The Renesis engine poses some very different challenges in a few areas due to very dramatic design changes made by Mazda.
DURABILITY- The six speed (or six port) has a very different track record when it come to longevity when compared to the automatic four port engine. I have been plaqued with 4- port automatic cars in which most have had three failed engines before the 100,000 mile mark with an average of 35K miles on them before losing part or all compression. One documentable Mazda replacement engine ran a dismal 11K after replacement. Although the six port (standard) has shown that it can last 120,000 miles in @ 60-70% of the units I encounter. Still the overwhelming majority of most of the RX8s I see, are exhibiting some sort of unacceptable starting or running at or before 100K
SIDE SEALING-. The side port configuration for both the intake and exhaust brings along with it some great basic engineering that has resulted in great horsepower gains, but it has also brought along a few basic problems. The exhaust exiting through the side plates create a large heat affected zone on the side plates. This same exhaust port design affords for a different configuration side seal which in turn fosters carbon build up. Additionally this angled side seal also has a smaller and unevenly loaded wear surface due to its keystone shape at both ends. This seemingly resulting in the side seal length decreases at a much faster rate than the old square cut side seals, thereby allowing compression to escape from the chambers- creating a low compression condition
OILING- Up until 2004 90% oil related failures I have seen were a direct result of operator error or neglect, either the vehicle was ran out of oil or oil changing was not done on any kind of regular basis. The majority of Renesis engines I disassemble exhibit obvious signs of low oil in the front rotor bearing. It may be that the oil coolers pathway being twice the length of the earlier designs, combined with the eight window rear stationary gear bearing may have significantly increased volume but regardless there has been a noticeable decrease in oil pressures, and starvation at the front rotor bearing is fairly common.
SSV/VDI - The controlling solenoids for proper VDI SSV operation are marginal at best. Resistance checks should be performed frequently, during rebuilding and whenever CEL is illuminated. Additionally the SSV tends to flutter and can make a clicking noise whenever cleaned and often after engine replacement. VDI/SSV sticking or being inoperative can reduce the performance of a six port to that of a four port and I have found multiple 4 port engines operating on the primaries (2 Ports) alone.
NOTEWORTHY** Online references published by major RX7/8 clubs I have found to be misleading and more often wrong than right. Recently I downloaded a wiring schematic for my technician, it was a simplified color wiring schematic published on a popular web site and it was found to be wrong in basic configuration, color code and flow chart when compared to the factory workshop manual.