At long last, a review of the BMC CDA (Carbon Dynamic Airbox) :)

[akula-ssh]

Okay, so I've had the CDA sitting at home for a while. Let's first take a look at some of the pictures I've posted a little while ago, just so we remember what the BMC CDA's filter element looks like:




Last Friday I finally decided to put it into the Avant. This is what the engine bay looked like before the exercise:



And what it looks like now:



A couple more pictures showing the CDA, and where I'm feeding air to it:




After driving the car with the intake for a few days, I feel that the engine spools up quicker than before. Also, I thought I noticed a bit more power, especially at the low end. With the help of a fellow Audi owner armed with a VAG-COM, I did some logs. First up, the MAF log:

There's a measureable increase in airflow. Mind you, it's a nice cool 14 degrees Celcius tonight compared to the previous log which was done at 23 degrees Celcius, but that only amounts to a 3% difference in density (for those who're wondering where that 3% came from, it's not from degrees Celcius but Kelvin, the absolute temperature scale which is the only physically significant scale. The conversion is K = °C + 273.15, and temperature in this unit is proportional to volume).

What about power/torque?

The statistical errors on the curves are less than 1%, so assuming VAG-logging is a valid way to measure power/torque, the increases are real, and confirms what the butt dyno suggests.

Last note: for this project, I decided to buy myself some double neoprene coated fiberglass ducting, which I got from McMaster-Carr, instead of using the aluminum flex pipe that came with the CDA. 3-1/4" ID is used for routing air into the airbox, and 3-1/2" is used for the little elbow from the CDA to the MAF. I've also bought a small 1" OD K&N breather filter, but as of yet it's not on the car; it'll be installed soon, now that I'm fairly certain things are running normally and thus am more willing to cut the breather pipe for the installation.

[MISTERJONES]

your cold air from- i.e; the bottom of the bumper? no worries as to pulling in water- or is it just the same as worrying about pulling it in from the stock locale? also- where did you get that? i havent see one.

thanks for the info and write-up.

[akula-ssh]

I feel quite safe putting the duct opening there, but of course only time will tell how wise that decision is. I doubt I'd suck up water unless I have the duct opening completely submerged...

I bought mine through Autobraun in Edmonton, Canada. BMC's corporate website lists a few distributors in the US; maybe you could give some of them a shout if you're interested in getting one.

[A4AdMan]

And I assume that since the CDA has a carbon fiber sleeve that is why there is no need to put a "heat shield between the CDA and the engine block? The carbon fiber sleeve must act as a heat shield allowing the cool air to stay cool while it it travel through the intake to the engine.

Keep use posted on how it performs and holds up over time.

Now you just need to install a chip and you'll have one of the quickest non-supercharged 3.0's on the street.

[A4Rye]

[jim'02a4]

[akula-ssh]

The actual install only took 'bout 30 minutes. (Silly me, it took 15min for me to take out the airbox when I did it for the first time; took me only a minute to yank it out the 2nd time).

Yeap, there's no need for a heat shield, just like there's no heatshield for the OEM airbox. Intake air temperatures last night when I did the VAG logs were the same as (or even lower than) the indicated outside temperature when the car was in motion.

I'm sure somebody's already got a manual 3.0 sedan with exhaust, intake and chip, so mine would never ever be the quickest non-sc'ed 3.0 :P

[akula-ssh]

Soon I'll put the 1" filter on it.

[akula-ssh]

It's certainly something worth considering. My opinion on that is if the pebble is large enough that it could puncture the filter element, it probably is too heavy to be sucked up, or even bounce up the flexible neoprene piping, which has got a few bends (space is tight going from the foglight grill to the engine bay). Then again, just like my believe that water won't be an issue, only time will tell...

[shadyraven]