Carbon Dynamic Airbox.

[Chris Y]

Has anyone had any experience with a "Carbon Dynamic Airbox"?

If you don't know what they're about, have a gander at: http://www.bmcairfilters.com/infoCDA.asp - I've heard of them, but don't really know how (well) they work.. The website has a range of graphs showing improvements in BHP and torque during rolling road sessions, but probably over 'standard' airbox setups.

Do they flow more air, increase the density of the charge, or a combination?

At the moment, I have no airbox, just a fresh air pipe aimed at the carbs (Twin 40 Webers). Not a particularly good setup I know. I'm wondering whether to build a large cold air box over the carbs (which suffer from heat soak), and just have a conical air filter stuck on the end of a pipe, or whether to use a smaller airbox and one of these CDAs (or even the cheaper alternative, the Dynamic Intake Airsystem)

There's also mention of 'venturi' conical air filters by the same company, which supposedly increase the speed of air flow into them.. Do these work?

[StephenRae]

I think the best the 'cone' can do is negate some of the loss of air flow through the filter, but I would guess that much of the air flows through the filter at the base of the cone, making it less efficient.

[phoenix]

I don't know how the pressure drop compares with other filters, but a lower pressure drop = better airflow, better airflow means more air in the cylinders which, with the right amount of fuel, will give more power than a filter which has a higher pressure drop across it.

[dtype38]

No personal experience, but fwiw - a personal opinion... The basic cylindrical construction gives good surface area for the volume it takes up (minimising the pressure loss through the filter itself) but compared to a straight through filter it suffers from pressure losses due to turning the flow through 90 degrees at least twice. The folks who've made this have recognised the problem and look to have spend a bit of time on the flow bench optimising the internal shape and baffles to minimise these losses. It looks like a good product for tight spaces, especially where a single intake tube is used like on turbo engines and single inlet branch manifolds. As for any claims for "increased performance", I would always read that with the addition of "compared to the car manufacturer's standard filter", and to be honest, in most cases that will probably be true. However, compare it to a completely open inlet and any pressure loss will adversly affect the density of the intake charge. The only exception would be where a large filter mounted direct on the carb inlets is suffering from drawing excessively "pre-heated" air, ie underbonnet radiator air. In this case, going for an air box with a cold air feed tube would ususally be better, and the inlet filters could be replaced by something like the CDA for an overall better compromise. :-)