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A comment on Why Palladium Is Suddenly a More Precious Metal. Parent comment

Re:Why Palladium Is Suddenly a More Precious Metal by noonespecial on Monday October 28, 2019 @08:07PM (#21383107)
Pollution concerns aside, your valves are timed and the manifold ports are shaped to work with the back pressure provided by a working cat.

If you didn't compensate for this during the modification you've likely cut the working life of you head(s) by half.

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Re:Why Palladium Is Suddenly a More Precious Metal by dsfyu404ed on Tuesday October 29, 2019 @07:48AM (#21386049)
>ports are shaped to work with the back pressure provided by a working cat.

This is a 100% urban legend BS myth.

There's a partial exception for two-strokes where if you tune the system right you get a resonance wave that lets you pack a little more mixture in on the intake/exhaust stroke. Literally no 4-stroke ICE benefits from back-pressure in any way. It's just that sometimes the things done to reduce back-pressure (small exhaust pipes being the primary one) seem like they would increase it and vice-versa hence the urban legend.

Edit: Who the heck is downvoting this? This is how ICEs work. Google it if you don't believe me.

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