Shimakid12

iTrader: (2)

This is very interesting. So there is definitely a point where the silicon content is too great, and where it would seen any sign of detonation (like in a high compression, all motor setup where tuning to avoid detonation is super important), the piston can literally shatter? So sometimes, it may be better to get a piston that doesn't have a crazy high amount of silicon to avoid too much expansion.

Can you think of any particular piston off the top of your head that has a great medium for common all motor setups. Something that has enough silicon to run tighter P2W clearances, which I feel is best for an NA app, but won't shatter at the hint of detonation? Good info guys.

gstrudler

How about the OEM piston out of the f20c? Forged, running 11:1 (or 11.7 in JDM trim) compression and obviously must be built to be reliable and not extremely noisy. Don't know the metallurgic makeup of them though.

iskate2

well the first thing you gotta ask yourself when it comes to piston choice is daily driver, weekend warrior, or full race? if its your daily, cast pistons and dont build it too hot. if its full race, forged, spend as much money as possible, and expect 40-50 hrs of track use. if its a weekend warrior, experiment. why not, right?

vinuneuro

Pirate, the OEM F20c (Mahle supplied) pistons are very similar (most likely identical) to the metallurgy of the Mahle H22 pistons, 4032 alloy. I think most of the aftermarket forged pistons are 2618. They are very different.

You'll find this thread pretty illuminating regarding the coefficient of thermal expansion of the two.

https://honda-tech.com/forums/all-motor-naturally-aspirated-44/my-k20-rebuild-2427270/

EDIT: looks like you read and posted in it.

88Hatchy

Wow. I looked like he did all his homework for that build. Wonder what went wrong?

Shimakid12

iTrader: (2)

Thanks for posting that link. I'll have to go through it.

RA22FEVER

correct me if im wrong but arn't F20/22c cylinder walls FRM? and dont they run forged pistons stock?

gstrudler

Here it is:

Justin Jones

That's interesting, I've never noticed that in the helms.

Maybe Honda's engineers subscribe to the theory that you can't really get the cylinders perfect with the block being honed at room temperature.

Have you ever heard of hot honing? Basically the theory is that you pump hot honing oil through the (sealed off) water jackets during honing to simulate the engine running at operating temperature.

It would be interesting to see how much the bores move around in our aluminum honda blocks... probably a lot.

Scott_Tucker

What seems to have failed first on that? It looks like it broke a rod bolt. How high were you revving it and what is the engines stroke?

Scott_Tucker

Yeah, thats just about 5000 feet per second mean piston speed which is about max (for reliability) on good rods and good bolts (properly tightened). So I guess 40k miles would seem pretty good.

4piston

Man I guess I know someone that should feel fortunate with a 90,000 mile 12.5:1 motor with Eagles in it turning 9500 and spraying a decent shot on it? HA HA!

Doobie/ej1

at wat point in cr do you have to start runinng 91/93 octane..
an wud itr pistons in an ls vtec gsr head b safe?

95skunkedgsr

so generaly what is the tightest you would go on forged pistons for ptw because of thermal expansion

mar778c

iTrader: (1)

^^^That can not be answered without a lot more details.

BTW, it's thermal expansion.

Justin Jones

Depends on piston silicon content, bore size and whether or not you're running forced induction or not. For example, Endyn reccomends .0022”-.0023” P/W clearance for an all motor 81mm engine with their pistons. An 84mm CRV with their pistons is reccomended to run .0027”-.0028” p/w clearance.

95skunkedgsr

i think that would proble be because the 84mm piston haves more ability to expend because its more material

Justin Jones

exactly.

95skunkedgsr

when i typed it and looked at it i thought to my self that there was no way it could be spelled right , if say someone was using wisco 11.5.1 pistons and looking for reliabilty , i belive wisco's are low silicone

vwbased

Have a nice day

Scott_Tucker

Oops. Yes.

Shimakid12

iTrader: (2)

Lol, if only all builds could be as fortunate...

This isn't exactly following the topic of this thread. However, if you think about it, most honda v-tec motors recomend/require premium fuel. This can be geared towards a couple of reasons (advertised HP numbers, higher RPM's) I'm willing to bet it's also partially due to the slightly higher compression numbers most of them have. I think the general consensus is anywhere around the 10.0-1 range to about a maximum of 12.0/12.5:1 range, again this is just what the general opinion seems to be. Some will say that higher comp can be ran on pump gas, and pump gas isn't required for compression as low as 10.1.

This is good. All of the things you listed alter how tight of a clearance is a 'safe' clearance for a piston. Sine you mentioned Endyn, any idea on where the roller waves stand as far as what material they're made out of and their silicon content? Anyone know of a brand that has a forged piston that has a GOOD silicon content and metal structure for common all motor builds; something that is plenty strong for the app, but doesn't undertake excessive thermal expansion allowing it to be ran with tighter P2W clearances?

Shimakid12

iTrader: (2)

Anyone have any opinions or experience in all motor apps with the super tech forged pistons:
http://www.jhpusa.com/store/pc/viewP...idcategory=334

The description listed here states that they are of a high silicone content made out of 4032 for low thermal expansion. At JHPusa, they offer quite a large range of bore sizes and compression sizes, which is great for customization.

Taken from the supertech website faq:

"Q: What is the piston to Cylinder wall clearance?
A: All our pistons come with a specification sheet, please read that sheet carefully. Piston diameter must be measured at the gauge point indicated on the sheet. Required clearence depends on the diameter, alloy, type or forging (full Skirt or Slipper design) application, operation conditions."

If anyone has used these pistons I'd be interested in hearing what size piston they purchased and what the P2W clearance spec sheet said.

Shimakid12

iTrader: (2)

Found this, some pretty good info, nothing too different then what's been discussed already but good info nonetheless. I'm going to add it to the first post.
http://www.team-integra.net/sections...?ArticleID=183