I have just made my airbox and am now wondering on the size of the hole to drill in the side for an intake, i am going to use ducting to the front nosecone and fit a cone filter, what size will the pipe need to be without restricting the engine?
Also the intake rubbers are 45mm each
45mm * 4= 180mm, would it have to be this side or can it be smaller say 70mm?

Big as possible really, 5 or 6 inch diameter.

90mm diameter is equal cross section to 4 x 45mm diameter. But that's not taking into account that only one intake would be breathing in at any time, so you may not even need to go that large.

Largest you can get and fit would probably be the best way to decide.

Would the expanding aluminium ventilator ducting fit?

I have a 24 valve V6 2.9i which produces 238 BHP, and that has an intake of 75mm, or 3" in old money. So I would say that 75mm is more than enough. IMHO Ray


Engine

[Edited on 27-10-10 by Chippy]