bpaspi

I don't know if the OEM pistons are out of 2618 or 4032 alloy.
But I have read that the Woessner pistons for the F20C are 2618-T6.
And due to the larger expansion module it seems a good explanation why they need more clearance.
My guess (!) is that the manufacturing process isn't as precise for these aftermarket pistons as for the OEM Honda pistons.
Makes sense in my opinion.

But I don't say that the Woessner pistons are FRM-friendly. Whatever that means - FRM friendly.
All I'm telling is that my N/A setup runs perfectly with them since more than 10,000 miles. Just as an information for the community.

Bernd

ya@inlinepro

We get these custom made from CP.

However, without a proper hone, it will consume oil. There is already a customer we did a build for running the car with it with 400+ rwhp.

Artisan7471

Frm compatible pistons as Honda designed them are coated with 3 different materials, they also have a hard anodized top ring land. The material is A390 aluminum, which is very close to 4032 aluminum's silicon content. The black coating on all stock pistons is a break in coating, most likely some thermosetting polymer. The other layers are ferrous metals. As far as I can tell Cp does not make frm compatible pistons as Honda specs them. They do however make forged 4032 aluminum pistons that will work with the stock bores, however the wear rate will be accelerated when compared to the stock piston. The reason for this is the lack of antifriction coating. I had called Cp multiple times asking about frm compatible pistons, When I started to press them about the technical issues they told me that they do not make a piston that is coated for frm bores. The other problem with running a non frm friendly piston is that they most likely will come with incorrect rings for running on frm walls.

Bpaspi, Honda specifies a max over bore of .25mm or .01inch. The reason for this is that the cylinder walls have primary silicon crystals embedded in them. The process for creating these primary crystals is not identical throughout the entire block. The crystal grain structure near the inside of the cylinder walls is much finer than other areas of the block. If you over bore the bore you run into two problems, the first is that you expose larger grains of primary silicon to run against with your piston, meaning accelerated wear. And secondly if you over bore the block you can actually cut into the fiber reinforced region of the block, thereby decreasing overall ultimate strength of the block material as well as expose the reinforcing fibers to piston contact and again accelerated wear.

So that being said I am thinking about developing and selling a low compression true FRM compatible piston as Honda had originaly designed them. Im, not sure how many people would be intrested in these, but I know I would be.

bpaspi

[QUOTE=Artisan7471,Oct 12 2009, 11:17 PM] Bpaspi, Honda specifies a max over bore of .25mm or .01inch. The reason for this is that the cylinder walls have primary silicon crystals embedded in them. The process for creating these primary crystals is not identical throughout the entire block. The crystal grain structure near the inside of the cylinder walls is much finer than other areas of the block. If you over bore the bore you run into two problems, the first is that you expose larger grains of primary silicon to run against with your piston, meaning accelerated wear. And secondly if you over bore the block you can actually cut into the fiber reinforced region of the block, thereby decreasing overall ultimate strength of the block material as well as expose the reinforcing fibers to piston contact and again accelerated wear.

PhantomAP1

I know there would be a couple of people, at least. And if you're pistons are up to the task, and people (like myself) start running them with higher boost while making good numbers, the trend could catch on. People are always looking for the "best bang for their buck", and this would fall in that territory. Sleeving can easily add an extra $1000 to your build, and I would much rather spend that money on other things when our FRM sleeves can handle the duties. I am also partial towards the realiability factor that FRM has when dealing with higher RPMs.

How would you propose to have these pistons made? Do you have access to the tooling, or would you outsource the job/s to a company? I like the idea, and I would really like to hear more about it.

Artisan7471

I am an mechanical engineer with access to a variety of resources. I have also done the research on this and was originally planning on doing a set for myself because I didn’t want to go the sleeved route due to its heat transfer issues as well as higher overall coefficient of friction. These above all are responsible for the high power to displacement ratios seen in the f20 and f22. Hypereutectic cylinders and pistons like those In the s2000, have been shown to consistently make 6% more hp and torque than cast iron, due to its lower friction coefficient. In addition to this the thermal conductivity of aluminum is much better than cast iron. High thermal conductivity means you can run higher compression ratios or higher levels of boost all while not over heating the cylinders. I think this is why many sleeved f20,f22’s have heat problems on the road course. The cooling system in the S2000 was never designed for the cooling load needed with cast iron sleeves.
Most likely I will be doing a prototype build late this year. The earliest you would see these items for sale would be early to mid 2010, after the R&D is completed.

Bpaspi
Honda designed these cylinders using 2 different fiber types. The cylindrical fiber-reinforced portion is formed of a mixture of an alumina-based fiber and a carbon fiber embedded in an light-alloy matrix. The alumina-based fiber has a fiber volume fraction set in a range of 8 to 20%, and the carbon fiber has a fiber volume fraction set in a range of 0.3 to 15%. The alumina-based fiber contains 25% or less, by weight, of silica, has an average aspect ratio of 20 to 150, and an alpha rate of 2 to 60%. The carbon fiber has an average aspect ratio set in a range of 10 to 100 and a Young's modulus set in a range of 20 to 30 t/mm^2. The carbon is in fact an excellent lubricant, however the silica coating on the aluminum fiber is very abrasive.
Even though the fiber s are very short, they do indeed increase the strength of the cylinder wall.

Dienekes

bpaspi

The MAHLE Gold H22 pistons have 31mm compression heights - one millimeter more than F20 pistons. They don't need to be machined - just use the K24 rods.

@Artisan: thanks. Appreciate your infos!

PhantomAP1

What needs to be machined in order to use the K24 Rods? I wouldn't imagine that they would fit the F20 crank with stock bearing? I appreciate all the information I've found in this thread. Thanks a lot to you guys!

chris_barry

K24 rod is 152mm long with 22mm pin and 51mm big end, so meets the deck height requirements and H22 piston pin and F20 crank pins sizes

Only problem is the width of the big end. K24 is ~19mm vs F20C ~24mm

I have run configurations like this where the little end width is sized so it locates the rod in the piston, and the rod floats on the crank pin.