"Blow, or Hardly Blown," or "My life under a Flow bench" by Monica L. & Size DOES Matter by I.M. Anonymous

[james accordino]

Boy, that's alot to swallow.  I'll add my $.02 anyway.
 First, if you add size, you'd reduce both pressure
and velocity.  This should hold true for both
pressurized and N/A engines.  I KNOW for a fact that
you can oversize/port N/A engines to the point where
you actually lose performance.  Reduced
velocity/pressure=less filling of the CC.  In
carburated engines you always ran the risk of the fuel
coming out of suspension and clinging to the runner
walls.  While this is not a problem with direct
injection, the pressure/velocity arguement still
holds(IMO).  As far as the CC itself, there are gains
to be had WRT flame spread or propagation.  Obviously
you like to burn as much of the fuel as completely and
quickly as possible to maximize power.  This can get
very involved and people have been known to change the
angle and location of the valves, the angle and
location of the spark plug and the shape of the CC
itself.  I've personally never gone this far, but have
"cleaned up" and equalized the CC's.  Most of the gain
I've experienced/heard of come from gasket matching,
smoothing any casting flash and smoothing of the
"bowls" directly above the valves.  On this list
there's been discussion about NOT port matching on the
exhaust side.  Something about pulse reversion.

Jim Accordino

--- mlp <mlped at qwest.net> wrote:
> In the absence of any known performance "benchmarks"
> (at least to me, if
> anyone has more, better or other information on the
> Audi 20 valve heads, I'd
> love to see it),  against which progress, if any,
> can be said to be made, I
> offer the following data point to the various 20
> valve lists (accompanied of
> course by the  general & usual "YMMV" caveats.)
>
> FWIW, and in with the hope that those who find this
> of any help can provide
> me with like information, if you are doing, or
> considering having head work
> done on a car and find your self wonder just where
> it was that you might
> have been coming from vis-à-vis what the factory
> originally delivered, more
> or less, out of the box:
>
> "Early AAN Head Stock Bench Flow Baseline"
> INTAKE - measured in Inches (") of lift / cfm
> Lift	  Cyl1    Cyl2	Cyl3	  Cyl4	Cyl5
> .050	   39.9    39.9	 41.5	   40.7	 37.6
> .100	   74.0    72.2	 75.5	   74.5	 72.2
> .150	  100.2   102.4	103.3	  100.3	 99.2
> .200	  132.6   128.9	130.9	  131.6	132.0
> .250	  159	    155.1	161	  158.4	157.5
> .300	  177.2   175.5	178.8	  178.4	175.3
> .350	  185.8   185.7	188.8	  190	 	184
> .400	  188.2   190.3	193.6	  194.4	188.2
>
> Total 1,056.9 1,050.0 1,073.4 1,068.3   1,046.0
>
> EXHAUST - measured in Inches (") of lift / cfm
> Lift	  Cyl1    Cyl2	Cyl3	  Cyl4	Cyl5
> .050	   31.8    32.9	 33.1	   31.8	 31.7
> .100	   61.2    61.2	 62.5	   61.4	 60.4
> .150	   85.5    84.8	 85.9	   84.1	 84.8
> .200	  109.1   111.3	110.6	  108.9	108
> .250	  120.3   123	123.5	  120.9	119.8
> .300	  126.5   128.4	129.5	  127.3	125.2
> .350	  129.5   132	132.7	  129.7	128.2
> .400	  131.4   133.7	134.8	  131.4	129.5
>
> Total   795.3   807.3   812.6   795.5     787.6
>
> - The flow figures were generated using a test
> pressure of 25" of H20,
> "normalized" I believe to reflect 25" at sea level.
>
> - This is a "Stock" Head, never been run in, with
> stock port & valve setup,
> i.e. a head presumably as it came/comes from the
> factory.
>
> Also offered for those who wonder about such things,
> are
> - www.turboford.org/faq/ta.htm and
> -
>
www.merkurencylopedia.com/motor/esslinger%20head.html
> - a bunch of stuff at http://www.pumaracing.co.uk/
>
> If anyone's got other suggested links &/or datum on
> Audi/Vw 20 valve head
> work and flow information, please let me know.
>
> Last, I offer for free beer conversation the
> following hypothesis regarding
> 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.""
>
> So do the listers have any facts, opinions or ??? to
> add?
>
> Cheers
> mlp
>
>
>
> -  Stock valve job (see Bentley,
>


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