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Old 06-21-2006, 03:53 AM   #1
STimo
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Default Forged pistons and rods?

I was over at IWSTI and in a thread over there people were saying that the new 06 STI comes with forged pistons and rods. Is this true?!?! I thought if anything they would have made the internals cheaper since they put in plastic motor mounts. I also heard something about better pistons i think but not sure. Anybody out there know for sure?
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Old 06-21-2006, 04:17 AM   #2
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nope not true, same damn engine like its been for 2 years.
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Old 06-21-2006, 05:42 AM   #3
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That's what i thought, but people over there are saying FOR SURE it has forged crank and rods. If they did have forged crank/rods, i think that would have been a VERY big deal and everybody would have known about it.
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Old 06-21-2006, 06:34 AM   #4
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Someone will correct me if I am wrong, but the crank is forged and the rods and pistons are not.
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Old 06-21-2006, 06:38 AM   #5
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The crank and rods are forged, but the pistons are cast.
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Old 06-21-2006, 06:49 AM   #6
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Quote:
Originally Posted by ilivas
The crank and rods are forged, but the pistons are cast.
^^^^^^
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Old 06-21-2006, 12:25 PM   #7
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Ditto; forged crank and rods. Cast pistons for all turbo 2.5s.
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Old 06-21-2006, 04:48 PM   #8
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Ok, so the 06 sti has forged crank and rods, what does the 05 sti have?
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Old 06-21-2006, 04:49 PM   #9
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They are all the same!
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Old 06-21-2006, 04:53 PM   #10
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I have been told, by a VERY respected engine builder, that early 2004s have much more brittle pistons (ringlands) than later revisions.
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Old 06-21-2006, 05:32 PM   #11
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^^^
I have heard that as well.
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Old 06-21-2006, 06:00 PM   #12
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oooooo yeah I just remembered reading a forum on that, yeah early 04's had some kinda ring prob and there engines would crap out even stock.
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Old 06-21-2006, 06:51 PM   #13
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Quote:
Originally Posted by ilivas
The crank and rods are forged, but the pistons are cast.
Is this true for EJ255's (LGT block) as well?
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Old 06-21-2006, 07:39 PM   #14
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Quote:
Originally Posted by wrxfactor
Is this true for EJ255's (LGT block) as well?
and the 2006 2.5l wrx?
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Old 06-21-2006, 08:16 PM   #15
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Replacement part numbers for 2004-2006 for crank, rods and pistons are the same, so they are the same for all. Stock sti rods are forged and Ive seen them do over 500 whp consistently withour breaking. the "weak" spot is the pistons. I say "weak" because they can take about 420 whp without breaking, so they are not that weak.
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Old 06-21-2006, 11:05 PM   #16
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Quote:
Originally Posted by wrxfactor
Is this true for EJ255's (LGT block) as well?
yes
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Old 06-21-2006, 11:06 PM   #17
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Quote:
Originally Posted by speedDman1
and the 2006 2.5l wrx?
and yes
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Old 06-22-2006, 12:16 AM   #18
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Quote:
Originally Posted by ilivas
yes
w00t! So when I want to go huge in the future are pistons the only internals that are necessary?
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Old 06-22-2006, 12:24 AM   #19
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depends on how big you wanna go...

Yes, an ej255/7 with pistons can hold a boat load of power, but companies offer aftermarket cranks, rods, and sleeves, if you wanna go further than that.

ported heads, and cams can go a long way in making power also.
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Old 06-22-2006, 01:42 AM   #20
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Quote:
Originally Posted by ilivas
depends on how big you wanna go...

Yes, an ej255/7 with pistons can hold a boat load of power, but companies offer aftermarket cranks, rods, and sleeves, if you wanna go further than that.

ported heads, and cams can go a long way in making power also.
I thought heads were only limiting at the 500+whp area? I don't need to make much more than 400whp, but I'm not doing it on stock pistons. I'll need a 6spd before I do any of that though I'm a ways from that, but one day, one day.
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Old 06-22-2006, 02:35 AM   #21
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Stock sti heads are good for ~500whp or so, after that i hear they become a restriction. Wow, so ALL sti's have forged crank and rods? I didn't know this at all. Why couldn't they just make the damn pistons forged too?!?!?! That would have been AWESOME!
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Old 06-22-2006, 04:29 AM   #22
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Quote:
Originally Posted by STimo
Stock sti heads are good for ~500whp or so, after that i hear they become a restriction. Wow, so ALL sti's have forged crank and rods? I didn't know this at all. Why couldn't they just make the damn pistons forged too?!?!?! That would have been AWESOME!
They're very restrictive, you can make 500whp on stock heads, but with just a swap of cams and ported heads. I wouldnt be suprised if you picked up 100whp.
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Old 06-22-2006, 09:55 AM   #23
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FYI, I don't think there's an engine manufacturer out there that would put a cast connecting rod in an engine with today's warranties. They are all either forged or powdered iron (neither forged nor cast but with the strength of a forging at the cost of a casting). They have been since the 50's.

Crankshafts on the other hand are more expensive items to make, they aren't as stressed as connecting rods (especially short stroke cranks), and the strength differences between cast and forged for the stresses the average street engine sees doesn't justify the cost of a forging...unless the manufacturer's engine configuration needs it, i.e., turbocharged. Multiple factors, of course, go in to why a manufacturer chooses a cast vs. forged crank and if the accountants can't justify the cost, then you know which they'll choose. High performance engines are expected to see more stress so quite often a forged crank is chosen but this isn't always the case.

Subaru owners are blessed since the cranks are forged.
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Old 06-22-2006, 05:59 PM   #24
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^^This is GREAT news, i can't believe i didn't know this. So all you really need is pistons to run 500whp safely correct? Wow, anybody know how much pistons cost to install?
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Old 06-22-2006, 08:00 PM   #25
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depends on what you call safely
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