Crank pulley vibration dampers & harmonics. Update: Lightweight crank pulleys = Bad

Split from: http://www.clubgti.com/forum/showthread.php?t=202640

I had a really interesting conversation at Autosport about the engines used in the Jonathan Palmer 1.8T single seaters.

... they made a bespoke 36-toothed trigger wheel - integrated to pulley - on the cambelt end (no vibration damper in it) + crank sensor & bracket mounted off the back of the block.

 

I looked at this also.
the lack of crank pulley having a damper in it tho with their rational on why they went external anyhows (high revs) make me wonder what longeveity it likely

did they say what revs they use?
Given I know mines been good for 4 years, never been used less than 8200rpm, and now see's 9000rpm, there is no crank trigger wheel related problems seen on mine.

Now a friends leon 1.8t racecar without a damper crank pulley, destroyed the crank big style... block exploded out.

it looked a neat installation to have the billet crank pulley with integral trigger wheel, but I would worry about its lack of crank damper.

Balanced built engines, both theirs I imagine, and my own.
I would'nt ever run mine without a damper pulley

Wondering what crank they use?

 

Did the Leon that threw the crank out have an internal trigger disc?

They use steel cranks.

 

I have an 8v digifant type damped crank pulley. I machined the centre inner parts diameter down a small amount and then fitted the trigger wheel off a 1.8 CVH sierra crank pulley. It is a good strong design and the pickup & bracket fits to the block on the 2 x M8 bolt holes in the block to the rear / left of the crank pulley.
I did this a while ago before mention of the vw internal trigger wheel "potential" issue.
I had heard of other after market pressed steel trigger wheels centrifuging apart in motorsport so went this way.

Maybe the vw internal trigger wheels give issues when the crank damper is removed and the resultant harmonics start to come into play. As discussed elsewhere it is extremly rare for any issue to come from this but may be there are other factors influencing the condition.
I am aware the high end TDI tuning folk take crank harmonics very seriously and get bespoke dampers made to suit. Do not think this relates to the trigger wheel as the rpm is not as high but does highlight some balance / harmonic issue.
If you lightening the std crank, flywheel and clutch reciprocating weight, apparently all the frequencies that the std harmonic damper was designed for change outwith its limits.
Dual mass flywheels?
At least if the trigger wheel is external any parts can be replaced easily and there is no issue with engine damage if it ever did have a problem.

 

yea.. internal disk





Neuspeed Power Pulley on there - 1st use on track, new motor.. this happens after 30+laps

 

I will add my ibiza runs a Fluid Damper on it which from all reports deals with any harmonics on higher revving motors than the stock unit.. I ran the stock one before, never a billet bling pulley like Neuspeeds or others..

For NHRA racing, its mandatory for cars to run Fluid Dampers I was told. Safety thing

 

That engine is done!

Std forged crank by the looks of it though (prior to wanting to get some air that is)

 

yep, engine "built" by Swindon Race Engineer.. balanced etc etc
Neuspeed pulleys were put on after.. and woops.

 

As in Swindon, the works Vauxhall engine builders?

 

no crank damper on mine - just billet - runs fine - std fitment by the chap who builds my motors on all his lumps and no issues to report

 

Arguably proof enough it can work just fine. No internal timing disc fitted though.

I assume this Leon didn't have a fluid damper on it, Bill?

 

Neuspeed are not some ebay junkshop - they are a pretty respectable tuning place. I would be suprised if they were selling things that did this to an engine.

 

I suppose they could be supplying billet pulleys for engines that normally run a dual mass flywheel and this would dampen the harmonics.
If people choose to fit them to modified engines with normal flywheels that is maybe where problems start?
The N/A 20v engines I have seen come with a dual mass flywheel and just a pressed steel crank pulley for the belts.

 

They sell them for VRs I think and as far as I know, these did not have a dual mass flywheel?

 

as in Swindon Race Engines

 

hmmm.
such conflicting info
resonant dampers are widely advised

how is crank resonance dealt with?
:confused:

 

Neuspeed pully on it.. simple billet jobbie

no damper pulley at all

 

Confused all round, indeed.

I take it Swindon didn't get the job of building it again, so no more came of it?

 

In this instance, I think its "sell" item, not engineered item personally.
Dampers are on these engines for a reason.

Most people who drop in rods and go bigger turbo's etc dont balance their engine during builds.. Removing one of the things which tries to cope with vibrations and harmonics seems like a bad idea to me. (the other thing being dual mass flywheels)

16v ABF motors did not suffer g'box rattles on their single mass flywheels and clutches, yet 20vt's rattle like a mofo when swapping from dual mass.. Hmmm - answers on a postcard, by I have my theories on why

 

they build his engines.. and continue to do so yea