[jpsimon]

Originally Posted by sd390r

i wanna see what your whp is with your fmic on.. really offtopic...

you and me both I can't wait

[sd390r]

is your car stick or automatic

[Kev]

Originally Posted by sd390r

is your car stick or automatic

From his sig:

Originally Posted by JP Simon's sig

335xi Coupe | Space Grey | Coral Red — PROcede V3.1 | RaceTec FMIC (coming soon) | UR Catless DPs | AutobahnExotics Catless Exhaust | Dual Cone Intake | Modified CDV | KW V3 Coilovers

Only found in MT

[5soko]

AE FTW!

[sd390r]

lol didnt even read that my bad im doing alot of shit at once

thank u

jp what do you launch at with the xi?

[Mr. 5]

RDSport,
If you don't like the AE video then too bad so sad. Just don't purchase it.

Yes, I believe that a lot of companies out there add an X pipe to their exhaust system for the sound.
I've experienced it for myself. I recently eliminated my X pipe to increase flow, and paid to have the X pipe put back because the sound sucked so badly.
In my experience, with our N54 engine, the X pipe takes the "rice" away.

I do think that it's amazing how AE has attributed an exhaust system that does not sound ricey, yet does not use an X pipe.

Maybe you know a lot about exhaust systems, but it sounds like you don't really know about exhaust systems with Forced inducted engines.
The statement below reminds me of the scene in "Good Will Hunting" where the Harvard guys starts spouting off clips of books that he read.
Reading and memorizing something is one thing but to understand it and to see the relevance of application is another.
I mean, is there really something in this book that sets up a case where an X pipe helped increase flow with a Turbo engine?
I find it hard to believe.

If it is so, may I suggest that you purchase, and read thoroughly, the book Flow and Combustion in Automotive Engines by C. Arcoumanis, Take Kamimoto, and Arcoumanis, or even better Further studies of noise characteristics of internal combustion engine exhaust systems (SAE) by S. W Coates. Both of these books, but there are many others, may shed some light on a subject that seems to escape you.

X pipes just add a restriction with a force inducted car, so if exhaust companies are using it in their system then either they don't understand the workings of a forced inducted engine or they added it for the sound.
I have one with my system and I only used the X pipe to get the sound I was looking for.
I don’t' give a crap about the 3-4 hp that I'm losing because I was going for a particular sound. But, if it wasn't there, then I'd have a better flowing system.

Why don't you read down below and learn about the workings of a turbo. This was posted by a Development Engineer from Garrett Turbochargers. I even Bolded the important stuff.

N/A cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here.

For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end.Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.

Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.

As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side. "

As for the geometry of the exhaust at the turbine discharge, the most optimal configuration would be a gradual increase in diameter from the turbine's exducer to the desired exhaust diameter-- via a straight conical diffuser of 7-12° included angle (to minimize flow separation and skin friction losses) mounted right at the turbine discharge. Many turbochargers found in diesels have this diffuser section cast right into the turbine housing. A hyperbolic increase in diameter (like a trumpet snorkus) is theoretically ideal but I've never seen one in use (and doubt it would be measurably superior to a straight diffuser). The wastegate flow would be via a completely divorced (separated from the main turbine discharge flow) dumptube. Due the realities of packaging, cost, and emissions compliance this config is rarely possible on street cars. You will, however, see this type of layout on dedicated race vehicles.

A large "bellmouth" config which combines the turbine discharge and wastegate flow (without a divider between the two) is certainly better than the compromised stock routing, but not as effective as the above.

If an integrated exhaust (non-divorced wastegate flow) is required, keep the wastegate flow separate from the main turbine discharge flow for ~12-18" before reintroducing it. This will minimize the impact on turbine efficiency-- the introduction of the wastegate flow disrupts the flow field of the main turbine discharge flow.

Necking the exhaust down to a suboptimal diameter is never a good idea, but if it is necessary, doing it further downstream is better than doing it close to the turbine discharge since it will minimize the exhaust's contribution to backpressure. Better yet: don't neck down the exhaust at all.

Also, the temperature of the exhaust coming out of a cat is higher than the inlet temperature, due to the exothermic oxidation of unburned hydrocarbons in the cat. So the total heat loss (and density increase) of the gases as it travels down the exhaust is not as prominent as it seems.

Another thing to keep in mind is that cylinder scavenging takes place where the flows from separate cylinders merge (i.e. in the collector). There is no such thing as cylinder scavenging downstream of the turbine, and hence, no reason to desire high exhaust velocity here. You will only introduce unwanted backpressure.

Other things you can do (in addition to choosing an appropriate diameter) to minimize exhaust backpressure in a turbo back exhaust are: avoid crush-bent tubes (use mandrel bends); avoid tight-radius turns (keep it as straight as possible); avoid step changes in diameter; avoid "cheated" radii (cuts that are non-perpendicular); use a high flow cat; use a straight-thru perforated core muffler... etc.

Oh, and if you'd like to become a vendor and sell your exhausts on here then let us know.

[jpsimon]

Originally Posted by sd390r

is your car stick or automatic

6mt

[jpsimon]

Originally Posted by sd390r

lol didnt even read that my bad im doing alot of shit at once

thank u

jp what do you launch at with the xi?

4k, slip the clutch... car takes off like a rocket

[sd390r]

i bet lol

[Nick@aep]

Hello Everyone,

We will be starting to have completed systems ready to ship very shortly.

Please refer to this thread for more information and pictures as well as ordering info-
http://www.e90post.com/forums/showthread.php?t=178080

Please call us @ 714-241-0298 with any questions or to place your order. You may also order online from our online store @ www.autobahnexotics.com

Thanks!

Nick

[Nick@aep]

Quads will begin shipping within a few days for those with open orders.

[Tony@AEP]

I need a 335 now so I can pick up one of these!

[Zeph]

you could probably get a 2007 model with 29.2 software at a discount

[Nick@aep]

Originally Posted by Zeph

you could probably get a 2007 model with 29.2 software at a discount

Haha.

[emjei]

how long is the list for sedan exhaust ???

[mmm def]

Yes I am interested in one for the E90.

[Andras]

Well guys, this morning I went installing my AE exhaust (high flow cats version) by the best italian exhaust manufacturer and installer.
He was astonished by the quality of the exhaust, and installation was a breeze.
It sounds amazing, I love the deep growling note on lower rpm band.
335i is supposed to be a sleeper, with this exhaust it sounds much like a raging dragon who just got awaken.
Big thump up for Nick and Autobahn Exotics

[Gen_E92]

Originally Posted by Andras

Well guys, this morning I went installing my AE exhaust (high flow cats version) by the best italian exhaust manufacturer and installer.
He was astonished by the quality of the exhaust, and installation was a breeze.
It sounds amazing, I love the deep growling note on lower rpm band.
335i is supposed to be a sleeper, with this exhaust it sounds much like a raging dragon who just got awaken.
Big thump up for Nick and Autobahn Exotics

Finally! we need sound clip ASAP!! can't wait to hear how it sounds with HFC and catless DP

[emjei]

the million dolar question......IS IT DRONE FREE FOR REAL ????

Originally Posted by Andras

Well guys, this morning I went installing my AE exhaust (high flow cats version) by the best italian exhaust manufacturer and installer.
He was astonished by the quality of the exhaust, and installation was a breeze.
It sounds amazing, I love the deep growling note on lower rpm band.
335i is supposed to be a sleeper, with this exhaust it sounds much like a raging dragon who just got awaken.
Big thump up for Nick and Autobahn Exotics

[Hit_Apex]

That is a very nice exhaust. Workmanship and sound is the best I've come across.

[emjei]

WTB....Single tip for a SEDAN....just in case anyone of you with those is planning to get the quads......

[mmm def]

Originally Posted by Hit_Apex

That is a very nice exhaust. Workmanship and sound is the best I've come across.

Do you have this exhaust?