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Discussion Starter · #1 ·
Hello,

I recently found out that both the cat. converters on my 2008 650i have failed and it's an upwards of around $4,000 to replace. So I was wondering on doing a straight pipe exhaust with a cat delete. And since I live in an area with no emission restrictions I just wanted to know if this is a good idea and does it really increase horsepower and performance? And if so, which exhaust system would u recommend?

Thanks
 

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But I don't have a Ford...

Sent from my SM-G955U1 using Bimmerfest mobile app
Their situation shows how dangerous it can be.
The explorer has 2 issues, one is the leaky exhaust manifold, second is the cabin sealing/venting issue.

Once you remove the cats you will have a lot more CO curling back onto the rear end of the car due to the aerodynamics. Then it will be the question of the sealing if it comes into the cabin or not.
And also the car coming right behind you will just suck in whatever your car exhales.

Get some used cats from someone who is parting out his car.
 

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Discussion Starter · #5 ·
Their situation shows how dangerous it can be.
The explorer has 2 issues, one is the leaky exhaust manifold, second is the cabin sealing/venting issue.

Once you remove the cats you will have a lot more CO curling back onto the rear end of the car due to the aerodynamics. Then it will be the question of the sealing if it comes into the cabin or not.
And also the car coming right behind you will just suck in whatever your car exhales.

Get some used cats from someone who is parting out his car.
Okay I got it. I'll take it under consideration.

Sent from my SM-G955U1 using Bimmerfest mobile app
 

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Hello,

I recently found out that both the cat. converters on my 2008 650i have failed and it's an upwards of around $4,000 to replace. So I was wondering on doing a straight pipe exhaust with a cat delete. And since I live in an area with no emission restrictions I just wanted to know if this is a good idea and does it really increase horsepower and performance? And if so, which exhaust system would u recommend?

Thanks
There are quite a few threads here on this that should answer your questions.
 

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I say go for it. I personally am going to drop the engine and install long tube headers with no cats.
The CO argument is pretty negligible. As long as you don't have an exhaust leak you will be fine.
It will definitely raise power, but also shift the power band to the top.

You should consider a tune also. Active autowerks can tune for cat deletes on this platform. That is the route I'm going.
 

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Removing the cats can be done, as long as the tune of the motor is kept within range of the DME. Removing to much back pressure can cause the motor to lose power. I would talk with someone like MagnaFlow, to see how they are designing their exhaust system's, just to make sure there is no loss of power when removing the cats. If you decide to remove the cats, save them in case your car will need to pass emission's at some point?

Some cats are built where they are easily gutted, leaving the design of the system to have the back pressure the motor was designed for. I have seen some Ford cats with nothing more than screen grids, which can be easily cleaned or removed for longer service.

You will change the sound of the motor, which is a personal preference. I personally don't loud exhaust systems any longer! :dunno:
 

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The only difference caused by loss of back pressure is shifting the power band upward. Too little back pressure = powerband shifting upward, including the torque curve. That is why many people feel a power loss down low, but in reality you're shifting it up maybe 500-1000 rpm max. It depends on your driving style and what your goals are for the car. Many people enjoy low end torque for spirited driving etc, and some people enjoy revving the hell out of the engine.

I personally think as long as you have two large mufflers in the back you will not shift the powerband up that much higher. My personal plan is to get aftermarket headers with no cats (supersprint reps), and then the stock catback setup remove the center resonator and replace it with an X pipe, and leave the two factory mufflers in place, and run dual tips out of each.
 

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The only difference caused by loss of back pressure is shifting the power band upward. Too little back pressure = powerband shifting upward, including the torque curve. That is why many people feel a power loss down low, but in reality you're shifting it up maybe 500-1000 rpm max. It depends on your driving style and what your goals are for the car. Many people enjoy low end torque for spirited driving etc, and some people enjoy revving the hell out of the engine.

I personally think as long as you have two large mufflers in the back you will not shift the powerband up that much higher. My personal plan is to get aftermarket headers with no cats (supersprint reps), and then the stock catback setup remove the center resonator and replace it with an X pipe, and leave the two factory mufflers in place, and run dual tips out of each.
So - it's been a few years since this post. I'm about to make a decision on what to do with my exhaust system. Did you cut out both sets of cats? Both the pre-cats (welded to the headers) as well as the secondary cats ( pre-resonator)? So all you have is a set of headers with straight pipes back to the X-pipe and then straight pipes to the mufflers? Any issues w/re-programming the DME to eliminate the Check-engine light? Any issues w/Fuel management / use? Noise? It would be nice to hear how the swap went.
 
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