Re: AIR BOXing

[Rolf Mair <waves@epix.net>]

Scott,

Let me clarify my position on the air box mods. And also. let me state 
for the recored, that i have not done very many mods on audis, i only 
repair them. The art of 'tuning' something is two fold. #1 tuning is done 
to a certain item to provide the best service to other items with the 
intent of making the engine more efficient. #2 Actual tuning of the 
intake manifold and exhaust manifold requires the use of a flowbench in 
order to ensure that each runner is flowing the exact CFM. The manifolds 
are what really should be called 'tuned'. 

Allow me to take a point in your post. I dont know for sure why Audi did 
what they did inside the airboxes. First, All F.I. rabbits and Sciroccos 
of the early years had horns, or at least directional scoops. Many times, 
these were taken off due to being to restrictive. And yes, the early CIS 
is antiquated even though they are used very late. The mechanicals of the 
system, with out the benefit of electricity, although very reliable, are 
frowned upon by EPA. 

I dont mean to come across as wanting an argument, I just want to bring 
up some ideas. I have spoken to factory reps and other people in the 
automotive repair business including racers, and although a racer 
himself, I don't normally give up allot of my secrets.
Scott, perhaps the fins inside of the airbox are for structural strength. 
OK, I'm sure to some extent, perhaps the airbox is 'tuned'. Audi wouldnt 
just make a box for the filter and leave it at that. With the interest of 
low noise and good cold weather starting, they had to design it with the 
known features such as a warm air valve. Again, I haven't done it on my 
audi yet, but on older VW, a few extra holes in the right places didnt hurt.

One last thing on your comment about tuned exhaust. You are right, the 
cat and muffs. are similar to an airfilter in the fact that "how can you 
tune through ...."  It the purest form of the word 'tuned'. After the 
cat, the exhaust is not tuned. Even though manufacturers say they are, 
they are not tuned in the way the word was originally designed. An 
exhaust manifold, or better yet, and exhaust header is tuned by ensureing 
no only equal flow per runner, but also for pulse direction/resonance, 
which is probably more important than flow. 95% of the exhaust tuning is 
done in the header. After that, one can aid the tuning by ensuring the 
exhaust diameter is not too larger or small, that the bends are smooth 
and not kinked (mandrel bent) and that the mufflers are not too 
restrictive.  Backpressure is possibly the biggest concern here, as it 
can be affected by mufflers, small pipe and lots of bends
Yes, essentially everything before the air filter and after the cat is 
tuned to an extent, just not in the true sense of the word and also not 
in the greatest of precentage of the overall picture.
sincerely,
r.mair