Difference between Usdm And JDM GT

Hey:cool:,

 

Can anyone explain the difference between the Usdm And Jdm Legacy GT EJ25 in relation to their power and torque output?

 

2.5GT (USA) 2009-2012 2,457 cc (2.5 L; 149.9 cu in) H4 turbo (EJ25) 265 bhp (198 kW) @5600, 258 lb⋅ft (350 N⋅m) @2000-5200

 

 

2.5GT (Japan) 2009-2012 2,457 cc (2.5 L; 149.9 cu in) H4 turbo (EJ25) 285 PS (210 kW; 281 hp) @6000, 350 N⋅m (258 lb⋅ft) @2000-5600

The horsepower difference is probably due to the turbo difference- the JDM version has a twinscroll, USDM is single-scroll. Same exhaust manifold, though, interestingly enough, the two separate flows just dump into one common inlet on the USDM turbo. The USDM single-scroll kinda falls on its face above 5500 RPM or so (gets outside its happy place and turns into a flamethrower), and it looks like the JDM twinscroll does a little better at higher RPM. Torque is limited to 258 lb-ft / 350 N-m through boost control and throttle angle in order to keep the transmission from grenading, and it makes sense that it'd be capped at the same number in both cases due to the 6MT being the limiting factor.

I think I want a twin scroll jdm turbo... but I recall fahrside saying something along the lines of they were cheap Chinese turbos. Hmmm...

The horsepower difference is probably due to the turbo difference- the JDM version has a twinscroll, USDM is single-scroll. Same exhaust manifold, though, interestingly enough, the two separate flows just dump into one common inlet on the USDM turbo. The USDM single-scroll kinda falls on its face above 5500 RPM or so (gets outside its happy place and turns into a flamethrower), and it looks like the JDM twinscroll does a little better at higher RPM. Torque is limited to 258 lb-ft / 350 N-m through boost control and throttle angle in order to keep the transmission from grenading, and it makes sense that it'd be capped at the same number in both cases due to the 6MT being the limiting factor.

I just did an entire JDM swap including the turbo. Are you saying I now have a twin scroll??

 

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Should be able to tell by looking at the turbine housing casting, it'd probably have 2 lobes around the outside rather than just being a smooth radius.

Should be able to tell by looking at the turbine housing casting, it'd probably have 2 lobes around the outside rather than just being a smooth radius.

These are the only pics I have of my JDM engine that sort of show the turbo. Very hard to see the housing . I'll check next oil change.

 

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Yeah, not really much to see there. Also, apparently those lobes could be a little less pronounced on smaller turbos like ours, so maybe take a peek at the housing right near the flange at the manifold. The two exhaust streams come in top and bottom rather than side by side, so there's gotta be some sort of twist in the casting to get those passageways rotated to where they need to go. Not sure what's on the outside of the exhaust housing as far as identifying marks, but if you see any, maybe someone with a turbo sitting in front of them (looking at you, wrxwhit) could compare your findings to theirs.

The horsepower difference is probably due to the turbo difference- the JDM version has a twinscroll, USDM is single-scroll. Same exhaust manifold, though, interestingly enough, the two separate flows just dump into one common inlet on the USDM turbo. The USDM single-scroll kinda falls on its face above 5500 RPM or so (gets outside its happy place and turns into a flamethrower), and it looks like the JDM twinscroll does a little better at higher RPM. Torque is limited to 258 lb-ft / 350 N-m through boost control and throttle angle in order to keep the transmission from grenading, and it makes sense that it'd be capped at the same number in both cases due to the 6MT being the limiting factor.

 

maybe I missed something... I was under the impression that all GT's came with the same VF54. The JDM set up has to be the same, turbo-wise, like the EDM as well. Our Russian and Philippine members have shown the same set up. If not, we would have that option floating around the internet markets - did I miss it? In doing my multiple turbo swaps (on my 4th), my research only showed the VF54 as we have it. Never have I come across a "which version" did I want.

 

Now, if we are looking at why the numbers/output are different by country - emission rules would play a big part - those in Cali know all about that.

maybe I missed something... I was under the impression that all GT's came with the same VF54. The JDM set up has to be the same, turbo-wise, like the EDM as well. Our Russian and Philippine members have shown the same set up. If not, we would have that option floating around the internet markets - did I miss it? In doing my multiple turbo swaps (on my 4th), my research only showed the VF54 as we have it. Never have I come across a "which version" did I want.

 

Now, if we are looking at why the numbers/output are different by country - emission rules would play a big part - those in Cali know all about that.

 

Fahr-side had mentioned it in a post about the 5th gen, but that is all I recall.

I've only ever seen the vf54 on these. Maybe the mention of cheaply made twin scroll was that it was an option if looking for twin scroll? Somebody would have put one on by now if it was available.

I've only ever seen the vf54 on these. Maybe the mention of cheaply made twin scroll was that it was an option if looking for twin scroll? Somebody would have put one on by now if it was available.

It's still a vf54 on my JDM engine .

 

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Yeah, not really much to see there. Also, apparently those lobes could be a little less pronounced on smaller turbos like ours, so maybe take a peek at the housing right near the flange at the manifold. The two exhaust streams come in top and bottom rather than side by side, so there's gotta be some sort of twist in the casting to get those passageways rotated to where they need to go. Not sure what's on the outside of the exhaust housing as far as identifying marks, but if you see any, maybe someone with a turbo sitting in front of them (looking at you, wrxwhit) could compare your findings to theirs.

Where did you see that it was a twin scroll in Japan ?

 

 

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I wonder how they make more power if the turbo is the same.

 

If you look at the tune of the JDM 2010 GT ts STI it actually runs less boost :

 

 

http://www.romraider.com/forum/viewtopic.php?f=8&t=9616

 

Would be nice to know the difference.

I wonder how they make more power if the turbo is the same.

 

If you look at the tune of the JDM 2010 GT ts STI it actually runs less boost :

 

 

http://www.romraider.com/forum/viewtopic.php?f=8&t=9616

 

Would be nice to know the difference.

I can't open that file.

 

Have a look at my build thread. I have a full JDM swap including turbo . With STI cams and a few bolt ons and a pro tune I made 285whp/320tq on bad gas, nearly maxed injectors and only 17psi.

 

Once the weather gets nicer I'll get under the car and take some pictures of the turbo so we can compare it to the USDM turbo.

I can't open that file.

 

Are you using ecuflash or romraider to open the file ?

Which definition file did you load?

 

I can take a screenshot of the boost map if it's easier but as per the thread link even tuner 'throttlehappy' points out that it has lower boost targeted.

 

 

I've had a good read of your build thread and will personally get some sti cams for my own rebuild which is due within a month.

 

Just need to get a hold of some headstuds as well while it's going to be apart.

 

I'm planning to copy all the tables from the JDM tune to my own car just to see what the difference is apart from the boost target. Maybe there will be something else noticible.