Whatever some of you guys are smoking, puff puff pass I want some
If you put a 4 cylinder in a Z then it will be called a Silvia/240SX instead, which I really wish they would do, and more in the range of what is being talked about. 2800lbs or less, 4 cylinder turbo direct injection 280bhp, 270ft.lbs. 8000 redline FTW
The history of the Z has always had some sort of 6 cylinder in it, and Nissan tends to be a bit purest. It would be nice to see them put a little forced induction back in to the Z, and bring back the twin turbo, but I personally highly doubt we'll see a 4 cylinder Z in the future, but more along the lines of a new model or the rebirth of an old one.
From looking at the data of new turbo 4 cylinder motors that are being produced it would probably look something like this realistically for a 4 cylinder Z based on what is out there now, and some future motors. Most likely you would be looking at maybe 50 to 75lbs of weight reduction if you're lucky, if it's still in the Z34 chassis. A displacement size 2.0L to 2.6L, direct injection, turbo charged. No more the 300whp but mostly likely in the 270whp range. Torgue is a real guess anything from 200 ft.lbs to 300ft.lbs. depending how high strung they make it. I think we would be really lucky to the higher side of those numbers.
Right now I think the only 4 cylinder turbo gas engine Nissan has is the 1.6L MR16DDT which makes 188bhp and 177ft.lbs. and comes in the Juke, and the same motor is used as a base in the Deltawing. The only other gas turbo motor in Nissan's line up is the GT-R's VR38DETT. That might give you an idea where Nissan's head might be at.
I've seen a few 350Z's with the SR20DET which isn't the best motor but it would be fun as hell. Here's a video of one.
I was told there is almost zero weight saving between the VQ35HR and the SR20DET both weigh in at around 330lbs.