What is the underlying source of HP increases from the introduction of the 13B in the 84/85 GSL-SE to the eventual 160 hp of late-80s naturally aspirated RX-7s?

Is it something simple like EFI programming, or more complicated like port shape/position, runner dimensions, or rotor weight/compression?

Reason for asking - our emissions window is 20 years. We will soon be allowed to run early 13Bs w/o emissions testing, but will have to wait many more years to do the same with 160hp versions. If it is an easy upgrade, one could buy an old 13B and tweak it w/o worrying about the sniffer.

Thanks.

 

Port differences, lighter rotors, higher compression, MUCH better EFI. There is a brochure on my website for hte '86 RX-7, which basically explains it...http://www.aaroncake.net/rx-7/media.htm

 

you do realize that you still have the fastest na rx7 produced though don't you? i mean it only beat the s5 by like .2 or something in the quarter, but its still the fastest.