[urq] Alternator Whine and Airflow Direction

[mike schowengerdt]

hello all you aero engineers out there...
let a mechanic explain this to y9ou...the alt fan is basically a centrifical air pump, as it rotates it throws air out, that air being sucked thru the alt from the back, hence the duct to direct cool air in.   IMHO sharpening the blades etc srves no purpose   Direction of rotation is impportant for this operation and if the fan blades is turning in hte wrong direction it probably makes noise and doesn't do its job very well..........consider how  reality  AND  how theory applies to the problem you're trying to solve


----- Original Message ----
From: "a2000sportster at aol.com" <a2000sportster at aol.com>
To: urq at audifans.com
Sent: Tuesday, November 7, 2006 11:57:33 AM
Subject: [urq] Alternator Whine and Airflow Direction


Regarding the whine, man that's fantastic that a hopefully the source of the  noise might be the fan. Great idea to smooth the leading edges of the fan blades...six pack and a few hours and I wouldn't be able to see the blades ;^)

But the direction of the airflow would have to be from the front of the car to the rear! If the fan pushes the air out the front at speed it wouldn't be able to exit, because the fan would be pushing against whatever air speed the car had. And the car would overheat, but only at speed, idling it would come back down to normal temps....I had a leaking radiator replaced a number of years ago on a 200 20V, and the shop that did it couldn't find the problem of the overheating. Even though the front metal fender and hood got hot when sitting at idle, with the hood closed..because the fan was connected in reverse and could only push the air out the front when the car wasn't moving! I asked them why they couldn't drive it a couple of miles to see the problem, but their answer was if it happens in the shop we can fix it, it can't possibly be happening while you are driving it. Great Shop huh! My regular mechanic was on vacation, and it was at this new shop for over a week, idiling
 in their lot...limped to the regular shop. When he opened the hood he noticed the metal could hardly be touched it was so hot, looked at the connection to the fan, flipped the switch connection, problem solved!

Jack

Message: 5
Date: Mon, 6 Nov 2006 15:25:20 -0500
From: "Louis-Alain Richard" <laraa at sympatico.ca>
Subject: [urq] RE :  alternator whine - SOURCE determined!!
To: <brogers at terrix.com>,   <urq at audifans.com>, <quattro at audifans.com>
Message-ID: <BAYC1-PASMTP11894F3EB910EB072FDEC8CEF30 at CEZ.ICE>
Content-Type: text/plain;   charset="Windows-1252"

Technical question for all:

In ETKA, the tin-metal back cover (? 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 
________________________________________________________________________
Check out the new AOL.  Most comprehensive set of free safety and security tools, free access to millions of high-quality videos from across the web, free AOL Mail and more.
_______________________________________________
Audifans urq mailing list
Send posts to: mailto:urq at audifans.com
Manage your list connection: http://www.audifans.com/mailman/listinfo/urq
Have an urq question?  Check the Audifans Knowledgebase!
http://www.audifans.com/twiki/bin/view/Audi/UrQuattro
Have an urq answer? ... Please help others by adding to the KB ... all contributions welcome!