Sweet, this is coming along really well. Nice detail with the bolts but if you need a few more polys, they'd be the first to go in my opinion. You could probably optimise the inside of the big rim on the turbine itself, the one with the square bits but that might be a last resort (reducing the inside rim from 36 to 18 sides). The little tube thing below the turbine could be optimized a bit too, the thing that is directly beneath the cone+fans. It looks like it's roughly 16-20 sides at the front, could probably do with being halved without looking too bad
