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Stock sized lightweight pulleys - good or bad?

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Stock sized lightweight pulleys - good or bad?

Post by jmc on Tue Jan 19, 2010 6:04 am

Given the weather has been keeping me of the car for a bit, I've been hunting round for new toys, and come across some people using stock sized but lightweight pulleys. However there seems to be as much bad press for these as good. I can understand how underdrive crank pulleys would be bad for the G60 as it would reduce the charger speed, but what about light weight versions in standard sizes? Is the harmonic damper really that crucial as I've had the engine rebuilt and balanced? Answers on a postcard, or preferbly on here please...
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Re: Stock sized lightweight pulleys - good or bad?

Post by mrbeige on Tue Jan 19, 2010 10:31 am

Was the engine balanced with or without the pulleys?

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Re: Stock sized lightweight pulleys - good or bad?

Post by jmc on Tue Jan 19, 2010 11:01 am

You know I have no idea - will check though.
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Re: Stock sized lightweight pulleys - good or bad?

Post by mrbeige on Tue Jan 19, 2010 11:13 am

I think the only thing you need to worry about is taking too much weight of the pulleys. They do act as a harmonic damper, and are weighted in line with the flywheel, from what I can remember. I think you will be ok, if everything was balanced together. If not the reduction in weight may cause undue flexing of the crankshaft and the obvious problems that would ensue. That may only be in extreme cases, so I might just be talking out of my anus Smile

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Re: Stock sized lightweight pulleys - good or bad?

Post by Yandards on Thu Jan 21, 2010 9:57 am

I would retain the crank pulley in stock form because of the vib damper. Regardless of the quality of your balance the engine still produces vibration.

I would and am looking at fitting lighter versions of the intermediate and cam pulleys though, they are only drive pulleys and have no vibration absorbtion function.

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Re: Stock sized lightweight pulleys - good or bad?

Post by jmc on Fri Jan 22, 2010 3:17 am

Thanks for the input guys. I've not been to reach Darren yet to confirm how my crank was balanced, however I am also running a lightened flywheel. Been speaking with the guy that runs Gruven parts in the US as he has started making G60 ones now - this was what he had to say (and yes I appreciate he wants to sell them which will make him biased)....

"Guys, we've run light weight crank pulleys on G60 and VR6 for many years. It absolutely does not increase engine vibration one bit. The stock crank pulley is not a damper, its simply a mass. It is intended only for slowing the rate of revs of the motor both accelerating and decelerating. The factory wants to slow revs accelerating so your grandmother doesn’t redline the car in the walmart parking lot by accident. They want to slow revs decelerating so engine feels more smooth when you dump the throttle (ie, it doesn’t blip once or twice coming down to 750 rpm). That’s it, nothing more is intended by rotating the factory pulley cinderblock about the crank axis. By installing a light weight crank pulley, the engine will be able to rev much more freely, the engine feels more like a motorcycle, exactly what the G60 needs. It also makes for very easy match rev shifting on track – literally stab the throttle in neutral and you can zip the motor up to the right rev for super quick downshift. Watch any in road course driver, this is exactly how they shift. Another fantastic mod is the lightweight flywheel, I highly recommend doing them both. You will wonder why you ever drove it heavy."
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Re: Stock sized lightweight pulleys - good or bad?

Post by dirtytorque on Fri Jan 22, 2010 3:20 am

I don't run the damper.
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Re: Stock sized lightweight pulleys - good or bad?

Post by JNLRacing on Mon May 17, 2010 1:54 am

Always retain the damper, Although your crank is precision balanced the engine will suffer from secondary harmonics of the combustion cycle which can cause horrendous consequences if not adequately balanced. To the extend I have seen tha back of a 16v block break of running lightweight pulleys without a dampener.

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