^well not an RX7 really..the redesigned engines...the Spirit-R engines are a bit different than the older 1993-1995 and 1995-1997 3rd gen engines....intake/exhaust ports are bigger, repositioning of intercooler more to the front and newer apex seals and fuel map made the engine a bit more boost friendly (cause that was raised ,the boost that is, to help with the power increase) and slightly more 'detonation tolerable'
the renesis engines are much more reliable than the older rotaries tho...the whole build is different...ports are placed differently so the intake/exhaust cycles dont overlap as closely...icant find a cross section of both engines to show u but if i do i'll link u
there is a process that is done that realigns the entire lattice work of the metal that makes up the rotor housing, rotors, apex seals, and seal springs that makes the engine alot stronger in terms of tolerance to high boost levels and detonation n stuff called
cryo treatment sum to do wid liquid nitrogen n sheit...not sure how its done but i works

expensive like hell as u wud imagine but really great in the long run if u intend to push ur car really hard often (regular racing n stuff)
I do believe Honda and Mazda have it on the circuit
damn straight!

hope i helped a bit man...dragzter knows about the renesis build up more than me i'm sure so maybe he can explain why its better and more reliable