Quote:
Originally Posted by Eazy-V
So, my car is FI tuned up to E75 with 3” downpipe, 3” overpipe, 3” catted frontpipe and 2.76” catback exhaust, so would changing to 3” catback make a big difference?
Also, I know that air can only move as fast as the narrowest part of the exhaust, so is it safe to say that the 3” portions I have make no difference since my catback is 2.76”?
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The real answer is "It Depends"....
At what point do you have a bottleneck? do you have an open wastegate or does it feed into the exhaust stream? How long are you at a high enough load to cause restrictive backpressure?
The fluids(in this case exhaust gases) will open up into the 3" portion and then at the 2.76" portion they will start to back up. The longer you have enough load to create enough back pressure through the whole pipe to limit power, the less power you'll make.
This is because the bottleneck will force the fluid in the 3" portion to start to back up but it has to get all the way back to the turbo/engine before the engine will recognize the restriction.
If you are no longer at enough load for the back pressure to increase all the way back to the engine(in a truly discernible way, technically the backpressure will START to increase immediately), and the gases can flow freely through the 2.76" section without unduly increasing back pressure, there should be no noticeable or even measurable difference.
Jaden