Understanding the Renesis Rotary

The Renesis engine is a unique naturally aspirated rotary that powers the Mazda RX-8. Unlike piston engines, it uses a triangular rotor orbiting an eccentric shaft to create power, enabling extremely high RPM – often over 9,000 – with a compact, light package. However, the Renesis has inherent limitations: modest low-end torque, relatively low peak horsepower from the factory (around 238 hp in the high-output version), and a reputation for oil consumption and apex seal wear. For many enthusiasts, forced induction is the answer to unlocking the true potential of this rotary.

Turbocharging addresses the Renesis’s weak points by dramatically increasing air density, allowing the engine to burn more fuel and produce far more power. The Garrett GT35 series has become a favorite for Renesis builds because of its robust engineering, wide compressor map, and ability to support 350–500 bhp when paired with the right supporting modifications. This guide walks through the complete installation, from parts selection to final tuning, aiming for a reliable 100+ horsepower increase on a stock or mildly built motor.

Why the Garrett GT35? Turbo Selection

Garrett Motion’s GT35 series includes several trims, with the GT3582R being the most popular for rotary applications. The GT3582R features a 84mm turbine wheel and a 61mm compressor wheel, offering a balanced combination of spool speed and top-end flow. For the Renesis, a smaller .63 A/R turbine housing provides quicker response, while a .82 or .84 A/R housing shifts the power band higher. Choosing the right housing size is critical – too large and you’ll sacrifice low-RPM driveability; too small and you’ll choke high-RPM output.

Compared to the smaller GT3076R, the GT35 delivers roughly 10–15% more airflow at the same boost level, making it better suited for targeting 350–400 whp. It also handles higher boost pressures (up to 25–30 psi) on race gas or E85, though a street car on 93 octane typically runs 10–15 psi safely. The Garrett unit’s dual ball bearing cartridge and billet compressor wheel ensures durability and quick spool, crucial for a rotary that thrives on immediate throttle response.

Supporting Mods: The Real Cost of 100+ HP

Installing just the turbo and manifold won’t yield a reliable 100+ horsepower increase. The Renesis requires significant supporting upgrades to handle the added heat and fuel demands:

  • Fuel system: Minimum 550cc secondary injectors (or a larger single injector) and a high-flow fuel pump (Walbro 255 or AEM 340). The factory 200cc injectors are quickly maxed.
  • Intercooling: A front-mount intercooler (FMIC) with a core around 24”x12”x3” to keep intake air temperatures (IATs) below 120°F.
  • Blow-off valve (BOV): A properly vented BOV to prevent compressor surge, which can damage the turbo and stall the rotor.
  • Turbo manifold and downpipe: A quality mild steel or 304 stainless manifold from companies like Pettit Racing or BNR Design. Mandrel-bent downpipe, 3-inch is ideal.
  • Oil routing: The Renesis uses a side oil injection system; you’ll need a turbo oil feed line (usually from the oil cooler adapter) and a drain line returning to the oil pan.
  • Coolant lines: Water-cooled turbos like the GT35 require coolant supply and return; tapping into the heater core lines or adding an auxiliary pump is common.
  • Engine management: A standalone ECU (Haltech Elite 2500, AEM Infinity, or Power FC) is essential to control the larger injectors and map timing/fuel. The factory PCM cannot handle boost.

Pre-Installation Preparation

Before you begin turning wrenches, gather all tools and parts. Expect the full project to take a weekend for an experienced mechanic; first-timers should allocate three to four days. Safety is paramount: disconnect the battery, lift the car safely on jack stands, and use eye protection.

Tools and Materials Checklist

  • Garrett GT3582R turbocharger (choose A/R housing: .63 for quick spool, .82 for top-end)
  • Turbo manifold (Renesis-specific, e.g., BNR or Rotary Performance Solutions)
  • Intercooler kit (pipe kit + core – 2.5” or 3” piping)
  • Blow-off valve (HKS SSQV, Turbosmart, or Tial)
  • Wastegate (external, ~38mm to 50mm – Tial or Turbosmart)
  • Oil feed & drain lines (AN -6 feed, -10 drain minimum)
  • Coolant lines (AN -4 to -6)
  • Fuel injectors (flow-matched, low impedance or high impedance with resistor box)
  • Fuel pump (Walbro 255 lph or higher)
  • ECU & tuning software
  • Gaskets (exhaust manifold, turbo to manifold, downpipe to turbo, intercooler couplers)
  • Hand tools: metric socket set, wrenches, Allen keys, torque wrench, pliers, wire cutters, terminal crimpers
  • Coolant, oil (synthetic 10W-40 recommended for turbos), assembly lube
  • Boost controller (manual or electronic, e.g., MAC valve)
  • Boost gauge and wideband AFR gauge (AEM, Innovate)

Engine Inspection & Compression Test

Before adding boost, ensure the Renesis is healthy. Perform a compression test (rotary-specific tester) – a loss of 30% or more on any face indicates worn apex seals, which will fail under boost. Oil pressure should be over 30 psi at idle hot. If the engine has more than 60,000 miles or known oil consumption, consider a rebuild with stronger seals and solid corner seals. Installing a turbo on a tired rotary is a recipe for rebuilds within a few thousand miles.

Installation Process Step by Step

Step 1: Remove Stock Intake, Exhaust, and Cooling System

Disconnect the battery. Drain the coolant from the radiator and block (petcock on passenger side). Remove the airbox, MAF sensor, and factory intake ducting. Unbolt the exhaust manifold from the engine (seven 12mm nuts on the studs). You may need to lower the subframe slightly to clear the manifold.

Disconnect the O2 sensors and pre-cat if equipped. Remove the power steering pump bracket if it obstructs turbo placement. Remove the factory oil cooler lines if planning to relocate the cooler.

Step 2: Install the Turbo Manifold

Apply a thin bead of high-temp RTV copper gasket sealer to both sides of a new exhaust manifold gasket. Align the gasket onto the studs, then position the manifold. Use new locking nuts; torque to 25–30 ft-lb in a cross pattern. Ensure the manifold flange is flat – warped manifolds cause leaks. Many Renesis builders opt for a tubular equal-length manifold to reduce reversion and improve scavenging.

Step 3: Mount the Garrett GT35 Turbo

Install the turbo onto the manifold using the supplied gasket or a thin copper gasket. Securely tighten the V-band or bolt flange (torque to spec). Now route the oil feed line. The Renesis’s oil injection system provides pressure from the front cover; it’s common to tap into the oil pressure port near the filter. Install a .035” restrictor in the feed line to prevent over-oiling.

Connect the -10 drain line to the turbo bottom, running it above the oil pan with a gentle slope back into a bung welded on the pan (above oil level to avoid siphoning). For coolant, connect the water lines to the turbo’s inlet and outlet; a common setup runs from a T in the heater hose and returns to the water pump inlet.

Step 4: Intercooler and Charge Piping

Position the intercooler in front of the radiator behind the bumper. Remove the crash bar or notch it if necessary. Mount using brackets. Route the 2.5” or 3” aluminum charge piping from the turbo compressor outlet to the intercooler, and from the intercooler to the throttle body (MAF-less or after-MAF location). Install the blow-off valve on the intercooler-to-throttle pipe within 12 inches of the throttle body.

Use silicon couplers and T-bolt clamps. A proper intercooler setup should see less than 1 psi pressure drop at peak flow.

Step 5: Wastegate Installation and Boost Control

Mount an external wastegate on the manifold or the downpipe. Proper wastegate placement is critical – it must receive exhaust pressure from a dedicated source (not from the downpipe). Use a 1/8” NPT port in the manifold collector. Run a boost reference line from the compressor outlet to the wastegate’s top port. For electronic boost control, install a MAC valve or boost controller between the reference source and the wastegate.

Step 6: Fuel System Upgrades

Replace the factory fuel pump with a Walbro 255 or AEM 340. Install a new fuel filter. Upgrade injectors – typically 550cc (low impedance) or 1100cc (high impedance) for a 350 whp setup. If using high-impedance injectors, you may need a resistor bypass or a standalone ECU that supports them. Run a new fuel return line (AN-6) from the rail to the tank if the factory line is undersized (common on older RX-8s).

Step 7: ECU Installation and Initial Tune Setup

If using a standalone like a Haltech Elite 2500, wire it in using a plug-and-play harness or splice into the factory wiring. Map out the inputs: crank and cam sensor (Renesis uses Hall-effect sensors on the eccentric shaft and front housing), throttle position, air temperature, coolant temperature, oxygen sensor (wideband), MAP sensor, and knock sensor. Set the base fuel map for idle at 14.7 AFR, and zero boost fuel for 12.0-12.5 AFR. You’ll need a base ignition map (typically 15-25 degrees at idle, ramping up to 30+ degrees under load, but rotaries need less timing under boost – start with 15-18 degrees at 10 psi).

Tuning the Renesis for 100+ HP Gains

The Renesis requires a tuning approach distinct from piston engines. The rotary’s combustion chamber is long and narrow, making it prone to detonation if timing is too advanced. Set the leading spark plugs to around 15-18° BTDC under boost, trailing about 5-10° after leading. Use a knock monitor or det cans to listen for pinging. Keep air-fuel ratios between 11.0-11.5:1 under full boost to aid cooling.

The rotary lacks the thermal efficiency of a piston engine, so intercooling and fuel enrichment are critical.

Target boost: 8-10 psi on stock internal Renesis (with good compression) yields a safe 100-120 whp gain. With a built motor (thicker apex seals, chrome side housings, hardened rotor bearings), 15-20 psi can push 350 whp. But the stock side oil seals often fail above 400 whp. Reliability is a trade-off; stick to 10-12 psi and a conservative tune for longevity.

Base Map Loading and Start-up

Load a base map from your ECU manufacturer that is pre-configured for a Renesis turbo. Prime oil system by disabling fuel and cranking engine for 10 seconds. Start engine, let idle for 2 minutes, then check for oil and coolant leaks. Let it warm up to operating temperature (180°F) and adjust idle trim to 800-900 RPM. Verify the wideband reads stoichiometric (14.7) at idle.

Testing and Final Adjustments

Leak Testing

Boost leak test the charge system: block the turbo inlet with a special cap, pressurize to 15 psi, and listen for hissing. Repair any leaks with tighter clamps or fresh couplers. Vacuum leak test on the intake manifold (post-throttle blade) – a rotary vacuum leak can cause erratic idle and lean conditions.

Road Tuning and Data Logging

Take the car to a safe area. Perform a series of partial-throttle pulls, logging RPM, MAP, AFR, and timing. Focus on transient throttle enrichment – the Renesis needs extra fuel when boost builds suddenly. Use the ECU’s data capture to trim the fuel table. After 3-4 pulls, review knock counts.

Retard timing 2 degrees in any cell where knock is detected above a threshold.

A final dyno tune is recommended. Expect peak power around 7500-8000 RPM. A well-tuned Renesis turbo kit (GT35, FMIC, standalone) typically produces 300-330 whp on 10 psi – a 100-120 hp gain over the stock 198 whp (on a dynojet). Torque peaks early, around 4000-4500 RPM, providing a significantly fatter curve than the NA engine.

Maintenance and Longevity Considerations

Turbocharged rotaries require more frequent oil changes (every 3000 miles with synthetic). Monitor oil temps; install an oil cooler if not already present. Allow the engine to idle for 30 seconds before shutdown to cool the turbo bearing. High EGTs (above 1600°F) indicate lean tuning or excessive timing – back off boost or add fuel immediately. With careful maintenance and conservative tuning, a GT35-equipped Renesis can last 50,000+ miles without issue.

Conclusion

Installing a Garrett GT35 turbo on a Renesis engine is the fastest way to gain 100+ horsepower while retaining the high-revving character that makes the RX-8 special. The process is involved, requiring careful planning for fuel, cooling, and engine management. But the reward is a car that pulls hard from 4000 RPM to redline, transforms the driving experience, and remains reliable if done correctly. Use trusted parts, invest in a proper tune, and enjoy the new level of performance. For further reading, consult Garrett’s official GTX3582R page for technical specs, and visit the RX-8 Club forced induction forum for community build threads.

Professional rotary tuners like Rotary Performance offer turnkey solutions if you prefer a shop installation.