I think a 4 cylinder would be a very big mistake. Especcially a 1.8 liter. The z's a 6 cylinder car, I wouldnt neccesarily car if its v6 or L6 but it would be like putting a 4cy in the challenger concept. Id like to see a dohc unicam strait 6 like honda dirtbikes. Nissan cant keep getting larger and larger a motor or we'd have a 560z, so probably just a 3.5 liter. At some point you have to realize car companies really dont care about the old z's design unless theyre loosing buisness and theyre a demand for a retro car. And from what Ive seen it doesnt look like 350z sales are slacking.