Quote:
Originally Posted by sw20kosh
Its 2013... The backpressure theory has been debunked. In no way shape or form is back pressure beneficial to FI. In most cases back pressure isn't even useful in NA applications.
I gained 400 rpm of spool upgrading from 2.5" to 3" piping on my Mr2 turbo and had HP gains everywhere.
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Was anything else changed at the time?
Alot of 'proof' on this point on the net are dynos where a 3" has been installed and more boost or the tune altered.
By the same theory, going to 4" would be even more benefical, and having no exhaust at all would be better again.
I don't want to further clutter this thread on this point, but happy to discuss further in another thread specifically about this.
Edit - one last point I will make, is consider that 95% of the time you aren't driving on boost. Now, if you're not on boost the car is effectively less powerful than the same car with no turbo attached at all. Whether its rev/load dependant, its going to spool quicker with some back pressure. I'm not at all arguing whether back pressure is needed once there is boost, the point I am making is back pressure is better for off boost and boost transitition (spooling). I would much rather lose a few peak numbers to have the car perform better, in the range that I am using it for 95% of the time. Sure, if the size of the exhaust was robbing 10-20% of peak power, thats a different story.