FYI, he Japanese gentelmen's agreement you refer to was 276 net hp Also, there was no agreement between tho companies, tacit or otherwise. It all had to do with Japanese Grand Touring Car racing homologation, and it was almost immediately ignored by engineers at all of the major Japanese motor companies, and only really referred to in sales and advertising documents listing the vehicle specs for each company's halo cars (3000GT, Supra, RX-7, NSX, Skyline, 300ZX). Every one of those cars left the factory with over 300 hp. From Super Street:
The JGTC or All-Japan Grand Touring Championship (I hate to say it, but if you've ever played Gran Turismo 2 or 3 then you'll recognize the name VERY quickly) is a prestigious race series in Japan, similar to our NASCAR in popularity. It was created in 1994 and it's governing body the GT-A has VERY strict rules/regulations. The JGTC is seperated into 2 classes the GT 500 & GT 300; the numbers designate the ROUGH hp limits for cars competing in those classes. Motor swaps are restricted to the same manufacturer and the car's body MUST be mostly stock and fucnctional. Aero mods and suspension tweaks are the very limit of what is allowed, so in essense it is mostly stock VS stock, especially in the GT 300 class; are you beginning to see the picture?
While anything from Vipers to Ferraris to Lambos compete in the GT 500, the 300 is more homegrown. The cars that traditionally competed in the GT 300 class were the cream-of-the-crop of all of the Japanese auto manufacturers, and it's line-up consisted of cars like the Mazda FD-3S RX-7, the Mitsu 3000 GT (GTO) and afterwards the EVO, the Nissan 300ZX & Skyline, the Honda NSX, the Toyota Supra, and a few others. Ok, now are you seeing a logical trend here?!?
The JDM manufacturers wanted each of their flagship cars to be able to compete against one another without engine modification within the limits of the GT 300 Class horsepower limitations, so they all "claimed" that none of their cars made over 280 hp at the crank (but most of them underrated their vehicle's capabilities, in essense they all cheated). What better way to advertise your flagship car and prove that yours is better than your competitors than by having your mostly stock sportscar kick theirs' *** in the most prestigious, most watched racing circuit in all of Japan?!? It also made it easier for a potential team/owner to field a GT 300 Class car instead of a 500 because it was much cheaper since no engine mods would be needed. That made the GT 300 more popular than the GT 500, although the "big brother" Class attracted fans of the exotics.
Click the image to open in full size.
Thus, the hp "limit" was born, although it was mostly bogus, because for example, some "stock" RB26DETT's (R33/34 Skyline motors) have repeatedly dyno'd well over 320 whp, but the abuses of the rule were generally allowed/ignored because they (the JDM manufacturers) were all doing it, fudging their net hp numbers to gain an advantage on the track. It was only cracked down upon by the GT-A if the races became uncompetitive, as when the Nissan Skylines dominated in the mid-90's and were banned for a short time.
So there you have it. The reason why you are seeing and will be seeing more and more cars being produced that will exceed the limit is because they will not compete in the GT Series, so they see no need to restrict them any longer (but it's obvious that cars like the 350Z and R35 are lined up for the GT 300 & Honda will increase the hp on the NSX to possibly compete in the GT 500 Series in the near future, as will Toyota's new version of the Supra).
Anyway, The RB26DETT is a fantastic engine, but I'm pretty sure its overall length would prohibit it from fitting in an Xterra engine bay without extensive firewall modications. The AWD transaxle from the Skyline GT-R's would definitely not work the same as transmission/transfer case combo.
