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Old 03-16-2011, 03:21 AM   #26
aesthetect
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Quote:
Originally Posted by FuJi K View Post
Combustion Chamber VS Bore Size
Here is a 2.0L combustion chamber on a 2.2L 97mm bore.

Here is the 2.0L combustion chamber on a 2.5L 99.5mm bore.

Here is a modded 2.0L combustion chamber to a 97mm width on a 2.2L 97mm bore.

Here is a modded 2.0L combustion chamber to a 97mm width on a 2.5L 99.5mm bore.
do you have the combustion chambers sizes for each different displacements? also could you explain what these pictures demonstrate. ive been reading into combustion chamber sizing for bores but not sure what i should be getting from those pics
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Old 03-16-2011, 03:34 AM   #27
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^^^^ I'll get some quick measurements in the morning with more pics. but a heads up, the EJ257 bores as of current; B25, V25B, W25 all have a combustion chamber with a width of 99mm-100mm. The D25 heads come with a 97mm width. The EJ205/EJ207 have a combustion chamber width of 92mm.


Time for bed .. zzzzzZZZZZzzzZZzz.....
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Old 03-16-2011, 03:44 AM   #28
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ahh nice, thats actually even more what i was looking for. heres a few chamber volumes i had written down to get things started..
207: 49cc
205: 52cc
257: 57cc
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Old 03-16-2011, 04:14 AM   #29
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255 is 50cc
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Old 03-16-2011, 10:05 AM   #30
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Quote:
Originally Posted by aesthetect View Post
do you have the combustion chambers sizes for each different displacements? also could you explain what these pictures demonstrate. ive been reading into combustion chamber sizing for bores but not sure what i should be getting from those pics
they are hand ground combustion chambers, so they aren't going to be a usable number for you.

when doing this kind of work, you need to chambers individually.
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Old 03-16-2011, 12:37 PM   #31
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real good info, great work
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Old 03-16-2011, 12:39 PM   #32
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edit Never mind someone already asked
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Old 03-21-2011, 08:02 PM   #33
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Any updates with final measurements of w25 heads? or pics with the 97 mm bore?
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Old 03-21-2011, 09:46 PM   #34
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Aren't 205, S20 castings, 49 cc not 52cc?

Edit: I get it, you're compiling the modified chamber info...

Last edited by theotherguy; 03-21-2011 at 09:52 PM. Reason: I'm illeterate
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Old 03-21-2011, 11:13 PM   #35
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hi guys great stuff,
any idea what comperssion piston you would have to use to get like an 8.4:1 compreesion or maybe this way would be easier, what would an advertised 8.3:1 or 9.0:1 piston net you on the 75mm stroke ej257 with long rods, and better yet if you use an jdm sti version 8 heads, would what would the compression be like?
thanks
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Old 03-21-2011, 11:23 PM   #36
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OP.

I am considering rebuilding my ej2.5, you are now god to me on this forum.
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Old 03-22-2011, 12:08 AM   #37
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Quote:
Originally Posted by swi dragon View Post
hi guys great stuff,
any idea what comperssion piston you would have to use to get like an 8.4:1 compreesion or maybe this way would be easier, what would an advertised 8.3:1 or 9.0:1 piston net you on the 75mm stroke ej257 with long rods, and better yet if you use an jdm sti version 8 heads, would what would the compression be like?
thanks
you need more info than that alone. A simple online calculator for compression ratio will answer what you need and then you can simply search to see/learn what info you don't yet have.

but shooting off the cuff, I'll say the 9.0:1 will put you in the low to mid 8 area...assuming you have a proper rod length for the given piston.
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Old 03-22-2011, 12:13 PM   #38
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Quote:
Originally Posted by Homemade WRX View Post
you need more info than that alone. A simple online calculator for compression ratio will answer what you need and then you can simply search to see/learn what info you don't yet have.

but shooting off the cuff, I'll say the 9.0:1 will put you in the low to mid 8 area...assuming you have a proper rod length for the given piston.

thanks homemade
i will be running the 2mm (long rods) and hoping to do just the simple ej257 piston, next question (just to be sure) does the pins holes in the block aling for the 2mm longrods and standard pistons?
when i say standard i mean the spec but forge units

Last edited by swi dragon; 03-22-2011 at 01:13 PM. Reason: additional info
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Old 03-22-2011, 12:57 PM   #39
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...edit

Last edited by Homemade WRX; 03-22-2011 at 03:46 PM.
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Old 03-22-2011, 03:38 PM   #40
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cool, i think i need more info on your setup then, i am not a fan of putting the pistons on the rods then the crank, then joinging the 1/2's, could be messy plus i wonder if it can move the bearings, butttttt
thanks a million.
i'll do some more research and read some of yours and the others older post
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Old 03-22-2011, 03:46 PM   #41
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If you're doing an actual long rod there is no way to avoid getting messing...end of story. There are a few trade secrets, well you just get better when you've done more of them
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Old 03-22-2011, 04:04 PM   #42
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So I'm planning to take this EJ22T block, do the 257 crank and rods, different pistons (probably CPs) and then a set of EJ20K heads that I found for a steal. I'm still trying to figure out what headgaskets to run with this setup but I also would like to know what the cc's of the heads would be because I don't have them in my possession yet.
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Old 03-22-2011, 05:44 PM   #43
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I think they are 46.6 cc like the phase 1 dohc.
I'm going to run a ej255 block, crank, eagle rods and 100mm cp pistons with phase 1 dohc heads. Don't want to rewire the hydra to run the non avcs b25 heads that I have right now.
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Old 03-22-2011, 08:04 PM   #44
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Combustion chamber pictures added to 2nd post; B25, D25, S20 heads.
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Old 03-22-2011, 08:38 PM   #45
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Quote:
Originally Posted by Prevent View Post
255 is 50cc
Just wanted to slightly correct....

The EJ255 on '05-'06 LGT/BajaXT/OBXT are B25 heads, which are 57cc.
The EJ255 on the '04-'05 FXT are B25 heads, which are 57cc
same longblock as EJ257

The EJ255 on the '07+ LGT/OBXT are D25 heads, which are 50cc
The EJ255 on the '06+ FXT/WRX/OBXT are D25 heads, which are 50cc
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Old 03-22-2011, 09:49 PM   #46
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what would be reaaaaaaaaalllly helpful is if you were to be able to compile which heads (codes) came on which models
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Old 03-22-2011, 09:52 PM   #47
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Quote:
Originally Posted by FuJi K View Post
Just wanted to slightly correct....

The EJ255 on '05-'06 LGT/BajaXT/OBXT are B25 heads, which are 57cc.
The EJ255 on the '04-'05 FXT are B25 heads, which are 57cc
same longblock as EJ257

The EJ255 on the '07+ LGT/OBXT are D25 heads, which are 50cc
The EJ255 on the '06+ FXT/WRX/OBXT are D25 heads, which are 50cc
Thanks!

No one by me has LGT, baja or forester turbo's so i forget about them a lot, lol.
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Old 03-23-2011, 11:11 AM   #48
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This is an awesome resource. Thanks Fuji! I've been meaning to do some research on the EJ205 head/EJ22T block combo and the necessary mods to the combustion chambers - you just put it all in a single place.

Might want to also mention the max piston speeds of various configurations. That was the first thing that popped into my head when someone above started asking about the reliability of small-bore, long-stroke setups.

EJ205's have a max piston speed at redline of 3,441 feet/second, whereas the earlier (7000rpm redline) EJ257's are around 3,628 f/s. Piston speed is dependent upon the length of the stroke as well as the redline, so before you decide you're going to build a stroked 2.7L EJ257 with an 8500 RPM redline, you may want to consider how far outside factory parameters you're pushing that piston speed. Not to mention the potential for valvetrain unhappiness.

Engines with longer stroke have higher piston speeds because the piston has to travel a physically longer distance at every RPM versus a short-stroke version. This can lead to added wear and tear on the pistons and cylinder walls - there's a reason that sportbikes, which are designed to survive very high RPM, tend to be oversquare with a very short stroke.

The reason I'm considering an EJ22T block rather than an EJ257 is to produce a good compromise between low-end torque (greater displacement than my EJ205) and mid/high RPM reliability (retains the 75mm stroke and lower piston speeds).
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Old 03-24-2011, 08:13 PM   #49
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This is awesome! Like everyone else, this is tons of information that I've been looking around for. Subscribed and thanks!
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Old 03-24-2011, 08:39 PM   #50
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The reason I'm considering an EJ22T block rather than an EJ257 is to produce a good compromise between low-end torque (greater displacement than my EJ205) and mid/high RPM reliability (retains the 75mm stroke and lower piston speeds).
See destroked EJ25

Also mean piston speed as you described is just tip of the iceberg for acceleration and speeds on the piston.
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