I looked at going bigger turbos or turbo. My BNR34 N1 turbos supply plenty of power for an all rounder (440HP at all four, 500 RWHP, 600 ENGINE HP) so i have decided to keep the setup the way it is.
A friend who has a fairly standard 32GTR took my car for a drive and felt no difference in drivability from his except my car came on alot stronger once coming onto boost and then much much stronger from mid range to top end.
Turbos arent the be all and end all...I know another GTR that has a shmick HKS t04R kit on stock engine with the right fuel and ignition timing tune and right fuel mods. The thing only makes 385 RWHP compared to my 500RWHP and my turbos are rated at 100HP less air.. I think alot of it is due to camshafts, intercooler, oil cooler and all the other bits that add up at the end of the day.
Ive driven a gtr with a big turbo and was not that impressed. I driven gtr's with smaller bolt on GT2540 & GT2530 kits that are nicer to drive and actaully feel like they have more stomp because you can actually feel the torque working to youre advantage, not frying the wheels.
SydneyKid is right, im not aware of any quick tsukuba track cars that make much over 650HP. I once read an article (attempted to read) from option magazine that was showing the power difference to weight advantages of big turbo kits on track cars.
The big turbo kits weighed more, developed power at the wrong time and within too narrow a power & torque band, the cars required much large brakes & clutches and hence even more weight, bigger fuel systems were needed, fuel economy was down and engine rebuilds were a more common occurance.
The smaller turbo kits supplied broader power and torque bands, required smaller lighter clutch and brake setups with less reciprocating mass, used less fuel and had lighter fuel systems by carrying lighter loads, engines lasted longer so more time was spent tuning suspension and lap speed..
Not all of the above principles relate to street driving, but most do. Big kick arse turbos are good for two things: 1. Gloating horsepower sheets to your mates 2. Drag racing
If you want an all rounder with shitloads of power under the foot, go buy a set of Apexi t517/8Z low mount turbos, HKS GT-RS or a set of td05-20g high mount turbos, im sure if Kier Wilson decided to go track racing or all rounding instead of drag he probably would have kept his smaller td05 or small td06 turbo setup, over the larger ones he runs now.
TG