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Oh, beleive me I have.

Show me one SAE document that shows a performance INCREASE from backpressure or exhaust velocity increase post collector. I'll wait.


Get informed and save the world

Part of the reason my setup includes 3” cats and mids, then necks down to 2.5” catback all the way back. To keep up exhaust velocity not to maximize back pressure. Open up your exhaust too much without enough power/velocity behind it and the pressure atmospheric becomes more than that in the exhaust, cause the air to take the path of least resistance i.e. back pressure no bueno
 

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I'll just assume you were trying to agree with me based on the videos you shared.
He's not agreeing with you.

Engines have changed since the 70s, you should watch the first video. Great information.
 

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He's not agreeing with you.

Engines have changed since the 70s, you should watch the first video. Great information.
Take a look at the diagrams he is showing you. He does not draw anything past the collector. Or really anything past the primary tube in the header.
He isn't super clear in the video - I'll give you that, but listen to what he says about the pulse returning at the collector and that the pulse also returns at the end of the exhaust pipe.

The amount of time that more than one cylinder is breathing at the same time is minimal.
If you have the correct header primary size in order to have "velocity" like you want, how in the world could anything past the collector have more than an extremely minor tuning effect? Have you ever seen a car where the primary exhaust diameter is the same as the exhaust beyond?
There are only 2 times when you'll see this. Single cylinder engines and engines with "zoomie" headers.

I won't litter this post with any more common sense.
 

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Take a look at the diagrams he is showing you. He does not draw anything past the collector. Or really anything past the primary tube in the header.
He isn't super clear in the video - I'll give you that, but listen to what he says about the pulse returning at the collector and that the pulse also returns at the end of the exhaust pipe.

The amount of time that more than one cylinder is breathing at the same time is minimal.
If you have the correct header primary size in order to have "velocity" like you want, how in the world could anything past the collector have more than an extremely minor tuning effect? Have you ever seen a car where the primary exhaust diameter is the same as the exhaust beyond?
There are only 2 times when you'll see this. Single cylinder engines and engines with "zoomie" headers.

I won't litter this post with any more common sense.
Nobody here is saying that the collector is not important in determining exhaust pulse flow, velocity or scavenging. However, your comment that "everything beyond the header doesn't matter" is largely false - which is why I responded as such.

I am not going to draw you free body diagrams for the force vectors of the exhaust, or post multiple links further. I simply wanted to ensure that for historical record purposes, someone doesn't read this post and think they can straight pipe with OD 4" and have the engine run the same as when it had various changes in diameter and resistance, which are designed that way for a reason (other than emissions).
 

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I installed a full SRT factory exhaust on my '12 R/T w/5.7 engine, used the shorty factory headers and the factory SRT mids w/cats & O2 bungs in the correct places, and installed a 3" Flowmaster American Thunder SRT cat back exhaust system. Everything bolted right up, used factory header gaskets w/hi-temp silicone around the ports to seal completely, and cat back pipes went right on hangers and fit perfectly. Headers are a BEOTCH to do on these cars for sure, took most of a day per side to install them. :censored:
End result is that my Challenger definitely woke up with this exhaust mod and it cost me less than a grand to do, and will pass a smog test in other states with flying colors. Exhaust note got deeper and a bit more throaty but no drone issues on the highway at all.
Gets a best of 27 mpg on the highway with factory tune, 93 octane tune in the works in the near future.
Works for me!
 
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