custom radiator/intake system

[theonlyred16v@hotmail.com (Brian Haygood)]

Scott,
   There are few guildelines to this, partly because fluid flow over odd 
shapes is still tough to analyze, and also because "the bigger the better" 
pretty much applies to this situation.  Here are a few guildelines and/or 
rules of thumb that came up in my intake design project.  I don't have much 
basis for any of them, nor do I know which are true or false.  One 
comparison you might make is with the stock airbox hole, or even the ram air 
inlets on a CLK-GTR or Maclaren.  It doesn't take a lot of area to feed an 
engine.  In fact, anything bigger than the throttle/s is a starting point.

1.  If you have to diffuse or the flow (i.e. from a thin cross-section to a 
thicker one in ANY direction, try to keep the walls of the diffuser close to 
7° total angle.  Restriction can be done at somewhat greater angles.  If you 
have crazy angles (something like 30-45°, then there are tricks you can pull 
with baffles and deflectors that will help a lot.  If you run into this, 
holla back, yo.

2.  If you were to try and calculate something like the volume of air that 
will pass through the opening, be aware that it is markedly less than the 
volume that would pass through the opening (i.e. cross-section) at a given 
road speed.  That probably won't have much of a bearing on anything, since I 
doubt you would use an intake area that small.

3.  More than anything, worry about how you are going to prevent losses in 
air pressure due to bends, twists and angles in the path of the flow.  One 
big question is how you plan on filtering the air.  For example, the air 
filter arrangement on a lot of individual-tb bike engines really sucks 
because the air has to come in the sides of the filters instead of getting a 
straight shot down the stacks.

4. Filter size:  K&N recommends the following formula:

A = CID x RPM / 20,839.  CID is cubic inches.  I have seen and been told 
other formulae, almost all of which agree that K&N's recommended filter size 
is really small, so don't go any smaller than that for sure.  Keep in mind 
that changing the direction of the flow is a bad thing when you select 
filters and layout.

5.  Give me good measurements and I will help design a filter box, scoop, 
etc.

6.  An engine that stays cool is more important than the last two hp.

BH



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