OK after a long, long wait, the BMC CDA (carbon dynamic airbox) has finally arrived from Italy. Matt C already has his plumbed in; his was designed for the 16v, except BMC omitted the crucial element - a means to connect it to the throttle body! He knew about this already and got a throttle body adapter made up to take a silicone hose direct from the outlet of the box.
The parts of the CDA including the custom throttle body attachment I tried to build!
http://www.nickread.pwp.blueyonder.co.uk/images/forumhost/cda/parts.jpg
My aim was to hook up a CDA to the original airbox feed coming from down by the nearside wheelarch, then up to the throttle body with a simple 90 degree bend of Samco hose. Using this hose would also mean I could plumb in a connection for the breather pipe that used to go in the back of the original airbox. I measured the space with the original airbox out and the dimensions I got suggested I could go wider than the recommended CDA for the 16v, but it had to be much shorter or there would be no chance of it fitting vertically in the gap between the gearbox and radiator. One of the custom CDAs that BMC build is for the BMW 3.0 Z3 and that seemed to be the right size, short and fat with big 80mm inlet and 85mm outlet - 85mm the same diameter as for the throttle body connection, 80mm the same size as the original airbox feed. So far so good.
The shape that the whole inlet tract ended up having to be (the bend you can see here is nowhere near tight enough yet!) and an alternative pipe made of an R19 16v induction pipe
http://www.nickread.pwp.blueyonder.co.uk/images/forumhost/cda/complete tract.jpg">
Anyway, it arrived, I whipped off the original airbox and tried out the CDA in the space that was left. Oops. It was still too long and wide for the space that it was meant to fit into. To cut a very long story short, after two days of experimenting, building mounting plates and hose joining sections and skinning my knuckles, I basically found it wasnt going to work. The bend that you need between the top of the CDA and the throttle body is just too twisted and tight to be able to do it in 85mm hose! Remember 85mm is big enough to put your whole arm down. Theres no way I can make that in silicone hose either, it would need either a totally custom pipe (£150 at least), or be made out of 3 different bends which would still end up at £70 because of the big bore.
Try making this twisted bad boy out of silicone hose. In fact try making it out of anything with an 85mm bore and youll have a job. This is *still* not tight enough!
http://www.nickread.pwp.blueyonder.co.uk/images/forumhost/cda/twisted hose.jpg">
So it looks like Ill have to wait for some 89mm brake ducting hose to arrive and lets hope its flexible enough to take the tight bends, but strong enough not to collapse under the vacuum from the manifold. For the 10 minutes that I had it working before the connecting pipe popped off the throttle body, the car did seem noticeably more perky than with the original airbox.
Ill add more details once Ive tried to hook it up again; at the moment my Clios off the road with no air filter...
