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Bah.. this is such a non-issue. People on vwvortex have such a flair for the dramatic. Everyone remember before the WRX came out how everyone said the engine would never make any real power because of the open deck? And here we are a few years later with 400hp WRXs on every street corner (which by the way also uses cast pistons). Even the EJ20 STi uses cast pistons.

I wouldn't lose any sleep over this.
 

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Lisa Simpson
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15,043 Posts
Forged versus cast won't come into play at the outputs we are living with. IMO, a forged steel piston isn't worth the weight anyway. A forged aluminium one would be worth the cost, but again, not at 1.8t outputs.

Modern casting methods are designed to produce the strongest part with the least waste. They work great.
 

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1st Gear
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17,568 Posts
Discussion Starter #8
I think for those that want Stage 3 this might be the issue.

Also Mac. Theres few people that blow their engines just by appling more boost. Lowest one I seen was 17psi which is about what a chipped 1.8t puts out. As far as STi......we will see. I know its not a big deal but for those that go crazy with mods might have to reconsider or take the risk.

I figured it would be a good idea to inform you all. That might be another difference in HP difference of previouse models.

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There are at least 2 AWP transverse engines in Texas(AWP engine code has cast pistons) making 405+whp and have been making that power for the past year. With todays casting technology, there is not a giant gap between cast and forged like there used to be. If someone is concerned about blowing an engine from power, then they need to worry about rods, not pistons. Rods on these engines whether they be 170hp or 150hp will become questionable around mid 400whp. I bet most of you guys would be surprised to know that SupraTT pistons are cast :shock: . Shocking a cast piston has held 950rwhp 8). Like I said, forged may be stronger in the end, but a beefy cast can be almost as strong with much less weight and no piston slap :wink:
 

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Forging strengths come into play when engines don't work as perfectly as they're supposed to: specifically, when a modded motor (especially under increased boost) detonates, the forging tends to be less brittle and tends to "give" without yield or beakage more than castings. If everything works perfectly all the time, a cast piston is fine. If you are a conservative tuner, ditto. It's when people push the flow-rate limits of their injectors or lean out the motor too much in search of the last 5 inconsequential hp on the dyno that the trouble comes into play. I think most castings these days of the "hypereutectic" category, which is essentially a high silicone content in the aluminum, and this indeed does close some of the gap between them and forged aluminum.
As has been said, with a typical chip mod, I wouldn't sweat the differences in pistons. But if I were swapping turbos, and especially if I were pushing power levels in the high 200s and up, I'd want to be very conservative on the tuning if I weren't replacing the pistons.

Alex, I haven't heard of forged steel[i/] pistons - does anyone use such things? I can't imagine them working worth squat with the extra mass they would entail! All the very advance race motors these days (think F1 and such) are using very-short-skirt designs to reduce weight and drag, and very high pin placement to reduce rocking forces. But to my knowledge, they are all still forgins of aluminum alloys (although said alloys may be pretty exotic). Come to think of it, I'll have to ask a knowledgeable friend if anyone is using Titanium or other unobtanium for pistons.
 
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