2010 2011 BMW 5 Series Forum F10
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
 

2010 2011 BMW 5 Series Forum F10 F10 Technical Topics Engine, Transmission, Exhaust, Drivetrain, ECU Software Modifications Downpipe Question
Post Reply
 
Thread Tools Search this Thread
      11-30-2014, 11:50 PM   #1
bake
Major
bake's Avatar
United_States
28
Rep
1,147
Posts

Drives: 2011 535i M-Sport
Join Date: Apr 2010
Location: Long Island, New York

iTrader: (4)

Downpipe Question

Can someone explain how an aftermarket downpipe makes additional horsepower in comparison to a stock unit? I totally understand turbocharging, but don't really understand the role of the DP. Thanks.
__________________
Bake
2011 AW on Black 535i M-Sport
20" Style M303's | ACS Springs | M Perf Mufflers w/Quad Tips | M Perf Rear Diffuser
Gloss Black Roof | 3D Roof Spoiler | M5 LCI Grille | CF M Perf Spoiler | BMS Intake
Appreciate 0
      12-01-2014, 03:41 AM   #2
phil7027
Private
3
Rep
80
Posts

Drives: 2015 550xi
Join Date: Nov 2014
Location: Staten Island, NY

iTrader: (0)

depending on whichever you go will give you different power gains.

Catless being the most power gain vs. catted being less of a gain

Downpipes give you more power because they let the exhaust from the motor flow more freely (catless flows more freely than catted hence the power gain).

picture a hose with a kink in it being your stock down pipe…. then remove the kink from the hose thats your aftermarket down pipe…… flows better without the kink right? Thats the dummy way of explaining it lol
Appreciate 0
      12-01-2014, 08:45 AM   #3
bake
Major
bake's Avatar
United_States
28
Rep
1,147
Posts

Drives: 2011 535i M-Sport
Join Date: Apr 2010
Location: Long Island, New York

iTrader: (4)

Quote:
Originally Posted by phil7027
depending on whichever you go will give you different power gains.

Catless being the most power gain vs. catted being less of a gain

Downpipes give you more power because they let the exhaust from the motor flow more freely (catless flows more freely than catted hence the power gain).

picture a hose with a kink in it being your stock down pipe. then remove the kink from the hose thats your aftermarket down pipe flows better without the kink right? Thats the dummy way of explaining it lol
I understand that a catless DP makes more power because you are removing the restrictive cat, but if we are talking a catted DP, is the increase in HP that significant? Just seems like the pipe is so short, I don't see how it makes huge gains.
__________________
Bake
2011 AW on Black 535i M-Sport
20" Style M303's | ACS Springs | M Perf Mufflers w/Quad Tips | M Perf Rear Diffuser
Gloss Black Roof | 3D Roof Spoiler | M5 LCI Grille | CF M Perf Spoiler | BMS Intake
Appreciate 0
      12-01-2014, 08:56 AM   #4
valbmw
First Lieutenant
valbmw's Avatar
Russian Federation
24
Rep
347
Posts

Drives: F10 535d xDrive M Sport
Join Date: Nov 2013
Location: Moscow, Russia

iTrader: (0)

Garage List
I've been just reading about the same, so please have a look at this very simple and clear article: http://forums.nasioc.com/forums/showthread.php?t=445812
Appreciate 0
      12-01-2014, 11:32 AM   #5
badblack550xi
Lieutenant Colonel
badblack550xi's Avatar
94
Rep
1,566
Posts

Drives: F10 550xi 2013
Join Date: May 2013
Location: NJ

iTrader: (0)

Quote:
Originally Posted by Valery.BMW View Post
I've been just reading about the same, so please have a look at this very simple and clear article: http://forums.nasioc.com/forums/showthread.php?t=445812
Good article !
Appreciate 0
      12-01-2014, 12:32 PM   #6
valbmw
First Lieutenant
valbmw's Avatar
Russian Federation
24
Rep
347
Posts

Drives: F10 535d xDrive M Sport
Join Date: Nov 2013
Location: Moscow, Russia

iTrader: (0)

Garage List
Quote:
Originally Posted by badblack550xi View Post
Good article !
Thanks, bud! Good to see you like it, you owner of the brutal black bullet with catless DP, methanol injection and race exhaust!
Appreciate 0
      12-02-2014, 03:29 AM   #7
phil7027
Private
3
Rep
80
Posts

Drives: 2015 550xi
Join Date: Nov 2014
Location: Staten Island, NY

iTrader: (0)

Yes you will still see gains even with an aftermarket catted DP because it still flows better than the stock cat. My hose reference explains it the best. Any free up in the restriction of an exhaust system (especially a turbo motor) will see an increase in horsepower.

Before I got my 550 2 weeks ago I had a 2012 mustang GT. Back when I deleted my cats before adding headers, i gained 20rwhp just from deleting them.
Appreciate 0
      12-02-2014, 09:54 PM   #8
bake
Major
bake's Avatar
United_States
28
Rep
1,147
Posts

Drives: 2011 535i M-Sport
Join Date: Apr 2010
Location: Long Island, New York

iTrader: (4)

Yep I get. So gain is mainly realized with the removal of the cat, or replacement of the OEM cat with a less restrictive one. Basically what I was getting at is there is more to it that just replacing a very short length of exhaust piping. My next question is, are our cars able to pass emissions testing with the catted DP options? I already know they won't pass without cats.
__________________
Bake
2011 AW on Black 535i M-Sport
20" Style M303's | ACS Springs | M Perf Mufflers w/Quad Tips | M Perf Rear Diffuser
Gloss Black Roof | 3D Roof Spoiler | M5 LCI Grille | CF M Perf Spoiler | BMS Intake
Appreciate 0
      12-03-2014, 04:03 AM   #9
phil7027
Private
3
Rep
80
Posts

Drives: 2015 550xi
Join Date: Nov 2014
Location: Staten Island, NY

iTrader: (0)

Quote:
Originally Posted by bake View Post
Yep I get. So gain is mainly realized with the removal of the cat, or replacement of the OEM cat with a less restrictive one. Basically what I was getting at is there is more to it that just replacing a very short length of exhaust piping. My next question is, are our cars able to pass emissions testing with the catted DP options? I already know they won't pass without cats.
I see your in NY so your in the same boat as me. In NY as long as the 02 sensors are all turned on and there is no CEL, you will pass.

You can pass with the catted down pipe, Catless will be more of a hassle, but it can be done. I am going carless on mine
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 11:34 AM.




5post
5post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST