THe belts are better based on reduced overall friction and weight.
Think
about the fact each link overlaps the other. That means you have 2 friction
points on each end of each link. Not to mention the 2 sprockets sliding into
the chain as it turns...and last but not least...the tensioner is usually some
form of plastic that slides across the rough surface of the chain. True...the
oil does reduce some of the friction but...
As for the weight...most chains
weigh more than the belts so belts would reduce the rotating mass by some
fraction.
Just my thoughts...I could be wrong but hey....
Dan
-----
Original Message ----
From: mike rambour <lists@dinospider.com>
To:
spridgets@autox.team.net
Sent: Wed, January 20, 2010 5:54:24 PM
Subject: Re:
[Spridgets] Question
Ferrari in the old days also used chains, chains stretch
and are a
major pain to change after they stretch, granted that is way more
than
the 30,000 miles a belt lasts. Not all Ferrari's require a motor out
to
change the belts, 308, 328, Mondial's do not require the engine out,
348 I
think are engine out but not sure, 355's and newer require a
engine out.
Before 308's they were chain driven.
The belt is quieter and supposed to be
less susceptible to stretch,
basically they go on and stay put until they
break, so your cam timing
remains perfect (assuming perfect work to install
it). Belts also steal
less horsepower from the motor although I don't fully
buy this one,
spinning a belt vs. spinning a chain would seem to be about the
same to
me, but in the world of performance where every 100th of HP is
desired,
belts are supposed to make a difference.
At least in the Ferrari
world the chains require a little more periodic
maintenance then the belts
because the tensioners are really from the
dark ages, I check the tension on
my chains every 2 years but its a
quick/easy process, the tensioners are a bit
of pain but that is
supposed to be because the motor spins at 8,500RPM and
Ferrari made sure
they don't accidentally unlock and lose tension on the
chains. On the
belted Ferrari's the tensioner needs no maintenance.
Any by
the way, change those belts on the Ferrari on schedule its not a
pretty sight
when the pistons make love with the valves at 8,000RPM.
mike
On Wed,
2010-01-20 at 13:36 -0800, Kirk Hargreaves wrote:
> A Porsche has it's cams
driven by an internal chain. . the same as I think
> about it as the straight
6 Jaguar engines hailing from the 1950's (and
> possibly earlier).
>
> Many
high end cars have their cams driven by an internal chain with a
> tensioner
which needs very little maintenance, if any, compared to an
> outside belt
drive.
>
> The Ferrari, and I am guessing the Lambo and other super high end
cars have
> their cams driven by outboard belts .. . which need to be changed
out at
> around 30k miles.
>
> With the Ferrari, I understand that it is a
big process in that the engine
> has to be pulled to change out the belts. I
have read that it can cost up
> to 10k to have the dealer change out the belts
in a Ferrari.
>
> So why would Ferrari, as well as others, go with an
outboard belt drive on
> their cams?
>
> Is it because the system is lighter,
gives a better response, or? I am
> guessing that the thought is that
outboard belt driven cams enhance
> performance?
>
> Just a question that has
been in my head for a while. . I never have heard
> anyone explain the theory
behind the out board belt as opposed to the
> internal timing chain for
driving cam shafts?
>
>
> Kirk
> Pushrod Drive 1275
_______________________________________________
Support Team.Net
http://www.team..net/donate.html
Suggested annual donation $12.75
You are
subscribed as maine2me@yahoo.com
http://www.team.net/archive
http://autox.team.net/mailman/listinfo/spridgets
_______________________________________________
Support Team.Net http://www.team.net/donate.html
Suggested annual donation $12.75
http://www.team.net/archive
http://autox.team.net/mailman/listinfo/spridgets
|