I am kinda stuck between these two turbos and have not found much info on the net. But I also suck at searching the net so I figured I would post on here to see if anyone has compared the two.

 

If i remember correctly the GT-K 850 is their 72mm, like the older Super-72. It's a good turbo, personally I don't think (I should say I haven't seen) anything in that size range out pace the billet 71mm BW...it's just an excellent wheel. I'd probably go that route if I were you. I just got one of them for one of my customers cars, it's only 134 ci so we'll see how it does. The GT-K series for the 72 and 76, if I remember my conversations with them correctly use a ~3.2" ish turbine wheel which is about the same size as the GT42 and the S400SX.

That said, remember there are two S400SX offerings, one is the 71, one is the 75.

 

GTK turbine wheel is smaller (3.11ind), but very efficient with its new re-design. The pitch is very aggressive and the Bwidth on it is also profiled for high flow without low end sacrifice. The 400SX will lag a good bit more,since its a larger wheel, heavier assembly, but the compressor wheel does make up the difference on the top end. The 400SX uses the standard 71mm and 74mm comp wheels used on the DD series BW's. Also the 71 used outflows and out pressures the Triple K billet 71.

Jose

 

Thanks for the feedback, I am thinking about the 75mm SX. I just did not know if it would be any real advantage over the BW to spend the extra few hundred dollars on the GT-K. I am not really worried about lag since the car is built for open track/ solo, street driving, and the ever so seldom top end blast, I doubt that I will ever take the car to a drag strip since I have had my fill of the drama that is always there. I just wanna have fun again and have something that makes pretty good power on pump gas. I know it sounds over kill but here is my build list so far, R blocked long rod 308, Victor JR heads, Victor 5.0 intake, 75# injectors, FAST bank to bank, 5 speed, 3.55 gears, and the cam is still in question but I will see what I can come up with.

Thanks again for all of the help if you have anymore input please feel free to add it.

 

Good info Jose, I didn't know they were running a different 71mm on the S400SX, but you're saying it's superior to the Billet 3K wheel used on the PT71's - good to know. When I talked to turbonetics, they were telling me it was a 3.2" wheel, I know their "S Trim" turbine is a 3.11 and they modified that for use on the Super T72 and T76, I guess it just carried over and they can build them with the 3.2" wheel.