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Yes, the resonator probably DOES restrict exhaust flow and increase backpressure as opposed to a straight pipe or a freer flowing resonator but who cares! I would be willing to bet big bucks that the cats create far more backpressure.




I understood your point...
But I think in the case of the Contour, you are probably incorrect. I have not seen any pre-post dynos with resonator removal alone so I did the next best analysis..catback change where LOTS of data show a gain. It is pretty universally accepted that resonator is worst part of catback so I think the 3 HP estimate is pretty accurate (may actually be 2-5FWHP I would say).

Similarly, I have not seen the main cat removal ALONE dynoed pre-post in Contour but other cars it is rarely more than the 2-5 HP gain that I estaimat for the resonator. Further, I have seen data with SHO SHOP Y pipe, which includes a straight pipe in place of main cat..gain was 8 HP, and I suspect the Y pipe alone counts for about half of that (MSDS Y with stock cat showed +6HP..though Y is different style and not directly comparable).

So my point was that I think the 2 mods are likely pretty even in power gains (+/- 1-2HP) and I myself would NOT bet big bucks on the cat removal being better. Doing both would be best but more noise. The resonator change has the advantage of being emmisions legal.

1999 Amazon Green SVT Contour (#554/2760) "People demand freedom of speech as a compensation for the freedom of thought which they seldom use." -Soren Kierkegaard (as posted by Jato)