Good article on using lightweight crank pulleys...
11-25-2004, 08:58 PM
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ETKA and Bentley's refer to that pulley as a 'vibration damper with pulley for ribbed belt'
I'd surmise the engineering bore in mind material composition along with the mass of the pulley.
11-25-2004, 09:17 PM
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Re: ETKA and Bentley's refer to that pulley as a 'vibration damper with pulley for ribbed belt'
Correct - but its still just a metal pulley. I have mine sitting next to me after putting on the ECS UDP - its just a hunk of metal. There is no rubber to act as a harmonic balancer.
11-25-2004, 09:38 PM
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It still works as one. Mass is effective as a damper.
The mass of the flywheel serves as a damper on that end of the crank. Lightening the mass at the front end will result in less dampening at that end.
Whether that is a real issue on the 1.8t I can't say but I do note that when a light weight pully is used with a LWFW, steady idle (especially with the A/C compressor running) is a distant memory.
Whether that is a real issue on the 1.8t I can't say but I do note that when a light weight pully is used with a LWFW, steady idle (especially with the A/C compressor running) is a distant memory.
11-25-2004, 09:44 PM
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Re: It still works as one. Mass is effective as a damper.
That is simply not correct:
My idle is completley steady running a 15lbs LWFW and a UDP.
LucasGChips has the same setup and his idle is likewise rock solid - as is AXE's with the same set-up. (as do others).
In fact the UDP with the LWFW seems to run a lot better than just a LWFW - its more balanced.
If you run a LWFW with a stock pulley your unbalancing things a lot more - period.
Further to this: I did over 100kms city driving today in 37 degree celsius heat with the A/C on the whole time - and perfect idle.
My idle is completley steady running a 15lbs LWFW and a UDP.
LucasGChips has the same setup and his idle is likewise rock solid - as is AXE's with the same set-up. (as do others).
In fact the UDP with the LWFW seems to run a lot better than just a LWFW - its more balanced.
If you run a LWFW with a stock pulley your unbalancing things a lot more - period.
Further to this: I did over 100kms city driving today in 37 degree celsius heat with the A/C on the whole time - and perfect idle.
11-25-2004, 11:24 PM
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If weight was an issue there whould be a different ETKA part number for...
...the different weight of a manual flywheel or an automatic adapter plate. Also, there's atill going to be a dampening (stabilizing) effect because of the loading of the rubber belt driving the alternator, A/C, P/S, etc. While the ETKA does call it a "vibration damper", there is only one part number for manual, auto, and with or without A/C. However, the 3.0L looks to be a different technology for the larger displacement engine. Perhaps the inline, four-cylinder 1.8T, which also doesn't need the counter-rotating balance shaft of the 2.0L, doesn't need the traditional harmonic balancer either.
Per the Bosch Automotive Handbook, 5th edition, page 407: "Vibration dampers are required to reduce the crankshaft's torsional vibrations to acceptable levels (e.g. bonded rubber vibration dampers or viscous vibration dampers)." The stock 1.8T doesn't have either so it's not a critical element. The V6, on the other hand, has much different torsional forces. Again, Bosch says, "the torsional vibrations of the resonant system...become increasingly critical with higher numbers of cylinders." This, along with the movements associated with V6 engines (page 403), and that end pulley is far more critical.
Bottomline: feel free to lighten that pulley on the 1.8T (keep the same diameter) but don't mess with the V6.
The link will show you the extremes VW/Audi will go to to resolve this problem.<ul><li><a href="http://www.sae.org/automag/techbriefs/11-2003/1-111-11-29.pdf">See last page for ICD</a></li></ul>
Per the Bosch Automotive Handbook, 5th edition, page 407: "Vibration dampers are required to reduce the crankshaft's torsional vibrations to acceptable levels (e.g. bonded rubber vibration dampers or viscous vibration dampers)." The stock 1.8T doesn't have either so it's not a critical element. The V6, on the other hand, has much different torsional forces. Again, Bosch says, "the torsional vibrations of the resonant system...become increasingly critical with higher numbers of cylinders." This, along with the movements associated with V6 engines (page 403), and that end pulley is far more critical.
Bottomline: feel free to lighten that pulley on the 1.8T (keep the same diameter) but don't mess with the V6.
The link will show you the extremes VW/Audi will go to to resolve this problem.<ul><li><a href="http://www.sae.org/automag/techbriefs/11-2003/1-111-11-29.pdf">See last page for ICD</a></li></ul>
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11-26-2004, 03:01 AM
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On the AEB and ATW there IS a seperate damper for with or without AC.
058 105 251 D without A/C
058 105 251 E for with A/C
Along with a different crank there is a different damper for the AWM. Could one even get an AWM in the US without A/C?
The 2.7t and 2.8 both call for a single damper part number and make no distinction between automatic or manual.
Bottomline . .feel free to run a lightweight pulley but expect decreased dampening on that end of the crank and expect to have no idle if you are also running a LWFW<ul><li><a href="http://www.impexfap.com/partlist.cfm?getpart=43529&43528&70949& ;43528&43529&75381&PARTNUMBERSEARCH=05 8105251#part43529">Apparrently VAG is very proud of this damper</a></li></ul>
058 105 251 E for with A/C
Along with a different crank there is a different damper for the AWM. Could one even get an AWM in the US without A/C?
The 2.7t and 2.8 both call for a single damper part number and make no distinction between automatic or manual.
Bottomline . .feel free to run a lightweight pulley but expect decreased dampening on that end of the crank and expect to have no idle if you are also running a LWFW<ul><li><a href="http://www.impexfap.com/partlist.cfm?getpart=43529&43528&70949& ;43528&43529&75381&PARTNUMBERSEARCH=05 8105251#part43529">Apparrently VAG is very proud of this damper</a></li></ul>
11-26-2004, 03:36 AM
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Perhaps your good idle has to do with the difference between the two masses of the flywheels.
Folks who've cited issues with idle were running lighter wheels than 15lbs. IIRC ~12 lbs.
It simply is true
that mass is effective as a damper. The mass of the flywheel performs a dampening function on that end of the crank. The farther from the flywheel the greater the effects of torsional 'vibration'.
See the comments from Mat in your previous thread on this subject. His comments echo those of other folks who added a lightweight pulley to a 12 lb LWFT set up.<ul><li><a href="https://forums.audiworld.com/performance/msgs/71074.phtml">https://forums.audiworld.com/performance/msgs/71074.phtml</a</li></ul>
It simply is true
that mass is effective as a damper. The mass of the flywheel performs a dampening function on that end of the crank. The farther from the flywheel the greater the effects of torsional 'vibration'. See the comments from Mat in your previous thread on this subject. His comments echo those of other folks who added a lightweight pulley to a 12 lb LWFT set up.<ul><li><a href="https://forums.audiworld.com/performance/msgs/71074.phtml">https://forums.audiworld.com/performance/msgs/71074.phtml</a</li></ul>
11-26-2004, 04:25 AM
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Re: Perhaps your good idle has to do with the difference between the two masses of the flywheels.
I cant speak to the effects of running a UDP with a 12lbs. LWFW - but I now know from experience(and the experience of LucasGChips, AXE and others) that there is NO issue with a 15 lbs. flywheel.
As I said - mt idle is ROCK SOLID - even with AC on. And LucasGChips and AXE have the same setup as me and likewise have no issues.
Perhaps the 12lbs. flywheel is that little bit too light - that idle stability becomes an issue?
Running a 15lbs. LWFW and UDP is great - car revs freely, feels great and is easily St. driveable. Personally, I cant see the need to go lighter to 12lbs. I know a couple of ppl who have had 12 lbs. and found it too light.
As I said - mt idle is ROCK SOLID - even with AC on. And LucasGChips and AXE have the same setup as me and likewise have no issues.
Perhaps the 12lbs. flywheel is that little bit too light - that idle stability becomes an issue?
Running a 15lbs. LWFW and UDP is great - car revs freely, feels great and is easily St. driveable. Personally, I cant see the need to go lighter to 12lbs. I know a couple of ppl who have had 12 lbs. and found it too light.