RE: Audi cylinder head porting

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

> I think it doesn't really matter,whether the engine is normally
> aspirated or force-fed.If a port flows well,it does it in both cases
> giving more power.
> 
... while I condone the engagement of the grey matter as much as possible,
might I suggest that it takes a bit more than cogitation to qualify onesself
as a flow master ... :-)

While in no way would I suggest that I am any sort of expert either, from my
reading and things I've learned from the q-list I can say that there are
significant differences between naturally aspirated and force fed
applications, especially on the intake side.  With a turbocharged app you
don't have to completely rely upon the draw of the piston to get the mixture
into the cylinder.  This means that when determining the optimal tradeoff
between the sizes of the intake and exhaust valves, a turbo app can
apportion more valve diameter to the exhaust than would be best for a NA
motor.  When it comes to porting this may imply that it is better to focus
on improving exhaust flow ... 

In any event there is an element of "black magic" to porting.  Some things
that appear to be impediments to flow caused by a clumsy design might
actually be deliberate features which improve flow.  The anti-reversion lip
in the exhaust is one such example.  I personally have been interested in
more information about the "turbulent flow" porting techniques that The
Metric Mechanic uses on their BMW engines.  Smoother is not always better
... and unless you've got a supercomputer and a great flow modeling package
the flow bench rules!

Steve Buchholz
San Jose, CA (USA)