20V power curve

[gfl@cc.bellcore.com (grant f lenahan)]

> Can some one out there give me an idea of why my '90 90Q20v is such a
>turtle off the line and doesn't really make significant strides in the
>power band until she's over at least 3500rpm.  I know that nothing is
>wrong with the car and that this is a trait of the 20v, but I'm very
>curious about the dynamics involved.  Much like some people I know, she's
>much easier to love when she's breathing hard and screaming.
>
 
    Part of the problem is in the throttle.  Audi used to use a straight line
    throttle whereby if you pushed the peddle down 1/3 of the way, the throttle
    would open 1/3 of the way.  I read that in 1995, they switched to a new
    throttle which opened more in the first 1/3 peddle travel.  This gives the
    feeling of newer Audis being quicker off the line.
     
     Not sure if this helps or not,
      
      - -DMR.

No dobt true, but irrelevant nonetheless.\

The 20V engine, like many 4V/cyl engines, breathes BETTER at high RPMs
than 2Vs, but WORSE at low RPMs.  Manufacturers also have to trade off
torque tuning for low-RPM (where the HP payoff is smaller per ft-lb) vs
higher RPMs (where it is relatively higher).  Audi simply chose to
exploit the high end at the expense of the low end.  Some newer 4V
designs (eg: the Northstar) have two sets of intake runners.  one set is
used at low RPMs and another at high RPMs.  For a small-production motor,
Audi did not go to this length.

BTW, I find the torque to be similar to my old 10V engine, until about
3000-3500, where it sort of explodes.  The torque curves per audi support
this premis.

Now, according to my favorite dealer mechanic, a number of the 20Vs
were, in his words, "dogs".  Dunno why, but there is significant
variation from unit to unit.

NOTE: I find that this engine needs to be revved out and cleaned (regular
cheapo carb cleaner) regularly to avoid pre-detonation.  Pre-detonation,
generally at lower RPMs, causes the knock sensor to retard your timing
(there's a joke in there about Audi engine management in general), which
wqould lead to lower off-the-line torque.

Grant
gfl@cc.bellcore.com