Aftermarket exhaust aerodynamics

MrHarris · 12-16-2008, 06:29 AM

Is there any noticeable aerodynamic disadvantage with the way the aftermarket exhausts are designed compared to the stock exhaust?

PunjabiM3 · 12-16-2008, 09:36 AM

I doubt it makes much of a difference, but this is something I took into consideration when purchasing the Eisenmann muffler. it seems to be a lot closer to the stock design than the other systems out there with two seperate (dare I say generic) canister mufflers.

swamp2 · 12-16-2008, 03:22 PM

This is a concern I raised very early.

The diffuser and meshed part of the rear bumper conver are designed to work in conjuntion with the under body panels of the car. This system, along with the shape of the OEM exhaust canister provide one or more of the following:

Exhaust cooling
Differential cooling
Reduced drag
Downforce (prob very minor)

Changing the geometry of this area the way many aftermarket exhausts do will certainly change some of the above effects. For the better or worse we won't know but it WILL be differnt than BMW designed and engineered it.

masmole · 12-16-2008, 03:45 PM

Quote:

Originally Posted by swamp2

This is a concern I raised very early.

The diffuser and meshed part of the rear bumper conver are designed to work in conjuntion with the under body panels of the car. This system, along with the shape of the OEM exhaust canister provide one or more of the following:

Exhaust cooling
Differential cooling
Reduced drag
Downforce (prob very minor)

Changing the geometry of this area the way many aftermarket exhausts do will certainly change some of the above effects. For the better or worse we won't know but it WILL be differnt than BMW designed and engineered it.

+1

Exactly! I'm not a physicist or aerodynamicist but based on the fact that I've stayed at many holiday inn express hotels, in the case of aftermarket exhausts with separate canisters and nothing in between, you are actually promoting more differential cooling at the expense of increased rear underbody turbulence from the differential to the valence which increases drag and lift. Very minimal to make a whole lot of difference on a 3700lb car in the course of a lap so I don't think it's anything to worry about.

Krueger///M3 · 12-16-2008, 03:48 PM

Quote:

Originally Posted by masmole

+1

Exactly! I'm not a physicist or aerodynamicist but based on the fact that I've stayed at many holiday inn express hotels, in the case of aftermarket exhausts with separate canisters and nothing in between, you are actually promoting more differential cooling at the expense of increased rear underbody turbulence from the differential to the valence which increases drag and lift. Very minimal to make a whole lot of difference on a 3700lb car in the course of a lap so I don't think it's anything to worry about.

???

MrHarris · 12-16-2008, 06:05 PM

^ I was wondering what that meant too lol.

consolidated · 12-16-2008, 06:25 PM

Quote:

Originally Posted by MrHarris

^ I was wondering what that meant too lol.

humor.....haven't seen the commercials I'm guessing.

Kadarin · 12-16-2008, 07:02 PM

Quote:

Originally Posted by MrHarris

^ I was wondering what that meant too lol.

It's from a Holiday Inn advertising campaign that jokingly implies that the mere fact of staying at a Holiday Inn will leave you so rested that you have more time and energy to excel at everything.

masmole · 12-16-2008, 08:42 PM

LOL! Damn, I guess some of you don't watch any TV at all. Those Holiday Inn Express commercials are everywhere and have made its way well into pop culture and everyday conversational humor in the workplace, etc. Kinda like "I just saved a bunch of money on my car insurance" Geico commercials. Corny I know.

GregW / Oregon · 12-16-2008, 09:59 PM

Quote:

Originally Posted by masmole

LOL! Damn, I guess some of you don't watch any TV at all. Those Holiday Inn Express commercials are everywhere and have made its way well into pop culture and everyday conversational humor in the workplace, etc. Kinda like "I just saved a bunch of money on my car insurance" Geico commercials. Corny I know.

Haven't made it into my culture. Hey, but with free internet and a breakfast bar (per the website) you're good to go!

corbz · 12-17-2008, 07:13 AM

The BMW release says that the factory rear muffler was designed to have the specific effects of rear diff cooling, lower underbody drag and a downforce effect. Read into that what you will

12-16-2008, 06:29 AM	#1
MrHarris yodog 197 Rep 5,026 Posts Drives: '86 Corolla Join Date: Jun 2007 Location: Diamond Bar, Ca iTrader: (5) Garage List 2009 BMW [10.00]	Aftermarket exhaust aerodynamics Is there any noticeable aerodynamic disadvantage with the way the aftermarket exhausts are designed compared to the stock exhaust? __________________ 2009 E92 M3 \| Alpine White \| Black Extended \| Advan RS \| Turner Test Pipes \| Dinan Axle-Back \| OETuning \| Eibach Springs \| UUC SSK \| VRS Front Lip \| VRS Type I Diffuser \| Matte Black \| RPi Scoops \| MS Filter \| Yokohama AD08 \| F1 Pinnacle Special Thanks: Gintani \| OETuning \| eAs
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12-16-2008, 09:36 AM	#2
PunjabiM3 Colonel 253 Rep 2,091 Posts Drives: M5 CS Join Date: Mar 2008 Location: Flower Mound, TX iTrader: (1)	I doubt it makes much of a difference, but this is something I took into consideration when purchasing the Eisenmann muffler. it seems to be a lot closer to the stock design than the other systems out there with two seperate (dare I say generic) canister mufflers. __________________ 2012 Audi R8 V10TT\| 6MT\| Suzuka Grey 2015 Ferrari 458 Speciale\| Rosso Scuderia 2020 BMW X7\| Mineral White 2024 718 GT4 RS \| Arctic Grey
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12-16-2008, 03:22 PM	#3
swamp2 Lieutenant General 609 Rep 10,407 Posts Drives: E92 M3 Join Date: Sep 2006 Location: San Diego, CA USA iTrader: (3)	This is a concern I raised very early. The diffuser and meshed part of the rear bumper conver are designed to work in conjuntion with the under body panels of the car. This system, along with the shape of the OEM exhaust canister provide one or more of the following: Exhaust cooling Differential cooling Reduced drag Downforce (prob very minor) Changing the geometry of this area the way many aftermarket exhausts do will certainly change some of the above effects. For the better or worse we won't know but it WILL be differnt than BMW designed and engineered it.
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12-16-2008, 06:05 PM	#6
MrHarris yodog 197 Rep 5,026 Posts Drives: '86 Corolla Join Date: Jun 2007 Location: Diamond Bar, Ca iTrader: (5) Garage List 2009 BMW [10.00]	^ I was wondering what that meant too lol. __________________ 2009 E92 M3 \| Alpine White \| Black Extended \| Advan RS \| Turner Test Pipes \| Dinan Axle-Back \| OETuning \| Eibach Springs \| UUC SSK \| VRS Front Lip \| VRS Type I Diffuser \| Matte Black \| RPi Scoops \| MS Filter \| Yokohama AD08 \| F1 Pinnacle Special Thanks: Gintani \| OETuning \| eAs
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12-16-2008, 08:42 PM	#9
masmole Captain 266 Rep 770 Posts Drives: blue, gray, brown cars Join Date: Sep 2005 Location: Chicago, IL iTrader: (0)	LOL! Damn, I guess some of you don't watch any TV at all. Those Holiday Inn Express commercials are everywhere and have made its way well into pop culture and everyday conversational humor in the workplace, etc. Kinda like "I just saved a bunch of money on my car insurance" Geico commercials. Corny I know. __________________ 2021 A6 Allroad, 2020 SQ7, 2019 M5 Comp, 2011 GT3 past: A4, S4, X5 4.8is, SLK55, E60 M5, RS4, ML63, E92 M3, Q5, Touareg TDI, Escalade, SQ5, RS7, Velar FE, Q7
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12-17-2008, 07:13 AM	#11
corbz New Member 1 Rep 15 Posts Drives: s15 Silvia Join Date: Aug 2007 Location: Australia iTrader: (0)	The BMW release says that the factory rear muffler was designed to have the specific effects of rear diff cooling, lower underbody drag and a downforce effect. Read into that what you will
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