Re: Alfa Mongrels

["Rich Wagner" <drsavage@usa.net>]

Brian:

Sorry it's taken me so long to reply to your email.  Too busy lately.  You
wrote:

>i disagree.  the designer isn't the only person who can understand how
>ride height affects a car.

I don't mean to be a bastard about this, but he is.  Let me explain. 
Reverse-engineering is a VERY difficult and error-prone task.  Why? 
Because to reverse engineer a product, you have to make assumptions about
what the original designer had in mind.  There are many cases when your
assumptions will be incorrect.  Let me illustrate by example:  On a number
of their motorcycle engines with point-gap ignition systems, Honda actually
designed the points to float (just like a valve) above a certain RPM. 
That's right, float open.  With the engine above this critical RPM, you
could actually take your fingernail and pull the points open, and the
engine wouldn't skip a beat.  This is an esoteric fact that I learned from
one of our factory tech reps who had a close relationship with the original
engineers.  Now, you and I can sit here all day and discuss the different
reasons that the engineers did this, but in the end, only they know their
reasoning.  Now imagine a third party making a set of aftermarket points
for the engine.  If they make their points with a different moment of
inertia, or different translating mass, the critical floating RPM will
change.  Will they be thorough enough in their reverse engineering to
actually replicate the dynamics of the original points?  Probably not.  Who
would think to?

In any major design, there are lots of these cases--from the rear deck
spoiler of the Porsche 930 to the Kruger flap on the leading edge of the
Boeing 727's wing.  (If I knew my Alfa better, I'd probably be able to site
you a few examples there, too.  Oh, how about the use of different length
nuts on the driveline?  That's an easy one for us to figure out--especially
since Alfa explained it in the manual.  But what if some owner assumed--as
most of us often do--that this nonsequitur of manufacturing resulted from
his car being built on Friday, and replaced the nuts with new ones? 
Reasoning backwards took him to the wrong place.)  Working forward from the
designer's original reasoning, you'll end up with what you see before you. 
Working backwards, you can end up at a multitude of starting points, none
of which may be the actual starting point for, and reasoning behind, the
design.  And that means that you don't fully understand how the damn thing
operates!  Accurate performance prediction under these conditions is next
to impossible.  Imagine how hard this makes reverse engineering something
very complex, like a Russian
fighter aircraft.  Sure, we laughed at the tube-based electronics we found
in the first captured MiG-25.  But that was when we figured that their
designers' intentions were the same as ours.  Later, we found out the true
intention of the design and realized that this design decision actually
gave these systems capabilities ours lacked.

To truly design, say, a suspension system for a car, you have to have data
on the mass, moment of inertia, and structural responses of the parts
involved.  Aftermarket designers simply aren't privy to this data, and
can't afford the testing necessary to obtain it.  Worse, since we're
talking about a manufactured product, the data is statistical.  Especially
in complex, difficult cases like suspension mods, an
aftermarket designer just can't accurately predict the responses his mods
will have on YOUR car.  In fact, and this is a MAJOR point, were he to
install his system on two "identical" vehicles, they would both drive and
handle differently.  Manufacturers like Shankle, Ward and Dean, and Zat do
their best to glean knowledge of the vehicle with testing on the track, and
that's fine--especially if that's where you actually intend to use your
vehicle.  But the critical question to ask these guys, is where their mods
will DIMINISH the performance of the vehicle.  Their mods have closed some
perceived holes in the performance.  What new holes have opened up?  If
they tell you, "none", walk away.  You're being taken to the cleaners.

This was the point with my previous post.  Jerry Baker, a fellow
aerodynamicist says, "there is no free lunch."  That's really what I'm
talking about.  Even with a complete package, you're CHANGING the
performance of your vehicle,
not necessarily (in fact, rarely) improving it.  Many facets of performance
are diametrically opposed.  For
example, having a suspension system that's stiff enough to provide a
sufficiently high natural frequency works against having a system with
enough compliance to keep the tires on the ground during braking or
cornering on a washboard.  Stiffen up your machine like a kart, and you'll
gain an improvement in cornering during transients on smooth road. 
(Steady-state, there is little improvement.)  You'll also experience a LOSS
of cornering and braking ability on rough (washboard) surfaces, because the
tires lose contact with the ground.  Does that sound like something you
desire while you're making a panic stop at your local stop light?  Put a
set of high-lift/high-duration cams in your engine, and you'll see more
power at high RPM.  You'll also see more rebreathing at low RPM, resulting
in a poor mixture, and low power there.  Cross-drill your rotors, and
you'll see improved response when the calipers are fouled with foreign
matter.  You'll also reduce the effective friction area, which means that
the same braking action will require more pedal force, reducing pedal feel
and making it harder to keep the wheels at imminent lock.  No free lunch. 
The idea is to find that spot in the spectrum which allows the machine to
work best in the given situation.  Let's face it, if you're REALLY racing,
you're going to change your suspension setup, your engine setup, and your
gearbox setup for EVERY track.  Catch that?  You're not going to improve
it, you're going to change it.  And with each change, you'll emphasize one
area of performance while diminishing another.

Again, I don't have a problem with anyone who wishes to do something to his
own car.  How could I?  It's his car, not mine.  What I do mind, is having
someone tell me that they "improved" their machine when they really have no
idea what portion of their car's performance they have enhanced, and more
importantly, what areas they have diminished.


Rich
Manitou Springs, CO
'82 GTV6 Balocco