| first off let me start by saying that I only half know what I'm doing, so corrections and input are appreciated (lookin at you aliaZ) What I started trying to do was to compare the compressor maps from the BW6758 and the GT3071 to see if I could glean any information. This particular EFR turbo is selling ofr just over 1500 each, and it's unsure at this point whether or not they will work in the stock location. the length of the snout on the turbine housing seems like the biggest hurdle. In any case I found a compressor map for the 6758 HERE but quickly found it was useless for a visual comparison since the scale and units were off compared to the maps Garrett puts out. So I traced the map in photoshop, did some math the convert the units and scaled it to overlay over the 3071 map i pulled from ztechz.net. The 3071:
 and the modified 6758 map using the same scale:
 I put those first because when they are overlaid it's pretty tough to tell what's going on:
 Now for my rudimentary analysis. From the looks of it, the EFR can reach the same pressure ratio as the 3071, but has both a better surge line, and a better choke line, meaning that it has a much larger operating range, sounds like a dream right? well I did notice one caveat. The efficiency islands on the EFR turbo are much smaller, and the EFR caps out at 75% efficiency while the 3071 goes up to what looks like 78%. To illustrate this I highlighted the 74% efficiency islands on both maps: 
so what does this mean? well I'm not entirely sure, and I'm hoping some of the more knowledgeable members here can help me pull together a complete picture. what it seems to tell me is that while the EFR operates better under a larger set of conditions, that it is less efficient and will heat up the charge air more than a 3071. This is probably completely wrong, so please chime in
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Comparing EFR6758 to GT3071 compressor maps. - 
