RE: Original V6 tensioners

["Mein, Roger G" <meinrg@domain.elided>]

> Date: Thu, 8 Jul 1999 17:59:01 +0100
> From: graham.frisby@domain.elided
> Subject: Re: alfa-digest V7 #866
> I can understand this with the bi-metal detensioner but then how did the
> original oil pressure detensioner work?  Did the engine size actually
> change with higher pressure?  I'm doubting it. ????
> Scott Swanberg
> 
> My guess is  that when cold, the oil pressure is higher, as the oil heats
> up,
> (presumably linear with the heat absorbed by the engine), the oil pressure
> drops
> and changes the amount of tension applied
> Graham Frisby
> 
The oil pressure drops as the engine warms up, but only if you maintain the
same revs.  The pressure will be quite different between idle and full
throttle.
My understanding is that the purpose of the original oil pressure set up was
to ensure that whenever the engine was started, hot or cold, the tensioner
exerted the maximum spring tension on the belt, as during the first couple
of revolutions the oil pressure would effectively be zero.  
The purpose of this was to ensure that if the engine backfired on startup
the increased tension on the belt would reduce the likelihood of the belt
jumping a cog.  After the engine was running for a few seconds and had built
up oil pressure this reduced the force applied by the spring to the normal
running tension.  Any expansion of the engine would be accommodated by the
spring.

Roger Mein
1977 - Alfasud ti
1990 - Alfa 75 3.0 Cloverleaf

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