Joe Elliott wrote regarding belt detensioners:
"the Zat detensioner has no accomodation for
the thermal expansion of an all-aluminum engine. Don't other
manufacturers just use a spring? It seems to me that that would work
beautifully, because the engine doesn't expand enough for delta x in
Hooke's law to be appreciable, so the force exerted by the spring would
remain rougly constant as the motor expanded, and consequently belt
tension would remain roughly constant. At least a lot more constant
than with the scary (albeit reliable, thus far, knock wood) Zat device.
And a big ol' spring probably won't leak or break either. Joe Elliott
'82 GTV-6"
JOE: YOU'RE BEATING A DEAD HORSE, YOUR ZAT DETENSIONER IS THE BEST AND
MOST RELIABLE RESOURCE TO RESOLVE THE DETENSIONER ISSUE. MOREOVER, AS
MANY OF US KNOW THERE IS A BAD BATCH OF SPRINGS IN MANY OF THE
DETENSIONERS BEING SOLD BY MANY OF THE ALFA PARTS SHOPS... I'VE DONE
SOME CALCULATIONS ON THE MOTORS THERMAL EXPANSION AND THE TRUTH IS ALFA
NEVER NEEDED TO PLACE AN "ADJUSTABLE" DETENSIONER BECAUSE THE ALLOY
EXPANSION IS THE EQUIVALENT OF THE THICKNESS OF A SHEET OF PAPER! IN
TODAY'S MODERN ALL ALLOY BLOCKED MOTORS LIKE HONDA, ACURA, NISSAN, FORD,
ETC... NO ONE USES A DETENSIONER ANYMORE DESPITE THEY'RE ALL ALUMINUM
BLOCK. WHY? BECAUSE MOST MANUFACTURERS NOW KNOW THAT THE SO-CALLED
THERMAL EXPANSION IS NEAR NIL OR NEGLIGIBLE AT BEST. SO... MY
RECOMMENDATION IS WORRY ABOUT SOMETHING ELSE, B/C IF YOU'RE USING THE ZAT
DEVICE YOU'LL BE FINE. THAT'S WHAT I'M USING IN MY CALLAWAY. AND THAT'S
WHAT MODERN MANUFACTURERS ARE DOING TODAY...
My 2 cents.
H. Martin de'Campo
I agree that the dynamic aspect of Alfa's tensioners was silly, but do
other manufacturers really use a fixed mechanism like Zat's? I could have
sworn that BMW used a spring so that tension would remain roughly constant
even if the engine did expand. And the expansion must be more than the
thickness of a sheet of paper--just feel the tension in the belt on a
Zat-equipped car when it's cold, and again when hot--it gets appreciably
tighter.