Re: So what's good about FWD?

[dmiller@iea.com (Doug Miller)]

>But why doesn't anyone build a rear-drive, *rear-engined* economy car?
>It would have the advantages of a short, simple drivetrain without
>working against weight transfer.  And, it would have extra weight over
>the drive wheels.  It seems to me that this would be just as cheap
>as a front-engine/front-drive car, and would perform better under all
>conditions.  Why doesn't anyone build it that way?
>--
>Shields.

The Beetle is the classic example of this layout, so it has been done
successfully in the past.

Factors against it today are fairly straightforward.  Where FWD is safer
due to its inherent understeer, the RWD/R. engine is the opposite.  I speak
here of the average citizen (John Q. Public) and the typical slippery
condition crashes, *not* a track setup, where even RWD/R can be made to
understeer. So that advantage of FWD is lost.

Next is crashworthiness. Having the engine and drivetrain all up front
(FWD) creates quite a sturdy structure for passing Federal impact tests.
The public is also vaguely reassured by having the engine up front to
"protect them". If you put the engine in the back, you'd need a sturdy
structure back there for engine forces, AND one up front for
crashworthiness, which would create a significant net weight gain and
commensurate MPG loss. The public also likes having the fuel tank in back
of them while they move forward down the road, and the RWD/R means the fuel
tank is probably going to end up in front of them for weight balance
reasons.  It's tough passing Federal crash tests with that, though it is
certainly possible given wide enough cost constraints and clever
engineering.

Finally, and this is a fairly vague one, there are the development costs of
designing and supporting a unique platform.  Nearly all manufacturers use a
great deal of "parts bin" engineering, which simply means the Taurus and
Windstar share powertrains and some suspension components, the
Jetta/Golf/Cabrio share nearly everything but sheetmetal, etc.  In today's
cost competitive climate, a manufacturer has to do this to get a car into
the public's hands at somewhere near their competitor's. Even the assembly
lines, engineering protocols, structure evaluations, and design phases are
setup around commonality of designs.  Creating an all new platform (RWD/R)
that would share less than any other platform a given manufacturer makes is
a tough call financially.  The expected sales would have to be huge (and no
manufacturer would stake the program's financial viability on a forecast),
or the price of the vehicle would have to be extremely high to justify the
program.

In a nutshell, such a platform would appear in the higher end of the
market, and would not be a candidate for an *economy* car.

Having said all that, I know VW is about to make me a liar with the new
Beetle.  They will accomplish it by doing as much parts bin engineering as
possible, such as using a FWD assembly reversed for the layout (just like
the Fiero used the FWD GM 'X' car drivetrain).  Then they will hold their
collective breaths to see if the gamble pays off.  I think it's nothing
short of great they are doing it, and can't wait to see the results.

Doug Miller
dmiller@iea.com