Hey sorry for taking so long to respond! The new post e-mails weren't working for this thread for some reason
mele63 -- we'd like to get some housings in stock and do just that, and we will eventually but that takes a while to get a core exchange running smoothly where people aren't waiting until we get cores back from customers. Anyway, it wouldn't be the entire turbo, it would just be housings. Since the cartridges are wear-and-tear items and condition can be very different and very hard to determine, we don't want to be sending people turbos that aren't theirs. However, the housings are a different story and as long as they're physically okay, which is easy to tell, it's just fine. So.... we'd ship you a finished turbine and compressor housing, you'd swap them for the stock ones on your turbo and ship the stock ones back to us. Don't worry, it's REALLY easy. Anybody can do it, I promise. Way way way easier than most people assume
We've had a few customers purchase used stock turbos and send us the housings or the whole turbo. When they get the turbo back, they put the housings on their cartridge and sell the used one they bought. You'll break even and you wont have any down time.
Bu11dog2 -- quicker spool and better response is a big thing. The improvement depends on the particular turbo and how good the castings were to being with and how good the cartridge is, etc. My VF22 hit full boost about 300 rpm quicker than it did prior to P&P. Also responds better on and off the throttle and after shifts and whatnot. 100 to 300-or-so rpm is pretty typical. Because the efficiency does go up, it's usually good for a couple ponies. But I would not call this a power modification. Some turbos are bad enough that they actually will push out more air afterwards but not all. Let's just say I wouldn't expect to gain power, but if you do you shouldn't be surprised
. ...and the other benefit is a good reduction in underhood temperatures because of the barrier coating on the exhaust housing.
Worth it is a personal question, of course. It's not the cheapest thing in the world so that's up to you. I think it's money well spent when you buy a new turbo and get it done before installing it in the car. ...you want the most out of your new setup and you've spent lots of $$$ on tuning, injectors, pump, turbo, and all sorts of other goodies so you want everything working as well as possible. That's most of the turbos we do, btw. Probably like 75%. The remainder are turbos that people take off of their car to have done.
SC GT -- MadDad/GT Spec have a very large uppipe diameter. Unless you're running a massive turbo, porting to match that diameter is not going to be possible. Well... possible, but not advisable. Matching the diameters is good because it makes for the smoothest possible flow with the least turbulence. One of the worst places for turbulence is immediately before the turbine so it's a good place for a smooth transition. Additionally, if it's going to be off one way or the other you would want the uppipe to be slightly smaller than the turbine inlet. With the lip on the inside, it will not cause exhaust pulse reversion like large uppipe/smaller turbo inlet will, and it will actually help bounce pulses back into the turbo. Also, a transition in that way doesn't cause as much turbulence as going from large to small via a 90* lip. ...and.... more volume in the pre-turbo exhaust means lower velocity and energy and slower spool. You're supposed
to have high pressure in the pre-turbo exhaust, and you do not want more volume than necessary.