Mazda RX-8 Cat-Back Exhaust: HKS vs Borla vs Invidia

A Mazda RX-8 cat-back exhaust is the single most satisfying bolt-on for the Renesis 13B rotary — it drops weight off the back of the car, uncorks that unmistakable high-rpm rotary scream, and cleans up the tailpipe presentation, all without touching the emissions hardware ahead of the cat. The 2004–2011 RX-8 (SE3P) spins its 1.3L twin-rotor to a 9,000 rpm redline and makes up to 232 horsepower and 159 lb-ft in 6-speed trim, so the way it sounds at the top of the tach matters as much as the numbers. In our Tampa, FL shop we get asked which RX-8 cat-back is worth the money more than almost any other rotary question, so we lined up four in-stock systems — the HKS Legamax Premium, the Borla S-Type, the Invidia Q300, and the HKS Hi-Power — and broke down sound, materials, weight, warranty, and price.

Why Upgrade the RX-8 Cat-Back Exhaust?

A cat-back exhaust is the best first breathing mod for the RX-8 because it addresses the rotary's biggest factory compromise: weight and restriction behind the catalytic converter. The stock 2004–2011 RX-8 exhaust uses a heavy twin-canister muffler assembly that can weigh 40–60 lbs; a quality stainless cat-back typically cuts that roughly in half, taking mass off the rear of the chassis where the RX-8's near-50/50 balance rewards every pound saved. On a naturally aspirated Renesis, expect modest but real gains — usually in the 3–8 wheel-horsepower range from a cat-back alone, with the bigger dyno numbers coming later if you add a high-flow mid-pipe.

The real reason enthusiasts buy an RX-8 exhaust is the sound. A twin-rotor Renesis has no valvetrain and revs to 9,000 rpm, producing a smooth, turbine-like wail that a good cat-back amplifies into one of the best noises in the sport-compact world. The trade-off is drone: rotaries push a lot of exhaust volume, so muffler design — straight-through versus resonated — determines whether your highway cruise is tolerable or a headache. That single decision separates the four kits below.

How We Compared These RX-8 Exhausts

Every kit here is a direct bolt-on cat-back that connects to the factory RX-8 mid-pipe with no cutting or welding, and all fit the 2004–2011 model years (some listings extend to 2003 JDM cars). We weighed five factors that actually change the buying decision:

• Material: aircraft-grade T-304/SUS304 stainless resists rust and heat far better than the T-409 or aluminized steel found on budget systems.
• Sound character: straight-through designs are louder with more high-rpm scream; resonated designs tame cruise-rpm drone.
• Weight savings: how much mass comes off the rear of the car versus the heavy factory muffler.
• Warranty: stainless exhausts should be backed for the long haul; coverage ranges from limited to a lifetime, million-mile warranty.
• Price & availability: RX-8 exhausts in our catalog run from around $860 to $1,610, and a couple are special-order from Japan.

Borla S-Type Cat-Back — Best All-Around (Top Pick)

The Borla cat-back is the RX-8 exhaust we recommend to the widest range of owners. Borla builds it from patented, aircraft-grade T-304 stainless steel — a step above the T-409 stainless most rivals use — and finishes it with a single round, rolled, angle-cut tip. The heart of the system is Borla's straight-through, multi-core muffler technology, which produces the brand's signature aggressive-yet-refined tone without the raspy resonance cheaper mufflers add to a high-revving rotary. It is made in the USA and backed by Borla's million-mile warranty, so it is effectively the last cat-back you will buy for the car.

HKS Legamax Premium — Best Premium Build

If you want the most refined, OEM-plus RX-8 exhaust, the HKS Legamax Premium is the connoisseur's pick. HKS builds the Legamax from SUS304 stainless with mandrel-bent piping and dual polished tips, and it is tuned to a deep, controlled tone that stays JASMA-compliant on sound level — noticeably more civilized at idle and cruise than the free-flowing kits, yet still unmistakably rotary at 8,000 rpm. It is the most expensive of the four at $1,610 and ships as a special order from Japan, so plan for lead time, but the fit and weld quality are exactly what you would expect from HKS.

Invidia Q300 — Best for Daily Drivers

Rotaries are loud, and if you commute in your RX-8 the Invidia Q300 is the exhaust that keeps the peace. The Q-series uses a resonated, quieter muffler design in SUS304 stainless with a single rolled tip, so it noticeably reduces the cruise-rpm drone that makes straight-through systems tiring on the highway — while still opening up on a high-rpm pull. At $934.80 it is also the value play among the stainless kits, which is why the Q300 is one of the most popular exhausts in the RX-8 community.

HKS Hi-Power 75mm Ti-Tip — Loudest & Best Value

The HKS Hi-Power is the enthusiast's budget-loud pick and, at $860, the least expensive cat-back here. It uses a large 75mm single outlet in SUS304 stainless (no coating) capped with a titanium-burnt tip, and its free-flowing muffler makes it the most aggressive-sounding of the four — the classic HKS Hi-Power scream that made the brand famous on high-revving Japanese engines. It sheds the most weight thanks to its simple single-pipe layout, but it is also the one most likely to drone on the freeway, so it suits weekend and canyon cars more than long-haul commuters.

Which RX-8 Cat-Back Exhaust Should You Buy?

For most RX-8 owners, the Borla S-Type is the smart buy: premium T-304 stainless, a great signature tone, USA construction, and a million-mile warranty at $1,399.99. If build quality and a refined, drone-managed sound matter most, spend up to the HKS Legamax Premium at $1,610. Daily drivers who want the rotary sound without the highway headache should choose the resonated Invidia Q300 at $934.80, the best value of the stainless kits. And if you want the loudest, lightest setup for a weekend car on a budget, the HKS Hi-Power 75mm Ti-Tip at $860 is the one. Whichever you pick, pair it with a high-flow mid-pipe later to unlock the biggest power gains on the Renesis.

Installation and What to Pair With Your RX-8 Exhaust

Installing an RX-8 cat-back is one of the friendliest jobs in the aftermarket. Because every kit here bolts to the factory mid-pipe with the OEM rubber hangers and slip/flange connections, most owners finish the swap in about 1–2 hours on a lift or a set of jack stands using basic hand tools. We recommend replacing the mid-pipe-to-cat-back gasket and applying anti-seize to the hardware while you are under the car, and leaving the clamps slightly loose until the tips are aligned evenly in the rear valance before final torque. Give a fresh stainless system a few heat cycles and expect a little blue discoloration on the tips — that is normal for 304-grade steel.

To get more than the modest cat-back power gain, the next step on a Renesis is a high-flow or catless mid-pipe, which is where the 13B really wakes up; that combination is what turns a 3–8 horsepower bolt-on into a genuinely quicker car. Many owners also pair the exhaust with a cold-air intake to round out the breathing package and sharpen throttle response. If you are shopping the rest of the build, browse our full performance exhaust collection and matching intake and mid-pipe options, and remember that a healthy rotary depends on good compression — no exhaust fixes a tired engine, so keep up with oil and ignition maintenance on any high-mileage RX-8.