enfin, autant je suis sceptique quand on me dit gagner des chevaux avec un échappement, autant je suis sceptique qu'on puisse en perdre autant.
contre-pression, je veux bien, mais tu gardes le collecteur et le pot catalytique d'origine... ce qui se passe après le cata, le moteur s'en fout un peu, c'est lui et la longueur des branches qui fait le max de contrepression.
voila ce que dit Nick Adams (ingénieur développement de chez Lotus) à propos des pots stage 1 & 2 :
"the standard exhaust silencer fitted to the 111R and Exige is a bespoke 24 litre volume unit made specially for us by CLF (aka Magnex). It is not a Toyota unit or even modified from a Toyota unit contrary to popular belief. This unit meets the European drive by noise standards of 74dBa and weighs in at 14kg.
The stage one silencer (part number LOTAC05334) is based on the standard unit but with a reduced volume of 20 litres and a consequent mass reduction to 11.5 kg. This unit offers a more pleasing sound quality while still meeting the vast majority of trackday organisers noise limits at 96.9dBa when measured to blue book regulations. It offers no significant power benefits as the standard system is already very efficient in terms of back pressure and therefore there is little to come from further reductions.
The stage two silencer (part number LOTAC05335) is a completely different design aimed at those who want a much louder exhaust note. The blue book test gives a figure of 104 dBa which will meet some but not all track day noise limits. This system weighs in at just 8 kg and has a volume of just 7 litres. The power benefit is once again very small, in the region of 2ps, although the enhanced engine note makes the car feel much faster! This system was designed to achieve maximum power improvement, so it is very hard for us to believe that anyone else will be getting much more power from the exhaust alone, although I'm sure they will claim they can!
Best regards, Nick"