Hawkeye 2.5 WRX / STi engine differences ?
31 October 2009, 10:58 PM
#1
Hawkeye 2.5 WRX / STi engine differences ?
Whilst trying to sort out the failed engine in my 2002 WRX I have considered a 2.5 as a replacement, this has raised a mountain of questions that I would like to get your views on.
I presume the Hawkeye uses the EJ257 engine, what are the internal differences between the WRX version and the STI ?
I have been told by several engine builders that the standard STi pistons are not forged items and should be uprated if looking for much over 350 bhp. Are the standard STi pistons any better than the WRX ones and if so in what way ?
Various sources claim that 'newage' rods are good for 450 bhp+ so are the STi rods the same as the WRX ones ?
I can't see that Subaru will make two different crankshafts for the 2.5, so once again are the STi and WRX items identical ?
I would expect that the STi will have wilder camshafts and maybe bigger valves so guess that the heads account for one difference ?
The Sti doesn't have a closed deck block, is it any different to the WRX one ?
I presume the Hawkeye uses the EJ257 engine, what are the internal differences between the WRX version and the STI ?
I have been told by several engine builders that the standard STi pistons are not forged items and should be uprated if looking for much over 350 bhp. Are the standard STi pistons any better than the WRX ones and if so in what way ?
Various sources claim that 'newage' rods are good for 450 bhp+ so are the STi rods the same as the WRX ones ?
I can't see that Subaru will make two different crankshafts for the 2.5, so once again are the STi and WRX items identical ?
I would expect that the STi will have wilder camshafts and maybe bigger valves so guess that the heads account for one difference ?
The Sti doesn't have a closed deck block, is it any different to the WRX one ?
01 November 2009, 01:23 AM
#2
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they're very similar apparently, dont know if this link will help u out, but here it is
2.5 WRX internals vs Sti internals - NASIOC
2.5 WRX internals vs Sti internals - NASIOC
01 November 2009, 11:01 AM
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consider them no different with regards to how much power they are okay too etc..
tend to consider upto 400bhp and 400lb okay.. but wrx gearbox won't like that lol
Simon
tend to consider upto 400bhp and 400lb okay.. but wrx gearbox won't like that lol
Simon
01 November 2009, 10:20 PM
#7
The Hawkeye WRX has the EJ255 Engine. Block is identical to the EJ257 but the pistons are different as is the the oil modine arrangement.
I've just bought one of these and am using it as the basis of my build. Heads are slightly different with smaller ports and slightly higher compression.
Rods are the same in both WRX and STI and would say these are easily good for 450bhp. As a minimum I would replace the crappy pistons with some forged items.
Daz
I've just bought one of these and am using it as the basis of my build. Heads are slightly different with smaller ports and slightly higher compression.
Rods are the same in both WRX and STI and would say these are easily good for 450bhp. As a minimum I would replace the crappy pistons with some forged items.
Daz
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04 November 2009, 09:44 AM
#9
Oil modine is a water fed oil cooler. On the EJ257 its the same as all the other models.
On the EJ255 the modine is shorter fatter and there is an additional bracket holding it to the block. One you remove the modine and bracket the block is identical so earlier modines will fit. The casting is identical.
The pistons differ in that they are of a slightly different design (slightly higher compression) and they have different part numbers.
EJ255 8.4:1
EJ257 8.2:1
The main differences are on the heads though.
Hope that helps.
On the EJ255 the modine is shorter fatter and there is an additional bracket holding it to the block. One you remove the modine and bracket the block is identical so earlier modines will fit. The casting is identical.
The pistons differ in that they are of a slightly different design (slightly higher compression) and they have different part numbers.
EJ255 8.4:1
EJ257 8.2:1
The main differences are on the heads though.
Hope that helps.
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