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2004 Forester XTi
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The Oct. issue of ‘Import Tuner’ magazine talks about the Subaru boxer engine at how we get the growl of a V8 but the sound of a 3 cylinder engine. They directed it toward the WRX, but I’m sure the EJ25 works the same way. They said that our engine fires @ 1-3-2-4, but our engine is set up with cylinders 1&3 on one side and 2&4 on the other side. With that said, it doesn’t work like it’s a full engine, but two separate two cylinder engines in one block. Although that may sound interesting, I don’t know for sure if our engines work like that. What’s the difference if the EJ25 fired at 1-2-3-4 (making it work like a whole 4 cylinder engine)? I’ve seen a video of an EJ20 sti engine internally working and it doesn’t look like it’s pumping the way ‘Import Tuner’ wrote.
 

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99 2.5 RS-T
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Not seeing the article, AFAIK, cyl 1&2 and 3&4 are moving at the same time (i.e. hit TDC and BDC simultaneously). Now on a 4 cycle engine the piston has an exhaust stroke and a compression stroke, so (taking cyl 1&2) one is expelling exhaust while the other is compressing. Now if the firing order were 1,2,3,4 then it'd fire on the exhaust stroke of cyl 2. Nope, 1,3,2,4 sounds right to me. Also, having a dual coil (GC/GMs) cyl 1&2 are on one coil and 3&4 are on the other so you're firing coil 1,2,1,2, -vs- 1,1,2,2. You'd never get any compression into cyl 2 b/c it'd constantly be firing on the wrong stroke.


--- disclaimer, this is AFAIK, I could be wrong.
 

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MY00 Impreza 2.5RS, Aspen Whit
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This reminds me of a question. NE1 know where the cam is in the EJ25? I have looked and looked but its just mind boggling. I was trying to think of where it could be but with the opposible 4 I had no clue.
 

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The cams are on both sides. With either SOHC or DOHC they are set on the sides where you see the spark plug wires, on opposing ends of the cylinders.
 

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99 2.5 RS-T
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Subadan, Sjt is right. The enigne block is in the center, the cylinder heads are on either side of the block. The cam pulleys and timing belt are under the plastic cover in the front of the engine (right behind the radiator).

 

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:drool: that makes me want to come...but anyway, why are there two dishes in the piston head. shouldn't you only need one per valve, yet there are two per valve in the picture :confused:
 

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99 2.5 RS-T
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I'd say artistic license, I don't recall two dishes when I had my cylinder heads off.
 

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MY00 Impreza 2.5RS, Aspen Whit
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So if you have a SOHC shouldn't you have one cam shaft driving another or is there just one cam? I am trying to figure out how it works with this type of engine.
 

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99 2.5 RS-T
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You have one cam per head, two heads per block, driven from the crank via timing belt. Notice the 3 large pulleys in the front of the picture? The large one is the crank pulley, the one on the left is the powersteering pulley, the cutaway one is the drivers side cam pulley, there is an identical one under the black cover on the passenger side. Hope this helps.
 

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MY99 GF4 EJ227 JDM 6spd
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The MY98 has 4 cams!! MY99-01 has 2 cams........:biggest:

get? welll.....

When you get it, you get it........

hA!
 

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99 2.5 RS-T
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Fuji, good point. I neglected the DOHCs b/c he asked specifically about the SOHCs but you're right, the DOHCs have 4 cams, 2 per head, intake and exhaust. The DOHC heads provide much more control of cam timing (read: more potential power) but have some flow issues. A port/polish/valve job on a DOHC head would be a superb chioce mated to the 00-01 block if you're staying N/A and to a beefed up 99 block if you're going FI. Sorry fugi, the 98 blocks had some issues, not that the 99s are all that much better (since I blew one up N/A :curse: ).
 

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MY00 Impreza 2.5RS, Aspen Whit
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Thanks you all, that helps. I understand it now.

so

SOHC = 2 cams
DOHC = 4 cams

thanks
 

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Only in the boxer world. Be very careful when explaining that to, well anyone (specifically Honda folks), they usually don't get it ever.
 

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SubaDan said:
Thanks you all, that helps. I understand it now.

so

SOHC = 2 cams
DOHC = 4 cams

thanks
that is true on boxers and most Vs. inlines are SOHC=1 DOHC=2. and then there is the VR6. its a narrow angle V, but it only has one cylinder head, so its the same as an inline as far as cams go.
 

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95 Impreza L AWD
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that is true on boxers and most Vs
Actually, it depends what kind of V you are talking about. Most import cars with V engine layouts have two cams, but most caveman cars such as the corvette, camaro, older Mustangs, and generally almost all domestic cars before ~1993 or so, and still a lot of the ones newer than that only have one cam total! Pushrods suck!:barf:
 

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Egg-shaped cylinders 2 and 3. Probably a defect, this problem pops up every once and a while. The car was a demo (4000 mi when I bought it) but had full warantee so at 59,000 mi I paid the dealer a visit, by 60,000 a new block was in thanks to SOA.
 

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MY00 Impreza 2.5RS, Aspen Whit
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10th Warrior said:


that is true on boxers and most Vs. inlines are SOHC=1 DOHC=2. and then there is the VR6. its a narrow angle V, but it only has one cylinder head, so its the same as an inline as far as cams go.
Yes this is why I asked the question in the first place. I understand it now though.
 
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