating anything except for the skirt.
Richard
That is a little insight into their coating process.
The other thing I found interesting is the possibility that the ring lands have the least opportunity of contacting the cylinder walls. This site has a picture of piston slap. I would find it highly improbable that the ring land would impact the wall; rather the crown and the skirt would likely do so long before the land would in an engine with proper clearances.
found new info in R&D motorsport's s2k/spoon section http://www.randdmotorsports.com/spoonsports.html
scroll down to the bottom with the s2k parts --
"Forged Aluminum Graphite Pistons"
look at this photo- it appears that the pistons have graphite, or graphite-coated skirts:
when i get home from work tonight i will email R&D to see if they have any more detailed/technical info on the construction of these pistons.
Originally posted by Artifex Swain seems to stick to just Moly/Teflon as you say.
Swain does not use Teflon, as it is known to flake off over time. Swain uses a tungsten-molybdenum disulfide polymer, which works with the oil to give a very low friction coefficient, and reduce cylinder bore scuffing.
This is what will be going on my piston skirts, along with Swain GoldCoat on my piston crowns.
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. I wonder why. Do you know of a technical reason it isn't done?
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