The AMG GT is already a formidable machine straight from the factory, blending Mercedes-AMG's racing heritage with everyday usability. Yet for a select group of enthusiasts, the stock output—even the 577 hp of the GT R—leaves room for more. Enter the HPE800 Supercharger from Hennessey Performance, a turnkey forced-induction upgrade designed to transform the AMG GT into a bona fide supercar killer. This article breaks down the real costs, the tangible performance gains, and the critical considerations before committing to the install.

What is the HPE800 Supercharger?

The HPE800 Supercharger is a complete bolt-on supercharger system engineered specifically for the Mercedes-AMG GT (chassis C190 / R190). Developed by Hennessey Performance Engineering in Texas, the kit is designed to increase output to around 800 horsepower at the crank—roughly a 200-250 hp increase over the standard AMG GT and GT S.

The system replaces the stock twin-scroll turbochargers with a positive-displacement supercharger, mounted on a custom intake manifold. Key components include:

  • Whipple twin-screw supercharger unit with integrated heat exchanger
  • High-flow air intake system with larger filter and ducting
  • Larger fuel injectors (typically 1000cc or higher)
  • Upgraded fuel pumps to maintain sufficient delivery
  • Custom intercooler system (air-to-water, often a larger core)
  • High-flow catalytic converters or off-road downpipes
  • ECU calibration via handheld programmer or remote tuning

Unlike a centrifugal supercharger, the twin-screw design provides instant boost from low RPM, which massively transforms throttle response. The HPE800 is not a "universal" kit—it's engineered for a precise fit inside the AMG GT's engine bay, which requires some modification to ancillary components.

Cost Breakdown: What You'll Actually Spend

The price of the HPE800 installation varies widely based on geographic location, shop rates, and whether you opt for supporting modifications. Below is a realistic breakdown of the major cost centers.

Supercharger Kit (Hardware)

The base HPE800 kit itself runs $8,000–$10,000. This includes the supercharger, intercooler, fuel system components, and the required brackets and plumbing. Prices fluctuate with supply and any current promotions from Hennessey or their distributors.

Labor Costs

Installation is intensive. The engine bay must be partially disassembled to access the intake and exhaust manifolds, fuel rails, and cooling system. A skilled shop will quote $1,500–$3,000 for the labor, depending on whether additional modifications (exhaust, intercooler pipes, etc.) are included.

Tuning and Calibration

Proper ECU tuning is mandatory for drivability and reliability. Hennessey provides a base calibration, but local dyno tuning is highly recommended to optimize for your fuel quality and climate. Expect $1,000–$2,000 for a custom tune, including dyno time. Some shops bundle this with labor.

Supporting Modifications

To handle the extra power safely, most owners plan for the following upgrades. Prices are estimates for parts only:

  • High-performance exhaust system (cat-back or full): $1,500–$3,000
  • Larger intercooler cores or upgraded heat exchanger: $800–$1,500
  • Transmission software upgrade (7-speed DCT): $500–$1,000
  • Upgraded charge pipes / intake elbow: $300–$600
  • Cooling system upgrades (radiator, oil cooler): $1,000–$2,000
  • Brake pads / fluid for track use: $500–$1,000

If you do only the essential supporting mods (exhaust + intercooler + tune), add another $1,000–$3,000. A comprehensive reliability build can push the total well past $20,000.

Total Install Range

A conservative estimate for a properly executed HPE800 install (kit + labor + tune + basic supports) is $11,500–$18,000. A full "stage 2" setup with transmission upgrades and heavy-duty cooling can exceed $25,000.

Performance Benefits: From Grand Tourer to Supercar Slayer

Horsepower and Torque

On 93 octane pump gas, the HPE800 consistently delivers 780–810 hp at the crank and 720–750 lb-ft of torque. On the dyno, this translates to roughly 650–680 whp, depending on the dyno type and drivetrain losses. The gains are not just peak—the torque curve is massively fattened across the entire rev range, eliminating the slight lag present in the turbocharged M178 engine.

Acceleration and Quarter-Mile Times

With the HPE800 installed, a well-prepped AMG GT can achieve:

  • 0–60 mph: 2.8–3.1 seconds (down from ~3.6 stock)
  • ¼ mile: 10.3–10.8 seconds @ 130–135 mph
  • 0–100 mph: ~6.2 seconds

These numbers put the HPE800 AMG GT in the company of the McLaren 720S, Ferrari SF90, and Porsche 911 Turbo S. The supercharger's instant boost makes launches easier—you don't need to build boost like a turbocharged car.

Throttle Response and Drivability

The positive-displacement supercharger eliminates turbo lag entirely. In normal driving, the car feels like a much larger-displacement naturally aspirated engine. Throttle response is nearly instantaneous, which makes the car more confidence-inspiring on track and at highway passing speeds.

High-Speed Performance

Thanks to the extra top-end power, the HPE800 AMG GT pulls hard all the way to its revised redline (typically 7,200–7,400 RPM). Top speed increases noticeably—though most owners will hit the car's factory-limited 196 mph well before the engine runs out of steam. With speed limiters removed, 210+ mph is achievable.

Installation Process: What's Involved

Installing the HPE800 is not a weekend DIY project for a novice. The job requires familiarity with the M178 engine and meticulous attention to detail. Here is a high-level outline of the steps a professional shop will follow:

  1. Remove the stock twin-turbo system (turbos, exhaust manifolds, intake plumbing, intercoolers).
  2. Remove the factory fuel system components (injectors, pumps, lines).
  3. Install the new intercooler system (often a front-mount heat exchanger with dual pumps).
  4. Bolt the supercharger onto the custom intake manifold; secure the drive belt (the supercharger is engine-driven).
  5. Route new charge pipes and install the larger air intake.
  6. Replace the fuel injectors and pumps; upgrade the fuel lines if necessary.
  7. Install optional exhaust system (headers, downpipes, cat-back) if not already done.
  8. Reassemble the engine bay, checking clearances and routing (the supercharger is tight against the hood liner).
  9. Load the base calibration, perform a leak check, and then dyno-tune for final power.

Typical labor time: 20–30 hours for a well-equipped shop. Expect the car to be out of commission for 1–2 weeks while parts are sourced and tuning is refined.

Tuning and Calibration: Getting It Right

The factory ECU (Bosch MED17) is capable of being reflashed, but it requires specialized tools and knowledge. Hennessey provides a base tune, but every car reacts differently. You need a tuner who understands the AMG GT's torque-based control strategy.

Key tuning aspects:

  • Fueling: The supercharger increases airflow significantly; the stock fuel system peaks around 650 hp. Larger injectors and pumps are mandatory.
  • Ignition timing: Must be dialed back slightly under heavy boost to prevent knock; ethanol blends (E85) allow more aggressive tuning.
  • Torque management: The transmission's clutch pressures and shift firmness must be adjusted to handle the extra torque.
  • Boost control: A blow-off valve or diverter valve setup may be needed to prevent compressor surge.

Most owners report the best results with E60–E85 ethanol blends, which can push power to 850+ crank hp. However, ethanol requires a dedicated fuel system upgrade (flex-fuel sensor, stainless lines, larger injectors), adding $2,000–$4,000.

Supporting Modifications: Must-Haves vs. Nice-to-Haves

Essential Upgrades

  • High-capacity intercooler / heat exchanger – The stock cooling system suffers from heat soak under sustained abuse. An uprated unit keeps intake air temperatures (IATs) consistent.
  • Improved fuel system – 1000cc+ injectors and a secondary fuel pump are non-negotiable for 800 hp.
  • Dedicated engine oil cooler – The M178 runs hot; a larger oil cooler prolongs engine life.
  • Transmission cooling upgrade – The Getrag 7-speed DCT can overheat on track. A dedicated cooler (often a kit from European Auto Source or similar) is wise.
  • Upgraded clutch packs – If you plan on drag racing or repeated hard launches, stronger clutches prevent slippage.
  • Brake system upgrade – Ceramic brake pads, high-temp fluid, and stainless lines are minimal. For track duty, consider a bigger brake kit (e.g., Brembo GT-R).

Optional but Beneficial

  • Cat-back exhaust – Reduces backpressure and adds the soundtrack to match the power. Many owners love the whine of the supercharger combined with a free-flowing exhaust.
  • Lightweight wheels – Reducing unsprung mass helps handling and acceleration.
  • Coilover suspension – The added power upsets the factory suspension geometry; adjustable coilovers improve traction.

Considerations Before Pulling the Trigger

Warranty Implications

Installing the HPE800 voids the factory powertrain warranty. Mercedes-Benz has historically been strict about modifications. Some owners opt for a "dealer-friendly" tuner who can restore the car to stock, but that is not guaranteed. Consider a car with a remaining warranty you are willing to forfeit.

Insurance Costs

Notify your insurance company of the modification. Policies vary, but expect a premium increase of 15–30%, depending on the carrier. A few specialty insurers (e.g., Grundy, Hagerty for collectible status) may offer agreed value policies that cover modifications.

Maintenance and Reliability

The supercharger itself (Whipple) is robust and well-tested. However, the rest of the drivetrain is pushed to its limits. Oil change intervals should be halved (every 5,000 miles or annually). The supercharger oil should be checked every 15,000 miles. Also, the added heat stresses the cooling system—flushing coolant annually is recommended.

Common issues reported by owners:

  • Excessive heat soak on hot track days (mitigated with larger intercooler)
  • Transmission shifts becoming harsh if the fluid temperature spikes
  • CEL (check engine light) for minor emissions-related faults if using off-road downpipes

Alternatives: Comparing the HPE800 to Other Supercharger Kits

Hennessey is not the only player. Competitors include:

  • Weistec Engineering W.3 Stage 2 – Similar pricing and output, but uses a different Eaton supercharger. Weistec has a strong reputation for AMG builds.
  • VF Engineering VF800 – Centrifugal supercharger design, which produces power more linearly and may be easier on the drivetrain. Power delivery is less explosive but still very fast.
  • Autohaus Hamilton / Eurocharged 750+ – Custom builds with specialized tuning. Often slightly more expensive but more integrated.

The HPE800 is distinguished by its proven track record (Hennessey has been building high-horsepower AMGs for over a decade) and the comprehensive package it provides. However, the choice ultimately depends on your preferred powerband and local support network.

Final Verdict: Is It Worth It?

The HPE800 Supercharger transforms the AMG GT into a genuine 800-horsepower weapon that can humiliate cars costing twice as much. The costs—both monetary and in terms of warranty loss—are significant, but for the enthusiast who wants a capable daily driver that also demolishes track days and drag strips, it is one of the best-engineered upgrades available.

Plan for a total budget of $15,000–$20,000 to do the job properly, including supporting mods and tuning. Skimping on cooling or fuel delivery will lead to headaches. When installed correctly, the HPE800 delivers reliable, breathtaking performance that few other road-going mods can match.

For more details on the kit, visit Hennessey's official AMG GT page. Real-world owner experiences can be found on MBWorld's AMG GT forum. And for comparative dyno data, check out Weistec Engineering for an alternative take on the same platform.