Subaru Engine Conversion, Getting lost doing an engine build... Options

[tmcquinn]

My buddy has recommended this board as a potential place to have a mature conversation about a Subaru build. I'd like to know if it's ok with you guys to start a thread here about that? I don't own a 914 but I do have a 987 if that lends me any cred.

Here is the story, as mercifully short as I know how to tell it. I bought a 2003 WRX with the intention of teaching my teenager about engines (which is working) and maybe getting myself back into the game. In retrospect, I didn't know nearly enough to start down this path, though I could say that about a lot of things that ended up being great experiences. Well, it turned out that the prior owner had blown the engine, put in another motor, and blew that one. It had 2 broken rods, broken pistons, and a crankcase that was chock full of chewed up parts. But here is the part that I failed to fully consider: the owner had a 2.5 installed in place of the 2.0 and then just had them bolt the turbo on it. I bought a 2.0 short block from Subaru, some nice heads, oil pump, water pump, timing kit, etc., etc. My goal is a stock 2.0 or close to it. In other words, the exact opposite of nearly every WRX owner on the planet. So now I am in the process of trying to figure out which of the remaining 2.5 parts can't or shouldn't be used when building the 2.0? I will eventually figure this out. But if a conversation like this isn't out of line on this board I would sure like some input from you guys.

[matthepcat]

Are you able to tell if the 2.5 liter motor was out of an N/A, WRX or STI?

You don't want to use the 2.5l heads on a 2.0.

Most of the accessories are interchangeable, but the injectors are larger on a 2.5l. Do you plan to have the car tuned or trying to run off the stock tune, you need to find out if the ECU is for the motor in the car or the original motor. You also need to find out if it has an aftermarket tune on it.

You can buy a http://www.tactrix.com cable to interface with the ECU and view the logs.

[tmcquinn]

Are you able to tell if the 2.5 liter motor was out of an N/A, WRX or STI?

You don't want to use the 2.5l heads on a 2.0.

Most of the accessories are interchangeable, but the injectors are larger on a 2.5l. Do you plan to have the car tuned or trying to run off the stock tune, you need to find out if the ECU is for the motor in the car or the original motor. You also need to find out if it has an aftermarket tune on it.

You can buy a http://www.tactrix.com cable to interface with the ECU and view the logs.

I'm pretty sure it was from an N/A. You can see in the paperwork where the shop tried to warn him about just bolting a turbo onto the 2.5. The new heads are installed now but I believe the tops of the turbo pistons have relief cut into them, as opposed to the old engine:

Old Engine

Yes, injectors are one of the things I'm concerned about. Thanks.

The prior owner left me a Cobb A/P in the glove box. I believe I can use it to set the ECU back to stock and create a log file if need be.

[matthepcat]

That is why the previous motor blew....wow. The N/A motor is higher compression and different rods & Pistons. The head design is also different.

Nice that the guy included the Cobb. That's like a free $600 and will give you all that is needed to re flash.

What are the smog laws in your area? Only reason I ask, is there is no downside to using that Cobb tuner and running a high flow exhaust for an extra 5-7lbs boost at no effect on longevity. My 06 WRX has been "stage 2" with a Cobb exhaust and tune for 122k miles. (Only annoying thing in CA is swapping out the exhaust every 2 years)

Are you able to tell if the 2.5 liter motor was out of an N/A, WRX or STI?

You don't want to use the 2.5l heads on a 2.0.

Most of the accessories are interchangeable, but the injectors are larger on a 2.5l. Do you plan to have the car tuned or trying to run off the stock tune, you need to find out if the ECU is for the motor in the car or the original motor. You also need to find out if it has an aftermarket tune on it.

You can buy a http://www.tactrix.com cable to interface with the ECU and view the logs.

I'm pretty sure it was from an N/A. You can see in the paperwork where the shop tried to warn him about just bolting a turbo onto the 2.5. The new heads are installed now but I believe the tops of the turbo pistons have relief cut into them, as opposed to the old engine:

Old Engine

Yes, injectors are one of the things I'm concerned about. Thanks.

The prior owner left me a Cobb A/P in the glove box. I believe I can use it to set the ECU back to stock and create a log file if need be.