exhaust should i go full 3 inch or 2.5

[robwlf]

debating if i go full 3 inch or do the 2.5 cj one sounds pretty good for 2.5 or i was gunna go mbrp street 3 inch .. im guessing 3 inch will let that air gtfo from the s/c lol

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[SolarFlare]

2.5" here

 

[3beeps]

At no point is a restriction a good idea. You want 3".

 

[M151A2]

MBRP 3 inch. Loud. No idea if there is a power increase but the erection increase is there.
I’m an old dude too!

 

[Ninjak]

3 inch. now. Done.

 

[robwlf]

3 inch it will be .. mbrp street is what i like .. race is way to much imo

 

[ahl395]

I've been told a 2.5" will have more backpressure and help with low end torque.
I have a feeling that is a myth though. Anyone heard of this and/or tested?

FWIW I went full 3", better to let the engine breathe better with the supercharger I think.

 

[3beeps]

I've been told a 2.5" will have more backpressure and help with low end torque.
I have a feeling that is a myth though. Anyone heard of this and/or tested?

FWIW I went full 3", better to let the engine breathe better with the supercharger I think.

Back pressure is bad.

[ame]

 

[MikeyPee]

3"

 

[Burkey]

If anyone ever mentions back pressure, just nod your head and pretend that you're still listening.

 

[ahl395]

Back pressure is bad.

If anyone ever mentions back pressure, just nod your head and pretend that you're still listening.

Thanks guys, that's what I thought.

 

[oesman]

LoL "must need more backpressure" is something honda kids decided when their 140ft-lb engine lost getup at under 6,000 rpm with a 4.5" pipe and a 6" fart can. Then they spread it around everywhere and people say it all the time now. They're confusing several phenomenon such as exhaust velocity and how something like a header can be tuned so that cylinders help each other through negative pressure:

https://en.wikipedia.org/wiki/Tuned_exhaust#Extractor_manifolds

I'm not sure if an otherwise stock GT mustang would dyno higher and actually run faster with 1-7/8 mains and a full 3" vs 1-3/4 mains and a 2.5", but it'd be an interesting test. I've seen cars with a little less factory ouput actually get worse results going for the bigger mains and cat-back. However if you're FI it will certainly put down better numbers and times with the bigger setup. Especially in higher rpms with a supercharger where you're making all your power as it spools up.

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