Usually when one hears the roar of a V8 engine, the most immediate thought is that it's an American musclecar. But Mercedes-Benz has produced an engine that will challenge that instinctual thought process and provide fierce competition within the V8 class. Rivaling the "Big Three" American auto manufacturers, Mercedes has produced a powerful engine that still retains the elegant refinement associated with European automobiles, code named E55 AMG. Each supercharged 5.4-liter V8 engine is hand-built by AMG and then installed into a few select models of the Mercedes line. That it produces 493 bhp at 6100 rpm and 516 lb-ft of torque from 2750 to 4500 rpm makes it arguably one of the best engines of all time. And still we search for ways to make this car faster by trying and testing various products to find that winning combination.
The first thought that springs to mind when driving the E55 AMG is how could one possibly improve a 4,320-pound car with a stock zero-to-60-mph elapsed time of 4.5 seconds and quarter mile in the 12-second range. The distinctive whine from under the hood reminds us that this car is supercharged, and like a lightbulb switching on overhead... more boost. The simplest way to increase horsepower on a forced induction engine is to simply increase the boost. Unlike their turbocharged counterparts, supercharged engines run a set boost based on the size of the drive pulley and overall belt length. This is where the vehicle's owner, Armand Eulano, began his tuning project.
The first step when performance tuning any vehicle is to have it dyno tested for a base run. The stock numbers will form a basis of comparison against which all modifications can be measured. Subsequent runs were performed on the same dynamometer to allow for accurate evaluation of the modifications installed, to ensure they were helping and not hindering performance, as well as checking up on vehicle performance. The base numbers for this E55 were measured at 398 wheel horsepower.
The stage-one upgrade from Carlsson of Germany was chosen to start the quest for more power. The Carlsson CK55 performance kit consists of a smaller supercharger pulley and a matching engine management upgrade to remove the car's top-speed governor and ensure the air/fuel ratio was kept in line. The kit also contained a high-flow air filter and the signature shaped rear mufflers emblazoned with the Carlsson logo. These upgrades increased the max power rating to 446 at the wheels.
With the extra exhaust gases and exhaust waste (which subsequently converts into more backpressure) created by the increase in boost, the restrictive stock headers and an exhaust with just the Carlsson rear mufflers were not going to cut it. The second upgrade was provided by Al Hafner at Supersprint North America. Every bit of the factory exhaust system was removed and replaced with the Supersprint cylinder-head-back system. The system begins with a superbly designed header system which features long, 42mm (outside diameter) tubular,individual primaries mated smoothly together thanks to a patented, four-into-one Supersprint merge collector design, finishing in a 70mm outlet. Continuing down the system from the 70mm header outlets is a pair of 70mm, 100-cell HJS metallic catalytic converters. All of the factory Mercedes-Benz O2 sensors are retained to keep the vehicle emissions system happy. The system continues with 70mm piping and terminates with a center-mounted resonator with exclusive oval tapered cross-section mufflers with 120x80mm quad tips. These mufflers were developed specifically for Mercedes-Benz applications by Supersprint and the design has been streamlined to optimally use the available space for the exhaust system. This design feature places the mufflers tucked up and out of the way, which ensures the least wind resistance. Dyno numbers after this performance upgrade showed a dramatic increase from 446 to 483 whp.
To see if there would be any additional benefits with different software programming, Powerchip was enlisted to provide the third upgrade. Before programming the ECU, Powerchip verified that the engine was running the proper air/fuel ratio and proper timing. After the ECU was reprogrammed, the vehicle dyno showed a gain of 2 horsepower. Though this gain was minimal, there were interesting benefits that came with the software change. The power curve was smoothed out to eliminate a slight hesitation present from the start of the project, and gave the vehicle a much improved throttle response.
Although many assume that AMG would have already squeezed as much power from this engine as possible, we have recorded a gain of 87 whp with largely bolt-on parts. These simple modifications just scratch the surface of what can be done. By no means is the project completed; the quest continues.