F-150 Aftermarket Exhaust Database

[leverkyle]

Alright thanks guys. I think I'm gonna stick with the 4" just cuz I already told my wife that. I'm not too worried about a little bit of low end.

[Raiderfan1890]

Yeah you need back pressure for the turbos. 4" looks beast but a lot are pretty obnoxious

Not quite.
The loss in power from 4" comes from the exhaust gasses slowing down so much that they aren't evacuated like they should be. Once the FPS drops below a certain point and the gasses cool while they're still in the system, it acts as a restriction.
As far as back pressure goes, the less back pressure, the faster the turbos can spool due to decreased resistance. This would result in MORE power because you could start your boost curve sooner. This is why running open downpipes (or a cutout) would have more power than any exhaust.

Also, for whomever's interested; HERE'S a thread of aftermarket exhausts for the txverse platforms too.

Ok yeaI'ive heard the 3" has a siphoning effect.


It's the Thuggish Ruggish Bone

[JimiJak]

I think you mean "scavenging effect" but I get what you're saying.

the scavenging effect is an exhaust theory that involves mathematically efficient exhaust pipe combinations. (diameter, bends, collectors, mufflers, etc.) The gasses work together to carry all of the gasses out together, and keep everything up to speed. This typically isn't much of an issue when you're talking about forced induction engines, but is a huge deal in the naturally aspirated world. Even for our EcoBoosts though, it sounds like 4" is just too much inside area, and the gasses are becoming stagnant.
So surprisingly, the problem isn't that there's not enough back pressure...it's that there's too much since the exhaust can't evacuate the burnt gasses.