Introduction

The Mercedes-Benz M156 engine is one of the most celebrated naturally aspirated V8s ever produced, delivering potent power across a broad rev range. However, even this engineering masterpiece can benefit from forced induction. Installing a RENNtech supercharger kit transforms the M156 into a torque monster, reliably boosting horsepower from the factory 450-518 hp range to well over 600 hp, with peak gains exceeding 150 hp on many applications. This step-by-step guide provides the detailed procedures, safety precautions, and technical insights needed to complete a professional-grade installation in your shop or garage.

Before starting, always consult the latest RENNtech installation manual for your specific kit variant (e.g., stage 1 vs. stage 2). The M156 responds exceptionally well to supercharging when proper attention is paid to cooling, fuel delivery, and belt alignment. This guide assumes you have a moderate level of mechanical experience and access to standard shop tools.

Tools and Materials Needed

Gather all items before the first wrench turns. Beyond the standard list, specific torque wrenches (inch-pounds and foot-pounds), a belt tension gauge, and a multimeter for electrical checks will ensure success.

  • RENNtech Supercharger Kit (includes bracket, supercharger unit, pulleys, belt, intake piping, intercooler, hardware, and instructions)
  • Socket Set – metric 1/4″, 3/8″, and 1/2″ drive, including 8mm through 21mm sockets and hex/Allen sockets
  • Torque Wrenches – one low range (10-50 ft-lb) and one high range (50-150 ft-lb) with accurate calibration
  • Ratchet and Breaker Bar – 1/2″ breaker bar (24″ minimum) for stubborn bolts
  • Wrenches – combination wrenches 8mm-21mm, plus a large crescent wrench for pulley hub
  • Screwdrivers – flathead (medium) and Phillips (size #2)
  • Pry Bar – trim-safe plastic pry tools for connectors and covers
  • Shop Towels – lint-free for cleaning gasket surfaces
  • Engine Oil – appropriate viscosity for M156 (0W-40 or 5W-40 per Mercedes spec)
  • Coolant – Mercedes-approved blue or pink concentrate (distilled water for mixing)
  • Silicone Spray or Lubricant – for hose and duct installation
  • Safety Glasses and Mechanic Gloves
  • Fire Extinguisher – rated for Class B (flammable liquids)
  • Multimeter – for checking battery and sensor voltages
  • Battery Tender – optional but recommended to keep ECU memory alive
  • Digital Camera or Phone – to document wiring and hose routing before disassembly

Preparation – Critical First Steps

Proper preparation prevents costly mistakes. Work in a clean, well-ventilated area with adequate lighting. Raise the vehicle on sturdy jack stands if needed for lower access. Disconnect the battery’s negative terminal and isolate it to avoid accidental contact. Wait 10 minutes for the ECU capacitors to discharge.

Step 1: Disconnect the Battery

Using a 10mm socket, loosen the negative terminal clamp and remove the cable. Tuck it away from the terminal to prevent reconnection. Do not skip this step – accidental shorts can damage the ECU or trigger airbag systems.

Step 2: Remove the Engine Cover and Access Covers

The M156 engine cover is held by four rubber grommets and two clips on the ignition coil covers. Gently pull upward to release the grommets, then unclip the harness retainers. Set the cover aside in a clean area. Remove any plastic beauty covers over the intake plenum using a T25 Torx or 8mm socket.

Step 3: Inspect the Engine and Cooling System

Check for existing oil leaks, loose hoses, or worn belts. A supercharger places additional stress on the cooling system. If your coolant is old or low, replace it now. Drain the coolant from the radiator petcock to the appropriate level for intercooler installation (some kits require coolant line taps). Use a catch pan and dispose of old coolant properly.

Removing the Factory Intake System

Clear access to the front of the engine is essential for supercharger mounting.

Step 4: Disconnect Sensors and Vacuum Lines

Unplug the mass air flow (MAF) sensor connector(s) by pressing the release tab. Label or photograph the vacuum lines attached to the intake snorkel and throttle body. Disconnect the crankcase ventilation hose at the intake tube. Remove the throttle body boots by loosening the worm-gear clamps with a 7mm socket or flathead screwdriver.

Step 5: Remove the Factory Airbox and Intake Ducting

On most M156 vehicles (e.g., C63 AMG, E63 AMG), the airbox is held by two bolts at the bottom and a rubber grommet at the top. Lift it straight up after disconnecting the MAF sensor harness. Remove the entire intake tube from the throttle body to the airbox. Keep the hardware organized – you may reuse some clamps.

Step 6: Remove the Engine Fan and Shroud (if applicable)

For better access to the front of the engine, remove the electric fan assembly. Disconnect the fan wiring harness (two connectors) and unbolt the shroud from the radiator core support using a 10mm socket. Lift the fan unit out carefully to avoid damaging the radiator fins.

Installing the RENNtech Supercharger

This is the core of the installation. The RENNtech kit typically includes a specially cast aluminum bracket that mounts to the front of the engine using existing bolt holes on the timing cover and cylinder head.

Step 7: Install the Supercharger Bracket

Clean the mounting surfaces on the engine block and timing cover with a degreaser. Apply a small amount of medium-strength thread locker (e.g., Loctite 243) to the supplied bolts. Position the bracket and snug all bolts hand-tight. Then torque in sequence (refer to kit manual) to the specified value – commonly 25-30 ft-lb for M10 bolts. Do not overtighten – the timing cover is aluminum and prone to stripping.

Step 8: Prepare and Mount the Supercharger Unit

Remove the supercharger from its packaging. Inspect the inlet and outlet ports for debris. Some kits include a drive coupler that must be installed on the supercharger snout; apply a light coat of anti-seize to the coupler splines. Lift the supercharger into position on the bracket. Align the pulley with the crankshaft pulley and idler pulleys. Insert the bracket bolts and torque them gradually in a cross pattern to 20-25 ft-lb.

Step 9: Install Pulleys and Belt

Place the supplied supercharger pulley on the snout (if not pre-installed). Use a pulley installer tool to press it flush. Install the drive belt following the routing diagram in the manual. The M156 often requires a shorter belt than stock. Rotate the crankshaft by hand to verify belt alignment and tension. Use a belt tension gauge to achieve the specified value (typically 130-160 lbf for a new belt). Adjust the tensioner if adjustable, or confirm the tensioner spring is within spec.

Step 10: Connect the Intake Piping and Intercooler

RENNtech kits use an air-to-water intercooler mounted in front of the radiator. Secure the intercooler core using the supplied brackets and bolts. Connect the silicone charge pipes from the supercharger outlet to the intercooler, and from the intercooler to the throttle body. Use T-bolt clamps for a leak-free seal. Tighten to 4-6 ft-lb – over-tightening can distort the silicone. Reconnect the blow-off valve (if included) and ensure the vent hose is routed away from the intake stream.

Finalizing the Installation – Critical Checks

Before reassembling the intake system, double-check every connection.

Step 11: Reinstall the Factory Intake System with Modifications

Your kit may include a modified airbox or a new intake tube. Reattach the factory airbox or install the new one. Reconnect the MAF sensor(s). Ensure the air filter is clean – consider replacing it if it has over 15,000 miles. Reinstall the factory engine fan and shroud. Secure all wiring away from moving parts.

Step 12: Refill Coolant and Check for Leaks

Refill the cooling system with the correct Mercedes-approved coolant and distilled water mix (50/50). Use a vacuum filler tool if available to bleed air. Pressurize the system to 15 psi using a cooling system pressure tester and inspect all hose connections, especially the intercooler water lines. Fix any leaks before starting the engine.

Step 13: Reconnect the Battery and Prime the System

Reconnect the negative battery cable. Turn the ignition key to position 2 (engine off) for 10 seconds to allow the ECU to power up. Do not start yet. If the kit includes a separate supercharger oil reservoir, fill it to the indicated level with the supplied oil (often synthetic 75W-90 gear oil).

Step 14: Initial Start-Up and Leak Check

Start the engine and let it idle. Watch the check engine light – it should go off after a few seconds. Listen for any unusual whining from the supercharger (a slight whine is normal; a grinding sound indicates misalignment). Check for coolant leaks, oil leaks, and intake leaks. Use a smoke machine or carburetor cleaner around the charge piping to detect vacuum leaks. Let the engine reach operating temperature (coolant at 190°F). Cycle the RPM to 2000 and back to idle several times to purge air from the intercooler system.

Tuning – Essential for Performance and Safety

Installing a supercharger without tuning the ECU is dangerous. The M156’s high compression ratio and direct injection require precise fuel and spark adjustments. RENNtech typically provides a flashed ECU or a handheld tuner with the kit. If not, you must obtain a custom tune from a reputable shop like Eurocharged, Weistec, or an authorized RENNtech dealer. Skimping on tuning can lead to detonation, overheating, or piston failure. After tuning, log air-fuel ratios and knock sensors to confirm safe operation.

Test Drive and Break-In

After verifying no leaks and proper idle, take the vehicle for a moderate test drive. Avoid full throttle for the first 50 miles to allow the supercharger gears and belts to bed in. Pay attention to boost gauge readings (if equipped) – expect 6-9 psi on standard kits. Listen for belt chirps or slipping; adjust tension if needed. Perform a few hard pulls in 3rd gear (from 2000 to 6000 rpm) while monitoring coolant temperature and oil pressure. If everything remains stable, the installation is successful.

Performance Gains

A properly installed RENNtech supercharger on the M156 yields:

  • Horsepower: 600-650 hp at the crank with Stage 1, 700+ hp with Stage 2 and upgraded fueling.
  • Torque: 600-650 lb-ft, usable from 3000 rpm.
  • 0-60 mph: drops from the mid-4s to the low 3s (depending on vehicle weight and tires).
  • Drivability: Linear power delivery with minimal lag – far more tractable than most turbo conversions.

Maintenance and Long-Term Care

The M156 supercharger system requires attentive care to maintain reliability.

  • Supercharger Oil: Check every 5,000 miles. Change annually or every 10,000 miles using the specified synthetic oil.
  • Drive Belt: Inspect for cracks or glazing every service interval. Replace every 30,000 miles.
  • Intercooler System: Check coolant level in the separate reservoir (if used). Flush and replace every two years.
  • Hoses and Clamps: Retorque T-bolt clamps after thermal cycling (first 500 miles). Inspect silicone boots for softening or oil contamination.
  • Tune Updates: Re-check with your tuner after major upgrades. Ensure no check engine lights are pending.
  • PCV System: Upgrade the crankcase ventilation if not already done – excessive blow-by can cause oil ingestion into the supercharger.

External Resources

For further details, refer to the official RENNtech Supercharger product page for the latest kit specifications and software support. Learn more about the M156 engine’s architecture on Wikipedia. For community tips and troubleshooting, the MBWorld C63 AMG forum has dedicated supercharger threads.

Conclusion

Installing a RENNtech supercharger on your M156 is one of the most rewarding modifications you can make. The power increase transforms the driving experience while retaining the engine’s renowned character. By following this detailed guide – from preparing tools through tuning and maintenance – you can complete the installation with confidence. Always prioritize safety, use the correct torque values, and invest in professional tuning. The result is a street-dominating AMG that still remains civil in daily driving.