Oil starvation due to oil pickup tube snapping off...
07-27-2007, 01:08 PM
#17
Its cast, but at higher temperatures and pressures than regular casting to create stronger material. The metal molecules line up more along the lines of forging.
So yeah, the term is certainly BS, but it kinda does the job of describing the end result. The end result is a strength somewhere between cast and forged.
07-27-2007, 01:21 PM
#19
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Join Date: Oct 2006
Location: Sacramento - Watt & 50
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Car Info: Silver 06 STI - Helix catted dp - Cobb stage 2
Semi-forged is usually a process also known as high pressure casting.
Its cast, but at higher temperatures and pressures than regular casting to create stronger material. The metal molecules line up more along the lines of forging.
So yeah, the term is certainly BS, but it kinda does the job of describing the end result. The end result is a strength somewhere between cast and forged.
Its cast, but at higher temperatures and pressures than regular casting to create stronger material. The metal molecules line up more along the lines of forging.
So yeah, the term is certainly BS, but it kinda does the job of describing the end result. The end result is a strength somewhere between cast and forged.
07-27-2007, 01:43 PM
#20
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Car Info: Silver 06 STI - Helix catted dp - Cobb stage 2
I found that the stock US-spec STI pistons are hypereutectic cast pistons. Here's a good article on what hypereutectic means and the difference between stock and aftermarket pistons (casting and forging is also talked about). http://en.wikipedia.org/wiki/Hypereutectic_piston
07-27-2007, 02:15 PM
#21
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Semi-forged is usually a process also known as high pressure casting.
Its cast, but at higher temperatures and pressures than regular casting to create stronger material. The metal molecules line up more along the lines of forging.
So yeah, the term is certainly BS, but it kinda does the job of describing the end result. The end result is a strength somewhere between cast and forged.
Its cast, but at higher temperatures and pressures than regular casting to create stronger material. The metal molecules line up more along the lines of forging.
So yeah, the term is certainly BS, but it kinda does the job of describing the end result. The end result is a strength somewhere between cast and forged.
10-15-2009, 07:25 PM
#24
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PROTIP: forged pistons do not work very well on daily drivers.
the pistons will expand under heat so when the car is cold, there is a lot of piston slop until the engine comes up to temperature. When this happens, there is more then normal ware on the piston and block. Forged pistons are meant to be used on vehicles that are started up and run for a long period of time or not used very often.
semi-forged pistons are perfect for a street vehicle since they do not have the same expansion characteristics that the fully forged pistons exhibt.
the pistons will expand under heat so when the car is cold, there is a lot of piston slop until the engine comes up to temperature. When this happens, there is more then normal ware on the piston and block. Forged pistons are meant to be used on vehicles that are started up and run for a long period of time or not used very often.
semi-forged pistons are perfect for a street vehicle since they do not have the same expansion characteristics that the fully forged pistons exhibt.
If your looking for a forged piston that has tighter piston to wall clearances and doesn't have the thermal expansion than the stronger ductile forged pistons (2618 aluminum) do, go with a 4032 forged aluminum piston like the company Mahle makes. I was going to go with these pistons with my car, but ended up going with the stronger 2618 (with more thermal expansion) Wiseco's. But if you have your motor apart I would sure as hell put some forged slugs in that thing.
Oh and I drive my car 90 miles round trip everyday to work
Last edited by SR20steve; 10-15-2009 at 07:29 PM.
10-15-2009, 07:37 PM
#25
Speak of the devil... how's the bike? Or...better yet...the neon 
look at the age of the thread. heh.
Forged pistons are just fine for daily driving. For one there isn't a "semi forged" piston there is forged pistons, Hypereutectic (basically stronger cast, oem pistons), and cast.
If your looking for a forged piston that has tighter piston to wall clearances and doesn't have the thermal expansion than the stronger ductile forged pistons (2618 aluminum) do, go with a 4032 forged aluminum piston like the company Mahle makes. I was going to go with these pistons with my car, but ended up going with the stronger 2618 (with more thermal expansion) Wiseco's. But if you have your motor apart I would sure as hell put some forged slugs in that thing.
Oh and I drive my car 90 miles round trip everyday to work
If your looking for a forged piston that has tighter piston to wall clearances and doesn't have the thermal expansion than the stronger ductile forged pistons (2618 aluminum) do, go with a 4032 forged aluminum piston like the company Mahle makes. I was going to go with these pistons with my car, but ended up going with the stronger 2618 (with more thermal expansion) Wiseco's. But if you have your motor apart I would sure as hell put some forged slugs in that thing.
Oh and I drive my car 90 miles round trip everyday to work
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