Our proprietary ECU upgrade for the Mercedes M278 Biturbo engine offers huge gains in performance across the entire RPM range without sacrificing around town comfort or daily driver reliability.

With the newest update of their Software Upgrade for the M278 – 4.7L V8 BiTurbo, RENNtech boosts the 550-Series to AMG Power Levels. The RENNtech upgraded M278 now produces 540 HP and 705 LB-FT at crank.

Compared to power numbers by Mercedes-Benz, the GLS 550 gains up to 66 HP and 139 LB-FT. This Software update delivers up to 10 HP and 99 LB-FT more than the previous version.

The vast amount of increased torque across the entire RPM range gives the 550 an extra edge to compete with AMG powered vehicles. All this without sacrificing around town comfort and daily driver reliability.

X166 - GLS 550 – M278 | 4.7L V8 BiTurbo Stock Performance:

• Rated by Mercedes-Benz:       449 HP @ 5,250 RPM  |  516 LB-FT @ 1,800-3,500 RPM
• Rated by RENNtech:                474 HP @ 4,900 RPM  |  566 LB-FT @ 2,350-3,650 RPM 

X166 - GLS 550 – M278 | 4.7L V8 BiTurbo RENNtech Upgraded Performance:

• Rated by RENNtech:           540 HP @ 4,500 RPM  |  705 LB-FT @ 2,850-3,450 RPM

**VIN NOTE** RENNtech often requires your vehicle's VIN number to process orders. Please leave this information in a note during checkout or email us with your order number after order is placed*

RENNtech has become the premier Mercedes-Benz specialist and Hartmut Feyhl himself is regarded by many as USA’s foremost authority in Mercedes tuning. His vast experience comes from 12 years spent at AMG Germany before serving as the North American division’s Technical Director. Prior to the tuning company’s merger with Mercedes-Benz in 1999, by the request of AMG Germany, Feyhl branched out on his own to start RENNtech and service the existing AMG North America customers.

Performance without compromise. This is the foundation upon which we have built our reputation. Established in 1989 by Hartmut Feyhl, RENNtech has evolved and grown from servicing AMG’s customers into the foremost authority on tuning and customizing AMGs and Mercedes-Benz. RENNtech also offers tuning solutions for Porsche, Audi and Bentley vehicles, along with other European luxury cars.

Over the years, we have developed high-performance products for virtually all Mercedes-Benz AMG vehicles. Some of the most notable among these are the 200 mph RENNtech E7.4RS (which claimed ‘Fastest Sedan in the World’ honors by Car and Driver Magazine in 1996) and the more recent 945 LB-FT 5.5L V8 Biturbo RENNtech R3+ Monster. Each of these vehicles are just a sampling of what RENNtech has achieved, featuring extreme performance, upgraded aesthetics and a fit and finish that rivals factory vehicles.

We design, engineer and manufacture our proprietary line of tuning products in-house at our facility which features a full fabrication and machine shop with CNC and rapid prototyping capabilities; in-house performance dynos, complete engine management and software tuning capabilities along with a complete service/repair/installation facility and a full-time design, engineering and sales staff.

Our headquarter facility is located just north of the Palm Beaches in Stuart, Florida