[SamuraiSam]

Dear god. Don't read AshFrancis' post. Don't listen to somebody with back-to-back hands on information. Don't listen to any of those 2530 fanbois.

/sarcasm.

AshFrancis, it's good to hear, always, about solid real-world experience like you have. Thank you for posting.

I think a good analogy to the "everyday around town car" people that like N1's, or GT-SS, or GT2860-7's, is to compare those to a stock turbo on say a Volkswagen 1.8T. The auto manufacturer in that case was not concerned about absolute performance, but more about the perception of speed and lack of "Turbo Lag!!!" for the uneducated end-user which generally has little to zero high-performance driving skills. The turbocharger (a Borg Warner K03) develops lots of boost at low revs way before the engine reaches peak VE (which is analogous to peak torque on an NA engine or depending on how you look at volumetric efficiency vs pressure ratio) but is absolutely outflowed and chokes and dies at higher revs.

The benefit is that there is quite a bit of low-end and midrange power, and the drawback is that the engine is severely limited with top-end power. N1, GT-SS, GT2860-7's, stock turbo cars will all puke-and-die at the top end of the rev range, which is the tradeoff for lower powerband performance. The example is absolutely nowhere as extreme as the K03 on the 1.8T example, but in either case, in my opinion it is an example of poor turbocharger selection. The reason is that on-boost around town performance is not one of my required attributes when selecting a turbocharger, and I think that anybody who "requires" such on their high-performance sports car, "Poor man's supercar," is an idiot (at least in that respect. Or maybe just uneducated, or needs more work on their driving skills.)

GT2530s are a good match for the RB26 because they exhibit as much midrange power as possible without choking and dying up top, and the result is much more power and more "area under the curve" when you compare torque curves from a GT-SS car to a 2530 car. Area under the curve is THE THING that matters.

reza168, to answer your question, the car will not really lose boost, but as the turbos become less efficient they will overall flow less air and fall off performance wise in the upper revs.

If you go for 2530's i'd install some Procams not Poncams. Bigger cams mean more area under the curve, even if (due to overlap, can be tuned by playing with cam gear settings) they cause the turbocharger's boost threshold to rise ever-so-slightly, the overall power gain far offsets it.