need some opions going to replace pistons should i go with the forged, i will be spraying nitrous also- looking for some opions
I would really like you to explain to me the reasoning in that statement that you made. Were you joking?...............GSX800LTD said:OK, one more time. Forged pistons are for 4-strokes, CAST pistons are for 2-strokes.
I'll be happy to. (I wasn't joking) Forged pistons are indeed mechanically stronger than cast. This is great for high revving and/or force fed 4-strokes. The issue is, two stroke pistons typically don't fail by breaking, but rather by melting. (they may break up as the engine destroys itself after the melt) They melt at the edge of the crown near the exhaust port, or a hole in the center. The problem with forged pistons is they have a greater thermal expansion rate than cast. So the popular theory is to give them a loose fit and they tighten up when the engine warms. Except it's not quite that easy. They tighten up enough to stop (most of) the rattling as they warm up, but they still are too loose to EFFICIENTLY TRANSFER ENOUGH HEAT TO THE CYLINDER WALL. This goes along sorta OK until the chips are really down.... cold temps, long WOT run, poor fuel, etc. and then the heat being put into the crown by combustion temps rapidly exceeds the forged pistons ability to transfer that amount of heat into the cylinder wall for removal. The pistons crown melts and thus the failure.milrlite said:I would really like you to explain to me the reasoning in that statement that you made. Were you joking?...............GSX800LTD said:OK, one more time. Forged pistons are for 4-strokes, CAST pistons are for 2-strokes.
That's silicon, no "e" and it's in every aluminum alloy to varying degrees. I see you're having good results with the Wiseguys in your Yam, that's good. I'd also bet that your other variables are well inside the safe zone... ie, jetting that's fairly conservative rather than ragged edge lean. So the piston crown temps stay comfortably away from the failure point. Buuuutt.... if you take it across the lake at -25F, and the gas you got was not very good, and someone dumped methanol alcohol in it (the gas) before you bought it...... then you may aproach the temps where the difference would become an issue. Seeing's how that's pretty unlikely, they'll probably live a long happy life.mopar1rules said:doesn't the amount of different alloys that are put into forged pistons affect their expansion rate also? I think they even add silicone to the mix....right? When I rebuilt my SRX 700, I used Wiseco forged pistons and had great luck with them. Sled now has 1500 miles since rebuild and still runs strong.