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Ntseg Muag!
SRP MY00 Subaru Impreza 2.5RS
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518 Posts
Discussion Starter #1
I know alot about impreza and how to fix them but i'm curious about can a sohc get converted into dohc with the EJ25.:confused: Just wandering incase i want to do that one day.
 

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Premium Member
2001 Subaru Impreza RS
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586 Posts
Why would you want to do that?? There is no benefit as far as I know.

Nick C.
 

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Ntseg Muag!
SRP MY00 Subaru Impreza 2.5RS
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518 Posts
Discussion Starter #3
i want doch because it doesn't have to work as hard as soch when launching your car plus i heard that doch is faster off the line
 

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Premium Member
2001 Subaru Impreza RS
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586 Posts
DOHC was used on the first RS's. When they switched to SOHC, hp and torque ratings improved.

Nick C.
 

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Ntseg Muag!
SRP MY00 Subaru Impreza 2.5RS
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518 Posts
Discussion Starter #5
really, i thought that hp and torque was better on doch engines. well thanks for the info. what else you know?
 

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Registered
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95 Posts
you must be a Honda guy...

DOHC is better than SOHC on Honda's.

On Subaru's, however, DOHC is WORSE. Less Torque, and about equal horsepower.

So...in that respect, a DOHC Impreza will be SLOWER off the line.
 

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13 Years of RS
2005 Toyota Corolla :(
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5,532 Posts
The peak numbers on the SOHC vs the DOHC 2.5L engines are almost identical, with the SOHC having a slight lead. But what that doesn't show you is the powercurve of the engines. The SOHC has much more torque available downl low in the revs when compared to the DOHC. But if you go turbo, the DOHC might be a good way to go, as I understand it flows better than the SOHC. Plus, you can adjust the intake/exhaust timing better for the turbo app.
 

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Ntseg Muag!
SRP MY00 Subaru Impreza 2.5RS
Joined
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518 Posts
Discussion Starter #8
nope i'm not a honda guy. that's why i am in rs25 i like subaru. anywaise if that's true then maybe i'll just stay with soch. One more thing what about turbo charging it is soch better than doch in that for subarus too cause i don't to put too much stress on my engine when it is outputting 300hp +?
 

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Ntseg Muag!
SRP MY00 Subaru Impreza 2.5RS
Joined
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518 Posts
Discussion Starter #10
okay know we know that doch is better with turbo. That's why i'm thinking about converting it. Now back to my question on can you convert soch to doch with the 2.5L?
 

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13 Years of RS
2005 Toyota Corolla :(
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5,532 Posts
Lue V said:
okay know we know that doch is better with turbo. That's why i'm thinking about converting it. Now back to my question on can you convert soch to doch with the 2.5L?
Yes, it can be done, but it's not easy or cheap, as I think the sensors are different, and I don't know if the ECU you have will work right. DOHC if you plan on doing a big turbo build-up. SOHC if you plan on staying NA, or maybe a light to medium FI build-up.
 

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Ntseg Muag!
SRP MY00 Subaru Impreza 2.5RS
Joined
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518 Posts
Discussion Starter #13
i do some research on the ecu and see what i can do. Hey there's always a second choice. Customize a doch 2.5L especailly for turbo charging.
 
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