is there a diff between the jdm sti and the usdm sti?

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CrazyAzn

CrazyAzn

Senior Member
i noe this is a honda site and all, but i also know theres alot of honda peeps that jumped ship and sold out to subie and mitsu. but thats neither here nor there, is there a difference in the jdm sti bottom end and the usdm bottom end? i ask this because i ran into a guy who was driving an sti and said he had a jdm bottom end. . .

it puzzled me because i dont know any thing about them, and would like to know the difference. i tried searching the net, but its hard to search when you dont know what the hell your looking for. . . haha

also asking because we had a fun run, and he couldnt pull away. . .n i thought sti's were alot faster. . .

if someone could clear this up, it would be awesome.
 
tons. not sure about the 06 models, but in <05 models, the jdm model was still a 2.0 and used forged pistons as opposed to the usdm 2.5 and cast pistons. thats the obvious change, but there's tons more too.
 
06s are also 2.0s. Americans dont rally so we can have the easier, and better tempered 2.5 bottom end.

thats the only difference i know off hand....other than being RHD in japan.
 
hummm, cus i was confused because he couldnt pull away. are the usdm sti's 2.0L? which one is 2.5?
 
umm thanks for the info, i was wondering if anyone else agreeded with that statement. . .but thanks again

i thought they were all 2L, but whatever
 
WRX = 2.0l and the older STi's I believe were 2.0l's too. The new STI's here as someone said are a 2.5l turbo.
 
icic, thanks guys.

does any one know how much power the jdm sti puts out? i would search it, but like i said i dont know what to search for ie engine codes/chassie codes and such
 
The version 7 STi is rated at 276 HP, but is under rated. Probably making closer to 300 HP. One of the biggest differences is the intake manifold.

All USDM STis are 2.5L, they don't get a 2.5L STi in Japan, they are all the homogilated 2.0.
 
pissedoffsol said:
tons. not sure about the 06 models, but in <05 models, the jdm model was still a 2.0 and used forged pistons as opposed to the usdm 2.5 and cast pistons. thats the obvious change, but there's tons more too.
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to add to the fact that its 2.0l and contains forged internals, its also a closed deck motor as opposed to the usdm motor thats open deck.

If he had a STi, unless he has money to piss away he should have just stuck with the 2.5L bottom end or he's blowing smoke up your ass. He could have built the 2.5l to be rev happy like the 2.0l and have a bigger and better power curve for less than the cost of the version 8 jdm swap.
 
Turbo&Auto said:
WRX = 2.0l and the older STi's I believe were 2.0l's too. The new STI's here as someone said are a 2.5l turbo.
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No USDM STi was ever a 2.0l engine.

2002-2005 WRX = 2.0l ej205
2004-2006+ STi = 2.5L non forged
2006+ WRX = 2.5L (different piston profile than the STi, very small other differences noted in engine diagrams. not much of the difference is known yet)

Both the 2.0l closed deck, forged interal jdm version 8 STi engine and the USDM 2.5l open deck STi engine are rated at ~300hp. Ratings just were fucked up this year because of SAE ratings now being mandatory. On the STi limited I think they bumped the power rating back 5hp to 295hp because of the SAE ratings.

The intake manifolds really aren't that entirely different in the USDM/JDM engines, except the JDM engines don't have the TGV (tumbler gas valves) for emissions. You can remove, plug, port and polish the TGV on any suby engine - I have tumbler deletes in my WRX along with a whole sleu of other things. Its cheaper if you have your usdm manifold ported than buying a jdm manifold unless you buy an unknown manifold from the mid 90's off another ej20 engine since subaru has used the same engine for 20 years now.

Biggest differences as repeated five times already are cast vs forged internals, displacement, open vs closed deck, injectors, intake manifolds (if you're splitting hairs here)
 
there we go, thats the kinda of explaination i was looking for. . . thank you all very much.
 
VTEC_CBR said:
it's 293, and ALL STI's not just the Ltd.
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Close enough.

I was only quoting the limited, because at the time that i learned about the new power rating, only the '07 STi limited was listed on the website.

But we're just splitting hairs here. The car is a ~300hp car.
 
totalburnout said:
Close enough.

I was only quoting the limited, because at the time that i learned about the new power rating, only the '07 STi limited was listed on the website.

But we're just splitting hairs here. The car is a ~300hp car.
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You're right, and it really is no big deal, nothing has changed at all, you could say that the 04-06 are also 293. It's only a number.
 
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