Renesis will undoubtedly get a better specific fuel consumption than a PP.

  So for those that want the utmost in power, it sounds like the PP is the
way to go.  For other cheap old chaps the Renesis would appear to offer a
cost effective power increase.

Ed

Here Ed I have to totally DISagree. The side ported engine is used to provide more power, and has bigger side ports only workable with the Renesis, but must also pass smog regulations and provide low-end torque for car use. The need for the higher redline is the total giveaway. For ANY i.c.e. the key to higher bmep is higher RPM. Spin your 13B to 9k and provide it with an adaquate intake and exhaust I would bet money you will be within a few HP. While I don't want to sound like a broken record, and certainly not trying to be contentious, Mazda built the 26B for use in a race using an economy formula. If side ports were more efficient they would have used them!  P-ports make more power, but in the low to midrange so critical in a car they are much dirtier on HC. I really believe that the Renesis came from Mazda's hydrogen experiments. The ability to produce large ports WITH NO OVERLAP was critical to the success of that project. Much talk has been made of the fact that p-port rotaries have considerable overlap in the exhaust to intake phase. So does every high performance piston engine ever built. Tuners have even found the overlap phase to be beneficial to performance when the engine is properly tuned. The reason for the renesis is IMHO the need to pass smog and provide competitive power, Not that the Renesis is the "best" configuration. I'm glad they're building it since it is the key to Rotary survival. I simply harbor no delusions that Mazda wouldn't run a p-port with variable length intake tract if smog and noise would allow it. The advent of truly functional Direct injection may make the return of p-ports possible, but there is now a lot of inertia against them.

 As for cheaper I agree. Anything over-the-counter is a less expensive solution! 

Bill Jepson