Not LFS related, hence off topic. For my final year project at univeristy I am modelling a Lancia Fulvia engine in Ricardo's WAVE software to find why tuning the engine for competition work causes a 'hole' in the torque curve at around 4500rpm. Lancia had similar problems in the 70's with the works rally cars, and competition preparers (like myself) have also come across the same problem.

It is suspected that unequal length inlet and exhaust tracts could be causing a harmonic resonance at the above engine speed, but so far nothing conclusive is available. That's my job

However, for the purposes of writing up the report on the simulations I need a bit of information I am finding hard to find - airboxes. Why are they used, what influences the design, how is volume and shape important etc etc - if there was an 'everything you need to know about airbox design' then that'd be great. Does anyone here know stuff about airboxes? I don't want idiots saying 'yeah, drill it innit you'll get more power innit', I want reasonable scientific explanations.

Also, bear in mind that I'm working in relation to proper carburetted cars, not this girl injection malarky, so stuff about massflow sensors isn't required.

Surely there is some here who knows about airboxes? I can cope with the finer points of carbs, inlet manifold design, exhaust design and function etc, just not airboxes

Edit: Also, does anyone have useful information on how to make use of the Helmholtz Resonance effect for airboxes? I have a feeling this could be exceptionally useful!

This may already be obvious to you, but my understanding is that the airbox is a sort of buffer for the air where it settles and becomes less turbulent. It would seem to me that having the carbs open to the rather turbulent air flowing past the vehicle would produce wild fluctuations in pressure at the inlet.

I believe motorcycle manufacturers try to use as large of an airbox as possible so as to get the biggest buffer possible. One might think it would take longer for the air to settle in a larger space due to more volume per surface area (less drag on the fluid), but also consider that the overall rate of percentage of volume exiting the airbox is reduced with a larger airbox. Even my 250 has a rather large airbox for the size of the engine.

Beyond that, I haven't a clue, and I certainly have no idea how harmonics play into it.

hi tristan

try www.karting.co.uk forum, there are alot of techies on there who will be able to help you in detail

cya

First, I don't have proof for what I'm saying. But it may help to guide your search a bit.

Airboxes in cars are meant to calm down the air a bit and let the air flow through as much area of the filter as possible to reduce the resistance of it. The drilling holes in it thing is meant to reduce the resistance of airflow of the intake of the airbox but I wouldn't recommend doing that because airboxes are mostly placed in the engine department and sucking warm air through these holes wouldn't be a good thing. Enlarging the diameter of the snorcel or tube leading to the airbox may help if the resistance of that part is a restricting factor.
With motorcycles using ramair effect a larger airbox reduces the pressure drop when the engine takes the air out of the box. Without ramair a larger airbox would reduce the negative pressure in it while the engine sucks the air out of it but with cars and it's larger engines the airboxes would have to be huge to really have an effect.
I only know helmholtz resonators used for sound tuning, like in the Porsche 997, yet. Though it's basically a airspring causing the air in the airbox to swing at a desired frequency (or negate a nondesired one), so it may be useable to get a standing wave in the airbox with high pressure point in front of the exit to the carburator. Technically the resonatorsize could even be altered by a piston driven by an actuator according to the enginerevs. But I guess the calculations needed for that could drive people insane.