Exhaust systems also play a role in reducing noise levels, improving engine performance and reducing fuel consumption. To get the power level up to 785 hp, Shelby installs a Ford Performance supercharger, as well as a new carbon-fiber air intake tube, high-performance fuel injectors, and an aluminum heat exchanger. A Borla (cat-back) exhaust system rounds out the list of powertrain modifications.
This is achieved by burning off the excess hydrocarbons which result from the extra-rich mixture required for a cold start. Slightly lean of stoichiometric, the exhaust gases from the engine contain excess oxygen, the production of NOx by the engine increases, and the efficiency of the catalyst at reducing NOx falls off rapidly. However, the conversion of HC and CO is very efficient due to the available oxygen, oxidizing to H2O and CO2. However, the efficiency of the catalyst at reducing NOx is good, and the production of NOx by the engine decreases.
In California, it is illegal to select a catalytic converter for installation based solely on vehicle weight and engine size. The design of these systems often sees an increase in horsepower compared to the factory design of a vehicle. Because stock models try to minimise materials and maximise space, with horsepower as a lower priority.
The first widespread introduction of catalytic converters was in the United States automobile market. The exhaust system is crucial to a car’s performance, especially the catalytic converter which can go bad if it’s overworked. A stock exhaust system strives to minimize the car’s materials while maximizing space. This means that the exhaust system’s performance can suffer, having to work harder with less horsepower.
To maintain catalyst efficiency, the air–fuel ratio must stay close to stoichiometric and not remain rich or lean for too long. All of Milltek's performance exhaust systems are manufactured from T304L stainless-steel