the 17 is a bigger turbo, has a stronger main center shaft design than the vnt 15, bolts right up with a clip hose adapter and a modification to your factory vnt-15 exit hose and can handle more boost than a vnt-15.
HOWEVER, if you like the fun noises that a VNT-15 can make with an open exhaust you WILL miss these when you go to a VNT-17. it is just NOT as vocal as a 15.
FWIW, I put a 17 on my dads car after he blew up his 15 after getting a chiptune. (he is hard on cars) I did not however get his tune updated and his turbo lasted right up until the time he was pulling a hill full power and his timing belt let go.. it was for some reason rubbing against the tensioner sides and was about 2/3 a wide as it should have been so it just gave up.
anyhoo, a 17 is a great choice for mild tunes/injector upgrades when a 15 isn't able to produce/sustain the boost needed to keep the exhaust clear.
Thanks for the info but I was curious about something still ....
Boost level for boost level, does the 17 offer less resistance to flow (most likely exhaust side or maybe intake side ) compared to the 15 ?
Reason I ask is because in my readings, I have heard it said that the turbo is actually the most restrictive part of the exhaust system ... I am wondering, if the 17 is freer flowing in any way maybe it will help MPGs ( as compared to a car set up with the 15) if one is not driving aggressively ?
Or maybe put another way, if 2 cars are set up identically (with the exception of the turbo) at any particular level of boost which car would get better fuel mileage ?
On the flip side, If 2 cars are set up exactly the same except 1 had a 15 with optimized tune and one had a 17 with optimized tune , would one car get better fuel mileage compared to the other when driving in the same manner?
It is interesting to learn about the turbo sounds .... at some point in the future I will be getting an exhaust system but for now still stock ... cat and all
Thanks
Andrew