What the Cobb RSX Turbo Kit Delivers

The Cobb RSX Turbo Kit targets a specific sweet spot for Honda RSX enthusiasts: a bolt-on system that transforms the car without requiring a complete engine overhaul. Designed for the K20A2 (Type-S) and K20Z1 engines found in the 2002-2006 RSX, this kit is engineered to produce substantial horsepower gains while maintaining daily-driveability. The core of the system is a Garrett GT3071R turbocharger, paired with Cobb’s proprietary cast-iron manifold, a front-mount intercooler, and a blow-off valve. Compared to other kits on the market—such as the Full-Race or Rev9 offerings—Cobb’s kit leans toward a balance of reliability and ease of installation. Owners consistently report that the supplied components fit without major modifications to the chassis or engine bay, which is a significant advantage for a home mechanic.

Before diving into specifics, understand that any turbocharger kit for the RSX will change the car’s character. The K-series engines respond aggressively to forced induction. Cobb claims the kit can deliver 350–400 wheel horsepower on a conservative tune with supporting mods. Real-world dyno results from enthusiast forums and tuning shops typically show 330–380 whp on pump gas (93 octane) with a boost level of 12-15 psi. With ethanol blends or race fuel, numbers can climb to 420+ whp. These figures are impressive for a 2.0-liter four-cylinder, but they hinge entirely on the quality of the engine’s foundation and the supporting systems.

Performance Gains: More Than Just Peak Numbers

The most obvious benefit is the increase in horsepower. A stock RSX Type-S puts down around 160-170 wheel horsepower. With the Cobb kit and proper tuning, that figure more than doubles. However, the driving experience changes in ways that a peak number doesn’t capture. The torque curve flattens and widens. Where the stock K20A2 feels gutless below 4000 RPM, the turbo kit delivers meaningful boost as early as 2800 RPM. By 3500 RPM, the engine is making more torque than it ever did naturally aspirated. This makes daily driving easier because you don’t have to wring the engine to high RPM to merge or pass.

Throttle response is a nuanced topic with turbocharged cars. The Cobb kit uses a properly sized Garrett turbo and a twin-scroll-like manifold design (not true twin-scroll, but tuned for flow). This results in minimal lag. In second and third gear, boost builds quickly. The blow-off valve is a Bosch-type recirculating design, which is quieter than vent-to-atmosphere valves but helps maintain drivability. Some owners swap the BOV for a louder unit, but that can cause tuning issues if not matched correctly.

Beyond raw power, the kit improves engine cooling. The included intercooler core is 24x6x3 inches, which is sufficient for street and light track use. Intake air temperatures drop significantly compared to a top-mount or no intercooler. However, if you plan to track the car on hot days, an upgraded intercooler or a water-methanol injection kit becomes a good idea.

For context, the RSX chassis handles the extra power well with basic suspension upgrades. The factory brakes will become the weak link. Many owners pair the Cobb kit with a big brake kit from Wilwood or StopTech. The added weight of the turbo and intercooler is minimal, so the car’s balance remains neutral.

One area where the Cobb kit excels is the powerband. Unlike some aggressive twinscroll systems that hit hard and then fall off, the Cobb setup delivers smooth, linear power from 3500 RPM to redline. This makes the car easier to drive fast on a road course. The downside is that it does not produce the same “top-end rush” as a large frame turbo or a high-revving naturally aspirated build. For most street and weekend track drivers, this trade-off is welcome.

Installation Tips: What to Expect

Installing the Cobb RSX Turbo Kit is a substantial project. The manufacturer advertises it as a “DIY-friendly” installation. That is true only if you have solid mechanical skills, a full set of tools, and patience. The entire process can take 12 to 20 hours for a first-timer. Experienced mechanics may complete it in 8 hours. The key steps involve removing the stock intake manifold, exhaust manifold, and downpipe. You also need to relocate the battery to the trunk or install a smaller battery in the tray. Cobb provides a battery relocation kit with the RSX turbo kit, which is a nice touch.

Critical installation steps and common pitfalls:

  • Oil supply and drain. The turbocharger needs an oil feed line. Cobb includes a sandwich plate that mounts between the engine block and the oil filter. Some users report that the fitting can leak if not tightened properly. Use thread sealant. The oil drain line must slope constantly downward to the oil pan. Kinking the drain line causes smoking seals. Take your time routing this.
  • Coolant lines. The kit uses coolant lines to the turbo. You’ll be tapping into the engine’s cooling system. Bleed the system thoroughly after installation to avoid air pockets.
  • Intercooler piping. The hot-side pipe runs from the turbo to the intercooler. It requires cutting a small hole in the plastic undertray. This is straightforward, but measure twice. The cold-side pipe connects the intercooler to the throttle body. Fitment is tight near the radiator hose. Some installers wrap the pipe with heat insulation.
  • Wastegate and boost controller. The kit comes with an internal wastegate actuator. Cobb presets the spring to 7 psi. For higher boost, you need an aftermarket boost controller. If you install a manual boost controller, place it away from heat sources.
  • Downpipe and exhaust. The downpipe is 3 inches and coated. It mates to the rest of the exhaust. If you keep the stock cat-back, expect some reduction in backpressure. A 3-inch cat-back exhaust is recommended for full flow.

You must also consider the ECU. The kit does not include a standalone ECU or a reflash. Cob strongly recommends using a professional tuner with Honda-specific tuning software (Hondata K-Pro, FlashPro, or MoTeC). Do not attempt to run the car on stock ECU calibration. The engine will lean out and detonate.

Common mistakes that lead to problems include: not thoroughly cleaning the engine bay before disassembly (dirt in the intake leads to scoring), using the wrong thread locker on turbo bolts, forgetting to route the oil drain correctly, and neglecting to check the intercooler’s core for shipping damage. Also, be aware that the kit requires a 2.5-bar MAP sensor (not included). If you skip this, the ECU will not read boost pressures correctly.

Required Supporting Modifications

To safely and effectively use the Cobb RSX Turbo Kit, you need to address several areas of the vehicle. Cutting corners on supporting mods will result in poor performance, drivability issues, or engine failure. Here’s what is required and what is highly recommended.

Fuel System Upgrades

The stock fuel pump, injectors, and fuel pressure regulator are not sufficient for boosted applications. The kit includes larger injectors (550cc or 750cc depending on the version). If your kit includes smaller injectors, plan to upgrade to at least 750cc for future expansion. Additionally, install a Walbro 255 lph fuel pump or a similar high-flow unit. For higher horsepower (over 380 whp), a fuel pressure regulator with a return-style system is necessary. Cobb does not supply the regulator, so purchase one from AEM or Injector Dynamics.

ECU and Tuning

This is non-negotiable. You must have a programmable ECU or a reflash solution that supports boost. The most common option for the RSX is Hondata K-Pro. This replaces the factory ECU or piggybacks onto it. The cost is around $1000-1200. A good tune from a reputable shop will run $400-600. Do not trust an off-the-shelf tune. Each engine reacts differently to boost, and a custom calibration on a dyno is the only safe way.

Exhaust System

The Cobb downpipe uses a 3-inch outlet. If the rest of your exhaust is 2.5 inches or stock, you create a bottleneck. Upgrade the cat-back system to a 3-inch, mandrel-bent system from companies like GReddy, Apexi, or MagnaFlow. A test pipe or high-flow catalytic converter is recommended for track use; for street use, you may need to keep a catalytic converter for emissions compliance. Check local laws.

Intercooler and Intake Temperatures

The included front-mount intercooler is adequate for 350-400 whp. However, on a hot summer day, intake temperatures can rise above 130°F after multiple pulls. A larger intercooler core (like a 28x12x3) or a water-to-air intercooler reduces that. You can also add a turbo blanket and wrap exhaust pipes to keep underhood temperatures down.

Clutch

The stock clutch in the RSX Type-S is marginal at stock power. With 350+ whp, it will slip on the second or third full-throttle pull. Plan to install a performance clutch before or immediately after the turbo kit. Stage 1 clutch kits (e.g., Exedy, ACT, Clutch Masters) with a sprung hub handle the power without being noisy. For track use, a stage 2 or 3 unsprung clutch is fine but can be annoying in traffic.

Engine Internals

Can the K20A2 handle 350 whp on stock internals? The answer is yes, with a good tune and low boost (8-10 psi). Many owners have run these kits for tens of thousands of miles without internal modifications. However, if you plan to run higher boost (15+ psi) or use nitrous, forged rods and pistons are wise. The weak point is the stock piston ring lands. For 400+ whp, build the bottom end. For the majority of street users, stock internals + conservative tune + 93 octane is a reliable combination.

Pros and Cons of the Cobb RSX Turbo Kit

Pros

  • Complete kit. Includes turbo, manifold, downpipe, intercooler, piping, oil/coolant lines, and hardware. You don’t have to source parts individually.
  • Quality components. Garrett turbocharger and Cobb manifold are proven. The intercooler and piping are well-made.
  • Relatively straightforward installation. No major cutting or welding required. Battery relocation kit included.
  • Great powerband. Linear and powerful. Easier to drive fast than many other turbo kits.
  • Customer support. Cobb has a solid reputation for technical support and warranty.

Cons

  • Price. The kit costs around $3000-3500, depending on the retailer and current pricing. That’s on par with competitors, but not cheap.
  • Not CARB compliant. This is a race-only kit. If you live in California or other states with strict emission, it is illegal on public roads. You will need to keep the stock ECU for smog checks.
  • Included injectors may be small. Some versions come with 550cc injectors, which limit you to around 350 whp. Older RSX models may require adapters for the injectors. Verify what injectors are in your kit.
  • No boost controller or wideband. You must buy these separately. A wideband O2 sensor and gauge are essential for tuning and monitoring.
  • Downpipe clearance. The downpipe can be close to the transmission housing. Some owners need to modify the transmission bracket or add washers to gain clearance. Not a dealbreaker, but an annoyance.
  • No ECU included. You still need to purchase and program a standalone ECU. Adds $1000-1500 to the total cost.

Cost Breakdown: What You’ll Spend to Do It Right

Here’s a realistic budget for a full Cobb RSX Turbo Kit installation:

  • Cobb RSX Turbo Kit: $3,200 (average)
  • Hondata K-Pro or similar: $1,100
  • Professional dyno tune: $500
  • Clutch (labor extra if you do it at same time): $400-800
  • Fuel pump (Walbro 255): $120
  • Fuel pressure regulator (if needed): $200
  • Boost controller (manual or electronic): $50-300
  • Wideband O2 sensor + gauge: $200
  • Oil, coolant, gaskets, threadlocker, etc.: $100
  • Optional: upgraded intercooler, exhaust, engine oil cooler: $500-1500

Total: roughly $5,500 to $7,000 for a reliable, streetable setup. This does not include labor if you cannot do the install yourself. Shop labor for this job typically runs $800-1500. The final cost puts you near $7,000-8,500, which is comparable to a professional turbo build from a shop, but you get the peace of mind of the Cobb warranty and known part quality.

Reliability and Longevity

Any turbo kit stresses the engine. The K20 series is robust, but the extra heat and cylinder pressure take a toll. Oil changes become more critical. Use a high-quality synthetic 5W-30 or 10W-30 (depending on climate) and change every 3,000-4,000 miles. The turbo itself requires the engine to idle for a minute after a hard drive to cool down the oil. Many owners install a turbo timer to automate this. Also, avoid excessive back-to-back pulls on the street. The stock cooling system can handle moderate use, but on a hot day, the radiator may struggle. An aluminum radiator (e.g., Koyo or Mishimoto) is a prudent upgrade.

Common issues after installation include boost leaks, vacuum leaks at the MAP sensor, and oil leaks at the drain line. Check all clamps and fittings during the first 100 miles. Re-torque the exhaust manifold bolts after the first heat cycle. With proper maintenance, the Cobb kit can last 50,000+ miles without significant issues. However, if you constantly push the car to its limits on the track, internal engine upgrades become necessary sooner.

Tuning Options: Getting the Most from the Kit

Tuning is the single most important factor dividing a successful turbo RSX from a grenaded one. The stock ECU cannot control a turbo engine. You need a stand-alone or a reflash that allows changes to fuel maps, ignition timing, boost control, and VTEC engagement. The most popular solutions are:

Hondata K-Pro

This replaces the stock ECU or is installed as an add-on board. It provides full control. Its user interface is robust, and many tuners are familiar with it. K-Pro also includes built-in wideband control and data logging. The downside is cost and the need to send your ECU to Hondata or buy a pre-configured unit.

FlashPro

This is a simpler device that piggybacks on the stock ECU. It allows real-time tuning. It’s less expensive than K-Pro but offers fewer features. For a basic street turbo setup, FlashPro is sufficient. Some tuners prefer K-Pro for its robustness.

MoTeC or Haltech

These are professional-level ECUs. They are expensive and require expert tuning. Only consider these if you are building a dedicated race car and have the budget.

When you visit a tuner, ensure they have experience specifically with boosted K20 engines. A poor tune can cause detonation, leading to immediate rod failure. Typical safe AFRs for pump gas are 11.5-12.0:1 under boost. Ignition timing is retarded under boost; the tuner will dial it in carefully. After tuning, have the tuner create a failsafe (boost cut, fuel cut) in case of knock or over-boost.

Customer Experiences: Real-World Feedback

Scouring forums like ClubRSX, Honda-Tech, and Reddit’s r/Honda reveals a consistent pattern: owners who take the time to install the kit correctly and tune professionally are thrilled. Many mention that the kit makes the RSX feel like a completely different car. One owner reported a 0-60 mph time of 4.2 seconds on drag radials with 400 whp. Another uses his RSX as a daily driver in Minnesota winters; he runs a conservative tune at 10 psi and has over 60,000 miles on the kit without any major repairs.

Criticisms center mainly on the missing ECU solution and the need for additional parts. Several owners had to re-route the oil return line because the included line was too short for their engine bay configuration. Others noted that the charge pipe clamps provided are not the best quality and should be upgraded to T-bolt clamps. The most common “regret” is not upgrading the clutch at the same time, as it added labor and cost later.

A balanced view: if you are looking for a turnkey turbo solution that you can install in a weekend with basic tools, and you have the budget for supporting mods, the Cobb kit is one of the best options for the RSX. The refinement and fitment are superior to many universal or cheaper kits. The aftermarket support from Cobb also adds value—phones are answered, and replacement parts are readily available.

Frequently Asked Questions

How much boost can I run on a stock RSX engine?

With 93 octane and a safe tune, 8-10 psi is the general conservative limit for stock internals. Some tuners will push to 12 psi, but that reduces the safety margin. At 12 psi, you should upgrade fuel and use a wideband. For 14+ psi, build the bottom end.

It depends on your local emissions laws. The kit does not have CARB approval, so it is not legal on vehicles registered in California and other states that follow CARB rules. In many other states, it is legal as long as you maintain functional catalytic converters and don’t exceed noise limits. Check with your local DMV refer to EPA guidelines.

What is the warranty?

Cobb offers a one-year warranty from the original date of purchase against defects in materials and workmanship. The warranty does not cover damage caused by improper installation, tuning, or poor supporting modifications. Keep receipts and register your product on Cobb’s site. Refer to Cobb’s product page for precise terms.

Can I install the kit without a lift?

Yes, jack stands are sufficient. You need to access the underside for the intercooler, oil pan, and exhaust. A good floor jack and four jack stands rated for the car’s weight are essential. Alternatively, you can rent a bay at a shop with a lift.

Do I need to upgrade the transmission?

The stock RSX transmission (including the LSD-equipped units) is strong enough for up to 400 whp. However, clutches wear out faster. The transmission can handle it as long as you don’t do hard launches on sticky tires. For drag racing, a gearset with stronger gears is recommended but not required.

What about the BOV sound?

The included Bosch recirculating BOV produces a very subtle flutter sound. If you want a loud “psssshh”, you can replace the BOV with a vent-to-atmosphere type, but you will need a tune that compensates for the lack of recirculation during shifts. Many tuners recommend sticking with recirculation for drivability.

Final Thoughts

The Cobb RSX Turbo Kit delivers exactly what it promises: a substantial, reliable power increase that transforms the Honda RSX into a legitimate performance car. It is not the cheapest route, and it requires supporting modifications—some of which are pricey—but the end result is a balanced, enjoyable vehicle that outperforms many newer sports cars. For the mechanically inclined RSX owner who wants a true turbo experience without fabricating their own system, the Cobb kit is a proven route. Pair it with proper fuel, a quality tune, and basic upgrades to the clutch and cooling, and you will have a car that rewards every drive.

If you are on the fence, join a dedicated RSX forum. Read build threads from owners who have completed the install. You will quickly see that those who followed the recipe are happy, and those who cut corners regretted it. The Cobb RSX Turbo Kit is an investment, but for the right person, it is one of the best modifications available for the car.

External references: Hondata K-Pro details and ClubRSX forums for owner experiences and build threads.