The Virtual Timing Belt Gauge
Version 1.0A NOTE : THIS TONE HAS NOW BEEN VERIFIED BY THE PORSCHE GAUGE to be
5.3+/- 0.2 (First try!)
Download the .wav file Right mouse click and select "Save target as")
Background: A belt is just like a guitar string (bass guitar that is) under
tension it produces a note. The note is determined by the distance of the two
contact points and the tension of the belt. Using sound is an extremely accurate
method of measuring tension.
How to Use: Turn engine to TDC with CAM marks aligned. There is a significant
drop in tone right after TDC - so be careful!. In a quiet garage, pluck the belt
at the measurement point (same as the factory gauge) with a stiff plastic
instrument - e.g. a stiff plastic applicator. Compare the note from this wave
file to the sound of the belt & adjust accordingly.
The second or lower sounding group of tones on the wave file is approximately
where the timing switch makes/breaks contact. The first and last group of tones
is 1/2-2/3's turn in on the adjustment bolt.
Note: measured frequency (Audacity) at 82Hz on 10/25/2007 verified 5/23/09
You were right on at 82 Hz! Hope this helps.
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Using Audacity, this time I get 83 Hz for the tone for correct tension, and
approximately 59 Hz for the switch make/break tone. I did this this time by
actually counting the cycles/sec. Others may wish to verify, but this seems to
me to correspond with the remark at the end of the Jager instructions that the
writer used Audacity to verify the correct tension frequency as 82 Hz. I think I
must have omitted, in my original post, the the lower frequency was the
make/break tension (red: trigger the alarm), and also that I derived it from
Audacity's spectrum analysis, which I misread. Hope these comments are useful.
M.Requin
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82 Hz test signal
Porsche 928 tbelt test signal 82hz.wav