3” dual exhaust

dyezak

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May 4, 2017
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That's the biggest BS garbage you can ever quote. Look at the dual 2.25 option there. It says the max HP achievable is 371hp. Why do we have plenty of people pushing 650-750hp through our factory 2.25" dual exhausts if the max possible is 371hp?

I like the Budget Bimmer guys...besides reminding me of my younger self they are putting down 689hp on a Doc Race 6266 exhaling through the factory exhaust. 2.25". https://www.youtube.com/channel/UCoxxLX-fWmUKPOSIiXv7-Nw

If that "research" is off by a factor of 100%, then it is full of bullshit.
 
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colinod

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Aug 13, 2017
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Its just highly generalized for NA cars. once the turbocharging comes into play everything changes
 

fmorelli

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[...snip...] And the fact is that you can free up lost horsepower....but for the cost/benefit you get with an exhaust ... [...snip...]
I think your overall advise is probably pretty spot on.

I did my exhaust as part of my first phase of work. But I hated the exhaust on my Z4 and we happen to have a shop in the DC area, Mandrel Bend Solutions, that has German Transfluid Mandrel Bender which can do center line radius on most bends is 1.5 times the outside diameter of the tube. Their digital design work and mandrel bend exhausts is awesome. They also have equipment to take measurements on OEM bends and replicate. - I wanted to leverage their skills and product (as sometimes stuff disappears). Cost was under $2k for 2.5" dual behind the downpipes, with high-flow mid-pipe cats, and mufflers. The exhaust was a work of art. Car should be driven upside down. I've attached a photo below - wish I had one of the fit over the axles.

I'm also a bit weird, strategy-wise, as I chose to build up my car to support the power, not the other way around.

Traditionally BMWs don't leave much of any power on the table with the exhaust. This has been true for a long time. Same with intakes. Same with air filtration. Same with programming, once Bosch (at the time) figured out how to do it (turbo changes that, I'm talking NA Motronic 1.0 days V1,2 ...). It was not unusual to school people new to BMW that changing parts could actually make the car worse because BMW did a pretty good job - they leaned toward performance. On exhausts their stuff was just heavy, but that plays in to other priorities, since their MO has always been balanced performance (handling/power) with comfort.

When we talk exhaust, we're really talking post downpipes on the N54. Those seem to be worth doing sooner rather than later. I suppose I could have pushed for a bigger exhaust system, but I'm working toward a road-race style build with no more than 600whp.

Filippo

IMG_00002_BURST20160928131820_COVER.jpg
 
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The Convert

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Are you pre 1980? Its just a funny clip of a person fainting.Ive seen these
Kinds of post, but im talking logs, turbo spool/response by rpm range. how much are we really missing out on you know.and most cars now are far passed 600hp crank and wheel.
Back pressure actually increases low end torque though. So...depends on what you're after.
 
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Rcboosted2007

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So is it just not profitable for companies to produce these dual
3s for all of the guys over 650whp. The key is not that people push 700hp through a 2.25. Its why aren’t any vendors selling whats right, not just cost effective. $1700 for 3.5” stainless is inflated as hell.if thats the case why ever swap out down pipes to begin with
 

Rcboosted2007

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Yes, we've all seen the Supra video. It doesn't change what people have experienced on this platform. I don't know what you're hoping to accomplish by arguing with everyone? If you don't like what's available, make your own, have it made, or stfu. Pointlessly complaining solves nothing.
Your punk ass literally came here to argue. Understand what a question is
 

KevinC39

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Didn't you just source stuff from another platform?

If you want 4" for whatever reason, you're going to have to get one made locally from an exhaust shop. That's really all there is to it.
 
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Rcboosted2007

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Didn't you just source stuff from another platform?

If you want 4" for whatever reason, you're going to have to get one made locally from an exhaust shop. That's really all there is to it.
Above examples are all that is available. Again the goal was to see if anyone has collected data from dual 3” or larger, and also where to buy from. A lot of people are missing the point. This is not an exhaust flow physics quest. Its a log/dyno quest. With shitty examples from other sources since we have non at this point for 650-700hp + cars using larger than norm exhaust.
 

KevinC39

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Be the guy that tries it then I guess. Someones gotta be first. Looking forward to seeing the before and after, same day dyno numbers you get. I'm interested to see what you come up with .
 
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