645CI POWER LOSS WITH MAGNAFLOW
Senior Members
Joined: Aug 2008
Posts: 838
Likes: 0
From: Davie, FL
Originally Posted by crmb' post='890144' date='May 26 2009, 01:17 AM
The exhaust is TOO free flowing. You need some back pressure to get your power back. You can add a pair of those trick high-flow metal cats to the duals and I'm sure you'll bump right up back to factory specs + 10. If you look at a lot of the exhaust sytems that "DON'T" lose power, you'll notice they are basically just replacing the tail pipe leaving the stock catalytic converter in place or they add an additional restriction in line to replace what they had removed.
Contributors
Joined: Dec 2007
Posts: 1,706
Likes: 0
From: Calgary, AB - Canada / Buenos Aires - Argentina
My Ride: 2006 BMW M5
Originally Posted by crmb' post='890144' date='May 25 2009, 11:17 PM
The exhaust is TOO free flowing. You need some back pressure to get your power back. You can add a pair of those trick high-flow metal cats to the duals and I'm sure you'll bump right up back to factory specs + 10. If you look at a lot of the exhaust sytems that "DON'T" lose power, you'll notice they are basically just replacing the tail pipe leaving the stock catalytic converter in place or they add an additional restriction in line to replace what they had removed.
Engine ---------------------------------------------> Exit
= : pipe
+C+ :catalytic converters
[ ] : Resonators
{} : Muffler
Stock Exhaust of 545i:
+C+===[Stock]===\............................... /{Stock Final 1}=
................................{Stock Middle}===
+C+===[Stock]===/............................... \{Stock Final 2}=
I guess they are saying:
+C+===[Stock]===\.................................................. ../=
................................{Stock Middle}==={Magnaflow}
+C+===[Stock]===/.................................................. ..\=
Members
Joined: Jun 2008
Posts: 61
Likes: 0
There are pre-cats off the back of the headers, then dual resonators, then a dual inlet, single outlet catalytic converter with a huge choke point just in front of it. If your diagram is correct, then it's likely the system eliminates that single outlet catalytic converter which is what I did yesterday. I'm 99% sure we can't eliminate the single outlet catalytic converter without some loss. I'm going to add a high flow replacement cat in place of it and retest.
Originally Posted by miguex' post='890330' date='May 26 2009, 04:58 AM
Replacing the cats? which one?
Engine ---------------------------------------------> Exit
= : pipe
+C+ :catalytic converters
[ ] : Resonators
{} : Muffler
Stock Exhaust of 545i:
+C+===[Stock]===\............................... /{Stock Final 1}=
................................{Stock Middle}===
+C+===[Stock]===/............................... \{Stock Final 2}=
I guess they are saying:
+C+===[Stock]===\.................................................. ../=
................................{Stock Middle}==={Magnaflow}
+C+===[Stock]===/.................................................. ..\=
Engine ---------------------------------------------> Exit
= : pipe
+C+ :catalytic converters
[ ] : Resonators
{} : Muffler
Stock Exhaust of 545i:
+C+===[Stock]===\............................... /{Stock Final 1}=
................................{Stock Middle}===
+C+===[Stock]===/............................... \{Stock Final 2}=
I guess they are saying:
+C+===[Stock]===\.................................................. ../=
................................{Stock Middle}==={Magnaflow}
+C+===[Stock]===/.................................................. ..\=
Contributors
Joined: Dec 2007
Posts: 1,706
Likes: 0
From: Calgary, AB - Canada / Buenos Aires - Argentina
My Ride: 2006 BMW M5
oh I see....
My exhaust is different, I removed the 2 stock mufflers (middle and final mufflers1&2), installed an aftermarket muffler and moved the stock resonators after the muffler, like that...
xCx : Catalyst
= : pipe
{ } : Muffler
[] : Resonator
xCx======\......................./===[Stock]============
.....................{FLO-PRO MAX}
xCx======/.......................\===[Stock]============
My exhaust is different, I removed the 2 stock mufflers (middle and final mufflers1&2), installed an aftermarket muffler and moved the stock resonators after the muffler, like that...
xCx : Catalyst
= : pipe
{ } : Muffler
[] : Resonator
xCx======\......................./===[Stock]============
.....................{FLO-PRO MAX}
xCx======/.......................\===[Stock]============
Contributors
Joined: Dec 2007
Posts: 4,508
Likes: 0
From: Vancouver, BC
My Ride: See sig :)
So is it just the magnaflow that causes power loss? What about borla, corsa? My butt dyno says other though, and racing a few cars I've raced before, I pull on them now, So I'd say other.
Members
Joined: Aug 2009
Posts: 34
Likes: 0
I have the same magnaflow too and love it, you can usually get a used one on ebay or cragislist. I wanted a valid warranty so I got it here. Magnaflow 16966. Also some of the forum sponsors usually have a sale going on. Either way its a great exhaust system, sounds great, and very easy to install.
Contributors
Joined: Nov 2007
Posts: 693
Likes: 0
From: Toronto, Ontario
Originally Posted by stylezzza' post='799928' date='Feb 24 2009, 02:34 AM
makes me want to change out the magnaflow....but i love my quads and the sound!
i love mine too.
Thread
Thread Starter
Forum
Replies
Last Post
Specia1k
E60 Discussion
8
Nov 6, 2020 04:48 PM
