Back in 2023, when my original engine gave up, I decided to go a bit spicy. The same week my engine blew, a pre-built 13B/Renesis hybrid came up on marketplace. For those unfamiliar, a Renesis hybrid is essentially a 13B MSP where the exhaust porting has been combined with that of a non-MSP 13B. MSP stands for multi-side-port — meaning the exhaust ports are on the sides, on the side housings. On a standard 13B, the exhaust ports are peripheral, on the rotor housings. To build one, the recipe is simple: RX-8 side housings paired with RX-7 FB GSL-SE rotor housings. Mine is street ported, done using Mazdatrix templates. Some people swap rotors when doing a build like this, but I left mine as-is from the purchase — Renesis rotors with RA Super Seals apex seals and OMP deleted (premix ratio around 100:1).
One of the decisions I thought hardest about was the apex seals. A lot of people swap to RX-7 seals on a build like this, but I kept the Renesis ones. The reason: fitting RX-7 seals means wire-cutting the rotors and dealing with corner seal compatibility. RX-7 rubber corner seals tend to get clipped by the side ports, so you’d need solid corner seals, which kills compression. Keeping the Renesis seals was a risk to take.
For the exhaust, I had a custom log-style manifold built — five stainless elbows into a 2.5-inch pipe, with two O2 bungs; one for the wideband and one for the stock ECU’s closed-loop. I wanted to keep it quiet and streetable, and I’d say it delivers on that for now.
After almost 3 years and around 23,000 km, I’m really happy with how it drives. Low-end torque is noticeably better than stock (at least mine), and the power feels consistent all through the RPM range. I had a pretty prominent misfire early on, but it turned out to just be a fouled O2 sensor — easy fix once I noticed the AFR inconsistencies. Dyno is still on the list; my Jeep is simultaneously eating a good chunk of my budget in time and money.
The original build thread is up on RX-8 Club if you want to follow the full discussion.