Race Engine Forum UK

The Alfa flat four has 2 twin air trumpets at a 90 degree angle attached to an airbox in the middle above the block with a panel filter in the middle.

The air comes in through 1 x 63mm air intake tube. (about 10 inches long).

The boxer has a beautiful induction sound from the carbs without the airbox or with foam on the trumpets instead of the box.

Unfortunately we have dusty roads and foam filters would not give sufficient filtering.

Now I hear that cutting off the entire bottom part of the box below the panel filter releases this lovely induction sound from the carbs.

I do not have any spare airboxes to experiment with if things go wrong.

I am concerned about the fluid dynamics that may be affected if I cut the bottom off. I'm sure the 63mm pipe tunes the airflow and keeps the torque tight and crisp.


Does anyone have experience of fluid dynamics/airboxes/airfilter modifications?

Many people cut them off for the sound over here in the Netherlands. It's not good for intake temperatures or nice and clean air getting in the carbs. A spare filter box could probably be sourced over here, but I'd personally would try and get 2 air boxes with "trumpets" and large "lunch box" style filters fitted. If you supply the air boxes with cold air through the front grille, you get a lovely sound, good cold air and plenty filtration. This is not the cheapest or easiest solution, but in my opinion the best for the boxer engines.

Hi Whizzman,

Thanks for the tips. Been seeing lots of mods on alfaowner.com also. Spare boxes there are cheap and available. One guy had 10 of them but would have cost a fortune to send it over.

I'm looking for a used one here to experiment with. I realize I may get a little engine heat soak. Maybe just for the winter or as you said add some extra air intake tubes to bring in cooler air onto the block.

You should read Miro's post in Readers' Cars.

G

Thanks Guy.

Just beginning to read/view it now. Very nicely illustrated. I like that. on page 4 so far!

I started the same kind of thread with lots of photos on my rebuild before I found this forum:

http://www.alfaowner.com/Forum/Alfa-33- ... ulics.html

Maybe I'll start a new thread here when I get some more time (maybe after I finish the engine!).

What I'm thinking about doing is to just remove carefully the front part of the box leaving the 63mm air intake tube on (this is attached on the corner of the box, so at speed it still brings in the air.

Also the front opened will help to prevent too much heat coming up from the engine block, also TO RELEASE THE INDUCTION SOUND which is what I'm aiming for on a budget without too many modifications.

I will ensure that I can replace the piece of plastic removed easily with resin in case the results prove to be disappointing in terms of torque at low revs.

I could increase the length of the trumpets a little inside the box to compensate for the more open box with some plumbers piping.

It's fun to experiment even it it doesn't work but is reversible.

Or maybe this (I like this a lot, also be able to see my silver painted engine block!):