It's always been a peev of mine. I've heard people (both mfg's and customers) calling their piston forged, and because of the stigma that surrounds why one is better than the other,...(Forged vs Hyperutectic vs cast) they choose one because it's advertised incorrectly.
Just because a piston is "forged" does not make it capable of withstanding the abuse it's subjected to given the misrepresentations the industry uses describe them. Guys building hi power engines almost always stipulate that they want need a forged piston to handle the additional power/boost that they are anticipating building, then they run right out and buy a 4032 alloy piston.
Aka Mahle
Forged pistons are made of two alloys. Each one has it's pro's and con's. 2618, and 4032.
A 2618 alloy piston is what most people think they're getting when they buy a "forged" piston. This piston alloy is by far the most forgiving in high horsepower/big boost situations as the aluminum contains very little silicone. The lack of silicone in the aluminum makes the piston less brittle and much more forgiving when subjected to abuse. Abuse in this instance is detonation,or preignition, and the heat that typically comes when trying to tune an engine to it's edge of power when using a certain octane fuel (i.e. pump premium). No piston alloy has ever been found to better deal with the hammering effect of pre-ignition, or better be able to dissipate heat better than this alloy, and it has been and continues to be the best choice for big power for those reasons.
However,...2618 alloy "grows" and "shrinks" considerably in the cylinder bore when it heat cycles, and considerations have to be made in the build to accommodate that thermal expansion when the machine shop bores and hones the engine. The end result is audible. Engines w/ 2618 alloy pistons make a significant amount of noise due to the piston moving up and down and "rocking" in the bore as a result. Now to most car guys, this is a welcome or at least acceptable compromise, but on a relatively quiet engine otherwise, is quite noticeable, especially when first started. Additionally, because of the excessive clearances and subsequent rocking, they don't last as long in a daily driven vehicle.
Some 4032 alloy pistons can also considered "forged", because the word forged in this usage refers to how the piston is formed. At the same time, a 4032 alloy piston can also be cast.
4032 alloy aluminum contains a much higher percentage of silicone when being made. The benefits to the added silicone are many,...as the piston becomes significantly less likely to expand and contract during a standard heat cycle. The immediate benefit being it's not noisy. Tighter tolerances mean better ring seal, tighter ring seal means a more efficient, more powerful, cleaner running engine. It also adds significant life to the engine as a direct result of the tighter clearances. It makes for a perfect street car piston.
However,...a 4032 alloy is brittle. It won't tolerate being pounded on like our 2618 cousin can. A tune mishap, fuel delivery problem, or the excessive heat that comes when adding more power isn't tolerated by a piston that is made from 4032. It breaks ring lands, or shatters completely when subjected to the exact same circumstances a 2618 piston survives through. The 2618 piston will still eventually melt and fail if subjected to extremes, but therein lies the difference, 2618 is what people think they're getting when they buy a set of forged pistons. Certain companies out there call something one thing when most people think that it's something that it's not, especially when there are such important differences between the two. Some mfgs are misrepresenting the pistons as simply "forged," forcing the buyer (alot who don't even know to check) to check which alloy the piston is built from.
It's that missing piece of information that poor ole Jim Bob was thinking he was taking care of when he bought himself a set of Mahle pistons for his 347.
Don't be a Jim Bob.
Just because a piston is "forged" does not make it capable of withstanding the abuse it's subjected to given the misrepresentations the industry uses describe them. Guys building hi power engines almost always stipulate that they want need a forged piston to handle the additional power/boost that they are anticipating building, then they run right out and buy a 4032 alloy piston.
Aka Mahle
Forged pistons are made of two alloys. Each one has it's pro's and con's. 2618, and 4032.
A 2618 alloy piston is what most people think they're getting when they buy a "forged" piston. This piston alloy is by far the most forgiving in high horsepower/big boost situations as the aluminum contains very little silicone. The lack of silicone in the aluminum makes the piston less brittle and much more forgiving when subjected to abuse. Abuse in this instance is detonation,or preignition, and the heat that typically comes when trying to tune an engine to it's edge of power when using a certain octane fuel (i.e. pump premium). No piston alloy has ever been found to better deal with the hammering effect of pre-ignition, or better be able to dissipate heat better than this alloy, and it has been and continues to be the best choice for big power for those reasons.
However,...2618 alloy "grows" and "shrinks" considerably in the cylinder bore when it heat cycles, and considerations have to be made in the build to accommodate that thermal expansion when the machine shop bores and hones the engine. The end result is audible. Engines w/ 2618 alloy pistons make a significant amount of noise due to the piston moving up and down and "rocking" in the bore as a result. Now to most car guys, this is a welcome or at least acceptable compromise, but on a relatively quiet engine otherwise, is quite noticeable, especially when first started. Additionally, because of the excessive clearances and subsequent rocking, they don't last as long in a daily driven vehicle.
Some 4032 alloy pistons can also considered "forged", because the word forged in this usage refers to how the piston is formed. At the same time, a 4032 alloy piston can also be cast.
4032 alloy aluminum contains a much higher percentage of silicone when being made. The benefits to the added silicone are many,...as the piston becomes significantly less likely to expand and contract during a standard heat cycle. The immediate benefit being it's not noisy. Tighter tolerances mean better ring seal, tighter ring seal means a more efficient, more powerful, cleaner running engine. It also adds significant life to the engine as a direct result of the tighter clearances. It makes for a perfect street car piston.
However,...a 4032 alloy is brittle. It won't tolerate being pounded on like our 2618 cousin can. A tune mishap, fuel delivery problem, or the excessive heat that comes when adding more power isn't tolerated by a piston that is made from 4032. It breaks ring lands, or shatters completely when subjected to the exact same circumstances a 2618 piston survives through. The 2618 piston will still eventually melt and fail if subjected to extremes, but therein lies the difference, 2618 is what people think they're getting when they buy a set of forged pistons. Certain companies out there call something one thing when most people think that it's something that it's not, especially when there are such important differences between the two. Some mfgs are misrepresenting the pistons as simply "forged," forcing the buyer (alot who don't even know to check) to check which alloy the piston is built from.
It's that missing piece of information that poor ole Jim Bob was thinking he was taking care of when he bought himself a set of Mahle pistons for his 347.
Don't be a Jim Bob.
Yours will too. 
