Slip type Alternator pulley, WHY?????

dieselup

Member
Joined
Nov 21, 2004
TDI
97 jetta
Is the only reason that there is a slip type pulley on the alternator to keep the noise level down? or is it more important than that?
And why is there a 120 amp alternator on a Jetta?
 

compu_85

Gadget Guy
Joined
Sep 29, 2003
Location
Springfield VA
TDI
... None :S
Why 120 amps? Think, 4 engine glow plugs, plus 3 coolant glow plugs, plus headlights, plus engine management. That's a LOT of amps.

-J
 

QuickTD

Veteran Member
Joined
Feb 25, 2002
Location
SW Ontario
TDI
2003 Audi A4Q 5spd 2.0 TDI 2056VK R783, 2006 Audi A4Q 6spd 2.0 TDI, 2007 A4Q 6spd 2.0 TDI
The alternator spins at high speed and has a fair bit of inertia. The one way clutch prevents the alternator from backdriving the crank when the crank speed is fluctuating (as it is when the engine is idling.) This stops the belt tensioner from bouncing around. If you are familiar with the Canadian 1.9TD, you may have heard about problems with the crank pulley coming loose due to wear on the keyway. The one way clutch helps prevent this sort of damage by preventing torque reversals on the crank/crank pulley joint. The addition of the one way clutch as well as a slightly different method of "keying" the pulley to the crank seems to have solved the crank pulley problem on the TDI.
 
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