Engine difference - WRX vs Legacy GT

[blueoval_bowtie_guy]

First, I know the donor vehicle is a 2002-2007 Impreza. I've been wondering that if I picked up a really cheap non-turbo Impreza with a bad engine as a donor, would it be possible to use a good engine from an '06 - '07 Legacy GT? Is there a difference between an '06 - '07 WRX and an '06 - '07 Legacy GT? Do we have any Subaru experts here?

I bought a Legacy GT new in '07. The engine and trans were great! Got rid of the car after 2 years because the front seats were TERRIBLE! My wife got a back ache within 30 minutes after we bought it. It took about a month for me to get one, but I did. I ended up having to replace the head rests (tilted too far forward) and disconnect the lumbar support mechanism. Those seats either had too much lumbar support or way too much lumbar support.

[Mechie3]

I don't recall all the differences and what the cutoff years were.

06/07 WRX is the EJ255, same short block as STI except different pistons
Some of the LGT's had an EJ255, but the same exact short block as an sti (pistons and all)

Intercooler, turbo, and intake manifold on the LGT was also setup differently.

[BrandonDrums]

First, I know the donor vehicle is a 2002-2007 Impreza. I've been wondering that if I picked up a really cheap non-turbo Impreza with a bad engine as a donor, would it be possible to use a good engine from an '06 - '07 Legacy GT? Is there a difference between an '06 - '07 WRX and an '06 - '07 Legacy GT? Do we have any Subaru experts here?

I bought a Legacy GT new in '07. The engine and trans were great! Got rid of the car after 2 years because the front seats were TERRIBLE! My wife got a back ache within 30 minutes after we bought it. It took about a month for me to get one, but I did. I ended up having to replace the head rests (tilted too far forward) and disconnect the lumbar support mechanism. Those seats either had too much lumbar support or way too much lumbar support.

I have an '00 Legacy Outback wagon - I feel the same way about the seats. However, I found that because the electonic seat adjustment is only for the seat bottom-not the back, when I have the seat as low as I want it the lumbar hump is too high and my back hurts. I have to sit much higher than I want to the lumbar support is actually at my lower back. Perhaps you had the same issue.

As far as swapping engines into a 02-07 wrx, the engine I have in my 2005 wrx now is actually an EJ255 from an 05 legacy GT but with forged, STI spec compression (lower compression) pistons so you can call it an EJ25X because the only component that was different from an STI engine (the pistons) were replaced.

For an 02-05 wrx donor/ecu running either a EJ255 or an EJ257, you'll just need a cam sensor adapter. There are many vendors and 2-3 manufacturers for these. Mine is a Cosworth.

Cosworth at Rallysport Direct (http://www.rallysportdirect.com/Cosworth-Cam-Angle-Sensor-Bracket-Billet-Subaru-for-mounting-cam-angle-on-front-of-head)
Torque Solutions adaptor at Vivid Racing (http://thmotorsports.com/i-529697.aspx)

I'm not sure if the Drive By Wire system is the same in the 06-07 wrx and the Legacy GT. The Legacy GT also has AVCS which the 02-05 wrx does not have. If you can run the ECU from the Legacy GT, you'll need to run the legacy's intake manifold which has the drive by wire throttle. If you don't have that ECU, then you'll need to run the WRX's intake and throttle. Again, 02-05 wrx has a cable throttle, the 06+WRX has a drive by wire setup and AVCS.

If your donor WRX is 02-05 AND you have to use the 02-05 ECU without AVCS, it is recommended but not required that you plug the AVCS cam's oil passages and run non-avcs cam pulleys. There are a few opinions on this but my personal thought is that the AVCS cams which work by oil pressure being sent through a oil passage in the front of the camshaft into the cam pulley itself have a bit of "float" or play when the avcs control solenoids are unplugged as they are when you swap to a non avcs wrx.

I haven't found much proof of this but on my build which had the unplugged AVCS cams still on the engine, I felt some lack of low-end torque that wasn't present on my 2.0L. Below 2500 rpm, the engine would bog when I used more than ~15% throttle. That wasn't an issue on my 2.0L and regardless of AVCS, a larger engine should have at least a little more torque down low.

Here's probably the best write up on how to plug the AVCS passages. It's easier than you think.

http://forums.nasioc.com/forums/showthread.php?t=1356918

The last tidbit of mine is the Legacy GT most likely is an automatic and there can be some issues running an ECU for an auto when you swap a manual transmission in it. You may be able to flash a manual transmission Map/Rom to the auto's ECU unit and go OR tune around it. However, I don't know enough about the specific ECU's to confirm cross compatibility and with what.

You can probably find some of that information over at openecu.org along with the tuning sections on NASIOC.

[PhyrraM]

The major difference between the '06-'07 2.5 WRX and the '05-'09 Legacy GT is the turbo, intercooler, and intake manifold.

'02-'07 WRXs (and '04-'08 Foresters and '04-'06 Bajas) use a turbo with a slip coupling on the outlet, using a hose and hose clamps to connect that to the intercooler. Finally, the intercooler outlet dumps into the rearward facing throttlebody with another short hose and clamps.

The Legacies (and '08+ WRXs and '09+Foresters) use a turbo with a bolted flange to the intercooler. The intercooler then uses a short hose and clamps to the throttlebody, which is tucked underneath, and offset from center to the now plastic intake manifold.

[blueoval_bowtie_guy]

Thanks guys! This really helps. Once I get closer to ordering a kit, I'll stick with looking for an '02 - '07 WRX. With my Cobra (oops, I mean Roadster) build, I ended up way over budget because I kept adding stuff (like horsepower). I am going to try to keep the 818 build as close as possible to the 'donor'. This was one of those wild ideas thinking that I might be able to get an exact replacement engine from a Legacy GT. I am at least a year away (possibly more) from getting the 818, so I will continue to scan craigslist for local WRXs. I'm going to want to drive it for a while before I put it into an 818.

[BrandonDrums]

The major difference between the '06-'07 2.5 WRX and the '05-'09 Legacy GT is the turbo, intercooler, and intake manifold.

'02-'07 WRXs (and '04-'08 Foresters and '04-'06 Bajas) use a turbo with a slip coupling on the outlet, using a hose and hose clamps to connect that to the intercooler. Finally, the intercooler outlet dumps into the rearward facing throttlebody with another short hose and clamps.

The Legacies (and '08+ WRXs and '09+Foresters) use a turbo with a bolted flange to the intercooler. The intercooler then uses a short hose and clamps to the throttlebody, which is tucked underneath, and offset from center to the now plastic intake manifold.

As always, thanks for your awesomeness! TMIC and turbo compressor housing design aside, is the throttle input fitting on a Legacies and 08+ wrx's and 09+ forester compatible with the 3'' slip fitting outlet found on the 02-07 WRX/STI?

I assume so but we want to be sure you can use a WRX/STI style turbo and intercooler on a legacy intake/throttle for the OP. I guess it also matters in that case if the DBW throttle body found on the legacy differs from the DBW throttle body on the 06/07 wrx and the STI. That will determine which ECU he'll need to use with which intake and also determine if he needs to do something else if auto trans ECU control can't be modified to allow a manual transmission to operate.

Lots to consider. My gut is to use ONLY the longblock from the Legacy and use all the manifolds/accessories from the WRX including the ECU regardless of year WRX donor unless the proper parts are identified and confirmed for cross-compatibility. Personally, I'd rather disable AVCS and run a turbo/throttle/intake manifold combo I know works than try to fiddle with retrofitting an auto trans ECU to work for manual and trying to source upgraded turbos with the bolt-on style compressor output which are far less common and have far fewer choices.

[fateo66]

Also, some early 05 LGT's have B25 heads which are the same as a 04-06 STI. However the late 05 and 06+ LGT's have D25 heads which came on 06+wrx's and not only flow more but also have more of a hemispherical combustion chamber which reduces knock and promotes even flame propagation.

Here is a nice link to a thread I started many years ago.

http://forums.nasioc.com/forums/showthread.php?t=1856856

also here is a few other useful threads dealing with flow characteristics of various subaru parts

http://forums.nasioc.com/forums/showthread.php?t=2229576

http://forums.nasioc.com/forums/showthread.php?t=2034555

[PhyrraM]

The Legacy "plastic manifold" style can be converted to a WRX/STI style by swapping turbo, intercooler and intake manifold. IIRC, the throttlebody is the same, but mounted differently. Parts of the engine harness will likely have to be extended in some way as the throttlebody moves position.

To the best of my knowledge ALL early style "straight inlet" throttle bodies have aluminum intake manifolds (painted on STI) - while ALL later "tucked and angled" throttlebodies are on plastic intake manifolds.

[blueoval_bowtie_guy]

Also, some early 05 LGT's have B25 heads which are the same as a 04-06 STI. However the late 05 and 06+ LGT's have D25 heads which came on 06+wrx's and not only flow more but also have more of a hemispherical combustion chamber which reduces knock and promotes even flame propagation.

Here is a nice link to a thread I started many years ago.

http://forums.nasioc.com/forums/showthread.php?t=1856856

also here is a few other useful threads dealing with flow characteristics of various subaru parts

http://forums.nasioc.com/forums/showthread.php?t=2229576

http://forums.nasioc.com/forums/showthread.php?t=2034555

I just KNEW I was asking in the right place!

[BrandonDrums]

Also, some early 05 LGT's have B25 heads which are the same as a 04-06 STI. However the late 05 and 06+ LGT's have D25 heads which came on 06+wrx's and not only flow more but also have more of a hemispherical combustion chamber which reduces knock and promotes even flame propagation.

Here is a nice link to a thread I started many years ago.

http://forums.nasioc.com/forums/showthread.php?t=1856856

also here is a few other useful threads dealing with flow characteristics of various subaru parts

http://forums.nasioc.com/forums/showthread.php?t=2229576

http://forums.nasioc.com/forums/showthread.php?t=2034555

Brilliant.

[HelluvaEngineer]

The 05 Legacy GT has a stronger transmission than the earlier 2002 - 2007 WRX. Also There is some debate about the plastic intake being better on the LGT. Less heat soak issues and a little lighter than the STI intake.

[Rasmus]

The 05 Legacy GT has a stronger transmission than the earlier 2002 - 2007 WRX.
What do you mean by "stronger"? I know the Legacy GT 5speed has a shorter final gear 4.111 vs the WRX's 3.900. I don't know that the case is stronger. The shorter final gear would place less stress on the case given the same gear ratios and tires.

[rjh2pd]

What do you mean by "stronger"? I know the Legacy GT 5speed has a shorter final gear 4.444 vs the WRX's 3.900. I don't know that the case is stronger. The shorter final gear would place less stress on the case given the same gear ratios and tires.
i think he meant the strength of the gears... but i would think the transmissions would be the same as the 06-07 wrx. They upgraded the strength of the transmissions in the 06-07 wrx's

[bbjones121]

What do you mean by "stronger"? I know the Legacy GT 5speed has a shorter final gear 4.444 vs the WRX's 3.900. I don't know that the case is stronger. The shorter final gear would place less stress on the case given the same gear ratios and tires.

The gears are thicker. Let me see if I can find the pictures.

[bbjones121]

Here you go. The WRX 03-07 gears are the same. Legacy gears are as thick as STI gears.

http://flatironsrally.typepad.com/faq/2010/05/comparison-of-subaru-gear-sets-wrx-legacy-gt-sti-ra-and-more.html

[bbjones121]

Let me see if I can find the link to the transmission housing on a legacy being stronger as well.

[Rasmus]

Thanks for the link (http://flatironsrally.typepad.com/faq/2010/05/comparison-of-subaru-gear-sets-wrx-legacy-gt-sti-ra-and-more.html). The LGT gears do look beefier.

[bbjones121]

Sorry. Try it now
http://flatironsrally.typepad.com/faq/2010/05/comparison-of-subaru-gear-sets-wrx-legacy-gt-sti-ra-and-more.html

Hey Mod, Why won't this work as a link?

[rjh2pd]

worked for me. I stand corrected. I thought that Subaru beefed up the wrx gears in 05 or 06, i guess i was wrong.

[Samiam1017]

What's the differences in 05 legacy gt 2.5 heads and sti heads. What marking should I look for to know what's I'm looking at is actually what there saying it is. I have a 05 wrx I was gonna go hybrid since I bought a ej257 short block but I'm thinking just putting on stock 2.5 heads. Will these heads work. I thought I read they are the same heads but different cams. Thx

[HelluvaEngineer]

What's the differences in 05 legacy gt 2.5 heads and sti heads. What marking should I look for to know what's I'm looking at is actually what there saying it is. I have a 05 wrx I was gonna go hybrid since I bought a ej257 short block but I'm thinking just putting on stock 2.5 heads. Will these heads work. I thought I read they are the same heads but different cams. Thx

I believe they are the same. I think the only differences are the turbo, intake, injectors, intercooler, fuel pump and ECU tuning.

[fateo66]

What's the differences in 05 legacy gt 2.5 heads and sti heads. What marking should I look for to know what's I'm looking at is actually what there saying it is. I have a 05 wrx I was gonna go hybrid since I bought a ej257 short block but I'm thinking just putting on stock 2.5 heads. Will these heads work. I thought I read they are the same heads but different cams. Thx


I believe they are the same. I think the only differences are the turbo, intake, injectors, intercooler, fuel pump and ECU tuning.


Also, some early 05 LGT's have B25 heads which are the same as a 04-06 STI. However the late 05 and 06+ LGT's have D25 heads which came on 06+wrx's and not only flow more but also have more of a hemispherical combustion chamber which reduces knock and promotes even flame propagation.

Here is a nice link to a thread I started many years ago.

http://forums.nasioc.com/forums/showthread.php?t=1856856

also here is a few other useful threads dealing with flow characteristics of various subaru parts

http://forums.nasioc.com/forums/showthread.php?t=2229576

http://forums.nasioc.com/forums/showthread.php?t=2034555

I'm noticing more and more that people just do not read what is in a post before posting......

[philly15]

Does anyone know the dimentions of the 05+ LGT transmission? As stated the Lgt transmission has much stronger gears it would be well worth using if it will fit dimensionally into the 818

[Mechie3]

All impreza, 2.5RS, WRX, LGT, and Legacy transmission should all use the same case and fit in the 818 (all are 5 speeds). The newest LGTS (2010+ ?) have a 6 speed that fits in the 5 speed case. The STI 6 speed is a unique case that is longer and heavier.

[Xusia]

Oooh! Are you implying it might fit? Is it at least as strong as the 5mt? If so, THAT would be a nice transmission option! :)

[Mechie3]

It should fit.

There is one difference: The WRX (02-07 at least) have a speed sensor on the trans. The LGT took speed from the wheel sensor IIRC. You can add a sensor to teh LGT trans (friend did it when he swapped a WRX motor into a 2.5RS) but you have to drill into the case and add a plastic speed gear. Not sure all that it entails.

[THE ITALIAN]

Some of you guys are concerned about Beefier gears? Like the Roadster , we end up with 1000 lbs less do we not ? or about that so there will be a lot less stress on the trans

[Xusia]

Some of you guys are concerned about Beefier gears? Like the Roadster , we end up with 1000 lbs less do we not ? or about that so there will be a lot less stress on the trans

True, but some guys are planning on more than stock HP. There is also the issue of having 2 less drive wheels and how that affects forces inside the transmission.

[Xusia]

It should fit.

There is one difference: The WRX (02-07 at least) have a speed sensor on the trans. The LGT took speed from the wheel sensor IIRC. You can add a sensor to teh LGT trans (friend did it when he swapped a WRX motor into a 2.5RS) but you have to drill into the case and add a plastic speed gear. Not sure all that it entails.

So what does that speed sensor do? If it's just for the speedo, there is always GPS, but if the ECU bases decisions on that info...

[Evan78]

All impreza, 2.5RS, WRX, LGT, and Legacy transmission should all use the same case and fit in the 818 (all are 5 speeds). The newest LGTS (2010+ ?) have a 6 speed that fits in the 5 speed case. The STI 6 speed is a unique case that is longer and heavier.One fairly rare exception would be the 07-09 Legacy spec.B that I believe came with a 6 speed manual that is similar to (or same as?) the STi 6 speed. The 2006 spec.B came with a 5 speed.

[THE ITALIAN]

True, but some guys are planning on more than stock HP. There is also the issue of having 2 less drive wheels and how that affects forces inside the transmission.
Thats a dam good question and I think it should be guided toward FFR
there may be a balance issue with the internals ???
HEY YOU GUYS AT FFR <THIS IS A GOOD QUESTION
I found a good article on the gears and upgrades

http://www.turbomagazine.com/tech/0305_turp_2002_subaru_wrx_transmission_gears/viewall.html
How ever that is still a good question