Understanding the Hennessey HPE900 Upgrade

The Dodge Durango Hellcat already delivers 710 horsepower straight from the factory, making it one of the most capable SUVs ever built. Yet for enthusiasts who crave more, the Hennessey HPE900 kit transforms this beast into a 900-horsepower monster. Developed by Hennessey Performance Engineering, this package includes an upgraded supercharger, high-flow intake system, revised fuel delivery components, and a custom ECU tune. The result is a Durango that not only launches harder but also pulls relentlessly at highway speeds. This guide provides a detailed, step-by-step breakdown of the installation process, covering every critical aspect from preparation to final tuning.

What the HPE900 Kit Includes

Before diving into the installation, it is essential to understand exactly what comes in the Hennessey HPE900 kit. The package is designed as a comprehensive upgrade, not just a simple pulley swap. Typical contents include:

  • High-flow supercharger – a larger, more efficient unit (often a 2.65L or 2.7L) that replaces the factory 2.4L blower. It moves significantly more air, which is the foundation for the power gain.
  • Lower supercharger pulley – matched to the new blower to increase boost pressure safely.
  • High-flow intake system – a larger air filter, intake tube, and heat shield that reduce inlet restriction and keep charge air temperatures lower.
  • Revised fuel injectors and fuel pump – necessary to deliver the additional fuel required at higher boost levels. Hennessey typically uses 1300cc or larger injectors and a BAP (Boost-A-Pump) or upgraded fuel pump module.
  • Performance intercooler bricks – thicker or more efficient cores that help manage intake air temperatures generated by the increased boost.
  • ECU calibration – a custom tune loaded onto the vehicle’s PCM via an HPTuners or similar device. This tune adjusts timing, fuel maps, boost targets, and transmission shift points.
  • NGK spark plugs (one step colder) – essential for preventing detonation under higher cylinder pressures.
  • Gaskets, seals, and hardware – all new OEM-quality components needed for a leak-free installation.

Note: The exact contents may vary based on the current revision of the kit. Always verify the packing list against the official Hennessey documentation before beginning work. You can view the latest specifications on the Hennessey HPE900 product page.

Tools and Materials Required

Having the correct tools on hand is critical for a smooth installation. In addition to standard hand tools, you will need some specialized items:

Essential Hand Tools

  • Metric and SAE socket set (3/8” and 1/2” drive, deep and shallow sockets from 8mm to 21mm)
  • Combination wrenches (8mm–19mm)
  • Torque wrench (preferably two: one for low-range (5–75 lb-ft) and one for high-range (50–250 lb-ft))
  • Flathead and Phillips screwdrivers (large and small)
  • Pry bar or trim removal tool
  • Pliers (needle-nose and slip-joint)
  • Allen/hex key set (T-handle preferred)
  • Wire cutters and strippers (if rewiring BAP harness)
  • Vacuum gauge (for leak testing)

Specialty Tools

  • Supercharger pulley removal/installation tool (Hennessey supplies one, but a rental from an auto parts store works)
  • Fuel pressure test kit
  • Scan tool or HP Tuners MPVI2 (to flash the ECU and monitor sensor data during startup)
  • Lift or jack stands (vehicle must be safely raised for undercar work)
  • Coolant vacuum fill tool (to avoid air pockets when refilling the supercharger cooling system)

Consumables and Shop Supplies

  • Clean shop rags
  • Brake cleaner or degreaser
  • Thread locker (medium-strength Loctite 243)
  • Anti-seize compound
  • Dex-Cool (orange) or Mopar OAT coolant (specified in the manual)
  • Engine oil (if removing the supercharger oil system)
  • New supercharger oil (Hennessey provides it, but verify quantity)
  • Ziploc bags and marker for organizing bolts

Preparation: Workspace and Vehicle

Proper preparation prevents problems. Take the time to set up your workspace and prepare the Durango Hellcat before touching any components.

Safety First

  • Disconnect the negative battery terminal and isolate it with a non-conductive cover. Wait at least 15 minutes for the airbag system capacitors to discharge.
  • Work in a well-ventilated area – gasoline fumes and coolant vapors can accumulate.
  • Wear safety glasses and mechanic’s gloves at all times.
  • Use jack stands rated for the vehicle’s weight (Durango Hellcat is ~5,700 lbs). Never rely solely on a floor jack.

Vehicle Preparation

  • Park the Durango on a level concrete floor. Chock the rear wheels.
  • Allow the engine to cool completely (at least 2 hours after a drive). The supercharger and surrounding components get extremely hot.
  • Drain the engine coolant: locate the radiator drain petcock on the passenger side lower corner. Drain into a clean container if you plan to reuse it (Mopar OAT coolant can be reused within 30 days).
  • Remove the engine cover and any plastic trim that obstructs access to the supercharger – typically the intake crossover tube, strut tower brace, and the engine beauty cover.
  • Take reference photos of the belt routing, hose connections, and wiring harness positions. This will simplify reassembly.

Read the Manual – Twice

Hennessey provides a detailed installation manual with specific torque values, belt part numbers, and fuel pressure targets. Read it cover to cover before beginning. If you have any doubts, contact Hennessey technical support at 979-885-1300 or check their tech support page. They are responsive and can clarify steps.

Step-by-Step Installation Process

The following steps assume you have basic mechanical experience. Do not attempt this installation if you are not comfortable disassembling and reassembling engine components. If in doubt, have the work performed by a certified Hennessey installer or a reputable performance shop.

Step 1: Remove the Factory Supercharger, Intake, and Exhaust Components

The first major task is removing the OEM supercharger and clearing the area for the new hardware.

  • Remove the factory airbox and intake tube. Unclip the mass air flow sensor connector and set the sensor aside carefully. Remove the entire intake assembly.
  • Disconnect the supercharger cooling system. There are two coolant lines running from the front heat exchanger to the supercharger bricks. Use a drip pan and expect some coolant loss. Cap the lines to prevent contamination.
  • Unbolt the supercharger. There are 10–12 bolts (E10 Torx or 13mm) holding the blower to the intake manifold. Work in a crisscross pattern to avoid warping the manifold. Lift the supercharger straight up – it is heavy (approximately 60 lbs). Use a helper or a hoist.
  • Remove the lower pulley. You will need a pulley puller. Mark the position of the original pulley before removal; this helps with belt alignment later.
  • Remove the factory exhaust manifolds and downpipes. The HPE900 kit often includes upgraded headers or high-flow cats. Unbolt the manifolds from the cylinder heads (15mm bolts) and disconnect the oxygen sensors. It may be easier to remove the front wheels and inner fender liners for access.

Keep all hardware organized. It is common to reuse many of the factory bolts, but some (like supercharger mounting bolts) may be replaced with ARP studs provided in the kit.

Step 2: Install the Hennessey Upgraded Supercharger

Now you will mount the heart of the HPE900 kit.

  • Prepare the new supercharger. Transfer the OEM throttle body to the new unit (if the kit does not include a new one). Clean the gasket surfaces. Install the new intercooler bricks (these are usually pre-installed, but verify).
  • Add supercharger oil. The new blower may require oil filling before installation. Use the specified oil (usually Dexron III or a special synthetic). Fill to the correct level – overfilling can cause cavitation.
  • Position the supercharger. Lower it onto the intake manifold using a new gasket (supplied). Hand-tighten the bolts, then torque in a spiral pattern to the value in the manual (typically 18 lb-ft).
  • Install the lower pulley. Use the supplied pulley tool. Draw the pulley onto the supercharger snout carefully. Apply anti-seize to the snout threads. Torque the retaining bolt to 240 lb-ft (check manual – some kits use a different spec).
  • Route the new belt. The kit includes a shorter belt to accommodate the larger pulley diameter. Refer to your reference photo or the belt routing diagram. Tension the belt using the automatic tensioner.

Step 3: Install the High-Flow Intake System

The new intake must deliver clean, cold air to the supercharger.

  • Mount the intake heat shield. Secure it using the provided brackets. Ensure it seals against the hood liner to prevent hot engine air from being drawn in.
  • Attach the intake tube. Connect it to the supercharger throttle body adapter. Use a new silicone coupling and T-bolt clamps. Tighten evenly – overtightening can warp the silicone.
  • Reinstall the mass air flow sensor. Transfer it from the factory tube to the new tube. Ensure the orientation matches the factory position (arrow indicating air flow direction). Secure the wiring harness to avoid chafing.
  • Install the air filter. Hennessey typically uses a conical dry filter. Position it inside the heat shield and tighten the clamp.

Step 4: Install the Fuel System Upgrades

Higher boost requires more fuel. This step is critical for reliability.

  • Replace the fuel injectors. Remove the fuel rail (depressurize the system first by pulling the fuel pump fuse and cranking the engine for 3 seconds). Swap the injectors, lubricating the O-rings with clean engine oil. Reinstall the rail and torque the bolts to 8 lb-ft.
  • Install the boost-a-pump or upgraded fuel pump. If using a BAP, wire it according to the instructions – typically splice into the fuel pump power wire and ground. Mount the BAP controller in a protected location (the rear cargo area under the trim panel works well).
  • Check fuel pressure. With the key on (engine off), confirm the fuel pressure reaches 58–62 psi. If not, verify wiring and pump operation.

Step 5: Install the Exhaust System

Let the engine breathe out.

  • Mount the new headers or downpipes. Use new gaskets and apply anti-seize to the manifold studs. Torque to 18 lb-ft in a sequence from the center outward.
  • Install the high-flow catalytic converters or cat-less pipes. Ensure the oxygen sensor bungs are accessible. Use the supplied oxygen sensor spacers if needed to prevent CELs.
  • Connect the cat-back exhaust. The kit may include a Hennessey cat-back or require you to reuse the factory exhaust. Clamp all connections and verify the exhaust does not contact the underbody.

Step 6: ECU Tuning and Initial Startup

This is where the magic happens. Do not start the engine without flashing the new calibration.

  • Upload the Hennessey tune. Using HP Tuners VCM Suite, connect to the OBD-II port. Follow the instructions to load the custom calibration file provided by Hennessey. Do not start the engine during the flash; keep the battery charger connected as the process draws current.
  • Prime the fuel system. Turn the key to RUN (without starting) three times, waiting 5 seconds each time. This builds fuel pressure.
  • Start the engine. It may crank a little longer than usual. Listen for any strange noises – pulley chirp, belt squeal, or vacuum leaks. If the engine idles roughly, check for intake leaks around the supercharger and throttle body.
  • Check for coolant and fuel leaks. While the engine warms up, inspect all connections. Bleed the supercharger cooling system: run the engine with the coolant reservoir cap off until the thermostat opens and air burps out.

Important: Do not rev the engine past idle until it reaches operating temperature. The PCM needs to learn the new fuel trims and idle air control.

Step 7: Post-Installation Checks and Break-In

The installation is complete, but the work is not done.

  • Test drive carefully. Start with light throttle for 50 miles. This allows the rings to seat and the oil to distribute. Avoid full-throttle runs until the engine has been through at least one heat cycle (cold start, warm up, cool down).
  • Check belt tension and alignment. After 20 miles of driving, re-torque the supercharger pulley bolt and inspect the belt for wear.
  • Monitor data. Use your HP Tuners scanner to watch knock sensor activity, fuel trims, and boost pressure. Boost should peak at 13–15 psi on the gauge. If you see persistent knock (KR >2°), stop driving and contact Hennessey – you may need a revised tune.
  • Schedule a dyno session. To confirm the power output, put the Durango on a chassis dyno. Aim for 880–920 horsepower at the wheels (depending on fuel and ambient conditions). If the numbers are low, check for boost leaks or insufficient fuel pressure.

Common Pitfalls to Avoid

Even experienced mechanics can run into issues. Watch out for these:

  • Coolant air pockets. The supercharger cooling system is prone to trapping air. Use a vacuum fill tool to prevent overheating. If the engine runs hot after installation, suspect air in the intercooler circuit.
  • Overtightening the supercharger bolts. The aluminum intake manifold threads can strip. Always use a torque wrench and never exceed the specified value.
  • Incorrect belt routing. A misrouted belt can destroy the alternator or water pump pulley. Double-check against the manual and your reference photos.
  • Skipping the break-in period. The upgraded supercharger and fueling components need time to settle. Aggressive driving too soon can lead to detonation and engine damage.

Tools and Resources for Troubleshooting

If you encounter problems, these resources can help:

  • Hennessey Performance Tech Support – 979-885-1300 (Monday–Friday, 8 AM–5 PM CST)
  • Dodge Durango Hellcat Forums – The Hellcat Forum Durango section has owner experiences and DIY guides.
  • HP Tuners Forum – For custom tuning questions, visit HP Tuners Community.

Conclusion

Installing the Hennessey HPE900 kit on a Dodge Durango Hellcat is not a simple afternoon project – it requires mechanical skill, patience, and attention to detail. However, when done correctly, the reward is extraordinary: an SUV that can outrun sports cars while still seating seven. By following this step-by-step breakdown and respecting the installation procedures, you give yourself the best chance for a reliable, powerful build. Always confirm torque specifications with the supplied manual, use quality tools, and do not hesitate to seek professional help for the tuning phase. With proper care, your 900+ horsepower Durango will provide miles of thrilling, dependable performance.