[urq] RE : alternator whine - SOURCE determined!!

Brandon Rogers brogers at terrix.com
Mon Nov 6 15:49:10 EST 2006


Ahh interesting thought - yeah the cover from both my urq and 200 alts
does not fit this one - bolt holes don't line up.  The cover is missing
in this case.

Brandon

-----Original Message-----
From: Louis-Alain Richard [mailto:laraa at sympatico.ca] 
Sent: Monday, November 06, 2006 1:25 PM
To: brogers at terrix.com; urq at audifans.com; quattro at audifans.com
Subject: RE : [urq] alternator whine - SOURCE determined!!


Technical question for all:

In ETKA, the tin-metal back cover (à la urQ and 200q20v) is called an
"intake cover". So, does the air enter from the back to be pulled
through the body towards the front and exhausted by the fan? If so, then
maybe the source of the noise is in the absence/presence of said cover ?

LAR 

> -----Message d'origine-----
> Guys-
> We have made progress. A few people mentioned this possibility.  Drum 
> roll please.....
> 
> Alternator fan.  Creating a siren effect.
> 
> We had the car on ramps and revved the motor - and with your head
right
> there - it was obvious.  So we swapped on a different fan.  The 
> alternator I have to use for this bracket is a 4kq/CGT that has a fan 
> with a solid front face and fins on the back side.  We swapped on a 
> different fan, shimmed for identical pulley spacing, from an urq 
> alternator, which has the open blades and is the same fan as the 200
20V
> alternator, and it made a pretty decent difference.  The sound
> (whine?siren???) is still there but not as loud or as intrusive.
> 
> I haven't had any time to do further investigation or testing since
but
> now I wonder if the location of the alternator - _very_ close to the 
> front valence, and poking out underneath by about 3/4", is creating
some
> sort of air cavitation or something???? that causes the siren effect. 
> Any thoughts about what would quiet it down - either blocking direct 
> airflow or creating more airflow over the fan?  I don't want to cut up

> the valence further for nothing....
> 
> I do have pics of the setup I can send - will hopefully have them 
> downloaded in not too long.
> 
> thanks
> 
> Brandon
> '84 urq 20V



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