[Mk2] [Generic] Fitted my BMC CDA Filter (With Pics) - Do You Have One ??

[RST]

Na not really on my side Mark. And no offence hopefully Nik -but I'll bet I'm still gonna beat you by the way (personal joke)!!

Richard

[nikk1877]

RST, Teccyjim,

i'm not as technical as you guys but heres what i think i know -

you guys are talkin about fluid moving through a pipe right?
so a pressure drop at one end = increased velocity of the fluid?

right.

so that pipe has the throttle body at one end and the airbox(bmc or factory) at the other and then another pipe from the airbox to the vent.

so you open the throttle, pressure drops, drawing air from the airbox, then the pressure drops in the air box, drawing more air in from outside to keep a constant volume of air in the box.(at lower revs at least)
pressure is where i'm going wrong - it must be the volume thing.

On an NA you need that volume of air on demand at low revs so the engine is not using power to draw in air and in turn provides the low down punch that the factory(or BMC CDA) airbox gives.

So if that doesn't make sense then try explaing why I have lost the low down grunt after fitting a direct air filter?
And also why have the other 2 guys noticed a difference over the K&N after fitting the BMC CDA?


and Richard, you forget, I now have the plans for the ultimate intake setup.
And after one more re-map, I'll be still be the champion.

[teccyjim]

Im no expert on automotive matters to be fair, think we are travelling into fuel injection and how it works etc but a few theories none the less....

The OEM unit is 'metered' in that the ECU/timing is set up to accept a known volume of air for any given rpm.

The properties of air (with regards to speed and pressure) travelling through a tube are slightly different unless you are using a venturi, but can be manipulated. In your system (cone filter) air is allowed to rush into the tube, as the engine makes a huge full throttle demand. the problem here is that as you make that demand, the drag created from the turbulent air moving through the tube may actually slow the air moving through it.

The CDA system works by producing a vortex. Vortex generators are used on aircraft to assist the boundry layer (irrelevant) and to reduce drag (very relevant). If that air is spun (vortex) and the drag inside the tube reduced, the air must therefor accelerate providing the engine with a greater volume of air at the cylinders. The speed of that vortex will be varied by the throttle demand so a linear amount of air is provided as the rpm increases. The fuel injection adds more fuel....more power etc

Th CDA/cone filter i am confident about, as for the OEM box im not so sure.

Jimbo

[nikk1877]

after re-reading my last post, it seems i've went of on another tangent agian it was late.

heres the the marketing blurb from BMC

CDA filtering system is composed of a cylindrical carbon air box containing a washable filtering element. Substituting the original air box with our CDA, cold air is directly channelled through an internal airflow deflector to the filter and drawn into the engine with a very small pressure drop (patented system). The CDA system also includes a black alloy ducting (60 cm length) for connecting the system to an air intake on the front of the car. The system is available in two different dimensions: we advise Type 1 for engines up to 1,600 cc; Type 2 for bigger displacements. Every type is also available in different diameters on engine side for connections. Dyno and Datron Laser tests demonstrate the great performance of CDA filtering system
CDA EVO 2
CDA filtering system, now available in the second step EVO 2, is connected to an air intake in the front of the car through a black alloy ducting. Thanks to the dynamic air intake you have a true supercharging system that conveys cold air at a speed and capacity much bigger than with traditional systems. The airflow entering through the dynamic intake is still further accelerated due to the conical flow variator inside the carbon dynamic air box. Finally, dynamic overboosting, greater airflow, higher pressure and colder air are the elements assuring a considerable increase in engine performance in power and torque. Thus demonstrated by several tests on a Dyno. CDA EVO2 WING, available in 2 dimensions, can be fitted on every kind of car.

'true supercharging' dynamic overboosting' 'higher pressure' but no 'vortex'

make of that what you will

[RST]

Hmm, sounds very convincing but I wouldn't like to use the words supercharging in any of this lot. Sounds a bit like a sales blurb to me but Jimbo's take sounds reasonable.

Patrick Mortell has a very neat party trick with an enclosed filter on his G-Ltd race car. He asks you to put your hand over the end of the intake duct the gives a very quick blip on the throttle. You'll be amazed by the "suck", it gives you a bit of a fright. One of the things he mantioned was maybe actually better to avoid a true direct intake to the air flow at the side of the car, as the engine gets to a stage where it can draw more air than is passing the end of the duct, so the theory is that you could even possibly hinder air feed to the intake. I've not looked into that one though.

I'm not really convinced you can store air in an air box of any kind. I think in N/A stuff you have to treat air as an incompressible fluid. So in an air box, volume drawn out equals volume drawn in although the size of the inlet / outlet ports dictates the speed of the flow. But there must be something in the air flow profile that's different from a cone filter. Actually our engines are bit different as you know, and I was initially warned about creating a vortex in the intake -better to avoid but I don't know how true that is. I'm guessing that's because of the little propellor in the AFM. The SARD filter is a different shape from what I've seen on most other filters which I'm guessing is maybe linked to that.

I can well believe comments about different resonance between open cone and enclosed cone or OEM air boxes. The same thing can't happen in either of those three and I'd expect that enclosed filter manufacturers are looking at this when they're doing their R&D.

I think that last point I'd hit on when it's K&N vs. expensive kits. Even when you read through the mag's most of the review's I've seen say to avoid oiled filters if possible. They're NOT the same and you pay for what you get in the end. I think just about anything would have the edge on your HKS kit though. They've not got a good reputation with the folk I've asked.

You might need to watch what your doing with the AFM Nik if you go hybrid. I fancied a combination of Power Enterprise filter and SARD AFM tube but I passed my old filter kit on before I got round to having a play with it. I've been thinking how to enclose / duct the SARD filter (just cos it's matched to the AFM housing) but haven't got round to it yet -it'll mean it's a pretty bulky item by the time it's enclosed. Maybe it'll not work properly in an enclosure if it wasn't designed to in the first place.

BTW I'm still considering itb's and something like a Link ECU -I just need to see whether they'll fit first.

[teccyjim]

Nik,

There is no direct mention of the word 'vortex' but it blatently says the air is 'accellerated' and a 'slight pressure drop'. The only you can accelerate air through a tube is by using a venturi (not applicable here) or by using 'something' to generate a vortex/swirling motion which from their marketing blurb sounds like what they've done.

I imagine the 'internal airflow deflector' and 'conical flow variatior' are, as i suspect, vortex generators.

As the old saying goes "bullsh!t baffles brains" and theyve used it to good effect. Regardless, i think we can agree it works judging by peoples opinions of them- i, scientifically (at least) can understand the principal of why it would work.

Jimbo

[teccyjim]

RST,

You NEED to get throttle bodies!!! That would scream!!! Look on Youtube, theres a few S2000's with ITB's and the noise is out of this world.

Think im gonna buy a cheap knackered n/a that needs a new motor for example and do some experiments with the engine.

Jimbo

[nikk1877]

yeah jimbo - i know where you're coming from with the vortex thing, just can't see the wood for the trees sometimes lol.
"bullsh!t baffles brains" - * writes that one down for later.



Richard - volume drawn out equals volume drawn in - this obviously depends on the demands of the engine, which i think is why larger airboxes are offered for larger displacements.
So, in IMO you can 'store' that volume in the airbox up until the point where its exhausted (at higher rpm's), then the effects of the 'conical flow variator' come into play.

I just need to try this out because at the moment I am not happy with the HKS. I need to find a setup that I'm happy with until I can get the throttle boddies And I just wont go back to the OEM box as I need that uber induction roar in my life.

If it works and it makes 200,000ton per square inch of torque at 1200rpm, I'll be jumping on couches and Daniel Bernoulli can get stuffed. If not then you can all have a good laugh at my Heath Robinson antics.

[teccyjim]

I do recall another motorcycle mag article, think it was related to two-stroke engines that mentioned that the shape and capacity of the airbox 'held' the air before entering the combustion chamber but not sure if this was relevent to four stroke applications.

What I have read elsewhere is that the length and area of the induction 'tube' is is relative to engine performance but it didnt go ito detail as to how. I'm out of my depth when it comes to automotive engines!!!

Jimbo