So there is a little known fact that the xi only comes with and a oil cooler if spec'd with the sport package AND the 18" wheel package. It is also limited to 135 mph without the 18s but the COBB AP took car of that...
Mine was spec'd with the sport package but not the 18" wheels so no oil cooler.
The options for aftermarket oil coolers are AR (smallish, really meant to augment the stock oil cooler, that I don't have), Stett (great option but pricey), and the place with the dual oil coolers that was going to be $2500 (Ultimate Racing??). Anyway, the Stett option is a grand but only if you have the factory setup. I did not and so it was around $1500 all said and done. I wasn't willing to spend that much and figured I could do it on my own for cheaper.
Step 1 - get an oil filter housing with thermostat capable of using an oil cooler. Mine was not setup for that and there is no way to make my stock housing work. I could have ordered the parts from Tischer but figured I'd try the salvage yards. Car-part.com does not list the oil filter housing as a separate item so I just called the yards that had long blocks for sale and asked. I would email this pic to make sure they had what I wanted.
This is my actual engine bay. Again, suck.
Luckily I found a shop that had the parts in Houston and $225 later I had the oil filter housing and thermostat.
Now the tricky part. How do you get that housing to fit aftermarket stuff?? Stett would not sell me their block off plate by itself and the $2500 oil cooler shop would not sell me their fitting either. Undaunted, decided to tap the thermostat housing with a 3/8" NPT fitting and run a 3/8" NPT to -8AN fitting. -8 AN is the same size that the Stett system uses and it sizes perfectly to 3/8" NPT. If you want -10, you need a bigger NPT thread. Tapping this thing is no small deal. I needed a vice, a friend, a big tap holder, and a break when it was all done. That's a big tap... If you already have an oil cooler, you just order the thermostat housing (iirc it's less than $100) and have it tapped.
Next up: mounting. The next several images are me looking at the space and identifying the right size cooler.
Close up of the brake duct with the cover on the mesh removed
half of the brake duct
Cover on the mesh - I removed this of course.
Duct out and fully assembled
There's a screw holding the duct in place in the front of the car that holds onto this tab.
The screw is on the opposite side of this plastic area. Sorry, best I could do.
The next four are of a box that I used to size up the area. It's tough to get an idea of how much space you have without something to reference by. I figured others might be able to use this.
I settled on an Earl's 34 row narrow cooler. This is not as wide as a SETRAB cooler so the capacity is lower but it's probably double the stock cooler. I bought my -8AN fittings, adapters, cooler, and lines from anplumbing.com which is the Earl's store. I spent a lot of time researching the parts I needed but went with the black Ano-tuff fittings and Pro-lite hose. All of the hoses have a 300 deg F tolerance and I didn't want to mess with the wire braid. I believe Stett uses this as well. They have great videos of how to make the AN fittings go on the braided lines. All in all it was great experience dealing with Earl's. They're always willing to answer questions and even took returns when the 60 deg fittings I bought didn't work for the space. I ended up with the 34 row narrow Earl's cooler, 7 ft of Pro-lite hose, two 3/8" NPT to -8AN adapters, two 45 deg -8AN fittings Ano-Tuff, and two 90 deg -8AN fittings Ano-Tuff.
Now we're on to mounting the thing. I have spent the most time with this part. It's is VERY time consuming and frustrating to try and develop a mounting strategy with home depot brackets and a dremel tool... I eventually just bought some steel angle that had holes and went to work. I'm sparing you the THREE different SETS of steel brackets made and just showing the final option. I made these, sanded and painted them and then glued cut up heater hose on the side that will contact the frame rail.
I'll be essentially squeezing the main frame rail with these two steel pieces and mounting the cooler to the outside steel. This way I don't have to drill anything into the car. That's my personal preference and others can do as they wish. I just didn't feel comfortable drilling there.
Next we have to make the cooler attach to the steel. I bought a $45 piece of Al angle and went to work with the dremel tool to make the upper and lower brackets. All coolers are made to work with brackets. YOu should not try to use the cooler top and bottom to secure the cooler. They are not strong enough. I got the idea for this design from the brackets that are actually sold for the Earl's cooler. I need it to extend out on one side so I just made mine. I have a love/hate relationship with my dremel tool now - especially since THREE separate SETS of Al brackets were fabbed before this one...
Note the notch. It plays an important role.
Cooler mounted: The notch holds the cooler in place so the squeezing steel brackets don't slide down the frame rail.
Top view from engine bay. I put heater hose around the bolts to cushion everything.
More views of the mounted cooler
Now with the lines
My fender liner was cut all to hell during several mock ups. I'm ordering a new one because these NUMEROUS cuts aren't necessary but this gives you an idea of the tightness.
This is a view without the fender liner of the bottom of the cooler when mounted. It's real close with the 34 row cooler.
Here's a shot from the front bumper mesh. I never removed the bumper during the whole thing.
More shots from the mesh. Note the notch doing its thing.
One thing is clear. I need a new Iphone with a better camera....
I painted my oil filter housing with caliper paint. I never understood why BMW left it bare Al as it just oxidizes and looks like shit. I followed this DIY for removing the intake manifold. http://www.e90post.com/forums/showthread.php?t=520922
but got to the part with this bracket and gave up.
I could never get mine off and didn't want to spend too much time fooling with it.
Turns out you can remove the oil filter housing bolt but just lifting the intake manifold with all of the nuts and bolt removed. It's a pain but it does work.
I don't have pix of the install as time was short but here are some shots of the lines on my housing, etc.
More with a POS LED flashlight. Ooooh blue....
Not wanting my lines to rub. I'll be ordering an Al line holder from anplumbing to pretty this up.
I let the car idle for about 20 min while buttoning everything up and promptly beat the shit out of it. Oil temp never went over 245 and the cooler was hot. I'm guessing that's what my thermostat opens at. I was going to remove it altogether but read the Mr.5 thread about the housing and from it it seems without the thermostat, the oil won't go through the cooler. If anyone knows differently please post up. I don't like it that high but I doubt it'll go any higher...