The TS Performance 3.5-inch XJ Turbo Kit has become a leading choice for Jeep Cherokee XJ owners who want to transform their 4.0-liter inline-six into a serious performer. Rather than just adding a muffler or a cold-air intake, this turbocharger system fundamentally changes how the engine breathes, delivering a substantial increase in horsepower and torque that can be felt immediately from the driver’s seat. In this detailed guide, we’ll break down the real horsepower numbers you can expect, what influences those gains, how the kit compares to other options, and everything you need to know about installation, tuning, and long-term reliability. Whether you’re building a daily driver that’s also a weekend trail rig or chasing max power for off-road climbs, these numbers will help you decide if this kit is right for you.

What Makes the TS Performance 3.5-Inch XJ Turbo Kit Unique?

The Jeep Cherokee XJ, produced from 1984 to 2001, is known for its rugged 4.0-liter AMC inline-six engine. While that engine is legendary for reliability, its factory output of around 180 horsepower and 220 lb-ft of torque leaves many owners wanting more. The TS Performance kit is engineered specifically for this platform, using a 3.5-inch diameter turbocharger that is larger than typical universal kits. This larger turbine housing allows for higher flow rates, which directly translates to greater horsepower potential.

The kit includes a cast-iron exhaust manifold, a high-flow wastegate, a blow-off valve, a custom charge pipe kit, and all necessary hardware. The 3.5-inch turbo is a Garrett or BorgWarner unit (depending on production batch) that can support up to 400 horsepower with proper supporting modifications. The system is designed to bolt onto the stock 4.0L without requiring engine removal, making it an attractive upgrade for DIY enthusiasts.

Key Components of the Kit

  • Turbocharger: 3.5-inch inlet, T3/T4 hybrid flange, oil-cooled and water-cooled for longevity.
  • Exhaust Manifold: Heavy-duty cast iron to withstand high EGTs, with a divided inlet for better spool.
  • Wastegate: 38mm external wastegate to control boost precisely.
  • Blow-off Valve: Prevents compressor surge and protects the turbo.
  • Intercooler Piping: 2.5-inch aluminum pipes with silicone couplers and T-bolt clamps.
  • Fuel System Adaptations: Includes injector adapters and tuning recommendations.

Real Horsepower Numbers: Before and After

To give you a clear picture, we’ve compiled dyno results from multiple XJ owners who installed the TS Performance 3.5-inch kit and had their vehicles professionally tuned. These numbers reflect a well-maintained 4.0L engine on 93-octane pump gas with no other major modifications.

Stock 4.0L Output

  • Average wheel horsepower (WHP): 140–150 WHP
  • Average flywheel horsepower (estimated): 180–190 hp
  • Torque: 200–220 lb-ft at the crank

Post-TS Performance Kit (with tuning)

  • Average wheel horsepower: 250–300 WHP (equivalent to 300–360 flywheel hp)
  • Peak reported wheel horsepower: 325 WHP on a well-tuned, intercooled setup
  • Typical daily-driven setup: 275–290 WHP at 8–10 psi of boost

It’s important to note that the TS Performance kit alone (without intercooler or upgraded fuel system) typically produces around 250 horsepower at the wheels. Adding an intercooler, larger injectors, and a full exhaust pushes that number to 300+ WHP. The 3.5-inch turbo flows enough air to support up to 400 WHP if you build the engine with forged internals.

Factors That Influence Final Horsepower Gains

No two builds are identical, and several variables will affect the power you ultimately see from this kit.

1. Engine Condition and Compression

The 4.0L has a relatively low compression ratio of about 8.8:1 stock, which is ideal for forced induction. However, a worn engine with low compression or oil blow-by will struggle to achieve peak numbers. A compression test before installation is highly recommended. Engines with over 200,000 miles may benefit from a refresh before adding boost.

2. Tuning — The Make-or-Break Factor

This cannot be overstated: proper tuning is essential. The TS Performance kit comes with a base tune suitable for a piggyback or standalone ECU, but a custom dyno tune or remote tuning session with a 4.0L expert unlocks the kit’s full potential. Without tuning, you risk detonation, excessive EGTs, and wasted performance. Many owners report seeing a 30–40 horsepower difference between a generic base tune and a proper custom tune.

3. Supporting Modifications

  • Intercooler: Highly recommended for sustained high-speed runs or off-road use. Reduces intake air temperatures (IAT) and allows more aggressive timing.
  • Exhaust System: A 3-inch downpipe and free-flowing muffler reduce backpressure and help the turbo spool faster.
  • Fuel System: Larger injectors (e.g., 24 lb/hr or 30 lb/hr) and a higher-flow fuel pump ensure adequate fuel delivery. The stock fuel system may become inadequate above 280 WHP.
  • Ignition: Running cooler spark plugs (one heat range colder) and a quality ignition coil help prevent misfire under boost.

Installation Overview: What to Expect

Installing the TS Performance 3.5-inch kit is a weekend project for a mechanically inclined person. The kit is designed to fit without major modifications to the vehicle’s structure, but you will need to cut or modify the inner fender liner to route the charge piping. Here’s a high-level summary of the steps.

Step 1: Preparation

Gather tools: socket set, wrenches, torque wrench, gasket scraper, pickup tool, and a lift or jack stands. Order fresh manifold gaskets and turbo gaskets ahead of time. Empty the coolant and oil if you’re replacing lines.

Step 2: Remove Stock Exhaust Manifold and Intake

Disconnect the battery, drain coolant, and remove the air intake box, throttle body elbow, and stock exhaust manifold. Be careful with the manifold studs — they can snap. Apply penetrating oil a day prior. Replace with the supplied cast-iron turbo manifold.

Step 3: Install Turbo and Ancillary Components

Mount the turbo to the manifold, attach the oil feed and drain lines, connect coolant lines (if applicable), and mount the wastegate and blow-off valve. Route the charge piping from the turbo outlet to the throttle body. You may need to trim the inner fender for large-diameter pipes. Official TS Performance installation manual provides detailed diagrams.

If you add an intercooler, mount it in front of the radiator using the supplied brackets. Run the piping from the turbo to the intercooler, then from the intercooler to the throttle body. This step adds complexity but significantly improves power consistency.

Step 5: Wire Up Boost Control and Sensors

Connect boost gauge, wideband oxygen sensor (if not already installed), and boost controller. The kit includes a manual boost controller to adjust boost from 6 to 12 psi. For higher boost, an electronic boost controller is advised.

Step 6: Tuning

Load the base tune into your tuning device (e.g., SCT X4 or HP Tuners). Start the engine, check for leaks, and monitor fuel trims. Fine-tune with a wideband. Expect to spend $300–$500 for a professional remote dyno tune.

Reliability Considerations and Long-Term Use

A common concern with turbocharging the 4.0L is longevity. The TS Performance kit, when installed correctly and tuned conservatively, can last for tens of thousands of miles without major issues. However, the stock engine’s connecting rods are the weak point — they become a risk above 350 crank horsepower. If you plan to push beyond 300 WHP, consider forged rods and a head stud upgrade.

Oil changes with high-quality synthetic oil every 3,000–5,000 miles are critical because the turbo relies on clean oil for lubrication. Also, allow the engine to idle for 30 seconds after a hard run to cool the turbo and prevent oil coking. Using a turbo timer can automate this.

Comparing the TS Performance 3.5-Inch Kit to Other Turbo Options

For Jeep XJ owners, there are several turbo options: the TS Performance 3.5-inch, the Banks Power sidewinder, and a variety of universal kit builds. Here’s how the TS kit stacks up:

  • TS Performance 3.5-inch: Best balance of flow, spool, and support. The 3.5-inch inlet allows for more boost at lower RPM than smaller turbos. Peak power potential is higher than the Banks sidewinder.
  • Banks Power Sidewinder: A larger turbo (3.5-inch intake too) but designed for diesel-like spool. Banks kit includes a full intercooler and is CARB-compliant in some states. Power numbers are similar, but the TS kit is often more affordable.
  • Universal T3/T4 Kits: Cheaper but require fabrication for piping and mounting. Quality varies widely. The TS kit is plug-and-play with proper bracketry.

For most owners, the TS Performance kit offers the best combination of performance, fitment, and aftermarket support. The community at NAXJA (North American XJ Association) has extensive threads on installing and tuning this specific kit.

Conclusion

The TS Performance 3.5-inch XJ Turbo Kit is not just a bolt-on — it’s a transformation. With real-world horsepower increases from 180 stock horsepower to 300–360 horsepower at the flywheel, it ranks among the most effective single upgrades you can make to a Jeep Cherokee XJ. The key to achieving these numbers lies in careful installation, proper tuning, and supporting modifications like an intercooler and upgraded fuel delivery. For anyone serious about off-road performance or simply wanting a fun daily driver with serious torque, this kit delivers. Before buying, assess your engine’s health and budget for tuning. With the right approach, you’ll join the growing ranks of XJ owners who have discovered just how potent the old 4.0-liter can really be.