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Old 04-06-2013, 08:15 AM   #196
The Radium King
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Join Date: Apr 2010
Location: Canada
Posts: 3,122
ok, what I think I've learned:

1. as per all the previous posts, air box will fit. it has a larger intake, much larger filter element, and larger output (3.25" OD vs 3" OD) - it is an improvement.

2. remove muffler. easy, messy work with a dremmel. get one of those automotive plastic welding kits from ebay ($25) to fix any mistakes you make. use a piece of the discarded muffler to weld on a plug over the muffler hole with the welding kit.

3. intake has to come off.

4. engine lid tab has to be bent up.

thanks to byprodriver et al for helping me through the steps above.

5. there are two vent lines (I think they are vent lines) with a bulky bracket that sits right under the new air box. this bracket has to come off for proper fit. I am also going to saw off the stub bolt that mounts the bracket to avoid rubbing on the vent lines.

6. the oem air box mounts with three bolts. the 987 air box mounts with two bolts and a plastic press-on fitting. in the 987 the highest, furthest back mounting point is a stub bolt and the air box has a plastic fitting that presses onto this bolt. make sure you get this fitting when you get your air box (part # 987 110 141 00). take your original bolt, saw the head off and thread it into the mounting point. the new plastic fitting can press onto this.

7. the air box outlet has a flange designed to mate specifically to the 987 maf housing. realise that if you use this maf housing it has an ID of 3.25" so will not work with a standard 986 tune (the exception may be the 2004 anniversary edition, but this is a 7.8 dme flash and won't work with pre-2002 cars that have the 7.2 dme).

options are (1) try a 996 flash (don't know if it will work, but will find out in a month or so) (b) get a custom flash (big $$$) or (c) use a maf housing with a 3" ID. for 3" ID maf housings, the easiest is to saw the maf housing off your oem air box. note that you lose the screen before the maf if you do this and should sort something else out for this. otherwise, many bmws use the same bosch mafs as porsche, so you can get a 3" ID bmw maf housing with screen and use one of those (I have model numbers if anyone is interested).

the issue becomes mating the 3" ID maf housing to the flange on the 987 air box. easiest is to saw the flange off and get a silicone coupler that joins the two, but what I've found is that, while the air box outlet has an ID of 3.25", the flange itself has an ID of 3.5". I've taken a 3.25" to 3" silicone reducer and found that it is a press-in fit to the flange. to make it more robust I took a thin-walled 3.25" coupler and sawed-off a 1/2" band. I inserted this band into the 3.25" end of the reducer to reinforce it. now the silicone reducer sits very snug into the end of the flange.

this is still a work in progress, so I reserve the right to change my info at any time. again thanks to the folks helping me with this. I think that 997 plenum, 987 air box, tb and maf housing, and 996 flash is going to reinvent the 3.2 for little $.

Last edited by The Radium King; 04-06-2013 at 08:33 AM.
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