Welcome to the North American Subaru Impreza Owners Club Thursday December 25, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo)

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Closed Thread
 
Thread Tools Display Modes
Old 11-19-2003, 10:31 PM   #1
APS
Scooby Newbie
 
Member#: 6894
Join Date: May 2001
Location: Melbourne, VIC, Australia
Default US Specification 2.5L STI Pistons

As there has been a good deal of discussion on the 2.5L turbo forum of NASIOC regarding pistons, we have taken the liberty of photographing both the 2.5L US Specification STI cast pistons and the International/JDM Specification STI forged pistons.

Also photographed are the differences between the two different piston pins.

The pictures can be found on http://www.aps-wrx.com/us_spec/subar...ns/pistons.htm

Regards
APS Web Team
* Registered users of the site do not see these ads.
APS is offline  
Old 11-20-2003, 12:09 AM   #2
Mudguts
Scooby Newbie
 
Member#: 46409
Join Date: Oct 2003
Location: Toronto, Canada
Vehicle:
04 STI
Blue/Gold

Default Great information, but misleading...

Here we go...

US spec STI pistons are made of stonger material than forged according to Subaru. Is this PR stuff or fact?

"This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. "

http://www.rallispec.com/product-eng_1.htm

-Posted by StrangerQ from previous discussion on US spec STI pistons. See http://forums.nasioc.com/forums/show...ghlight=piston

Your input is appreciated.
MG
Mudguts is offline  
Old 11-20-2003, 01:22 AM   #3
APS
Scooby Newbie
 
Member#: 6894
Join Date: May 2001
Location: Melbourne, VIC, Australia
Default

MG

I'm not sure who you are quoting. - I looked at both your refered threads and could see no STi Japan original source documents. All I could see were some comments from a North American component reseller.

If anyone believes any cast piston is as strong (or expensive!) as a forged equivalent, then one simply does not understand basic metalurgy.

From an application perspective, the choice is more complex than that. However, the basic strength issue is not debatable. Fact is, the U.S. spec Sti uses the high volume, production line Forester short engine. Not the handbuilt short used internationally. - Why? - Simple! - Cost!

An international spec STi costs over $40,000 U.S. A U.S. car $33,000. The short engine assembly represents a large part of that difference.

Dave

APS
APS is offline  
Old 11-20-2003, 01:23 AM   #4
totoherbs
Scooby Guru
 
Member#: 7321
Join Date: Jun 2001
Chapter/Region: NESIC
Location: waltham, ma
Vehicle:
.... 122 IggPoints
Work... ahhh... so tired.

Default

Forged> cast

The hypereutectic is stronger but will not hold up to det half as well as forged. The new ver8 jdm sti pistons have the hypereutectic pistons, so the ones aps is showing are from older motors?

Thanks for the pics aps guys.
totoherbs is offline  
Old 11-20-2003, 01:59 AM   #5
strangerq
Scooby Specialist
 
Member#: 13095
Join Date: Dec 2001
Default

Quote:
Originally posted by APS
MG

I'm not sure who you are quoting.

APS

Here: http://www.rallispec.com/product-eng_1.htm


Specifically regarding the EJ207 shortblock having cast, not forged pistons:

MY03 EJ207 STi Piston Set -- $1022
This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. The high silicon content of the aluminum also has the benefit of providing exceptional scuff resistance and reduced thermal expansion which allows for the use of tighter clearances. Compression 8.0:1.


I also respectfully question the comments regarding the reasons for the price of the US vs. International (UK?). STI. The UK STI makes 265 hp and doesn't even have DCCD standard. Why would it be more expensive to make? It's notoriously difficult to compare msrp's in different countries.
strangerq is offline  
Old 11-20-2003, 02:14 AM   #6
totoherbs
Scooby Guru
 
Member#: 7321
Join Date: Jun 2001
Chapter/Region: NESIC
Location: waltham, ma
Vehicle:
.... 122 IggPoints
Work... ahhh... so tired.

Default

Quote:
Originally posted by strangerq
Here: http://www.rallispec.com/product-eng_1.htm


Specifically regarding the EJ207 shortblock having cast, not forged pistons:

MY03 EJ207 STi Piston Set -- $1022
This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. The high silicon content of the aluminum also has the benefit of providing exceptional scuff resistance and reduced thermal expansion which allows for the use of tighter clearances. Compression 8.0:1.


I also respectfully question the comments regarding the reasons for the price of the US vs. International (UK?). STI. The UK STI makes 265 hp and doesn't even have DCCD standard. Why would it be more expensive to make? It's notoriously difficult to compare msrp's in different countries.
Its cost, thats all there is to it. It is cheeper to cast a piston then to make one threw the forging processes. The uk and international are useing the older ver7 style set ups still. For some reason subaru stuck it too the euro guys this time. And again the jdm ver8 sti uses the hypereutectic pistions.


As trusted as rallispec is here they are still....
Quote:
a North American component reseller.
Not an offical source.

Forged is stronger, and louder; cold forged piston slap may have had a little to do with the swich, but cost would be the more likely reason.
totoherbs is offline  
Old 11-20-2003, 02:16 AM   #7
APS
Scooby Newbie
 
Member#: 6894
Join Date: May 2001
Location: Melbourne, VIC, Australia
Default

totoherbs,

I am not sure what you mean by "hypereutectic is stronger". If you meant stronger than a regular casting, then you are correct. They are not stronger than forged pistons.

The pistons shown in our photos are current production, international spec / JDM spec version 7 (01/02) or 8 (03) pieces (same are used).

Dave

APS
APS is offline  
Old 11-20-2003, 02:35 AM   #8
APS
Scooby Newbie
 
Member#: 6894
Join Date: May 2001
Location: Melbourne, VIC, Australia
Default

Quote:
Here: http://www.rallispec.com/product-eng_1.htm

Specifically regarding the EJ207 shortblock having cast, not forged pistons:

MY03 EJ207 STi Piston Set -- $1022
This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. The high silicon content of the aluminum also has the benefit of providing exceptional scuff resistance and reduced thermal expansion which allows for the use of tighter clearances. Compression 8.0:1.


I also respectfully question the comments regarding the reasons for the price of the US vs. International (UK?). STI. The UK STI makes 265 hp and doesn't even have DCCD standard. Why would it be more expensive to make? It's notoriously difficult to compare msrp's in different countries.
Strangerq

You are just quoting the same source (North American component reseller). - My previous comments stand.

We engineer and supply components all over the planet. I was not quoting U.K. pricing specifically; after all, we are in Australia.
With regard to the short engine cost, the international spec STIís use a low volume, hand built, genuine STI short. (Rods, pistons, bearings, crank, block, all are unique). The US spec. car uses a high volume, assembly line, short engine from the Forester.

The difference in cost in parts and more particularly labour, resulting from these two approaches should be obvious.

All the best,

Dave
APS
APS is offline  
Old 11-20-2003, 02:41 AM   #9
bryan carbon
Scooby Newbie
 
Member#: 34060
Join Date: Mar 2003
Default

Check out the quench on the US STi pistons, neat design!
bryan carbon is offline  
Old 11-20-2003, 02:46 AM   #10
strangerq
Scooby Specialist
 
Member#: 13095
Join Date: Dec 2001
Default

Quote:
Originally posted by totoherbs
[b] Its cost, thats all there is to it.
Then why do the STI forged pistons for the version 7 cost the same as the version 8 cast ones: $1022????
strangerq is offline  
Old 11-20-2003, 02:54 AM   #11
strangerq
Scooby Specialist
 
Member#: 13095
Join Date: Dec 2001
Default

Quote:
Originally posted by APS
Strangerq

With regard to the short engine cost, the international spec STIís use a low volume, hand built, genuine STI short. Dave
APS

I see. So you are not referring to any of the production STI's - including UK, JDM and US version 8's?

You seemed to be making a distinction between the US engine being hypercast whereas others were not. But the actual distinction you are making is between the "handmade international spec", which is different from all of the production version 8's ?
strangerq is offline  
Old 11-20-2003, 03:13 AM   #12
totoherbs
Scooby Guru
 
Member#: 7321
Join Date: Jun 2001
Chapter/Region: NESIC
Location: waltham, ma
Vehicle:
.... 122 IggPoints
Work... ahhh... so tired.

Default

Quote:
Originally posted by strangerq
Then why do the STI forged pistons for the version 7 cost the same as the version 8 cast ones: $1022????

Thats rallispecs bissness..... forgeing costs more... google it.

I thought the ver8 were all hypereutectic.... Ill have to look it up.

As for the ej257 being assembly line build, that would make sense. As subaru is moving towards a 1 world motor, and not different sized blocks; which is why the xt, sti, legacy, and bajas will all have the same block, to help bring down costs.
totoherbs is offline  
Old 11-20-2003, 03:15 AM   #13
APS
Scooby Newbie
 
Member#: 6894
Join Date: May 2001
Location: Melbourne, VIC, Australia
Default

Strangerq,

Totoherbs just put things a little confusingly that's all.

ALL production international spec STi's, version 7 and version 8, use the piston we show (also the short engine I described; hence the vehicle cost). International spec is everywhere in the world, other than Japan and North America. We know the JDM version 7 uses the same piston and we believe the version 8 does also.

As for the spare parts price of the cast U.S. spec STi piston, anyone who pays $1022.00 for a set is making a large mistake! The piston in our photo was purchased from Renick Subaru in L.A. a couple of months ago for $80 USD.

All the best.

Dave

APS
APS is offline  
Old 11-20-2003, 03:43 AM   #14
strangerq
Scooby Specialist
 
Member#: 13095
Join Date: Dec 2001
Default

Quote:
Originally posted by APS
Strangerq,

International spec is everywhere in the world, other than Japan and North America. We know the JDM version 7 uses the same piston and we believe the version 8 does also.
All the best.
Dave
APS
The problem with that is that there is no EJ207 MY03 STi cast Piston Set in use in the EJ25 here in the US.

So the EJ20 MY03 STI cast pistons must be in use in either the JDM or International STI.

You would seem to be implying that STI is using MY02 forged 2.0 Pistons everywhere, and the MY03 cast STI pistons are actually not being used....anywhere?

strangerq is offline  
Old 11-20-2003, 03:48 AM   #15
strangerq
Scooby Specialist
 
Member#: 13095
Join Date: Dec 2001
Default

Quote:
Originally posted by totoherbs
Thats rallispecs bissness..... forgeing costs more... google it.


I know what google is, but what's forgeing?

I agree that all other things being equal, (alloy composition, etc..) forging is usually more expensive.
strangerq is offline  
Old 11-20-2003, 03:51 AM   #16
EJ2O
Scooby Newbie
 
Member#: 48596
Join Date: Nov 2003
Location: 626 310 818
Vehicle:
2004 IMPREZA WRX
BLACK

Default

simple. forged is ALWAYS better than cast.
EJ2O is offline  
Old 11-20-2003, 03:52 AM   #17
totoherbs
Scooby Guru
 
Member#: 7321
Join Date: Jun 2001
Chapter/Region: NESIC
Location: waltham, ma
Vehicle:
.... 122 IggPoints
Work... ahhh... so tired.

Default

Quote:
Originally posted by strangerq
The problem with that is that there is no EJ207 MY03 STi cast Piston Set in use in the EJ25 here in the US.

So the EJ20 MY03 STI cast pistons must be in use in either the JDM or International STI.

You would seem to be implying that STI is using MY02 forged 2.0 Pistons everywhere, and the MY03 cast STI pistons are actually not being used....anywhere?


Um...

ej257 usdm sti motor= cheeper cast pistons...

ej207 jdm sti motor ver6,ver7= stronger forged pistons....

ver8 pistons are still up in the air, I will take rallispecs word about them being cast before I take Daves. I guess ill have to find out about the ver8s.
totoherbs is offline  
Old 11-20-2003, 03:59 AM   #18
strangerq
Scooby Specialist
 
Member#: 13095
Join Date: Dec 2001
Default

Quote:
Originally posted by totoherbs
Um...

ver8 pistons are still up in the air.
This is the central issue isn't it? After all if ver8 pistons are hypercast just as USDM STI are, then essentially all the current STI's are. Actually I have yet to see any reference to an MY03 or later forged piston for the STI. I think this issue, via subject of thread has been phrased in a somewhat misleading way, frankly.

One would clearly get the impression that only the US STI has cast pistons.....and that is not the case.
strangerq is offline  
Old 11-20-2003, 05:12 AM   #19
RichQY
Scooby Specialist
 
Member#: 31948
Join Date: Jan 2003
Location: SoCal
Vehicle:
2004 STi
Aspen White

Default

aren't the pistons from APS 's site Ver 8s?
RichQY is offline  
Old 11-20-2003, 05:13 AM   #20
Turbo Dave
Scooby Newbie
 
Member#: 45743
Join Date: Oct 2003
Default

This should not have to be as confusing as it would appear to be, at least I do not think so!!

1) Production International Spec. 2.0 Litre Sti Version 7: Forged Piston, as per photo, in handbuilt short.

2) Production JDM Spec. 2.0 Litre STi Version 7: Forged Piston, as per photo, in handbuilt short.

3) Production International Spec. 2.0 Litre STi Version 8: Forged Piston, as per photo, in handbuilt short.

4) Production JDM Spec. 2.0 litre STi Version 8, TypeC and Type RA: the latter two at least are using the forged piston as in photo, if not the base street car as well. There are Japanese market reasons why they MAY have gone to cast pistons in the street car, which have NOTHING to do with strength and everything to do with new emissions regs which came into force in that market at the beginning of 2003.

5) Production USA Spec. 2.5L STi : cheap( $80 each), cast piston, as per photo, in mass production short.

The piston pin alone, as an example, indicates the difference in the durability of not just the piston, but the entire short. The 2.0L STi short features a tapered bore work of art. The Forester 2.5L short uses a conventional parallel bore mass production piston pin. We have tried to show this in our photos , however it is difficult to show accurately, sorry. The differences flow through every other part of the short, including the PISTON!

Just as an aside, for those of you with the experience to appreciate this fact, check the production clearances the STi version 7/8 forged piston runs at: 0.0004" to 0.0012 !!

On a bore in excess of 3.5"!!. Try THAT ( well actually, no, please don't!!), on your typical aftermarket forged piston!

Now , to be fair, when we are going to really lean on them, or road race them, we do increase the clearances to just under 0.002". However, still, this would be around half what you would typically have to run on a quality aftermarket piece. The current STi 2.0L forged piston, ( which is VERY different to version 6 and earlier), is truely a work of art! We cannot speak highly enough of them!

We just wish there was an equivilent for the 2.5 L engine, however, there isn't.

Now, I hope I have explained this clearly enough!

Dave APS
Turbo Dave is offline  
Old 11-20-2003, 09:52 AM   #21
strangerq
Scooby Specialist
 
Member#: 13095
Join Date: Dec 2001
Default

Dave, thanks. Perhaps you can contact Subaru and get accurate and specific info as the answers given beg more questions? (I will try as well)

This is from the site of a UK dealer:

In summary the STi models all have


280PS@6400rpm, 275lbft@4000rpm
Reinforced engine mounts
Cast pistons Molybdenum coated
Hollow inlet valves, Sodium filled exhaust valves
Shimless valve lifters ....... http://www.iwoc.co.uk/jpnewagesti.html

If STI has MY03 2.0 forged pistons, why does rallyspec only offer cast ones?
strangerq is offline  
Old 11-20-2003, 10:37 AM   #22
totoherbs
Scooby Guru
 
Member#: 7321
Join Date: Jun 2001
Chapter/Region: NESIC
Location: waltham, ma
Vehicle:
.... 122 IggPoints
Work... ahhh... so tired.

Default

Quote:
Originally posted by strangerq
Dave, thanks. Perhaps you can contact Subaru and get accurate and specific info as the answers given beg more questions? (I will try as well)

This is from the site of a UK dealer:

In summary the STi models all have


280PS@6400rpm, 275lbft@4000rpm
Reinforced engine mounts
Cast pistons Molybdenum coated
Hollow inlet valves, Sodium filled exhaust valves
Shimless valve lifters ....... http://www.iwoc.co.uk/jpnewagesti.html

If STI has MY03 2.0 forged pistons, why does rallyspec only offer cast ones?
Which would also make sense to what it says about the ej207 on www.spdusa.com

Ill look for the exact quote but its something like. The ej207 is the jdm sti motor with forged parts, aus used to get jdm motors uptill the ver8, and the world motor is a ej205 and has cast pistons...

The hypereutectic pistons are new to ver8s and would not be in the older euro motors....
totoherbs is offline  
Old 11-20-2003, 10:45 AM   #23
jdmhebek9
Scooby Newbie
 
Member#: 27877
Join Date: Oct 2002
Location: NY
Vehicle:
2004 STI
Java Black Pearl

Default OK

How about APS just tuning the hell out of the sti and see how much boost the stock pistons can take

I mean you guys have been around forever and I am sure you can afford to blow an engine.

I guess it doesn't really matter if they are cast or forged but how much abuse they can actually take. Of course Forged are better and in building an engine for boost that's what you would always choose but in our case people that own STI's or that are thinking about getting them we just want to know what the Max boost or power the stock engine can hold


Hope this sort of ends the whole forged non forged etc etc
trial and error
jdmhebek9 is offline  
Old 11-20-2003, 10:49 AM   #24
totoherbs
Scooby Guru
 
Member#: 7321
Join Date: Jun 2001
Chapter/Region: NESIC
Location: waltham, ma
Vehicle:
.... 122 IggPoints
Work... ahhh... so tired.

Default

Quote:
Originally posted by mr2guru
Only time will tell.

Are the pistons forged or cast? I know the ver8 2.0 sti has some cast AL pistons that uses a new casting technolgy that is "supposed" to be stronger. It is probably just cheaper. Anyway I know the syclone and typhoon guys have a lot of trouble with hypereutectic pistons not taking kindy to det. That is why many employ water injection. Pretty much eliminates det.

http://forums.nasioc.com/forums/show...reutectic+ver8

-Jim
Another who thought the jdm ver8s were cast...

Quote:
Hope this sort of ends the whole forged non forged etc etc
Its not so much how much the pistons can take, the usdm sti pistions are not half as good as thoes forged ver7 pistons, its more does the jdm ver8 have cast or forged pistons.
totoherbs is offline  
Old 11-20-2003, 01:17 PM   #25
dwx
Scooby Guru
 
Member#: 8343
Join Date: Jul 2001
Chapter/Region: MWSOC
Location: Atlanta, GA
Vehicle:
2005 2012 Jeep
2013 DGM BRZ

Default

Honestly I don't think cost has anything to do with it. You can't compare the cost of a car in the US to one from overseas. Cars cost more or less in different economic environments due to a number of reasons. In Japan the STI costs less than the US STI. You could buy one and have it shipped over to the US for under $35k. If the cost of the Aus STI is $40k USD, that's too bad, your car prices aren't very good.

If you look on Subaru of Japan's page for the 2003 V8 Twin-Scroll STI, it does not use forged pistons. Here is a babelfish-translated segment from the engine technical description:

The engine of STi has made most the private design in order to guarantee the potential with hard travelling. For example, as for the piston the casting aluminum alloy make which quite guarantees high strength. Also the crankshaft administering Tufftride processing,

They also have a picture of the piston and rod on the page with the caption "High-Intensity Cast Piston" This applies to both the RA Spec-C and regular STI street model.



So someone should go tell SOJ their website is incorrect...

As an aside, you can get those forged pistons for much cheaper than $1022, they are about $500 for a set...

There are no international/JDM spec motors this year. There are JDM spec engines, and everywhere else in the world has the same engine from last year. They are completely different.

Last edited by dwx; 11-20-2003 at 01:27 PM.
dwx is offline  
Closed Thread

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
FS: 2.5L STi Block with CP Forged Pistons Suby_06_STI RMIC Private Classifieds 9 03-23-2009 01:32 PM
Version 8 turbo kit, 2.5L CP pistons, sti block, wrx heads jermany755 Engine/Power/Exhaust 8 09-26-2008 01:54 PM
a realistic compression for 07 sti 2.5L FORGED PISTONS jhook Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo) 1 08-04-2008 09:58 AM
FS: Rays Engineering Volks TE37 White , ej207 shortblock, 2.5L sti pistons, kvr rotor GC8_SpecC VIC Private Classifieds 3 09-11-2007 02:42 AM
FS: 4 2.5l Sti pistons Turbo4me North West Impreza Club Forum -- NWIC 8 09-16-2004 07:28 PM


All times are GMT -4. The time now is 03:34 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.