[s-cars] Re: Timing belt vs Gears vs Chain

[Calvin & Diana Craig]

Wow, go away for a few days and a debate ensues :)  A couple of comments:

1) I guess I have never noticed a "loud" timing chain on a car.  But don't
worry, on most Audis after a few 10's of k miles it will be covered up by
valve lifter noise anyway ;)  I will have to admit though that most of my
cars that I had timing chains on had very healthy V-8s and the exhuast sound
was so intoxicating I didn't hear anything else.  If you really can hear the
timing chain in the car then I would insist that it really is a poor
design...gears are a different story they can be pretty damn noisy.

2) Maintenance every 60k miles is much different then "While I am rebuilding
the engine I might as well spend the $40 for the timing chain."  To get a
quality chain to catastrophically fail you are literally talking hundreds of
thousands of miles.  Slipping a tooth is OK, I don't destroy my engine, no
valves contacting pistons, etc.

3) Timing chain set more than a timing belt setup.....noway unless you are
talking the old Corvette ZR-1 with the 4 overhead cams connected by one
chain.  Even a nice double roller chain that keeps stretch to a minimum and
noise down to way less than audible usually will run you about $40 to $60
depending on engine make.

4) As far as variability of timing goes I don't think that's really true.
Yes there is some lash, but as long as the chain is of good quality and
doesn't stretch more than a rubber belt over time then that's easy to deal
with by the cam grind.


When it boils down to it I really just hate the catastrophic nature of the
failure of timing belts.  It seems like we took a step backwards.  We lost
the reliability of the chain and gained a new maintenance item....hmmmm I
wonder who wins on that one?  It's certainly not the consumer.

--Calvin


-----Original Message-----
From: s-car-list-bounces+calvinlc=earthlink.net at audifans.com
[mailto:s-car-list-bounces+calvinlc=earthlink.net at audifans.com]On Behalf
Of Gabriel Caldwell
Sent: Monday, June 21, 2004 8:30 PM
To: William Noland; s-car-list at audifans.com
Cc: forgied at direct.ca
Subject: RE: [s-cars] Re: Timing belt vs Gears vs Chain


"The neu S4 has a chain, because a belt of similar size just won't hack
it. Note the chains on the Audi CVT. Belts won't take the torque."  This
statement is incorrect.  Audi put the chain on the neu S4 and at the
back of the engine for space considerations.  There are many other belt
driven cars that make more torque than the neuS4.

Gabriel Caldwell

-----Original Message-----
From: William Noland [mailto:wenoland at pacbell.net]
Sent: June 21, 2004 7:15 PM
To: s-car-list at audifans.com
Cc: forgied at direct.ca
Subject: [s-cars] Re: Timing belt vs Gears vs Chain

Nothing wrong with a belt at all -- but, chains and gears will last
longer. On the other hand, belts
tend to be a bit quieter. I can hear the chain on my '04 S4, though it's
a nice mechanical sound, if
you know what I mean. OTOH, my old (chain drive) VR6 VW (Passat) was so
quiet, it wasn't always
clear that the engine was running at idle. When I checked with VW on the
recommended replacement
mileage for the VR6 chain, they didn't have a recommendation!

Only gear drive cam in the "stable" is on the '00 Honda VFR800. Not a
real apples to apples
comparison, as a motorcycle engine is relatively unenclosed. That puppy
"whined" like a sumnabitch,
until I threw on an aftermarket can. Honda started using the gear drive
on the VFR's, when timing
belts failed a little too regularly back in the 80's. (Life's a little
different at 12,000 rpm.)
VFR's from '02 on have belts, as do most bikes -- many of which rev into
the stratosphere.

The neu S4 has a chain, because a belt of similar size just won't hack
it. Note the chains on the
Audi CVT. Belts won't take the torque. What's this all prove? Different
motors are different?  :-)

Bill Noland






> 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.


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