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      01-13-2020, 07:45 AM   #1
DeonRFi
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Talking Cheap Exhaust Mod for 750i

I bought a 2009 BMW750i recently and was very impressed with the car,but.... Yes there is a but, I found the car sound like my granny's old Toyota Corona from the 70's vintage. I looked at all the mods on the net but decided to take on the mod myself. All I did was to remove the 2 back exhaust boxes and put a pipe through each side splitting into a "Y" on each side so it looks standard from behind but it is not. I found the car more responsive and more economical and it sounds SOOOOOO GOOD!!!! I wander if this could cause damage to valves, CAT converters and so on? Anybody can comment, I will like to hear your ideas on this.
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Deon South Africa.
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      01-13-2020, 08:53 AM   #2
SYT_Shadow
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I doubt there is any difference in your fuel economy due to the change, but I'm pretty sure you have nothing to worry about. People run catless exhausts all the time
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      01-13-2020, 09:02 AM   #3
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I know that removing catalytic converters is an offence here as they are part of the emission equipment.....that's not to say it doesn't happen.
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      01-14-2020, 04:22 AM   #4
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Quote:
Originally Posted by SYT_Shadow View Post
I doubt there is any difference in your fuel economy due to the change, but I'm pretty sure you have nothing to worry about. People run catless exhausts all the time
Maybe it is less economical as one tend to drive the car a bit harder now to hear the sound
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      01-14-2020, 04:24 AM   #5
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Originally Posted by Salty Dog View Post
I know that removing catalytic converters is an offence here as they are part of the emission equipment.....that's not to say it doesn't happen.
In SA the laws does not matter because nobody care.....
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      01-28-2020, 10:11 PM   #6
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Quote:
Originally Posted by DeonRFi View Post
In SA the laws does not matter because nobody care.....
Just so I'm clear, you removed your rear resonators right at the bumper and NOT your catalytic converters. I think there is some confusion here.
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      01-29-2020, 07:48 AM   #7
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Jip I just removed the the 2 boxes just before it exits at the back through the bumper and replaced with a pipe that connects the exhaust system to a "Y" at the back, so if you look from behind all you see is 2 pipes on each side.
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      01-29-2020, 08:12 PM   #8
cowboy750
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Quote:
Originally Posted by DeonRFi View Post
Jip I just removed the the 2 boxes just before it exits at the back through the bumper and replaced with a pipe that connects the exhaust system to a "Y" at the back, so if you look from behind all you see is 2 pipes on each side.
Could this be done On a F02? Also is it loud in normal driving or just when punching it?
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      01-30-2020, 04:45 AM   #9
DeonRFi
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Quote:
Originally Posted by cowboy750 View Post
Could this be done On a F02? Also is it loud in normal driving or just when punching it?
I'm no expert, but I found it to sound so good, there is a bit of a drone at low speeds but on free way it is gone. To me if you drive a V8 you want to hear the sound a bit. I must say it is not as loud as say a Mustang GT standard so I have not been in trouble with the law yet wit it, if I see a cop I just switch to manual and change to a higher gear then the car quiet down.
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      01-30-2020, 05:39 AM   #10
DeonRFi
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Originally Posted by cowboy750 View Post
Could this be done On a F02? Also is it loud in normal driving or just when punching it?
I don't know if you can do this on a F02, I did not know it can be done on a F01, but so far so good.
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      01-30-2020, 05:44 AM   #11
DeonRFi
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Quote:
Originally Posted by cowboy750 View Post
Could this be done On a F02? Also is it loud in normal driving or just when punching it?
I find when the car idle, it sound like a V8 but then as you pull off the drone sound a bit like the old M series, but the noise goes away at about 2500 RPM but what I like, is that it is not to loud at any time in or out of the car. I suppose it will be a lot louder once one remove the CAT units as well.
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      02-04-2020, 05:45 PM   #12
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So I've done all the cheap exhaust mods you can do to my F02 and here is the verdict.

Cut off Rear Mufflers: (like OP did) Sounds good but very annoying drone inside car at almost all cruising speeds both city and highway.

Straight Pipes: WAY TOO LOUD! won't pass emissions, etc.

I feel like my current setup is the BEST... but I have a tune to take care of check engine light and pass emissions.

Current Setup: 3" Catless Downpipes connected to 3" pipes, with all mid section resonators deleted, connected to stock rear mufflers (the ones OP cut off). So basically I've got just 3" pipe coming off each turbo all the way back to the mufflers. By enlarging the pipes all the way down I get way faster turbo spool and more flow. The stock pipes are 2.75" and have front and mid resonators.

The reason for keeping the stock mufflers is to eliminate the drone. Also, the stock mufflers have vacuum actuated valves on them that open and close automatically under load. So they're closed when you're idle or cruising and they open up when you get on the throttle. THIS is by far the BEST setup in my opinion... nice and quiet rumble in parking lots and wide open loud ass exhaust when you're on it!

If you didn't want to do the downpipes and larger exhaust pipes, you could just delete the front and mid section resonators under the car... this will give you a nice rumble without being overbearing or causing drone. Hope this helps!
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