Potential negative factor with third muffler bypass systems
03-19-2015, 10:08 PM
#16
Rennlist Member
Porsche states in their literature that the center muffler is part of the aero.
03-19-2015, 10:28 PM
#17
RL Community Team
Rennlist Member
Rennlist Member
This may very well be true, and as a complete neophyte to these things I have no idea if it is or not, but assuming it's true, I'm not nearly a good enough driver to notice.
As a sidenote, aside from the change in aero from swapping out a bypass, wouldn't aftermarket wheels also affect aero vis-a-vis OEM 991 GT3 wheels?
As I understand it, wheels have been shown to have a large influence on the global overall aerodynamic properties of a vehicle. Specifically, wind-tunnel testing has shown that the local flow field around the wheels and wheel housings is highly dependent of the rim design. And that the flow around the rear wheel is highly dependent on the front wheel geometry.
So lets say you add an aftermarket bypass like SW or GMG, and then swap out the wheels for something by BBS or Superleggra, then what?
Maybe we'll be have way to a true flying car?
As a sidenote, aside from the change in aero from swapping out a bypass, wouldn't aftermarket wheels also affect aero vis-a-vis OEM 991 GT3 wheels?
As I understand it, wheels have been shown to have a large influence on the global overall aerodynamic properties of a vehicle. Specifically, wind-tunnel testing has shown that the local flow field around the wheels and wheel housings is highly dependent of the rim design. And that the flow around the rear wheel is highly dependent on the front wheel geometry.
So lets say you add an aftermarket bypass like SW or GMG, and then swap out the wheels for something by BBS or Superleggra, then what?
Maybe we'll be have way to a true flying car?
03-19-2015, 10:33 PM
#18
Burning Brakes
03-19-2015, 10:59 PM
#19
Race Director
I am not an aerodynamics expert but at 150+ mph my a** says that the car feels very planted. I'm certain that removing the center exhaust probably makes a small change in aero, but I believe it's very minimal. We aren't talking about a full blown ground effect system in place with large venturi tunnel on bottom of car exiting rear skirt? Maybe at 195mph my car will shoot off straightaway like a F-18 Hornet but I won't ever see that speed in real world track stints so to me it's a non issue.
I'll take the minimal weight savings and the associated aero risk of the bypass.
I'll take the minimal weight savings and the associated aero risk of the bypass.
03-19-2015, 11:24 PM
#20
Rennlist Member
Hoopumpers, Nice looking part.
03-20-2015, 12:41 AM
#22
Burning Brakes
03-20-2015, 12:45 AM
#23
Instructor
Thread Starter
This may very well be true, and as a complete neophyte to these things I have no idea if it is or not, but assuming it's true, I'm not nearly a good enough driver to notice. As a sidenote, aside from the change in aero from swapping out a bypass, wouldn't aftermarket wheels also affect aero vis-a-vis OEM 991 GT3 wheels? As I understand it, wheels have been shown to have a large influence on the global overall aerodynamic properties of a vehicle. Specifically, wind-tunnel testing has shown that the local flow field around the wheels and wheel housings is highly dependent of the rim design. And that the flow around the rear wheel is highly dependent on the front wheel geometry. So lets say you add an aftermarket bypass like SW or GMG, and then swap out the wheels for something by BBS or Superleggra, then what? Maybe we'll be have way to a true flying car?
Why ruin something that has been designed aerodynamically by comparing it to the aesthetic changes that may allow thicker sidewall, better tire selections, and reduction in unsprung weight?
03-20-2015, 12:53 AM
#24
RL Community Team
Rennlist Member
Rennlist Member
due to the fact that aftermarket wheels will rotate under driving and with the size and offsets that are similar to the oem wheels, I don't think aftermarket wheels can affect the aerodynamics. in fact, wheels can't generate downforce. moreover, you can install jet engines and extensive side wings on the car to make it a true short distance random flying object.
Why ruin something that has been designed aerodynamically by comparing it to the aesthetic changes that may allow thicker sidewall, better tire selections, and reduction in unsprung weight?
Why ruin something that has been designed aerodynamically by comparing it to the aesthetic changes that may allow thicker sidewall, better tire selections, and reduction in unsprung weight?
And, really, I wasn't making a comparison, just noting that a change in wheel face geometry may have an affect on aerodynamics of the car.
03-20-2015, 02:05 AM
#25
Instructor
Thread Starter
Great observation, and I would venture to guess that you are correct. I'm not a fan of aftermarket exhaust parts (I feel they're a bit hacky), BUT an easy fix for this issue would seem to be just making a diffuser plate that bolts to the bypass and hangs down to match the bottom shape of the 3rd muffler.
I agree that this will have downforce effect. Most downfoece come from the underbody design versus from wing etc. Disturbing the airflow right where it matters the most (as it exits the underbody) will definitely have impact....
I suggested this as opportunity for a new part to sell along with bypass to SW .... Would love to get one!
I suggested this as opportunity for a new part to sell along with bypass to SW .... Would love to get one!
I have contacted hoopumpers and will get in contact with vision for more info. there is a possibility that i will visit them tomorrow and report back here.
03-20-2015, 02:51 AM
#26
GT3 player par excellence
Lifetime Rennlist
Member
Lifetime Rennlist
Member
i think you worry too much and too academic
1. if you want over all performance, reliability, durability, liveability, stay oem. it's the best. this is porsche, they have a few engineers there. not all smart, but some are.
2. if you want sound, get a bypass. pick the one that sounds to your liking
3. if racing, then yes aftermkt is better, you can bias it and do ecu mods to get the power and tq curve to your liking.
anything more than the above 3 point, is just some cerebral exercise
1. if you want over all performance, reliability, durability, liveability, stay oem. it's the best. this is porsche, they have a few engineers there. not all smart, but some are.
2. if you want sound, get a bypass. pick the one that sounds to your liking
3. if racing, then yes aftermkt is better, you can bias it and do ecu mods to get the power and tq curve to your liking.
anything more than the above 3 point, is just some cerebral exercise
03-20-2015, 11:26 AM
#28
Three Wheelin'
Could the side muffler delete by BBI be a better option?
The weight off the side locations should better the center of mass. A bit more difficult to install the by-pass.
The weight off the side locations should better the center of mass. A bit more difficult to install the by-pass.
03-20-2015, 03:16 PM
#29
Intermediate
