Im an evolution II rs driver, but i get my car serviced at a subaru dealers (was also planning on buying a v3 sti ra but didnt have enough money)
The boss there told me all stis come with forged pistons as standard (over the wrx)

Ive heard stis can be safely tuned to about 350, but already having forged pistons would you be needing forged conrods and crank etc, without getting new pistons, or are there stronger pistons on the market?


cheers, mike

 

The sti 7 was the last sti engine with proper sti forged pistons. Thereafter they changed to a hypercuretic (sp) variant that were cheaper and subsequently not as strong as the previous forged items.

Having said that. There are some high powered cars running around with stock internals without failure

 

420 on mine so far

 

UK sti 8 has forged pistons.

 

is that confirmed???

 

yes

 

good news for me then.

 

400 is the safe limit on a sti newage ~'#'~
anymore and you would be wise to add proper forged pistons and rods ,


is this correct

 

define "proper" forged pistons & rods

 

ones that dont fail , its not a trick question

more boost = more strain etc ......

 

so this means????

more power doesnt always need more boost

 

im not arguing i get my info from the pro mappers n tuners they all say 400 is max on standard internals .

check the info for yourself -
AndyForrestPerformance

 

so how come there are quite a few at over 400bhp now and reliable?

 

hey i dont think you understand

the people in the know say if you go over 400bhp then you need after market forged pistons and rods , check the link .

if your running over 400 on standard internals good for you i hope you dont have any concerns but its more of a risk .

 

bear in mind when tuners say x amount of bhp its rough guide, some cars will take a bit more, some will take less before they go bang

 

but if they are forged as Zen say, surely 400 is easily available. or are they not forged.

running 420 on mine at the moment.

 

I think that Paul and myself would like to include ourselves in that category , we have 3 Sti8's all running 410 - 430bhp on the stock internals....

 

OE forged pistons are good, but OE clearances are on the tight side. I've mapped a couple of cars running around 440hp on standard internals, but it's been very much at the owners request, and there risk.

 

so would it be wise to ignore the advice ? of an expert @ your perril

i dont think so , you do what you want ill go for the safer option .

 

if it goes bang it goes bang

 

:: GRD - Greenwood Racing Developments ::

:: GRD - Greenwood Racing Developments ::

 

lets put this to bed asap .
WOULD YOU RECOMMEND TO A CUSTOMER TO GO OVER 400BHP ON STANDARD INTERNALS ? , thats the question here .

 

been following this thread with intrest so far, im running circa 400 on my STi RA just now, but my blocks due to come out shortly due to a weeping headgasket, i s it worth uprating my OE pistons for aftermarket ones as long as my blocks been pulled? so whats the difference between OE Sti forged pistons and aftermarket forged pistons

 

iv just rang this place up and he told me he is running an earth shattering 457bhp on standard internals and he also said he cains the a£$£ off the car
now thats good infomation v8sti thats the ticket .
he also said the gearbox will take 500bhp 6 speed , wow !

still not sure id like to risk it after all we are talking new engine if it goes bang .

i guess you pay your money and take your chances .

 

looking at a few mappers results, 400bhp seems a bit pessimistic.

 

Put it this way. I wouldn't go any further without upgrading the internals.

I don't have K's sitting in the bank just in case.

 

I would be happy to run at around 420-430hp, which is what you can expect from a well setup MD321h turbo with all the trimmings.

 

or one of the similar spec GT30 hybrids.

I assume we are talking pump fuel here.

 

I wouldnt class the STi's pistons as "real" forged items tbh, and as for the hypereuetic pistons being weaker, that too is a myth (2ltr engine models are actually stronger than the "forged" pistons they replaced, the 2.5 was a bodge of an engine and those pistons are not as strong).
Ive also never known a 2ltr JDM hypereuetic piston go pop, but ive known the standard sti "forged" items go running similar power.
The new 2ltr engines are also stronger (in the new model hatchback) than the engine they replace, also not forged pistons

Tony

 

can you please explain what you mean by a forged piston that isn't real?

The STI forged pistons are every bit as forged as any other forged piston, granted they are not forged in the firey depths of mount doom, but they are forged.

Paul