Sharing with the group how I created ducting to my Karbonius airbox with the OEM flap using the standard M3's bumper. The goal is to feed air:
- to the snorkel, which is upsteam of (before) the flap on the OEM piece, or just the snorkel itself on the Karbonius snorkel. The snorkel is the beginning section off some airboxes that has a triangular nose.
- to small intake downsteam of (after) the flap, which is on the underside of the Karbonius airbox.
Note other CSL airbox products, like the Evolve and the new Turner airbox with its bellmouth, don't have these multiple inlet places so this post may be of little use.
You can also do this without removing the front bumper/brake duct but it is easier to remove both.
See warning below around this installation with factory power steering (its not proven).
The snorkel up first. We repurpose and modify the standard M3 intake ducting which sits on top of the driver's brake duct.
- We're talking about cutting up part #20, which sits in the top of the brake duct (part#4)
- Cut 1" section out of the duct. Its important to leave a lip on the piece that fits back into the brake duct.
The "lip":
- That lip allows the remaining section of part #20 to slip back over the lip and hold tight.
Here you can see everything installed, the 1" cut section gone, and the accordion section pushed back over the lip.
- One other thing I opted to do is flip around the bottom portion of part#20. Its cut on a slant and from the factory, that slant is rearward facing. Since we're changing the airflow in the brake duct and foregoing the original design, I chose to flip that slant around.
- To do that, you re-notch the brake duct so it can be spun around 180 degrees.
Factory notch on the left, new notch on the right:
So now it looks like this looking into the brake duct from the front of the vehicle:
That's all the modifying. Re-install the brake duct, reinstall part #20, and then install the snorkel. You can also reinstall part#20 onto the snorkel, then install onto the vehicle and snap it back into the brake duct. Light use of heat gun helps part#20 (which is round) fit tightly over the triangular snorkel - you need to force it on. As installed:
Now for the small intake downstream of the flap.
- On the brake duct, cut the small "bulb" off the left side.
Before:
After:
- That's all the modifying needed. This new opening in the brake duct connects to the underside of the airbox using brake ducting which you need to purchase
- You want to use flexible 3" diameter flexible ducting (3 ft length). I recommend the single ply offered by Pegasus: https://www.pegasusautoracing.com/pr...p?Product=3620
- 3" is slightly too big so on this particular Pegasus product, remove some of the inner support metal wire so that you can tightly ziptie the flexible line to the respective connections.
Installed and ziptied to the brake duct
The flexible duct running up the next to the frame. I have a ziptie pulling it tight against the frame rail. With the factory powersteering lines, you aren't going to have much room to run that 3" duct so be prepared to smush it, tie it away, etc. Interference with the powersteering and/or alternator pulley is likely. I did away with the factory lines so it fits well 😛
I don't have a photo of the other side of the flexible line connected to the airbox (too tight) but another large ziptie holds it in place. I also removed some of the inner support wire on that side to make a tight connection.
And now you can see in the brake duct both feeds in place. Done!
- to the snorkel, which is upsteam of (before) the flap on the OEM piece, or just the snorkel itself on the Karbonius snorkel. The snorkel is the beginning section off some airboxes that has a triangular nose.
- to small intake downsteam of (after) the flap, which is on the underside of the Karbonius airbox.
Note other CSL airbox products, like the Evolve and the new Turner airbox with its bellmouth, don't have these multiple inlet places so this post may be of little use.
You can also do this without removing the front bumper/brake duct but it is easier to remove both.
See warning below around this installation with factory power steering (its not proven).
The snorkel up first. We repurpose and modify the standard M3 intake ducting which sits on top of the driver's brake duct.
- We're talking about cutting up part #20, which sits in the top of the brake duct (part#4)
- Cut 1" section out of the duct. Its important to leave a lip on the piece that fits back into the brake duct.
The "lip":
- That lip allows the remaining section of part #20 to slip back over the lip and hold tight.
Here you can see everything installed, the 1" cut section gone, and the accordion section pushed back over the lip.
- One other thing I opted to do is flip around the bottom portion of part#20. Its cut on a slant and from the factory, that slant is rearward facing. Since we're changing the airflow in the brake duct and foregoing the original design, I chose to flip that slant around.
- To do that, you re-notch the brake duct so it can be spun around 180 degrees.
Factory notch on the left, new notch on the right:
So now it looks like this looking into the brake duct from the front of the vehicle:
That's all the modifying. Re-install the brake duct, reinstall part #20, and then install the snorkel. You can also reinstall part#20 onto the snorkel, then install onto the vehicle and snap it back into the brake duct. Light use of heat gun helps part#20 (which is round) fit tightly over the triangular snorkel - you need to force it on. As installed:
Now for the small intake downstream of the flap.
- On the brake duct, cut the small "bulb" off the left side.
Before:
After:
- That's all the modifying needed. This new opening in the brake duct connects to the underside of the airbox using brake ducting which you need to purchase
- You want to use flexible 3" diameter flexible ducting (3 ft length). I recommend the single ply offered by Pegasus: https://www.pegasusautoracing.com/pr...p?Product=3620
- 3" is slightly too big so on this particular Pegasus product, remove some of the inner support metal wire so that you can tightly ziptie the flexible line to the respective connections.
Installed and ziptied to the brake duct
The flexible duct running up the next to the frame. I have a ziptie pulling it tight against the frame rail. With the factory powersteering lines, you aren't going to have much room to run that 3" duct so be prepared to smush it, tie it away, etc. Interference with the powersteering and/or alternator pulley is likely. I did away with the factory lines so it fits well 😛
I don't have a photo of the other side of the flexible line connected to the airbox (too tight) but another large ziptie holds it in place. I also removed some of the inner support wire on that side to make a tight connection.
And now you can see in the brake duct both feeds in place. Done!
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