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Rock-S
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121 Posts
Discussion Starter · #1 ·
Reflexion about catback... stupid or not?

I just want an opinion about the following reflexion concerning aftermarket catback.
Many people claim that; 2.36in exhaust like WS2 SP2 give no gain in terms of hp especially for 05-06 model cause the OEM flows pretty well (even it isn't straight thru). It seems that dynos confirm that. Anyway this an infinite debate.
However people who have a RH and dyno their car after / before adding a catback show that the same straight thru exhaust discussed before (SP2, WS2...) could provide a very nice gain... clearly better than with the OEM header.

My reflexion is the following : The OEM header restrict the flow such that with or without catback the flow is too weak to feel the difference and to enable the catback to play its role.
With the RH the outing flow is sufficiently strong to enable a straight thru catback, even with a diameter < 2.5in, to play its role and to add whp to a given setup of mods.

Thanks for your opinion.

PS: I speak french so I am sorry for my english...
 

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del
Joined
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7,360 Posts
It makes sense. Things are getting slowed down before they even make it to the cat back too much with the stock header. When you switch to a race header that bottleneck in the system now moves further down the line. It's like increasing the diameter of a pipe of water, but only the last 10 cm of it, but the first 10 meters is the smaller diameter, it won't help overall flow. But if you increase the size the entire way back then you'll get better flow.
 
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