The RSX has long been a favorite platform for enthusiasts seeking high-performance builds, particularly with turbocharging. Upgrading to a 70mm turbocharger is a proven way to unlock substantial power gains, moving the car from daily driver to track-ready contender. This article covers everything you need to know about selecting, installing, and tuning a 70mm turbo on your RSX, along with the real-world performance benefits you can expect.

Understanding the 70mm Turbo: Specifications and Selection

A 70mm turbocharger refers to the compressor wheel inducer diameter—the inlet size where air enters the compressor. This measurement directly influences the turbo's flow capacity and power potential. For the RSX's K20 or K24 engine, a 70mm turbo sits in the "medium-to-large" category, offering a strong balance of spool speed and top-end horsepower.

Compressor and Turbine Design

Modern 70mm turbos often feature billet compressor wheels, dual ball bearings, and advanced turbine blade geometries. These design elements reduce rotating inertia, lowering lag and improving transient response. Common compressor trims for this size range from 55 to 62 on the inducer/exducer ratio, while turbine housings come in AR (aspect ratio) options like 0.63, 0.82, or 0.90 for the RSX. Choosing the right housing depends on your power goals and driving style—a smaller AR gives faster spool but restricts top end, while a larger AR sacrifices low-end response for higher peak power.

Matching the Turbo to Your Engine

The RSX’s K-series engine responds well to 70mm turbos when coupled with proper supporting modifications. A fully built bottom end (forged rods and pistons) can handle 500–700 whp with this turbo size, while a stock engine with upgraded fuel system and tuning can safely achieve 350–450 whp. It's crucial to consider your overall build goals: a 70mm turbo may be oversized for a stock engine without valve train upgrades or oil pump modifications. Forums like Honda-Tech contain owner experiences that can help you decide which specific 70mm turbo model (e.g., Precision 6266, Garrett GTX3576R) best matches your RSX.

Installation Preparation: Tools, Parts, and Supporting Mods

Before touching a wrench, gather all necessary tools and components. The installation is not a simple bolt-on; it requires removing the front bumper, intercooler, and possibly the radiator for clearance. Plan for several days if you are new to turbo swaps.

Required Tools and Fasteners

  • Metric socket set (8mm–22mm) and ratchets
  • Torque wrench (ft-lb and in-lb)
  • Pry bar and gasket scraper
  • Jack and jack stands
  • Transmission jack (for heavy turbo manifold assemblies)
  • Flare nut wrenches for oil/coolant fittings
  • Vacuum gauge and boost leak tester
  • Die grinder or Dremel for clearance issues

Critical Supporting Components

Upgrading to a 70mm turbo without addressing the fuel system, intercooling, and oiling is a recipe for disaster. You will need:

  • Upgraded fuel injectors (e.g., 1000–1300cc for high boost)
  • High-flow fuel pump (Walbro 450 or AEM 340)
  • Aftermarket engine management (Hondata K-Pro, MoTeC, or Haltech)
  • Large intercooler (3.5" core minimum, bar-and-plate design)
  • Mandrel-bent intercooler piping (2.5" or 3" diameter)
  • Oil feed and drain kit with restrictor for journal-bearing turbos
  • Coolant lines (if turbo is water-cooled)

Many owners find that upgrading the exhaust manifold to a top-mount design simplifies access to the 70mm turbo and reduces heat soak.

Step-by-Step Installation Guide

1. Remove Stock Components

Disconnect the battery negative terminal. Remove the front bumper, crash bar, and headlight assembly on the driver side to access the turbo area. Drain the coolant and engine oil. Unbolt the factory exhaust manifold, downpipe, and intake manifold if they interfere. On the RSX, the stock intake manifold often needs to come off to reach oil and coolant lines.

2. Prepare the New Turbo Manifold

Inspect your new manifold (e.g., Full-Race, Lovefab, or custom) for any casting debris. Install the 70mm turbo onto the manifold using new gaskets. Apply anti-seize on studs if the manifold is stainless steel. Tighten bolts in a crisscross pattern to spec (typically 35–45 ft-lb). If using an external wastegate, mount it to the manifold’s dedicated flange before bolting the manifold to the engine.

3. Install the Turbo and Manifold Assembly

With the turbo attached to the manifold, carefully lower the assembly onto the engine’s head. It's heavy—use a transmission jack or helper. Torque the manifold nuts in stages. Connect the wastegate vacuum lines. Fit the downpipe to the turbine outlet using a new V-band clamp or gasket. Do not fully tighten downpipe bolts until the intercooler piping is aligned.

4. Connect Oil and Coolant Lines

Feed the oil supply line from the engine block (usually at the oil pressure sender port) to the turbo’s oil inlet. For the drain, attach a -10 or -12 AN line from the turbo bottom to the oil pan, ensuring a gravity-fed downward slope. If the turbo is water-cooled, route coolant lines from the engine’s heater hose or water pipe using proper adapters. Check for kinks and rub points. Garrett's installation guide offers torque specs and thread sealant recommendations.

5. Plumb the Intercooler and Charge Pipes

Mount the intercooler behind the bumper, using brackets if needed. Run charge piping from turbo compressor outlet to the intercooler, then to the throttle body. Use silicone couplers and T-bolt clamps. Confirm the intercooler piping clears the radiator and fans; you may need to trim the plastic fan shroud. Boost leak test the system at 20 psi before proceeding.

6. Reassemble and Setup

Reinstall the radiator, fans, bumper, and headlight. Refill engine oil (5W-40 or 10W-40 synthetic recommended for turbo cars) and coolant. Prime the turbo oil system by pulling the fuel pump relay and cranking the engine for 10–15 seconds. Then reconnect everything, start the engine, and check for leaks immediately.

Tuning and ECU Calibration

A 70mm turbo is far too large for the RSX's stock ECU to manage. You must install aftermarket engine management. Hondata K-Pro is the most popular option for K-series engines, allowing you to adjust fuel maps, ignition timing, and boost control. Start with a safe base map from your tuner. Do not drive under boost until a proper dyno tune. Expect to dial in idle, part-throttle, and wide-open-throttle parameters. Dyno tuning sessions typically cost $400–$800 but are essential for reliability.

Performance Gains: What to Expect

Power Output

With a 70mm turbo on an RSX, you can see 400–550 whp on pump gas (93 octane) and 600+ whp with ethanol blends (E85). The increase over a stock RSX (200 whp) is dramatic. Mid-range torque will shoot up, often exceeding 350 lb-ft at 4,000 rpm. Dyno graphs show a strong, linear curve if the turbo and manifold are matched properly.

Daily Drivability

Contrary to myth, a properly sized 70mm turbo can be very streetable. Spool begins around 3,200–3,800 rpm, with full boost by 4,200–4,500 rpm. Smaller turbine housings (0.63 AR) improve response, while larger housings (0.82 AR) shift power higher. Expect some turbo lag compared to a smaller 57mm unit, but the payback is significantly more top-end pull. The RSX’s light chassis makes even 400 whp feel exhilarating.

Longevity and Reliability

With good oil, proper cooling, and conservative tuning (e.g., 11.5:1 air-fuel ratio on pump gas), a 70mm turbo can last tens of thousands of miles. Weak points include the RSX’s stock oil pump and clutch. Upgrade to a ported sump and an aftermarket clutch (e.g., ACT or Exedy) if you plan to track the car. K20A.org forums have detailed reliability reports from RSX owners running 70mm turbos for years.

Conclusion

Upgrading to a 70mm turbo for your RSX transforms the car into a high-horsepower machine capable of keeping up with far more expensive sports cars. The installation is intensive but achievable for an experienced DIYer with proper planning. When paired with the right supporting mods and a professional tune, a 70mm turbo delivers breathtaking power, improved throttle response, and a new level of driving engagement. Whether you’re chasing quarter-mile times or carving canyons, this upgrade is a worthwhile path to RSX performance excellence.