Benefits of running THE flap?

[Cubieman]

Besides noise reduction and an OEM-like setup what are the benefits of running the snorkel flap?

[Obioban]

Sound reduction and not pulling hot air when stopped.
(that said, logging IATs, my IATs are ambient as soon as the car is over ~10mph, and I'm traction limited at that speed even with hot air, so the cooler air when stopped isn't that significant of a benefit IMO)

[Cubieman]

Is there a way to route the intake piping behind the flap without a CSL bumper that would pull cold air and not be a total hack job?

[Obioban]

Is there a way to route the intake piping behind the flap without a CSL bumper that would pull cold air and not be a total hack job?

Sure, though you'll have to get crafty-- there's no product sold to do it.

A black piece of PCV piping down in the brake duct would be pretty subtle and completely functional.

[mainstreamer00]

Is there a way to route the intake piping behind the flap without a CSL bumper that would pull cold air and not be a total hack job?

You could run "9,10,15" in this scenario, which I believe is meant to draw air from below the car/outside engine bay when the flap is closed.
As said above - for main snorkel intake, could run an Eventuri scoop or piece of ducting to connect with the hole in the top of the brake duct.

[Cubieman]

You could run "9,10,15" in this scenario, which I believe is meant to draw air from below the car/outside engine bay when the flap is closed.
As said above - for main snorkel intake, could run an Eventuri scoop or piece of ducting to connect with the hole in the top of the brake duct.

So would parts 9/10/15 mount up to a US spec car?
I was totally mistaken in my understanding of the ducting. I thought the parts 9/10/15 (behind the flap ducting) went to the hole in the bumper, but its the snorkel part #8 that goes to the bumper hole.

[mainstreamer00]

So would parts 9/10/15 mount up to a US spec car?
I was totally mistaken in my understanding of the ducting. I thought the parts 9/10/15 (behind the flap ducting) went to the hole in the bumper, but its the snorkel part #8 that goes to the bumper hole.

I'm running a flapless snorkel, and chose not to bother with the secondary ducting (looks like a PITA to run lol)
From what I've seen you should have no issues getting that stuff to work, as it doesn't interact with the bumper.

[repoman89]

Yeah 9,10 and 15 just sort of point down into the belly pan once assembled. I have them lying around in my closet but haven’t been bothered enough about it to actually install. You might need to drill a hole in one of those thin sheet metal mount things behind the bumper but not a big deal. The bendy insulated tube wraps around the front snorkel tube so it might be awkward or unstable without the front tube, not totally sure.

Like others here I’m really not convinced the extra PITA of all these tubes and new bumper is worthwhile ... I’d be perfectly happy if my Karb box came without the lower hole and no flap. I programmed the flap to stay open at anything above 100 RPM anyway. It was a lot of extra work to install the wiring and H-bridge on the DME for something I don’t even use.

[ethan]

I'm running a flapless snorkel, and chose not to bother with the secondary ducting (looks like a PITA to run lol)
From what I've seen you should have no issues getting that stuff to work, as it doesn't interact with the bumper.

Same here. I capped the inner hole which 9 attaches to on my Karbonius box. Then I use this thing:

https://karbonius.net/producto/bmw-m3-e46-snorkel/

Have it hooked up to the CSL bumper hole. Flap just seemed like a lot of work for no real benefit.

[heinzboehmer]

Same here. I capped the inner hole which 9 attaches to on my Karbonius box. Then I use this thing:

https://karbonius.net/producto/bmw-m3-e46-snorkel/

Have it hooked up to the CSL bumper hole. Flap just seemed like a lot of work for no real benefit.

What did you use to cap the hole?

[SQ13]

I had no idea that there’s a hole at the bottom of the CSL intake. What’s the point of that when the snorkel already points downward?

[ethan]

I had no idea that there’s a hole at the bottom of the CSL intake. What’s the point of that when the snorkel already points downward?

I guess it's for bringing in air when the flap is closed. It's a hole on the bottom right behind the junction between the airbox and the flap housing.

What did you use to cap the hole?

Just CNCed a little piece of HDPE and siliconed it in place haha.

Edit: IIRC Karbonius actually has caps specifically for this purpose, but I didn't want to wait for one in the international mail.

[jbfrancis3]

The flap acts as another throttle; its not just about noise control. Frank at TTFS knows a good bit about the function and design.

There is an easy way to connect everything in a functional manner:
The driver's side brake duct (#4) serves as the intake for the factory system. That's the starting point.
In the diagram, #20 tube gets cut down by an inch or two. Orient the tube so it fits back in the duct hole by 180 degrees from factory (its cut on an angle, you want to install with the long end towards rear of the car so as to catch the air). I think you'll need to grind down a plastic locating key.
Squeeze the upper portion in your hand to fit over the triangular portion of the snorkel. The bottom portion fits back in the hole of the duct.
On the duct, there is a bulbous protrusion designed to direct clean air into the factory system. Its not visible in the diagram. Cut the end of the bulb off you have another side duct, essentially.
Get 3" neoprene air duct (single layer) from Pegasus Racing meant for brake cooling. 3 ft length is needed. Connect air duct to your newly formed "side duct," and the other end to the intake of the CSL airbox, the intake downstream from the flap. You'll want to cut away the wire of the air duct for a good seal. 2.75" air duct would be perfect but I didn't find any in that size.
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 alternator pulley is likely. I did away with the factory lines so it fits well.

For those to whom its applies: some vehicles have blanking plates on the rear of the factory brake ducts (visible from the wheel wells). My driver's side came with a partially closed blank and passenger side with a full blank (nothing can pass through). You can swap plates to direct maximum air into the driver's duct which feeds your airbox.

[Cubieman]

Great info!

[///M3_MD]

The flap acts as another throttle; its not just about noise control. Frank at TTFS knows a good bit about the function and design.

There is an easy way to connect everything in a functional manner:
The driver's side brake duct (#4) serves as the intake for the factory system. That's the starting point.
In the diagram, #20 tube gets cut down by an inch or two. Orient the tube so it fits back in the duct hole by 180 degrees from factory (its cut on an angle, you want to install with the long end towards rear of the car so as to catch the air). I think you'll need to grind down a plastic locating key.
Squeeze the upper portion in your hand to fit over the triangular portion of the snorkel. The bottom portion fits back in the hole of the duct.
On the duct, there is a bulbous protrusion designed to direct clean air into the factory system. Its not visible in the diagram. Cut the end of the bulb off you have another side duct, essentially.
Get 3" neoprene air duct (single layer) from Pegasus Racing meant for brake cooling. 3 ft length is needed. Connect air duct to your newly formed "side duct," and the other end to the intake of the CSL airbox, the intake downstream from the flap. You'll want to cut away the wire of the air duct for a good seal. 2.75" air duct would be perfect but I didn't find any in that size.
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 alternator pulley is likely. I did away with the factory lines so it fits well.

For those to whom its applies: some vehicles have blanking plates on the rear of the factory brake ducts (visible from the wheel wells). My driver's side came with a partially closed blank and passenger side with a full blank (nothing can pass through). You can swap plates to direct maximum air into the driver's duct which feeds your airbox.

Excellent post. This is exactly what I was thinking about doing, but without the extra side duct. When I talked to Matt Coyne (Coyne/Kassel Performance) he said that anyone running an oversized alternator pulley will want to be careful as it can make contact with the OEM CSL ducting (I believe #9 in the diagram from post #5). Dafoe (M3F) had issues with his setup for that reason.

I'm just waiting on #10 (from post #5 above) to arrive from Lithuania so I can get this installed. It doesn't seem too difficult once you get everything apart.