Supersprint has developed a new set of headers and sports cats for the 476/500 Hp Mercedes G55 AMG 5.5 V8.
The stock headers are extremely restrictive and undersized if you consider the power available from this engine, the design is obsolete and the internal diameter is very small, down to 40mm in a few spots.
The length of the primary pipes is negligible, as there are very short branches that merge in the main pipe. This involves heavy interferences given by the pressure waves from one cylinder to the other. The scavenging effect is deeply compromised.
The design freedom of these headers has a limit, brought by the proximity of the tires inside the wheel arches to the pipes. You can actually see the headers from the side of the cars, without removing any cover.
The suspensions and steering have very big excursion, as this car is a “real” 4x4.
This is the reason why the 4 into 1 design used on previous 55 AMG models was discharged in favor of a 4 into 2 into 1, with a smaller section but still much more efficient than the stock system. The cylinder firing orders was respected, and the primary pipes keep the pressure waves of consecutives discharges as far as possible.
The result is a set of headers that fits perfectly inside the space available without invading the wheel arches, with efficiency miles ahead of the OEM components.
A new set of catalytic converters, 100 CPSI HJS units, have been fitted instead of the stock four ceramic items.
During the dyno testing the qualities of this setup were very clear. The car used for the development was already fitted with a number of modifications that made bottleneck given by the headers even more evident:
-reduced diameter pulley for the supercharger
-bigger throttle body
-ECU remap with A/F ratio adjusted for the increased boost.
-Gearbox ECU remaps
The dyno testing of the car with the OEM exhaust were not satisfying, inconsistent results between the runs. Power and torque were sometimes higher than a stock car but weren’t representative of the modifications made on the engine, especially at high rpm.
The runs with the new exhaust fitted were revelatory; the engine was finally free to discharge that huge amount of gas.
Aside from the torque available at 3000 rpm, + 90 Nm, the top end of the rev range and the peak power were shocking. It’s possible to go beyond 6500 rpm without a power decrease, while the car with the stock exhaust hits the wall at 6000 rpm, and peak power gain is more than 100 hp!
To better understand the difference between a stock car and one with these modifications, the torque gain at 3000 rpm is an astonishing 170 Nm.
The sound is obviously better too, thanks to the new free flowing setup, and even with the stock rear mufflers the V8 rumble is more aggressive and involving on the whole rev range, but a sufficient level of comfort is retained.
Pictures, videos and dyno charts are available on the specific car page, linked below.