by johnc55 » Sat, 15 Jan 2011 6:17 +0000
As far as I remember when I read up about all of this, the restrictive part of the whole original air intake set up is the air flow meter in the crossover pipe. This is in the NB. In the NA, modifying the headlight to draw air directly from outside brought colder air in.
Getting colder air into the intake pipe was shown to make some difference - can't remember the figures. Apparently, in the NB, the location of the oem intake pipe - i.e. down low behind the headlight on the passenger side, is the best location to get air unless you want to go through the bulkhead to draw air from the lower edge of the windscreen. This location is a known higher pressure air intake point. There are good write-ups online about this. Problem is drilling and cutting a fairly large hole in the body panel here and, in my case, the abs unit is in the way.
The other location to draw air in would be through an intake pipe (flexible, like extractor fan hosing) from the front area - radiator opening or front bumper area. Some have used foglight openings to pipe air in.
I decided to replace the crossover tube and use a K&N style filter. I then built an intake box around the filter enclosing a fairly large space behind the headlight. All original plastic piping removed.
I did a not-very-scientific test at the time by using a lidl temperature probe to read the temperature inside the box and outside the box on a short run. The inside box temperatures were lower by a few degrees.
I reckoned that was enough justification for doing it.... At some stage I will insulate the box but haven't gotten around to it yet.
Can post pics if you are interested.
JohnC