I just want to clear this up, a friend told me his new sti6 has not got these as standard but i thought all sti,s were forged. also while we're on the subject could someone explain what the changes were through the years with the sti's (engine wise). or is there a specification site i could go on to.

Cheers James

 

Yes they do.

 

Thanks i thought so.

 

U sure??

Pretty sure V7 was the first with forged pistons from the factory

 

well all the v2 and v3 STI's that i have stripped have forged pistons so v7 cant be the first

 

As above - they are fitted with HF forged pistons from the factory.

Mick

 

I think this is one for APIDavid to put us right on TBH.

I thought that forged pistons for STi Classics were offered as a cost OPTION when the car was ordered new from the factory? I'm sure I read that from a reputable source . So, if that was the case, then most STi's will probably have them... but not necessarily ALL

I'm sure if you ask David, then he'll proffer that Subaru's 'forged' pistons aren't really worthy of the name i.e. not all that good, in any case.

David?! Where are you when we need you?

 

it's the other way round iirc, the 7 onwards has hypereutectic?

 

V7 was the last one with forged pistons. Blob onwards for hypereutectic.

 

blob is v7

 

Bug

 

:gets coat:

 

Yup V7 Bugeye STi - last with forged pistons and very good strong block as standard
V8 Blobeye STi - hypereutectic pistons

 

It's Friday night, I have a 6hr stupidity licence.

 

That made me laugh. Hey at least you're honest. There are those on here who would have backtracked or fought their case all the way.

 

I have no problem admitting my retardedness, it's just something i have to live with unfortunately.

vaguely back on topic, there is probably the usual mix an' match of parts present, so I wouldn't guess at a clear cutoff. Someone who strips a lot like David at API could probably tell us better.

Interested in an above posters comments about the quality of OE forged pistons though - anymore gen?

 

Right you lot - pin your ears back

STi limited editions from 1994 quite often have Subaru brand forged pistons fitted. This may be where the " option " tag has come from, but it may also be that they originally had forged, but have had a rebuild at sometime/ somewhere and the wrong pistons were fitted then. It is a bit too far back in time to be definite about that.

Sti vers 2 RA has the Subaru produced forged pistons fitted as standard MOST Vers 2 RA have have Closed deck block [ let's not go there for the minute ]

Then all STI and STi RA up to Vers 7 [ Bug eye ] have Subaru Forged pistons as standard.

Blob eye & Hawkeye [ & EJ257 ] have hyperEutectic [ usually spelt bullsh*t ] pistons fitted - which are an extremely good product for a manufacturer to use - but totally crap for any sort of performance engine.

The Subaru forged type look similar to a cast piston in shape and design and do not at all look like the billet types that you get from: Cosworth, Omega, Mahle CP, Ross, Wiseco, Wossner, Jun [ cosworth] et al.

Cleared that up then ?

David APi

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Just one more point. Sti 3/4/5/6/7 Forged Subaru brand pistons are OK up to circa 400 hp depending upon their mileage.

I would have no hesitation in leaving them in [ assuming good condition generally ] for a 400 hp conversion.

David

 

others on here have stated that the ver8 engine had forged aswell.

 

Good thread! You learn something new everyday

 

so my sti ra v2 engine is a cdb and has factory forged pistons then lol

 

i have a v2 sti. From what your saying this has forged pistons? Im going for 380bhp using bolt on bits. Will the internals handle this on an sti v2? I thought the gearbox was the weekpoint. Soz to hijack thread.

 

Thanks David

 

Should do, but or at least would do on a new one. Impossible to say how much abuse a 100k engine will take obviously.

I'd guess at your gearbox popping before your engine.

 

I told you that David would come up with the goods, didn't I?!

 

Lol, i thoght i had opened up a new can of worms then.

Thanks for the info.

James

 

Version 8 are hyper-eutectic. repeat after me........

 

Vers 2 RA forged pistons are big ugly old mothers. I don't think I'd like to run them at that power level.

The vers 3 STi on are more modern design pistons and do a good job.

I'd be wary of upping the power too far on something of outdated design and old fashioned manufacture.

Update I reckon.

David APi

 

What on earth does this mean? (Sounds like poor Mr Piston has some kind of anxiety disorder )

 

It's one of those words that companies use to make something sound good like they do with womens cosmetics. You know, ' It has hyaluronic betones' OR ' co-ordinated enzymes' That sort of crap - that makes you feel good, but is no better than anything else.

The pistons run NO clearance. If you measure the new bore and the new piston with the sort of equipment that we have in the aftermarket they are exactly the same size.

Dropping names; I had a conversation with Matt Clark when they first came out; relating to ' what do reckon to this ' and we had no firm idea except - that it worked, but shouldn't .

But also that they looked just like the cast pistons from a WRX and therefore couldn't really be trusted as a high performance piston.

It seems that the alloy for the piston has been created to expand at exactly the same rate as the block - so that there is no need for a clearance at first build and therefore should last longer because the surfaces will start off from a lower point, than an engine with a 1 thou clearance.

IN OUR OPINION - Don't ask any more about the damn things I don't really know, I just work here........

David