Understanding the Rotrex C38 Supercharger

The Rotrex C38 is a centrifugal supercharger known for its compact design, high efficiency, and linear power delivery. Unlike traditional positive-displacement blowers, the Rotrex uses a patented traction drive system to spin the impeller at extremely high speeds—often exceeding 100,000 rpm. This design allows the supercharger to build boost progressively with engine RPM, providing excellent drivability and peak power when you need it most. For the Ram TRX with its 6.2L supercharged Hellcat engine, adding a second forced-induction device might seem redundant, but the Rotrex C38 is typically used as an additional boost source in a compound setup or as a replacement for the factory supercharger in certain high-horsepower builds. This guide focuses on installing the Rotrex C38 as a supplemental or standalone system to significantly increase output beyond the TRX’s already potent 702 horsepower.

Tools, Parts, and Safety Equipment

Before you begin, gather everything you’ll need. A complete Rotrex C38 kit for the Ram TRX typically includes the supercharger head unit, mounting bracket, pulley system, intake and discharge piping, intercooler or charge cooler, oil supply and return lines, and all necessary hardware. Ensure your kit is specific to the TRX or the Hellcat platform to avoid fitment issues.

Required Tools

  • Metric and SAE socket set (3/8” and 1/2” drive)
  • Combination wrenches (8mm to 22mm)
  • Torque wrench (capable of 10–150 ft-lbs)
  • Hex keys (Allen wrenches) in various sizes
  • Pry bar or trim removal tools
  • Vacuum pump and coolant flush kit
  • OBD2 scanner for post-install diagnostics
  • Jack and jack stands (or lift)
  • Multimeter for electrical checks
  • Safety glasses, mechanic gloves, and fire extinguisher

Consumables and Supplies

  • Engine coolant (OEM or equivalent)
  • Supercharger oil (Rotrex specified)
  • Thread locker (blue Loctite)
  • Dielectric grease for connectors
  • Shop towels and brake cleaner

Pre-Installation Preparation

Working on a Ram TRX’s engine bay is tight, especially with the factory supercharger occupying the valley. Plan to remove the engine cover and potentially the intake manifold. Park the truck on a level surface, disconnect the battery (negative terminal first), and allow the engine to cool completely. If the vehicle has been running, the coolant and supercharger housing can reach temperatures that cause burns. Refer to the factory service manual for torque specs and specific procedures. It’s also wise to review the Rotrex installation manual thoroughly before turning a single bolt.

Step 1: Drain Coolant and Prepare the Cooling System

The Rotrex C38 system integrates with the engine’s cooling loop or uses a dedicated intercooler circuit. To avoid spills, drain the coolant from the radiator petcock and remove the reservoir cap. Disconnect the upper and lower radiator hoses as needed for access. If your kit includes a charge cooler, plan its location—typically in front of the radiator or alongside the factory intercooler.

Step 2: Remove the Engine Cover and Intake Manifold

The engine cover is held by push clips or bolts—lift it straight up after releasing all fasteners. Next, disconnect the intake manifold. On the TRX, this involves removing the throttle body, unplugging sensors (MAP, IAT, etc.), and disconnecting fuel lines if necessary. Use caution with plastic clips and electrical connectors. Keep fasteners organized in labeled bags.

Installing the Rotrex C38 Supercharger: Phase 1 – Mounting

With the intake tract cleared, you’ll see the front of the engine and the accessory drive area. The Rotrex C38 mounts using a custom bracket that positions the supercharger on the passenger side near the front accessory belt. This location is chosen for belt routing efficiency and clearance from other components.

Step 3: Install the Mounting Bracket

Bolt the supplied bracket to the engine block using the provided hardware. Do not fully tighten until you verify alignment with the crank pulley. Use thread locker on bolts that go into aluminum threads. The bracket must sit flush—any gap indicates an obstruction or incorrect part.

Step 4: Mount the Rotrex C38 Unit

Slide the supercharger onto the bracket, aligning the pulley. Install the bolts and torque to specification (typically 18–25 ft-lbs for M8 bolts). Install the drive belt according to the kit’s routing diagram. The belt should have a tensioner—adjust so that deflection is roughly 1/2 inch under moderate thumb pressure. Over-tensioning can damage the supercharger bearings.

Phase 2 – Plumbing and Oil System

The Rotrex C38 requires its own oil supply and cooling circuit. The kit includes a pump, reservoir, and hoses. Proper routing is critical for longevity.

Step 5: Connect Oil Supply and Return Lines

Locate an oil pressure source on the engine—many kits tap into the oil pressure sending unit port or use a sandwich plate between the oil filter and block. The return line should drain above the oil level in the pan or into the valve cover. Use only Rotrex-approved oil. Bleed the system by running the pump without engine start to circulate oil through the supercharger for 30 seconds.

Step 6: Install Intercooler and Intake Piping

Mount the intercooler (air-to-air or water-to-air) in the front bumper area. Secure it with brackets, ensuring no contact with the radiator or A/C condenser. Run silicone hoses from the supercharger outlet to the intercooler, then to the throttle body. All clamps should be stainless steel, torqued evenly to prevent boost leaks. Consider adding a blow-off valve or bypass valve if not included.

Phase 3 – Electrical Integration

The Rotrex C38 kit may include a dedicated oil pump and boost controller wiring. You’ll also need to integrate the supercharger’s bypass valve (if present) and possibly a MAP sensor upgrade.

Step 7: Wire the Oil Pump and Sensors

Run the oil pump power wire to a switched 12V source (e.g., fuse box under the hood). Use a relay to avoid overloading the circuit. Ground the pump securely to the chassis. For boost sensors, splice into the factory harness using t-taps or solder connections, and seal with heat shrink.

Step 8: Reconnect the Battery and Check Electricals

Reconnect the battery negative terminal. Turn the key to the “on” position without starting. Listen for the oil pump priming. Check for error codes on the OBD2 scanner. If the pump runs and no codes appear, proceed to the next step.

Final Assembly and Leak Testing

Reassemble all components removed earlier—the intake manifold, engine cover, and any trim pieces. Double-check all hose clamps, electrical connectors, and bolt torques. This is the moment to catch mistakes before starting the engine.

Step 9: Refill Coolant and Oil

Fill the cooling system with the correct mix. Bleed air from the system by running the engine with the radiator cap off (follow the TRX’s bleed procedure). Check the oil level—if you used a sandwich plate for the supercharger, top off the engine oil.

Step 10: Start the Engine and Inspect for Leaks

Start the engine and let it idle. Listen for unusual whining (beyond the normal Rotrex sound) or belt squeal. Inspect all connections for coolant, oil, or air leaks. Use a spray bottle with soapy water to check boost piping for leaks at idle and low RPM. If the idle is rough, recheck vacuum lines and throttle body connection.

Tuning Your Ram TRX for the Rotrex C38

This is the most critical step. Adding the Rotrex C38 without proper engine calibration can cause detonation, high exhaust gas temperatures, or catastrophic engine failure. The TRX’s factory ECU will not compensate for additional boost and altered air/fuel ratios. You have two main options:

  • Custom Tune: Work with a professional tuner who has experience with Hellcat/Ram TRX platforms. They will adjust fuel maps, ignition timing, boost targets, and transmission shift points via the ECU (often using HP Tuners or similar).
  • Standalone ECU: For extreme power goals, consider a MoTec or Haltech system that completely bypasses the factory ECU. This is more expensive but offers unlimited adjustability.

Most TRX owners with a Rotrex C38 on pump gas achieve 800–1,000 whp with a safe tune. Always perform a dyno session to verify air/fuel ratios and watch for knock. Install a wideband O2 sensor and boost gauge for real-time monitoring. Never drive the vehicle hard before the tune is finalized.

Post-Installation Break-In and Maintenance

After tuning, follow a break-in procedure for the supercharger itself. Drive gently for the first 100 miles, varying engine speed and avoiding full throttle. Change the Rotrex oil after the first 500 miles, then every 10,000 miles or annually. Check belt tension and condition regularly—centrifugal superchargers are hard on belts. Keep the intercooler clean for optimum intake air temperatures.

Frequently Asked Questions

Will the Rotrex C38 fit under the TRX’s hood?

Yes, the kit is designed to clear the factory hood, though some aftermarket intake pipes may require trimming of inner fender liners. Always test fit before final assembly.

Do I need to upgrade the fuel system?

For moderate boost (6–9 psi), the stock fuel system with higher-flow injectors may suffice. Above 9 psi, you’ll need an upgraded fuel pump (e.g., Fore Innovations) and larger injectors. Consult with your tuner.

How much horsepower gain can I expect?

With a conservative tune and 7–8 psi of boost from the Rotrex C38, expect a gain of 150–200 whp over a stock TRX. With aggressive tuning and supporting mods, 300+ whp gains are achievable.

Conclusion

Installing a Rotrex C38 supercharger on your Ram TRX is a major project that rewards you with spectacular power gains and a unique driving experience. By following this step-by-step guide, paying close attention to mounting, plumbing, and tuning, you can transform your already capable truck into a true track-day monster. For additional technical resources, consult the Rotrex official website and the HP Tuners software support pages. Join online forums like RamTRX.com for community-shared install experiences. Always prioritize safety and professional tuning—your engine will thank you.