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Old 11-20-2003, 01:31 PM   #26
cjm04WRX
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nevermind
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Old 11-20-2003, 01:37 PM   #27
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Quote:
Originally posted by dwx
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.
You know, the 1st time I actually heard about the cast piston in the STI, it didn't even have anything to do with the US production car. It had to do with the rally race cars. A rally reporter was questioning the future of the Impreza in rallying - it was too big compared to the Pug and Focus - Subara had switched to cast pistons, etc.. (ironic of course since Subaru went on to win the drivers championship in WRC yet again).

But that's why the whole idea that US = cast pistons whereas everybody else = forged...therefore US = ripoff....simply did not ring true. I don't particularly think it matters much personally, but i'm asking around in hopes that we'll at least get info. that we can eventually agree on.
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Old 11-20-2003, 01:58 PM   #28
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let's take a look at the homologation papers of the STi ver 8, yep the JDM STi ver 8 (GDBC4EH):

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Old 11-20-2003, 02:20 PM   #29
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and the late JDM STi ver 7 (GDBB4EH):


Last edited by EJ20K; 11-20-2003 at 02:29 PM.
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Old 11-20-2003, 02:32 PM   #30
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finally the early JDM STi type RA ver 7 homologated on 2001 (GDBA4EH), which is only a "variant option" of the GD WRX:



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Old 11-20-2003, 02:36 PM   #31
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Isn't it a "little" bit strange that the piston weight of the JDM STi type RA ver 7, and the latest JDM STi ver 7 (including spec C version) is 540g

..... and the piston weight of the JDM STi ver 8, the twin scroll turbo version is 568g

AFAIK Australia gets the new shape of STi but still with the old style turbo (IHI VF 30,34,35) not the twin scroll version, the twin scroll turbo version is only made for the Japaneese market .....

EJ20K
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Old 11-20-2003, 03:52 PM   #32
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I don't understand what is up with calling the STi short block the Forester XT short block.

Certainly the components are shared, but this engine was designed to be used in many vehicles, and it was important that it have a solid bottom end.

The USDM STi was the first production model with the engine in, so you could say the Forester has an STi 2.5 short block....

A huge amount of work went into engineering the 2.5 STi engine.

New rods, new lightweight cams, new semi-closed deck block with new cast-in main journal technology and dimensions (to increase strength and reduce noise), new material for the cast pistons, new rod bushing material, upgraded big-end bearing material, tapered piston pin boss....

I totally agree that if you want to make a lot of power you will need to upgrade components, but so what?

As far as cost goes:

Aust STi: AUD$56k (US$40k), no DCCD, cast wheels, 261BHP.
US STi: US$31k, DCCD, forged wheels, 300BHP, cast pistons.

Certainly cost was not an issue for selecting the engine components for the US STi.

Glenn
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Old 11-20-2003, 04:23 PM   #33
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Holy crap now im confused....

if the ver7 and ver8 has cast, where the hell did the forged slugs aps is showing come from?


Quote:
Originally posted by EJ20K
Isn't it a "little" bit strange that the piston weight of the JDM STi type RA ver 7, and the latest JDM STi ver 7 (including spec C version) is 540g

..... and the piston weight of the JDM STi ver 8, the twin scroll turbo version is 568g

AFAIK Australia gets the new shape of STi but still with the old style turbo (IHI VF 30,34,35) not the twin scroll version, the twin scroll turbo version is only made for the Japaneese market .....

EJ20K

In years past oz would get the jdm motors and not the same motors as the rest of the world, right?

And the euro ver7 motor is not the same as the jdm ver7 motor. It has smaller ports on the heads.


Quote:
Originally posted by AZScoobie
I dont know much about V8 heads Julio. Ron from Axis would be a better source of info on them. The head in the picture looks exactly like mine though. Thats the thin center devide port I have.

I think we need to start calling these different heads by a different name other then VX heads. Its confusing everyone and even myself.

As far as I know we could break this down into two groups.. Small port and large port DOHC heads. There are variations within those two groups such as valve size, Cams, Shimless and port and some having AVCS. Here is what I know:

Small port:
Version 5 WRX and STI
Version 6 WRX and STI
Version 7 WRX and STI-austalian and UK model
Version 7 WRX- US model
Version 8 WRX and STI -Austrialian and UK model.

Large port:
Version 6 STI RA (according the post above)
Version 7 WRX and STI-Japanese model
Version 7 Forrester- Japanese model
Version 7 Type RA-Japense model
Version 8 WRX and STI-Japanese model
Version 8 STI-US model

Anyone feel free to jump in and add/subtract from this.

Clark
http://forums.nasioc.com/forums/show...76#post5046576

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Old 11-20-2003, 04:57 PM   #34
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Totoherbs,

I am not saying that they are cast or forged, as you can see an all the homologation papers above it says: "piston material: aluminium alloy"

And yep it seems like the various versions of JDM STi ver 7's did have forged pistons (which normally weights less than a cast unit), but one thing for sure is that the pistons found on the JDM twin scroll STi ver 8 (not the low spec EURO, OZ and even South American version ,all of them have 265bhp) is different than the earlier pistons. Once again I am talking about the JDM engine, probably the euro and OZ STi ver 8 still have the older shorblock with the forged piston.

So the same piston maybe found on both the STi ver 7 and 8 that was exported to the Australian and European market.
But definetly Subaru of Japan has changed the piston they used on their STi ver 7 to a heavier unit on their STi ver 8.

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Old 11-20-2003, 05:00 PM   #35
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Question for APS...are the standard USDM 2.0l wrx pistons made the same way as the USDM Sti pistons?

Last edited by modvp; 11-20-2003 at 05:37 PM.
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Old 11-20-2003, 05:06 PM   #36
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..... just noticed that the guys from Rallispec were not wrong at all, if you look at the pic in their website of the MY03 STi piston:

it looks identical to the pic in the homologation paper

and this is also the case of the MY02 STi piston:


and it also says that the MY02 piston is forged while the MY03 piston is cast aluminum
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Old 11-20-2003, 05:10 PM   #37
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Quote:
Originally posted by Turbo Dave
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.

Now, I hope I have explained this clearly enough!

Dave APS
wrong ..... they are using a cast aluminum piston on the new JDM STi ver 8 engine, at least on the one they are using for rallying which could be the type RA or the spec C.
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Old 11-20-2003, 05:14 PM   #38
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Quote:
Originally posted by modvp
Question for APS...are the 2.0l wrx pistons made the same way as the USDM Sti pistons?
If by that you mean are they forged, no they are not.
Quote:
Originally posted by EJ20K
..... just noticed that the guys from Rallispec were not wrong at all, if you look at the pic in their website of the MY03 STi piston:

it looks identical to the pic in the homologation paper

and this is also the case of the MY02 STi piston:


and it also says that the MY02 piston is forged while the MY03 piston is cast aluminum

Ya... I just going to go with what rallispec says, they have alway hit the answer right on the head.
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Old 11-20-2003, 05:58 PM   #39
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damn... homolagation papers.. rofl..

didn't know how to read that darn thing..


anyway. let APS tune our STi.. we ll see how high/low the limit really is.
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Old 11-20-2003, 06:12 PM   #40
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Seems there are different type of cast pistons.

Hypereutectic cast
T6 hypereutectic cast

From Corky bells book he says don't be in a hurry to change cast pistons. Forged pistons are great for the track but not so good for daily startup. Piston slap seems to wear the motor pretty quick. He goes on to say that the best of both worlds is T6 hypereutectic which are strong and can be used for both worlds.

Nobody can say yet what the USDM STI pistons are made from. The material they say they are made of no one has been able to decifer code. Could they be T6 hypereutectic.

FWIW
APS has probably built 10 times more WRX motors than any 3 engine builders here in US combined. They do know what breaks.

IMHO
The one thing I do notice about the USDM STI piston is its smaller thickness from the top of the piston to the first ring land. This alone says its not as strong.

All this thread tells me is to put them to the test. I would if I had my UTEC. $1300 for a short motor is cheap. I've spent that on women in a day and got nothing.
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Old 11-20-2003, 06:39 PM   #41
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Guys,

We only posted to show why discretion is required with boost levels used on the US Spec 2.5 litre STi piston – that’s all.

Will we destroy the ones in our own engineering vehicle? - Quite possibly!

The previous fitment outline I posted is accurate. The only question is what is in the street JDM Version 8. If they are cast, the reason will be as I previously stated (emissions – cold start combustion chamber sealing).

Yes, the 2.0L WRX piston is made the same way as the US Spec 2.5L STi piston. However, I amazed none of you have picked up on the one fact that shocked me! A North American parts re-seller apparently charging $1,022.00 for four pistons, which can be readily purchased for $80.00 each, from any North American Subaru dealer! If I am missing something here, please tell me.

Oh, for those who wonder why we call the US Spec 2.5 litre short a Forester component and not an STi one, it is very simple. The 2.5 litre short is mass produced in the Subaru engine plant using components which are basically improved mass production parts. The production 2.0L International Spec/JDM Spec. STi engines are effectively hand assembled in STi’s facility, which is a completely different environment, using custom race components. I would have said that made our description both accurate and self evident.

Dave

APS
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Old 11-20-2003, 07:13 PM   #42
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I think the confusion comes into play because you are stating information that goes against all currently published information, that regarding the V8 STI. That includes the FIA homologation papers for the V8 model.

It has nothing to do with street versus whatever. The V8 JDM motors do not use forged pistons, in any application. The Aus V8 engine is not the JDM engine, it's completely different.

I wouldn't go as far as to call STI engines "race-built" engines or anything to that effect. They are just engines, that also use mass-produced parts.
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Old 11-20-2003, 07:22 PM   #43
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dwx you got the point ..... JDM ver 8 STi's do not use forged pistons
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Old 11-20-2003, 07:56 PM   #44
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I have a question:

Anyone know how many 2.5L STI motors have died due to piston or wrist pin failure?

I am not so concerned with the material that pistons are made of, in fact, I am more concerned with the piston design. The stock hypereutectic pistons in the Supra and Evo (I believe) seem to hold up just fine.

...so any known cases of piston failure?
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Old 11-20-2003, 08:27 PM   #45
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DWX,

(1) The FIA papers do not specify forged or cast, so I am not sure how you draw your conclusion.

(2) We are well aware that the International Spec Version 8 engine is externally completely different to the JDM Spec Version 8. However, that does NOT automatically mean the pistons are also different, particularly with the number of JDM variants.

(3) I did not call the STi engines “race built”. In fact, we “blueprint” them ourselves. However, if you had disassembled one of the US Spec Forester shorts and any Version 7 or 8 genuine STi short, as we have done on many occasions; you would have as little trouble as we do in distinguishing between a mass production assembly using relatively inexpensive mass production parts and a low volume, semi hand built assembly using much more expensive parts, which in the US aftermarket would normally be described as “custom race parts”.

Dave, APS.
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Old 11-20-2003, 08:29 PM   #46
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Quote:
Originally posted by APS
Guys,

...Oh, for those who wonder why we call the US Spec 2.5 litre short a Forester component and not an STi one, it is very simple. The 2.5 litre short is mass produced in the Subaru engine plant using components which are basically improved mass production parts. The production 2.0L International Spec/JDM Spec. STi engines are effectively hand assembled in STi’s facility, which is a completely different environment, using custom race components. I would have said that made our description both accurate and self evident.

Dave

APS
No wonder it’s easy to purchase assembled 2.5 Sti short blocks with pistons and crank for the very cheap price of about $1300...And suppliers are making a profit! Thanks APS, you guys are very informative.
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Old 11-20-2003, 08:39 PM   #47
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Quote:
Originally posted by APS
Guys,

A North American parts re-seller apparently charging $1,022.00 for four pistons, which can be readily purchased for $80.00 each, from any North American Subaru dealer! If I am missing something here, please tell me.
Dave

APS
What you are missing is that some of us are only interested in finding out the facts...not selling a product. Rallispec was not referenced as a bargin source for pistons....they were only referenced for the info. on whether they are cast or forged.
No need to be defensive.
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Old 11-20-2003, 09:11 PM   #48
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Quote:
Originally posted by modvp
Question for APS...are the standard USDM 2.0l wrx pistons made the same way as the USDM Sti pistons?
They are both cast but made of different material.
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Old 11-20-2003, 09:19 PM   #49
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Quote:
Originally posted by Wombat North
Seems there are different type of cast pistons.

Hypereutectic cast
T6 hypereutectic cast

From Corky bells book he says don't be in a hurry to change cast pistons. Forged pistons are great for the track but not so good for daily startup. Piston slap seems to wear the motor pretty quick. He goes on to say that the best of both worlds is T6 hypereutectic which are strong and can be used for both worlds.

Nobody can say yet what the USDM STI pistons are made from. The material they say they are made of no one has been able to decifer code. Could they be T6 hypereutectic.

I have seen that AC8A is T6, I don't know anything about the new material. I know that FHI thinks it is pretty damned good. I'm also being cagey because I know more than I can say.

To Dave/APS's point, yes, the USDM STi engine is mass produced. Your point is?

It will certainly be interesting to see how durable a well tuned STi 2.5 engine is.

Glenn
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Old 11-20-2003, 09:25 PM   #50
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Quote:
What you are missing is that some of us are only interested in finding out the facts...not selling a product. Rallispec was not referenced as a bargin source for pistons....they were only referenced for the info. on whether they are cast or forged. No need to be defensive.
Strangerg,

No defensiveness here . Just querying the credibility of the information source, that’s all. If one can make such a massive price error (over 3:1), why would one assume technical accuracy? After all, it takes a lot more effort to obtain accurate technical information, than getting pricing correct. Particularly when all you are doing is re-selling, not design and manufacture.

So no, I was actually not “missing” anything!

Dave
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