I agree that placement has some bearing on how well the EXWG will work. But size is very important, and there are numerous other factors to consider.
For example, where is "optimal placement" (turbo engineers have done this for us, its right where the internal hole is), and is it practical for me to put my EXWG there? EXWGs are big and get very hot, and you have to find a place to put it where you can access bolts, and access belts, and not have it too close to anything to cause heat damage. This limits placement. I've placed mine where 80-90% of dsmrs place theirs.
Also, the size of the WG depends on overal system efficiency. For example, my boost creep (while on the enlarged internal) got a LOT worse after I installed the large FMIC, and thats when I realized I needed a much bigger/external WG.
Is something out of wack on my car? I doubt it. I think my car runs very well. It runs so well that I need very little exhaust pressure to run the boost levels I need. I think this means my car is very efficient.
Lets get back on topic.
Nick was asking if he should buy a 38mm or a 40mm. With a big FMIC, good intake, exhaust, and cams (heaven forbid if he ever goes 2.4L), I would suggest to him at least get 40mm, and bigger if he can afford it.
To suggest that all DSM'rs could get by on a 38mm, regardless of mods, HP levels(and all the other factors that determine WG size), if they could just put their WG in the right spot is poor advice indeed.
