Okay I am about to pick up a EJ25 Forester XT engine to transplant into my 1998 2.5 RS, and I wanted to know what the difference is between the XT and the STI engine. I am basically refering to internals since I know the turbo/ intercooler differences that exist.

 

Yep that is what I thought. Good to know since I already have an STi ECU ready to go. I'll drop this in my RS and it will be blazing!

 

In a nutshell, differences are turbo, uppipe, intercooler, cams, and ECU tuning. Short block is identical, headcastings are identical.

 

Are you sure regarding the CAMS? It's not that I doubt it I just can't find any concrete evidence one way or the other. I do know that the CAM caps are different as the STI (or some of them anyway) have facility to house a cam position sensor the same way the WRX does (you have to drill it) where as all Forester motors require you build a mount point for it.

Mike

 

Nothing concrete, just anecdotal. With the different turbos, it would make sense for Subaru to develop seperate cams for emissions and fuel economy purposes, as well as the extra emphasis the Forester has on torque and low boost threshold. I'll make some inquiries. I hadn't yet heard about the casting difference, that suprises me. I can't think of any reason to make changes to those.

 

I think the emissions and fuel economy is taken care of by the remapping of the ECU rather than different cam profiling although I am not 100% sure (I can look at the stock mapping tomorrow to see what it shows).

We have a couple of FXT motors at the shop and more importantly one in a car with a vf34 setup (WRX) so when the owner gets through breaking it in we should see how well it performs in comparison to the STI motor (on cars with similar mods).

Mike

 

Here's the cam pickup bracket required when using a FXT (or some STI) long blocks in a WRX when trying not to rewire the ECU and add the peddle box and associated equipment for DBW.

 

Well after talking with the APS guy today, I have a totally different plan for my car. I think I will be selling my RS to my younger sister, so she can race it.