[200q20v] RE: Lifting Stains... and Gains

QSHIPQ at aol.com QSHIPQ at aol.com
Mon Jan 28 10:23:50 EST 2002

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Comments inserted below:

>"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

Mike:  you are adding the wrong way.  Totals are not lift cfm vs duration,
it's total cfm AT a given lift.  So your total for .400lift is 954.7....

>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

See above: at .400 lift you have a total flow out of 5 exhaust valves of
660.8.   IMO, it would be interesting to compare these numbers with the RS2
exhaust cam.  Looking at the above (as I'm sure porsche did), I'd want better
exhaust numbers.  This would also reflect the pretty impressive gains in
torque just adding a RS2 cam to the AAN delivers.

Current theory on the turbo heads is almost opposite the N/A heads.  Since
you have boost pressure as a variable, that really is "effective" valve area.
 IOW, you can change the size or lift of the intake valve, OR add boost, both
do the same thing.  In N/A cars you can ONLY add valve size or lift for
effective valve area.

>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?"

Well here's where the magic starts...  Javad is right that these numbers all
give you the theoretical amount of flow, and that reducing the restrictions
TO a valve is key.  This includes a bunch of variables to make it optimal:
temp, pressure and flow.  The smoother the flow TO a valve, the closer you
are to the ideal flow the valve generated.  These numbers also don't include
engine volumetric effieciency, which then includes cam overlap, exhaust pulse
theory etc....

>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.""

Vixen; it does, but the caveat is it's EFFECTIVE size that matters (insert
all inuendos here).  In a pressurized car, size is created by boost pressure
or a bigger valve or more lift, in a N/A car, size can only be created by a
bigger valve, or more lift.  That's why many of us turbo tweeksters (me
included, 2.5mm larger EV) leave the intake valves stock, go (physically) big
on the exhaust valve.   The side benefit, is more exhaust energy to spin the

I'm hoping you can buy me those Fat Tire Ales after I terrorize Steamboat
this weekend.  Monday?


Scott Justusson

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