underdrive crank pulley - Alfa Romeo Forum
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Alfa 147 JTDm

underdrive crank pulley

Anyone heard of the lightwieght underdrive crank pulleys ?

Are they any good?

any suggestions?
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Peter K
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Re: underdrive crank pulley

Yes, but it sounded like You really have to know what you are doing..Often a crank is balanced using the OEM pulleys to even out vibrations or unwanted frequencies. I heard about this type of tuning last year, but knowing GTA engines has a balanced crank, I didn't think it would be of interest to me. Maybe this "technology" has progressed a lot lately? Intersting concept!
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Re: underdrive crank pulley

I wouldn'y have thought it would make a lot of difference to be honest unless you have a very high state of tune.

The original pulley also has a damper built in which is like a ring of rubber, this cushions the drive and apparently if you use a pulley without it you can damage alternator, power steering pump and crank bearings.

I have also read about undersized crank pulleys as the concept here is that less torque is required from the engine to turn the auxillary belt. However unless your engine is revving fater you may have problems with battery charging, and other ancillaries.

You will never be cool driving a Vauxhall.
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Re: underdrive crank pulley

I think you usually only go to a smaller main pulley for the aux belt if you are running considerably higher revs than std.
If you are using normal revs, especially on the road, you will just end up with a flat battery & power-steering & A/C that isn't working properly.
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crank , pulley , underdrive

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