[ST] Airbox mods and filters...

["Nowak, Nick" <n.nowak@xxxxxxxxxxxxxx>]

This is my $0.02 on the airbox mod debate.  I have yet to play with the
intake on my RS, but I'll start with my experiences with my other vehicle -
a 1981 Datsun 280zx.  This car is fuel injected with an oval air filter
mounted in the front of the car.  The filter housing attaches to 3" plumbing
that leads to the MAF sensor.  One evening I did three back to back dyno
runs to test different intake ideas.  Run #1 - totally stock intake.  Run #2
- - filter and cover removed, but remainder of housing and plumbing was left
intact.  Run #3 - everything was removed leading up to the MAF.  Run #2 was
the best with about a 5% gain from stock.  Run #3 was the worst with about a
5% LOSS from stock.

I will do my best to explain the reasons for this.  First of all, turbulent
air flows very poorly.  With the plumbing in place, airflow is much more
laminar and flows better.  Secondly, air has mass, and thus has momentum.
When a piston pulls air form a longer intake tract, the momentum of the air
will force a little extra air into the engine even after BDC.  There is a
limit to this however.  Attaching 20 feet of PVC pipe to the front of your
airbox will NOT give you a boost in power.  These affects also vary with
RPM.  It is understandable that a K&N filter will give an increase in
performance, but I can almost guarantee that pod filters will noticeably
decrease performance.

Sorry, this still doesn't solve the debate of whether or not to cut the
airbox, and probably just confuses things more.

Nick "the dirtbag"
'00 yellow RS
'81 Datsun 280ZX - relegated to snow and rain duty

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