[200q20v] Re: "Blow, or Hardly Blown," or "My life under a Flow bench" by Monica L. & S...

JShadzi at aol.com JShadzi at aol.com
Mon Jan 28 01:22:21 EST 2002

<< .400   188.2   190.3 193.6     194.4 188.2>>

At Eurospec I spent some time porting a 16v head, I got about 250cfm at those
lift levels, playing with a 5v head we got over 300...there are definitely
improvements that can be made with your above those #'s.

 << Last, I offer for free beer conversation the following hypothesis
 heads, valves & "pressurized" operations thrown at me by one porting maven
 confronted by the question, "Well, if all that polishing and grinding you
 are doing isn't generating a number better than anything above, what the
 hell are you doing?"

 Bleary eyed hypothesis/theory/defense (??), "Well, A**H**, it don' make no
 difference in a pressurized car.  Pressurized {editorial clarification here,
 i.e. super & turbocharged applications) cars don't need to worry about all
 that flow bench B*S* (s/he'd had more than a few beers, and I believe
 his/her SO had recently tossed them out of the house, or something like
 that.)  If'n its pressurized, all you want to be go'n fur is SIZE!  S/he
 told me "SIZE matters."">>

Not sure what the context was during the above conversation, but that last
quote is all hogwash IMO.  There is nothing much more special about
pressurized systems that non... flow is still critical in both.  Many picture
pressurized system as air being forced into a motor and past restrictions,
which just isn't the case.  During WOT in a NA motor, you have a given amount
of flow at, more or less, atmorspheric pressure.  In a turbo application, you
have also a given amount of flow, at a pressure above atmosphere, wheteher
its 5 psi or 20 psi doesn't make a difference, it still needs to FLOW.

There isn't just this pocked of X psi sitting at the intake valve, waiting to
explode into the combustions chamber, a pressurized volume of air must flow
into the combustion chamber just as in a NA application.  Pressure loss due
to restriction is a reality..yes..even in forced applications!

My recommendation...Mike, it sounds like you are building an all out motor,
right?  At least have the ports flow equilized, do a nice 80 grit finish, get
rid of casting flash and irregularity.  Don't necessarily remove a ton of
material, but do a nice clean up job, what the factory would have done if it
mattered (in the stock application).  From there, shaping and removal can be
done to achieve whatever flow you'd like.

Improvements CAN be made, however, if you are doing work in the ports, and if
the numbers aren't changing, then maybe the laws of phisics are changing.
Flow is directly related to port shape and volume, change in either will
cause change in the other.  You definitely don't want to go in there hogging
things out, but you won't do any harm by simply optimizing the ports as they
are.  I'd say with the above you could not only equilize flow, but pick up
another 10-20%.


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