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TURBO 2.5's!! Look in HERE if you can add!


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Hey guys I picked up a 99 Legacy 2.5GT Limited last spring. I've been looking all over the place to try to find some information on other guys who have these and have perhaps turbo'd them, but I cannot find guys here in the states anywhere who have been doing them. I've done 7,8 Honda homemadeturbo setups so Its not a problem for me to do this to my subaru.

 

The only problem I'm having is finding out what other guys are doing for TUNING on their setups? I'm not overly familiar with the subaru world too much, but I've been told that there was a turbo 2.5 legacy that generation as well-just very rare.. although I have not been able to find that to be true. The other thing I was considering was to try to get ahold of an ECU from a Outback XT (the submodel may be off) but I heard they were 2.5 turbo from the factory.

 

I refuse to run an AFC hack as they arent real tuning, but there is no excuse to buy an expensive standalone. I'm only looking to boost it to get around better.

 

I'm sourcing a .42.48 T3 which came on the old Dodge Daytona Turbos and was looking to run only about 8psi. I like the car, it's just too turd for me. I regularly have a full car of people all the time and need more help gettin her up hills in the country. If anyone has experience turboing their 2.5's or know some leads on what guys have done.. POST UP! I look foreward to finding out what other guys have done.

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^^ this. easy enough to do if you know what you're doing. If you were to turbo your 2.5 and the headgaskets haven't been done, then you're only asking for trouble. Take the 2.5 out and build it if you have the time, patience, and money. New gaskets, valves, cam, crank...go crazy with the internals if you'd like. OR: drop in a wrx 2.0.
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Yea 2 weeks after I bought it I pulled the motor to fix both popped headgaskets. I also did the timing belt/water pump while I was at it along with 4 of the timing belt pulleys and hydraulic tensioner were all shot.. I've wasted TOO much money into this motor already doing upkeep/maintenance to just toss it and buy a WRX motor. I'm not looking for POWER, only some assistance to get my car around. I can build the entire turbo setup for about $550 in parts including doing a front mount intercooler setup for better efficiency. I just need to figure out the management issue... would a WRX ecu though being for a 2.o motor run the car addequately along with all the emissions systems on boost? not sure..?
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The USDM EJ25 didn't get a turbocharger until 2005. Before that there are no 2.5L Subaru motors that came from the factory with a turbo unless you go to Japan. There was a USDM EJ22T turbo with a closed block but in stock form it puts down about the same power and torque as a stock EJ25D, only without the head gasket issues and with turbo lag. The fact that the EJ25D didn't get a turbo is a good thing, since they tend to eat through head gaskets when naturally aspirated. Boosting them would just make them blow faster.

 

 

If you were to get custom gaskets made to lower the compression ratio a tad you could boost this motor a bit, but depending on the mileage of the engine, cylinder pressure, and the fact that the EJ25D is a completely open deck block I wouldn't push it past 6-8 pounds of boost.

 

 

I would stick with the stock ECU. If you go with an ECU that's older, like the EJ22T ECU, you won't be able to get an inspection sticker since the car won't be OBDII compliant. If you go any newer, like an EJ251 or an EJ253 you're going to run into problems. The EJ251 had a MAP sensor instead of a MAF sensor and the EJ253 had variable cam timing. You could use an EJ252 ECU but it won't net you any performance gains since its pretty much the same thing as the EJ25D ECU.

 

 

If you used the ECU from an EJ205 from a Pre-2005 USDM WRX you would run into problems as well. The EJ205 in the USDM WRX has a coil-on-plug ignition design, unlike the EJ25D engine you plan on using which has coil-pack ignition.

 

 

Just stick with the EJ25D ECU, it should be plenty good enough for light boost applications. Just make sure to get an ECU for the correct transmission you plan on using. This isn't hard since there are only two transmission types. The 5MT and the 4EAT.

 

 

 

 

 

Whatever you decide to do, welcome to the forums. Hopefully you will soon realize that the balanced design of a Subaru boxer engine is far superior to any I4 design, which requires heavy counterweights, heavy harmonic balancer, a heavy flywheel, and in the case of engines over 2.0L heavy balance shafts. So much parasitic loss just to keep the engine from shaking itself to pieces. Its all in the name of cost effectiveness and space requirements of a FWD transversely mounted driveline. The Subaru bottom end is also WAY tougher than an I4 engine, since they do not have main bearing caps or a main bearing bridge. Instead they have two block halves that bolt together around the crank. In order to blow the bottom end out of a Subaru motor, you must literally rip the entire engine in half. That, my friend, ain't never gonna happen. The low profile of the Subaru engine also lowers the CG of the car. The longitudinally mounted driveline makes for perfect left-right weight distribution, whereas a transversely mounted I4 design has the heavy engine on one side and the light transmission on the other side. Both front CV shafts are of equal length as well, rather than in a transversely mounted driveline where one CV shaft is significantly longer than the other which can actually impact the suspension geometry of the car in negative ways.

 

I hope that in time you will come to see the light, but if you don't I still wish you luck with this car. I always loved the look of a 2nd gen GT. :)

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Hey Plat_Racing,

 

Thanks for all the insight on the situation! That really is a great introduction to Subaru management systems and their setups. I really appreciate the help. On my hondas they only used MAP sensors, not MAF sensors so I'm still getting used to that too.

 

On my Honda, the factory NA MAP sensor was still able to read posative pressure up to 11psi so I was able to run it without a problem, just using larger fuel injectors than the stock 240cc injectors. Usually running DSM450cc injectors and chipping my ecu with correction on the fuel map for the larger injectors out of boost..

 

~If I was to run a factory EJ25D non turbo ecu that came in my car, there would be no way to run larger adequate fuel injectors without going mad Rich out of boost, and without going with larger injectors.. how much hp will the stock injectors support?(any idea the size of them?)

 

~Also, will the stock MAF sensor read positive boost pressure?

 

I'll try to get some pictures posted up soon,.. and I'm just keeping my 5MT

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~If I was to run a factory EJ25D non turbo ecu that came in my car, there would be no way to run larger adequate fuel injectors without going mad Rich out of boost, and without going with larger injectors.. how much hp will the stock injectors support?(any idea the size of them?)

 

I'm not sure how big the stock injectors on the EJ25D are, but you could probably get some injectors from a turbo EJ255. There are tons of options on the market. You can surf around on www.Boxer4Racing.com and find all sorts of performance parts. Boxer4Racing has 550cc, 660cc, and 850cc injectors from some company I've never heard of, and 800cc injectors from an aftermarket company specializing in Subaru parts (Perrin). I have never tried it, but I would think you could run up to 200 horses on good quality new or rebuilt OEM injectors.

 

~Also, will the stock MAF sensor read positive boost pressure?

If you want to try and hook a boost gauge up to the MAF sensor it won't work. With a MAP system like the Honda motors you're used to the MAP sensor reads the pressure inside the intake manifold to determine how much fuel the engine requires to maintain a proper stoichiometric air/fuel ratio. The EJ25D has a MAF sensor. Instead of having to read positive intake pressure it would read how much air the engine is consuming, including the air that the turbo is forcing into the manifold. In short, it will read how much air is moving into the turbo, not how much pressure the turbo puts into the manifold. You can mount it either before or after the turbo. There is a lot of debate out there on which is better, but it would seem to me that if you mounted the MAF sensor before the turbo right after the filter be better off. The further away from the turbo you put the MAF the better.

 

The MAF system on the Legacy only reads how much air the engine consumes at the filter. The MAF sensor is just a heated wire (Like the heating element in a toaster) and a temp sensor. The temp sensor tells the computer what temperature the intake air is at and the heated wire is used to tell the computer how much air the engine is consuming. As the intake air passes through the MAF sensor it cools off the hot wire. The computer will increase the electrical current flowing through the wire in order to maintain a consistent temperature. The more air the engine draws into the turbo, the cooler the wire gets. The cooler the wire gets the more electricity is needed to keep it heated. The computer can then figure out how much air the engine is consuming by looking at the temperature of the intake air and how much electrical current it takes to keep the heated wire at a consistent temperature.

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If I may, I have a little experience with building EJs & I'm going to tell you straight out that the pistons in an EJ25D are not built for very high boost at all, never mind the head gaskets. You're good for about 10psi max. Still, there is no need to drop in a WRX engine (2.0) as you'd be losing a lot of displacement. If you ever plan for a block swap (if the 2.5 thing doesn't go well), 2.2s are about as available as tap water & their internals are no weaker than a USDM WRX engine. Just swap your heads/parts onto it & enjoy. If not, there is a WIDE selection of parts in the aftermarket for the 2.5. Either way, you won't be out of luck :)

 

A lurker's 2 cents.

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