First thing is first, I have an r53 MCS that I'm upgrading to all JCW parts.

I figure I might as well pose the question. I'm debating how badly I want to do the vacuum lines and electrical. But if I remove the flap, I don't have to worry about that. However, does anyone happen to know how much it'll affect the MPG below the 4500RPM range? I would theorize that on long trips and highway driving, which I do a lot of, it would be beneficial to keep a functioning flap in for MPG sake. But if there really isn't that much savings then I won't worry about wiring it up

Any info is appreciated

 

No affect on MPG, as it would be just like a CAI by other makers by having it open all the time. Just my opinion.

 

I performed a flapectomy on my JCW cai 6 years ago and haven't noticed any change in mpg

 

the flap was put in due to noise restrictions in the UK (so ive read). you can either gut it, or wedge the metal deal to keep it open.

IMO, just take your Regular airbox, and cut a bigass hole in the back. if you wanna get "fancy", cut Another hole in the plastic wall behind it, and use a slice of PVC pipe or something to "connect" the 2. Thats literally all the JCW airbox is.

i just removed my diaphragm completely as of late, which put another nice little hole in that portion of the box. also found a big plug in the Bottom of the airbox (strange) that I removed.

 

If you've already spent the money on the JCW intake, the mod is straight forward and simple. You will need to remove the panel on the induction panel on the firewall and cut the hole to match the oval shaped hole on the intake. The car will perform a bit better than with the stock R53 air box and will allow you to pass smog without any questions being asked. And yes, lose the vacuum lines altogether... Best of luck and enjoy the new sound this will bring to your car!

 

So on the parts diagram it says " sound flap" but wouldn't you think that the flap helps with your air to fuel ratio.? Lower rpm's the flap allows for less air since you have "less fire". Higher rpm's require more air so the flap opens to draw in more outside air. I'm thinking about putting in an Alta air filter and debating doing the flapectomy at the same time but don't want the car to be doggy at lower rpm's I love the sound of the supercharger especially in a Cabrio.

 

It has no effect. Trust us.

 

I believe the flap is there to reduce a little noise at lower RPMs.
It is a compromise. The flap reduces the amount of air available but eliminates a little noise. The JCW Motorsports version of the intake has the flap removed.
I have the flapped removed and can now sometimes hear a little whistle at lower RPMs when cruising on the highway with little load on the engine.

 

Just removed my flap tonight and the vacuum tank and lines inside the box. Waiting for my new Alta filter to arrive to put it all back together.