[s-cars] Timing belt vs Gears vs Chain

[Tom Black]

Give me a chain any day. Many manufacturers are reverting to timing chains,
among them Audi in the NeuS4 V8. The new Mazdas, which means Ford may be
just behind them. I have never heard of a chain breaking or stretching
sufficiently to even make a measurable change to the timing. I would think
that one could not say the same for a timing belt. The Porsche 911 air
cooled engines had an abnormally long timing belt with no problems with
stretch that I am aware of, and that includes the 3.0l RSR engine, with
which I have more than a passing knowledge, having worked as #1 mech for a
racing team for four years (73 - 77).
My $0.02.
Tom Black.

----- Original Message ----- 
From: "Dave Forgie" <forgied at direct.ca>
To: <Eric_R_Kissell at whirlpool.com>
Cc: <quattro at audifans.com>; <s-car-list at audifans.com>
Sent: Monday, June 21, 2004 11:25 AM
Subject: [s-cars] Timing belt vs Gears vs Chain


> Gentlemen:  There is nothing wrong with the toothed rubber timing belt.
It is
> light. Is only one moving part. It is relatively inexpensive.  Gears or
chains
> are heavier.  Have more moving parts and would be much more expensive.  Do
you
> think a chain wouldn't wear and break (into many little pieces of
shrapnel)?
> Do you think gears (if you could figure out a way to span about 18 inches
with
> them) wouldn't wear and have all sorts of "lash" problems (it would give a
> whole new meaning to "variable valve timing" (it would be randomly
variable -
> always a good thing (NOT!))).  Rubber timing belts need to be changed
before
> they fail and they need to be protected from outside damage.
>
> This debate should not be about the timing belt.  It should be about
protecting
> the timing belt from damage if/when the serpentine belt
breaks/disintegrates.
>
> Dave F.
>
> Eric_R_Kissell at whirlpool.com wrote:
>
> > "Calvin & Diana Craig" <calvinlc at earthlink.net> wrote:
> >
> > >Of course all this would be solved if the damn manufacturer wasn't too
> > cheap
> > >to use a chain or timing gears in the first place.
> >
> > Which opens the door for a debate as to why Audi (& Volkswagen) chose a
> > timing belt rather than a chain or gears.
> >
> > What are the advantages of a timing belt over other options?
> >
> > What are the disadvantages of a timing belt over other options?
> >
> > In my job that we have to balance all of the design criteria and cost is
> > only one consideration. Has Audi chosen the timing belt alternative for
any
> > reason other than cost? Is the cost actually less than other
alternatives?
> >
> > Eric
>
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