Copyright jalopnik
For better or worse, Mazda and the rotary engine are connected like vintage champagne and Gouda cheese. The rotary has since made a comeback in the Euro-only Mazda MX-30 Skyactiv R-EV, but it has transitioned into a range extender instead of a high-revving, oil-drinking yet silky-smooth powerhouse. However, nothing compares to the FD RX-7 and its twin rotor, twin sequential turbocharged engine, which we called the most intense bone stock car that you could get your hands on. Mazda rotary engines are lighter, more compact, and have fewer moving parts than comparable piston engines, but they're not without downsides. Among other things, they're prone to developing sealing issues in the rotor housing, due to worn apex and other seals. Later Mazda rotaries (we're talking around 1985 to 2002) and their updated 2mm, three-piece cast-iron apex seals proved to be relatively durable in stock applications. Things change when adding some power-boosting engine upgrades, though, and you may need updated seals to cope with high-performance mods and nitrous oxide, à la Dominic Toretto from "The Fast and the Furious." The reputation for premature failure of apex seals began with early Mazda rotaries, specifically those with 6mm cross-hollow and impregnated carbon apex seals, which were notorious for early wear and tear and for infusing the inner rotor housing with chatter marks — what Mazda engineers referred to as the "nail marks of the devil." Newer rotaries with 2mm cast-iron apex seals were not as bad. Then again, the apex seals have an important job, and they sacrifice themselves to get it done with every rotation. Those seals are like piston rings, but they live a harsher life inside the rotor housing and without adequate lubrication and frequent maintenance, they can succumb to detonation, wear, and high-rpm chatter.
