Eric HSU
www.beyondthedyno.com/blogs/eric
Fact: Eric Hsu will be picking his favorite tech question for each installment of Question IT over the next few months, and we'll be hooking up whoever submitted it with some new threads from our go-fast homies at Eat Sleep Race. This month it's Justin White, whose rational engine swapping question (a Question IT first?) garnered a response from Eric other than "Don't do it." Good enough for us.
Send good questions; get free gear. questionit@importtuner.com
This Month's Winning Letter
Open Heart Surgery
I own a '95 Subaru Legacy that I would like to modify and was wondering if I would be able to transplant an EJ25 from a WRX, including the driveline and ECU. Is it really worth doing? I love my Legacy and would also love to do something different than the typical Subaru.
-Justin White, via importtuner.com
If you want your Legacy to have more balls overall, then I'd say it is definitely worth doing. The increase in displacement plus the turbo is going to be the best route for a sizeable power increase. What's more is that the engine and drivetrain bolt right in. However, the ECU from an '06-and-later 2.5L WRX probably won't be happy in your '95 Legacy since it will be looking for the CAN data stream from other computers present in a WRX, such as the ABS, Body Module, Air Bag Module, etc., and will require the throttle pedal assembly from a drive-by-wire Subaru. So if you must stick to a factory ECU, I would recommend:
1. An EJ255 from an '06-07 WRX, an ECU and engine harness from an '01-04 JDM STI that runs the AVCS variable intake cam, and an '02-04 WRX throttle body because the JDM ECU uses a cable throttle body, making your life substantially easier in the compatibility department. Since you aren't using a drive-by-wire ECU and throttle body, you will not need to install a throttle pedal assembly with a position sensor. You will, however, need to run a JDM intake camshaft in the engine since the cam triggers are different.
2. If you can live without the AVCS, then get yourself a 2.5L short block, a pair of good condition '02-04 2.0L WRX cylinder heads and cams, and a Cosworth 1.5mm EJ25 head gasket, and then use an '02-04 WRX ECU and engine harness. This method is going to be cheaper overall and less hassle, but you won't have the benefit of AVCS, which can offer substantial increases in mid-range power. But still, a turbo 2.5L is still a massive increase in power over your existing configuration.
Either way, you'll need to do something about the hoodscoop for the top-mount intercooler, or you can have a front-mount intercooler built for even better performance. I might suggest also finding yourself a set of '04-05 STI Brembos for increased braking performance.