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Old 04-14-2003, 11:43 PM   #1
stickygreen
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Question Sti - 2.5RS

What are the difference between the 2.5RS engine and the Sti engine, besides the fact that the Sti has a turbo? Are the engine blocks basically the same and what about the heads??
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Old 04-15-2003, 12:37 AM   #2
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wow, cast iron pistons! And bored out too make 2.5l from 2.5l?

sorry man, i dont want to be a total ass, but that paragraph made no sense and was full of misinformation.

Having not read all the specific posts concerning the new motor, IIRC the new block will be semi closed deck design, the heads include have sodium filled valves for better heat transfer and variable valve timing.

Last edited by Crawdads; 04-15-2003 at 12:44 AM.
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Old 04-15-2003, 12:40 AM   #3
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Oooh, more SCC disinformation.

I don't believe any of the major components are common with the 2.5 RS or Legacy (naturally aspirated) motors.

The STi 2.5 has unique: block, rods, crank, pistons, cams.

The heads are the AVCS 16v DOHC heads. The RS/Legacy etc use 16 v SOHC heads. Big difference.

Glenn
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Old 04-15-2003, 01:19 AM   #4
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Where are you finding documentation on the STi engine? Anywhere public?
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Old 04-15-2003, 12:48 PM   #5
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Quote:
Originally posted by CloNeGTS
Where are you finding documentation on the STi engine? Anywhere public?
It was printed in SCC that the motor was a tweaked EJ25 from the RS, which like Glenn said, is wrong.

AFAIK, it's pretty much the EJ20 STi block, only worked to make more displacement (prolly different stroke/bore).
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Old 04-19-2003, 01:23 AM   #6
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Quote:
Where are you finding documentation on the STi engine? Anywhere public?


Quote:
AFAIK, it's pretty much the EJ20 STi block, only worked to make more displacement (prolly different stroke/bore).
It is similar to the block but there are some new and important differences.

It does sound like there is a lot in common with the 2.5 XT Forester and Baja turbo and the STi engine.

I suspect the revised block etc. was used in all of them.

I was reading a SCC on the newstand today and found even more errors (picture of 04 WRX interior labelled as STi, and they also said the DCCD uses a "clutch pack", which it doesn't).

So, my advice is to pretty much ignore anything you see in SCC.... or at the least the finer details.

For anyone who wants to know more about the mechanical part of the DCCD, I direct you to the Legacy H6/WRX Auto VTD documentation.

Glenn
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Old 04-19-2003, 03:14 AM   #7
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I think this engines closest relative is the AVCS EJ25 in Japan, although the semi-closed block and special valve are aparently different I think the head design is simular. In my eyes, this engine is more of an emalgamation of various current EJ engines, most of which we dont have here in the states
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Old 04-19-2003, 11:13 AM   #8
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No, the block, crank, rods, pistons are all new modifications of current components.

Apart from heads etc, it is not a parts bin special.

Even the cams used in the heads are different (the metalurgy, don't know about the profile though).

I am not even sure it has an EJ designation.

Glenn
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Old 04-20-2003, 12:45 AM   #9
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Well I dont mean "from the parts bin" I mean previous design ideas. The closed deck design and forged parts are obviously 22B related experiments, combined with new technology like the valves and drive by wire, combined with recent JDM AVCS and DOHC tech. The ideas were all there, just not all put into the EJ25 before.
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Old 04-20-2003, 01:01 AM   #10
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This is not an EJ25...
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Old 04-20-2003, 02:15 AM   #11
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As far as ive heard, its still the same dimensions as an EJ25 but with the semi-closed block and different material construction... Still the same dimensions and everything, so why not an EJ25?
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Old 04-20-2003, 02:56 AM   #12
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I think we are running up against a dictionary definition of "all new" vs. "evolutionary".

The 2.5 turbo is an evolution of previous Subaru motors. In some ways it is definitely brand new - there was no 2.5-litre turbo factory motor before. In some ways it's merely evolutionary - much of the design isn't going to differ greatly from previous designs used in their flat fours.

Technically, the current JDM 2.0-turbo isn't terribly different from the original, hand-made motors in the Ver. 0 STi's. However, it's obvious nearly everything has evolved and been tweaked since then.

Base line - the 2.5 turbo motor is not a "tweaked" 2.5 NA motor. It certainly is related to it, but then, Whoopi Goldberg and Halle Berry's physical makeup also may technically be 90% the same, but it's the other 10% that makes a world of difference.

Cheers,

Paul Hansen
www.apexjapan.com
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Old 04-20-2003, 11:00 AM   #13
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I'll take Halle Berry.
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Old 04-20-2003, 07:55 PM   #14
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Ha! are you kidding?!? Whoopi Goldberg is a friggin' alien!!!
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