The Mercedes-AMG E63 S is already a benchmark in the high-performance luxury sedan segment. With a hand-built 4.0-liter twin-turbo V8 producing 603 horsepower and all-wheel drive, it offers blistering acceleration and refined daily usability. However, for enthusiasts who demand even more extreme performance, aftermarket specialists like Hennessey Performance Engineering have developed upgrade packages that push the envelope further. The Hennessey E63 AMG Performance Pack is one such option, and real owners who have installed it are sharing their candid experiences. This article compiles their dyno results, driving impressions, and long-term feedback to help you decide if this investment aligns with your driving goals.

Understanding the Hennessey E63 AMG Performance Pack

Founded by John Hennessey, the Texas-based tuner is renowned for extracting significant power increases from both American muscle and European luxury cars. Their performance package for the Mercedes-AMG E63 S is designed as a comprehensive upgrade, encompassing engine tuning, exhaust modifications, and optional suspension enhancements. The primary goal is to transform the already potent E63 into a super-sedan that can rival exotic supercars in straight-line and cornering performance.

Hennessey offers multiple tiers for the E63, but the most popular is the standard Performance Pack, often referred to as the HPE700 or HPE750 package. According to the official Hennessey product page, this package targets a 700+ horsepower output. For those seeking maximum power, the HPE800 upgrade includes upgraded turbochargers and a transmission recalibration. This article focuses primarily on the standard pack as reported by owners.

What's Included in the Package

The standard Hennessey E63 Performance Pack typically includes the following components:

  • Engine Control Unit (ECU) Tune: A custom calibration that increases boost pressure, optimizes fuel delivery, and adjusts ignition timing for maximum power while maintaining smoothness.
  • High-Flow Exhaust System: A cat-back or full system constructed from mandrel-bent stainless steel or titanium. It uses larger diameter pipes and less restrictive mufflers to reduce back pressure and improve exhaust flow. The sound is dramatically enhanced.
  • Upgraded Intercooler: A larger, more efficient intercooler helps reduce intake air temperatures during sustained high-performance driving, preventing heat soak and ensuring consistent power delivery.
  • Cold-Air Intake System: A carbon fiber intake housing draws cooler, denser air from outside the engine bay. Coupled with a high-flow panel filter, this improves throttle response and horsepower.
  • Optional Suspension Lowering Kit: Springs or adjustable coilovers reduce ride height by 20-30mm, lowering the center of gravity and reducing body roll. This kit enhances handling dynamics while retaining acceptable ride comfort.

Owners note that Hennessey provides a custom tune specific to each vehicle, factoring in local fuel quality and other variables. This level of personalization reduces the risk of detonation or drivability issues.

Verified Dyno Results and Performance Data

Real owner dyno runs from various platforms, including forums like MBWorld and BenzWorld, confirm significant gains. One owner documented a stock baseline of 557 wheel horsepower on a Mustang dyno. After the Hennessey pack installation (including ECU tune and exhaust), the same car produced 672 wheel horsepower — an increase of 115 wheel horsepower. Estimated crank horsepower jumps from 603 to roughly 760. Quarter-mile times drop from the stock low-11-second range to consistent 10.4-second passes at 132 mph. These real-world figures demonstrate that the package delivers on its claimed power levels, translating into quantifiable performance improvements.

Real Owner Reviews: Aggregated Feedback

We collected feedback from multiple sources, including Hennessey's own customer testimonials, automotive forums, and social media groups. The consensus is overwhelmingly positive, with owners praising the transformative effect of the package. However, a few critical points are worth examining.

Performance and Acceleration

Owners almost universally highlight the dramatic increase in acceleration. The phrase "neck-snapping" appears frequently in reviews. One owner wrote, "The Hennessey tune completely wakes up the engine. It feels like a different animal — throttle response is immediate, and the car pulls relentlessly all the way to the redline." Another owner noted that the power delivery remains linear and smooth, suitable for daily commuting, but the force when the turbos spool is addictive. Reported 0-60 mph times are consistently in the low 2.9-second range, beating the stock 3.3-second claim. Quarter-mile trap speeds are in the 130-134 mph range, placing the Hennessey-tuned E63 in the same performance bracket as the Dodge Challenger Hellcat Redeye and even the Ferrari F8 Tributo.

"The acceleration is brutal. It pins you to the seat and doesn't let go until you lift off. The Hennessey pack turns the E63 into a genuine supercar killer." - Forum user E63Power

Handling and Suspension Upgrades

Those who opted for the suspension lowering kit report improved cornering stability. The car feels flatter through turns with significantly reduced body roll. The standard air suspension retains its comfort modes, but with the lowering springs, the ride becomes firmer, especially on rough surfaces. One owner noted, "The handling upgrade transforms the E63 into a track-focused tool while still being usable on the street. But expect a harsher ride over potholes and expansion joints." Owners who track their cars appreciate the reduction in dive during braking and squat under acceleration, which improves confidence at high speeds.

Exhaust Sound and Aesthetics

The exhaust system is a standout feature. The stock E63 is refined, but the Hennessey system adds a raucous, deeper tone with pronounced crackles and pops on downshifts and overrun. Owners love the aggressive soundtrack in Sport+ mode. However, a minority noted a slight drone at highway cruising speeds (70-80 mph), which could be a consideration for long-distance drivers. Aesthetic enhancements, including Hennessey badges and carbon fiber accents on the intake and under hood, receive positive remarks for improving the engine bay presentation. The exterior badges are subtle, but owners appreciate the touch.

Key Benefits of the Hennessey Performance Pack

Based on comprehensive owner feedback, the primary benefits include:

  • Substantial Power Gains: Over 100 horsepower at the wheels is consistently achieved without sacrificing daily drivability. The car remains docile in Comfort mode but turns savage in Sport or Race mode.
  • Improved Sound: The exhaust note becomes more aggressive and engaging, matching the performance character. Owners report a sense of occasion every time the engine fires up.
  • Comprehensive Package: The offering includes tuning, exhaust, intake, and intercooler in a single kit, reducing the need to source parts from multiple vendors. Hennessey also provides a limited warranty on their components.
  • Proven Reliability: The vast majority of long-term owners (over 20,000 miles) report no major mechanical failures directly linked to the tune. The Mercedes V8 is robust enough to handle the added power, provided maintenance is followed.

Challenges and Maintenance Considerations

Real owners also highlight challenges that prospective buyers should carefully consider:

  • Warranty Concerns: A tuned ECU is detectable by Mercedes dealers, and any engine or drivetrain claims may be denied. Hennessey offers a limited warranty on their parts and installation, but it does not cover factory components that may fail due to increased stress. Some owners have faced pushback during routine service at dealerships.
  • Increased Maintenance Costs: Higher power output accelerates wear on consumables. Tires, especially rear tires, wear out faster — one owner reported needing new rears every 8,000-10,000 miles with frequent hard driving. Brake pads and rotors may also require more frequent replacement. Additionally, oil change intervals might be shortened, and spark plugs are recommended every 30,000 miles instead of the factory 60,000-mile interval.
  • Fuel Consumption: Performance tuning inevitably reduces fuel economy. Real-world combined fuel economy drops from the stock 18 mpg to around 14-16 mpg, especially when the performance is used regularly. Premium 93 octane fuel is required, and some owners report needing to add octane booster for track use to prevent knocking in high heat.
  • Installation and Tuning Time: While Hennessey offers professional installation at their facility in Texas, owners who ship their cars note that the process can take 2-4 weeks. Remote tuners are available through Hennessey's authorized network, but some owners experienced delays in final calibration adjustments.

These challenges are common with any high-performance aftermarket modification. Owners who accept these trade-offs tend to be more satisfied with the overall experience.

Comparing the Hennessey Pack to Other Tunes

The E63 AMG tuning market is competitive, with packages offered by Renntech, Brabus, and Weistec. Owner feedback suggests Hennessey offers the best value for power gains. Renntech tunes are often more conservative, yielding around 680 horsepower, but they emphasize drivability and torque delivery. Brabus packages, such as the B900, can exceed 900 horsepower but come at a cost exceeding $50,000 for parts and labor. Hennessey sits in the middle, with the HPE750 pack priced around $10,000-$15,000 installed, providing near-supercar performance at a more accessible price point. One owner summarized: "For the money, Hennessey gives you the biggest bang for the buck. The customer service was also responsive when I had a question about the exhaust drone — they sent me a revised resonator section at no charge."

Another consideration is that Renntech offers a plug-in module that is easier to remove for warranty visits, while Hennessey's ECU flash is permanent. Hennessey counters this by offering a full reflash to stock for a fee, but this adds complexity. For owners who track their cars heavily, Hennessey's intercooler upgrade and transmission tune (on the HPE800) are distinct advantages over some competitors.

Frequently Asked Questions from Owners

Will the Hennessey pack void my factory warranty?

Yes. Mercedes-Benz dealerships can detect ECU modifications during routine scans. The engine and drivetrain warranty will be voided. Hennessey offers a limited warranty on their components and installation, but it does not cover factory parts that fail due to increased power. Some owners recommend keeping the stock parts to revert to factory tune before dealer visits, though this is not a simple process.

Can I install the pack myself?

Hennessey strongly recommends professional installation to ensure proper calibration and avoid damage. The ECU tune requires specialized software and a dyno session. Some experienced mechanics install the intake and exhaust themselves and then have Hennessey remotely tune the ECU, but this is not standard practice.

The standard Hennessey performance pack is not CARB legal. It does not carry an Executive Order number for California emissions compliance. Owners in states that require smog testing (California, New York, Connecticut, etc.) must either reinstall stock parts before inspection or risk failing. Hennessey offers a stock tune option for emissions readiness, but the hardware (exhaust) may still fail visual inspection.

How does the car handle in winter conditions?

With Mercedes' 4MATIC+ all-wheel drive system and proper winter tires, the car remains drivable even after the tune. However, the increased power makes traction challenging on ice or snow. Owners recommend using a dedicated winter wheel and tire setup and exercising caution with throttle inputs.

Does the pack affect transmission reliability?

The stock Mercedes 9-speed automatic is robust and can handle up to 800 Nm (590 lb-ft) of torque. The standard HPE700 pack keeps torque within safe limits. For the HPE800 upgrade, Hennessey includes a transmission tune that increases clutch pressure and shift firmness to handle the extra torque. Owners with the standard pack report no transmission issues, though fluid changes are recommended every 40,000 miles instead of the factory 60,000.

Final Verdict: Is the Hennessey E63 AMG Performance Pack Worth It?

Based on extensive real owner reviews, the Hennessey E63 AMG Performance Pack delivers tangible, repeatable performance gains. The increase in horsepower and torque is dramatic, the exhaust sound is thrilling, and the overall driving experience is elevated to supercar territory. The handling upgrades, when chosen, further enhance the car's capabilities on track or twisty roads. The challenges — warranty concerns, higher maintenance costs, reduced fuel economy, and potential emissions issues — are typical for any high-performance aftermarket modification. Owners who prioritize raw performance and are willing to accept these trade-offs overwhelmingly report satisfaction. Many express that they would make the same decision again without hesitation. For the discerning enthusiast who wants to turn their E63 AMG into a track-capable street monster with a proven track record, the Hennessey package remains a compelling and rewarding option.