Here is my attempt at an airbox. My intention is for it to be under the bonnet and be fed cold air from the front via a remote BMC style filter.

There's not too much room and before I go any further I would like some opinions on whether or not it will work.

The inlet had to be constructed to get a 75 dia inlet into the narrowest part of the box. It sweeps over the top slightly and the flow is obstructed a little. You can see the line the cover will take over what I've already done and it will be totally brazed up and sealed.


Airbox front


Airbox back

Whats the general consensus chaps?

Thanks,
Steve

The top of those trumpets will be very near the top of the airbox!!! It'd be worth getting / making some shorter trumpets...

I've checked and the front one will be the closest at 35mm.....

I think the volume might be a bit small

this is what I use to get the noise down for track days on my 2.0L zetec

http://www.locostbuilders.co.uk/viewthread.php?tid=54014&page=2

I have to jet the carbs down or it runs way too rich, knocks about 10mph off the top speed compared to the pipercross foam filter and the bigger jets.

You want at least the diameter of the trumpet's distance between the mouth of the trumpet and the wall of the airbox. Ideally more.

The volume of the airbox, the diameter and length of the inlet pipe are tuned and create a resonant effect. You want the airbox to be resonant lowish in the rev range because at lower speeds it goes funny. The smaller the airbox, the more the resonant effect is, so larger is more tollerant to errors.

I'm strapped for space in front of the trumpets as I really don't want to cut holes in the bonnet. The front trumpet will just have the diameter between it and the front of the box

So, in an attempt to get more volume I fancy opening up the narrow end and putting an extra 'box' on it that can go down the side of the carbs. This will increase the volume and give me a bigger inlet area.

As the air will be coming in from a scoop at the front the air will be forced, AKA the original bike setup.

If it works out not be any good I'll be reverting to a sausage type filter, or just plain open carbs....

Steve

You're definately on the right track, thats the right setup for bike carbs, try and widen the box at the opposite end to the intake, so there is more air round the back carb inlets.

Here's my solution it involved cutting the bonnet but provdes a a good flow of cool air. It doesn't seem to affect power as it is putting out around 210bhp with a very flat torque curve peaking at 178ft/lb.
If necessary I can supply the fibreglass airbox.
Hope that helps.
Regds
Ian

[Edited on 18/1/08 by roadboy]

[Edited on 18/1/08 by roadboy]
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Thanks Ian, but I'm really trying to avoid cutting holes in the bonnet. If my homemade airbox doesn't work I'll go back to a foam sausage type

How much is one of them boxes your using?

Steve

Hi Steve,
I will have to check on the price as I have them made for me. I decided to cut the bonnet as it was the only way I could get a decent inlet tract length to retain the torque.
regds
Ian

Likewise:



XE throttle bodies



progress2

Right, I extended the narrow end with a 4x4" box that holds the 75mm inlet tube and lets the air flow the full height of the box. Still some boxing in to do but it just fits under the bonnet OK. I'll measure the volume once its finished...
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