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What are the differences between the Outback 2.5XT and WRX STI engines?


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8 replies to this topic

#1 mckeand13

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Posted 05 August 2007 - 04:22 PM

I like the newer 2005 and up Outback 2.5XT's but I know I would be greedy for more hp and especially torque.

Both engines are 2.5L with turbo. Do they really start with the same block/heads or what parts do they share. I noticed that the STI is intercooled.

Beyond that, what are the differences.

Is it possible to make an OBXT STI fast?

#2 beataru

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Posted 05 August 2007 - 04:34 PM

STIs are very fast but there not crazy fast, yes it would be possible to make it as fast as an STI, and I am pretty sure that the 2.5xt is intercooled right? I mean I though my car was the only one that they decided to go dumb on and not put a cooler. also Im not exactly sure but I think that the xt has a tdo4 not a VF so.... please new school guys correct me if I am wrong, I dont have a new school subaru but I know about most of the 90 through 2004 type stuff(then I lost interest)

#3 mckeand13

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Posted 05 August 2007 - 05:05 PM

Yep, your right. They are intercooled. I was just going by the specs on the Subaru website and they don't mention it under "engine" for the OBXT. I just looked at a picture of the engine bay and I guess the hoodscoop is a giveaway.

So, now what differences are left to make up the almost 50hp difference?

#4 beataru

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Posted 05 August 2007 - 05:07 PM

I am guessing boost, and turbo.... thats what I think.

#5 WRX2FFU

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Posted 05 August 2007 - 05:36 PM

Yep, your right. They are intercooled. I was just going by the specs on the Subaru website and they don't mention it under "engine" for the OBXT. I just looked at a picture of the engine bay and I guess the hoodscoop is a giveaway.

So, now what differences are left to make up the almost 50hp difference?


turbo and tuning.........

#6 86BRATMAN

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Posted 05 August 2007 - 10:39 PM

Yep, they use the same engine, ej257. Different intercooler, turbo and ecu tune. You can make just as much power as an STi.

#7 uh_infinity

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Posted 10 January 2013 - 09:32 AM

Thanks for the reply. That was what I was thinking. Maybe some others will post to confirm.

#8 GeneralDisorder

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Posted 10 January 2013 - 01:41 PM

It is NOT the same engine. The OBXT is the EJ255. It has higher compression pistons, runs a smaller turbo and less boost. There may be differences in the heads as well. Obviously the tune is different and most likely so is the cam profile, ect. The heads themselves may have different valve construction and they may not be the same size.

While it can be as fast as a stock STi with the right upgrades and tuning, it doesn't have the potential without changing the pistons. For that matter people break stock STi pistons at stock power levels so frankly they need upgraded as well. But the OBXT pistons are higher compression and would need to be swapped for significant HP gains to be safe.

GD

#9 86BRATMAN

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Posted 10 January 2013 - 02:12 PM

Well, at least 6 years after the thread was posted I know I was wrong.




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