I am building a rotary impreza to go rallying in I have a couple of questions regarding air box design for a 48mm Ida weber the motor is a 13b 6 port I don't have to much room under the bonnet(hood) and I need to know what is the minimum distance that the venturies & ram stacks can be from the top of the air filter currently I have about 35mm clearance from the top of the venturie to the bonnet which does not leave alot of room I can add in a air scoop to bonnet but I would like to know what my options are before I do this can anyone advise post-1-1047683358.gif me?

hehe can of worms there! I have clearance issues with my setup too, I just stuck a sock filter on there - which means it flows well up top (I have to fit larger needles than with the standard air-box) but mid-range is down a bit.



From what I have seen there is a bit of give and take with airboxes - you tune for a specific rpm and it generally works for that and a few hundred rpm either side, but it also drops performance at other rpm where instead of the airbox's resonance helping the airflow it hinders it - but properly designed the overall result is still improved drivability. Designing one of these is the hard part, the volume is the important thing, as well inlet pipe area and the physical shape.



To be honest unless you're experiencing a flat spot or really want to give it a shot I wouldn't bother, like I said I ended up with a sock filter. If you've a turbo all this has less of an effect, but either way I'd still read a book on it sooner than base my design on the opinions/recollections of a few strangers (no offence to anyone). HTH

Thanks for the info just seeing what people have done & I will read up on the subject would like to here other experiences if someone has them to share