UA and LFB

colin cohen cco ccohen5 at
Tue Aug 8 14:56:06 EDT 2006

Now this a thread really worthy of Audis.  We were the only people who could
discourse on this subject until the Mitsu and Subie boys learned how to do
it - at least in the USA.  The Euro types have been LFB for years and need
to given their real roads.

Anyway a couple of things not covered in the last few posts.  I agree that
in the older cars, pre the early 90 S-Car series (cannot remember what the
type number is) LFB was essential because the turbos were huge (as in my K27
for example) and these Ferris wheels required plenty of exhaust gas to
spool.  However with the advent of internal waste gates driven off the ecu,
by-pass or diverter valves that can be adjusted and better all round
software merged with more efficient smaller turbos, LFB becomes less
effective.  I race an A4 in SCCA and NASA events and have not found a
measurable difference in spool-up whether I LFB or not but in an SQ on the
track it makes big difference.

Tim O'Neil's rally school in NH has a couple of rally prepped Golfs which
taught me to LFB but we noticed that the technique was much more effective
on dirt than on asphalt or gravel.  It seems that the slower the corner the
more effective LFB will become because it allows you to enter the corner in
a higher gear and on boost rather than dropping a gear and being forced to
change up often before the track-out.  How the Rally drivers gauge this
stuff is beyond me as they have to make these decisions based only on the
their navigator's read back.

One last thing - as in so many other arenas, the size of 'Mericans is
another factor in the UA problem.  Besides the huge number of overweight and
obese in the population, we are increasingly a population whose feet have
spread to the size of 4x6s.  Thus the distance between the brake and
throttle pedals on many Euro cars can be easily bridged by these slabs even
when the right foot is pressed hard against the transmission tunnel.  I know
one race car driver who besides taking 10 minutes to leverage himself into
the car also has to bind his right foot to ensure that the spread is limited
to the throttle pedal only.


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