I can buy some nice drop forged tools, doesnt make them as strong as other forged items, hence the word "forged" being quoted, ie forged does not mean its as strong as another forged item (because there are different methods of forging).

Tony

 

Do those 'trimmings' involve methanol Paul?

 

forged an heres me thinking there not the real thing like forged pound notes doh lol only kidding

 

bill sit in the corner and pay attention the adults are talking ,

 

Can you please clarify exactly how you believe the STI forged pistons are inferior to any other forged piston?

 

mr zen are you saying the sti pistons are as strong and as robust as any after market forged jobbie #

i have no clue to the ins and outs but im interested in the whole topic of forged pistons etc

 

Pretty much yes. The standard forged pistons are very good indeed. But when rebuilding a 60,000 mile engine (which we do a lot of) there is little point putting standard sized pistons in, when the bore is 4 thou oval. So you're faced with oversized pistons, and STI units are in the region of £800 for a set without rings. For that sort of money you can buy any number of alternative pistons, hence STI pistons in rebuilds are few and far between.

 

Cheers for all the replies boys.

Not wanting to start a lancer vs impreza fight here, but one of the reasons i was asking about the sti (mainly v1-7) having forged pistons, is that a lancer of similar age WITHOUT forged pistons can be tuned to roughly 350-400 without too many problems, whereas the stis can also be tuned to roughly 350-400 but it already has forged pistons. Which is why Mr Burns may actually have a point. Pop some forged items into a lancer and your looking at 500..... I assume, pop some aftermarket forged items into a subaru and youre also looking at circa 500 bhp....

Btw, the stis dont have forged conrods do they????
mike

 

The forged pistons are not the weak point in the subaru STI engine, it's the rods, and they are not all that bad.

 

Ah, thats what i wanted to know i guess conrods seem to be the weak link in most high power engines. As long as an engine is running right (not rich or lean) then the pistons can take some big power, just a waiting game for the conrods to go snap
kinda strange matching up 500hp pistons with 350 horsepower rods, but hey

cheers guys

 

Forging is only a method of manufacturing, you can forge any metal but that
does not mean that the item made will be as strong as any other forged metal.
For instance, you can forge cast iron, you can forge mild steel, you can
forge alloy's, but which one is the best?
The material used denotes the strength of the item, not the fact that its
"forged", hence you get cast items that are stronger than the "forged"
pistons in STi's.

Tony

 

Well I'm just going to have to call BS on that one. While the alloy used in subaru's hyperspastic pistons may in fact be classed as stronger, we know it breaks much more easily. Toughness is not a strong suit of high silicone casting alloys. The whole point of forging is it allows you to use stronger alloys that are not inherently castable. You get finer grain structure, lower percentage of voids, and a flowing grain structure.

If you have some real facts by all means share them.

 

interesting reading

 

also can depend on if its hot forged or cold forged.


do you happene to know if theres a typical form of forging used for pistons or is it dependant on which company makes them?

 

Drop forged or press forged, too!
JohnD

 

All this "moaning" !
They are only suppoesed to "cope" with 330 bhp...

The rest is a bonus....
Here comes 400 please.... (V7)

DunxC

 

That was on my old car before we started rebuilding it for time attack(the orginal unopened engine is still sitting in the workshop in full working order), our 485hp(road map) standard internal sti 8 uk is still running fine aswell

 

amazing results thats what that is grd "cane the s h i t out of it ! good lads

 

Just finishing another big hp standard internal sti, but its on a spec c engine running a tsr70(aps rated at 700bshp) and the customer wants to preserve it untill he gets his 2.5cdb built motor.... which is probably for the best as its running hypereutectic pistons otherwise we may have been able to push our 504hp(race fuel) record a little further