stiffer valve springs

[Robert Myers <rmyers@wvit.wvnet.edu>]

Brooks,

I'm no authority, but I don't think a stiffer wastegate spring will have any
effect on your redline.  The difference will be in how fast you get to your
redline.  Depending on just how stiff your new spring is, you will probably
also need electronic modifications to prevent the ECU shutting off your fuel
pump when it detects what it will think is "overboost".

There are apparently several ways to accomplish this "modification".  At the
risk of oversimplification, these include:
1.  Hot-wire the fuel pump so that it's on whenever the ignition is on.
(Fire hazard if you wreck.)  
2.  Install a zener diode across the pressure transducer output to limit the
signal to the ECU.  (You lose overboost protection and probably some other
software features designed to make the engine more efficient.)
3.  Install a voltage dropping resistor to accomplish approximately the same
as #2.  (With the same drawbacks as #2.)
4.  Actually reprogram the EPROM of the ECU to allow the added boost while
retaining the other boost related features of the software.

There are probably several other ways of doing this.  Procedures 1, 2, and 3
have been pretty well documented here on this list in the last year or so.
The drawbacks associated with each of them have also been well discussed.
SuperChips uses #2.  TAP apparently (if I have it right) uses #3.  Intended
Acceleration *claims* to uses #4.  So far, other than IA advertising, I have
seen no information to back up those claims.

Procedures 1, 2, and 3 are relatively inexpensive (like well under $20) to
implement if you know where to install the zener or the resistor.  Actual
reprogramming of the EPROM, once it has been figured out, is also quite
inexpensive.  The expense would come from the "figuring out" portion of the
process.

Your fuel consumption will increase, but only in proportion to the amount of
lead in your foot.  Your are burning more fuel faster when the boost is
higher.  Of necessity, this will increase the rate of consumption.  My fuel
mileage is about 8-10% lower than before my "mods" were done.  I tend to
push the envelop rather hard for street driving.

Now, ask the next question.  "How does installing a stiffer spring (and
making one of the above modifications) effect the driving of your turbo
Audi?"  The answer:  IMMENSELY!!!  The low end isn't changed much but when
you get into the upper rpm ranges, the car simply comes alive.  A relatively
sedate sedan becomes a snarling beast at triple digit speeds and will lay
you right back into your seat simply by flooring the pedal in 5th gear.  It
will get to those triple digits speeds much more quickly once your rpms are
above, oh, perhaps 4K in the lower gears.  You will greatly surprise many of
the "red light warrior" set by simply driving off and leaving them after the
first hundred feet or so.

At 01:22 AM 12/30/95 -0700, you wrote:
>        
>        How would stiffer valve springs do for your redline? Would they bump
>it up a few hundred RPM? Perhaps lengthen the engine life for those of us
>who like to rack and roll near redline everywhere we go? 
>        Anything wrong with this idea? I assume that it would come at a
>minute fuel consumption increase, but not a noticeable one.
>
>brooks ( hey, it's 1 in the morning, I don't have to think very hard! :)
>
>
>
___
	Bob 
********************************************************************
*  Robert L. Myers                        <rmyers@wvit.wvnet.edu>  *
*  Chair, Department of Chemistry          304-442-3358 (office)   *
*  West Virginia Institute of Technology   304-574-2372 (home)     *
*  Montgomery, WV  25136                                           *
*            Obligatory Quattro and Sleddog Content:               *
*        My Siberian Huskies like to ride in my '89 200TQ          *
********************************************************************
To unsubscribe from the quattro list send mail to: majordomo@coimbra.ans.net
with this message:  unsubscribe quattro