underdrive pulley

[Sgtmeatsauce1]

I had two cars that I put an underdeveloped crank pulley on and honestly felt nothing. However on my Mustang GT V8 and most recently my G8 GT V8 I most definitely noticed quite a difference, especially the G8. It became much more responsive, had a better kick in the last 2,000 rpm before red line and most noticeable it revved towards red line much much quicker. These were V8's I noticed the big difference. Is there such a thing for the V6 SHO? Is it worth doing? Any input appreciated.

 

[Devin]

Wow, how heavy are those pulleys? I've heard of feeling fast revs from a lightened fly wheel but not from pulleys. Correct me if I am wrong but I thought the purpose of UD pulleys was to enable the engine to rev higher without damaging the accessories.

 

[Sgtmeatsauce1]

Not sure, the aftermarket crank pulley was aluminum vs iron stock and smaller changing the ratio, spinning the crank much faster with less effort. Definitely noticeable. Had to run different sized belts and on G8 raise the idle up 50 rpm for proper battery charging for when AC and headlights were on......

 

[OmaHahn]

Yes this is a very common practice - I have an Audi that I mod also and almost every single Audi owner especially with a supercharger switched to smaller pulleys. Now Audi is going the way of twin turbos also so I'm not sure if smaller pulley still makes a difference or not....?

 

[Sgtmeatsauce1]

I am referring to the crank pulley and not a underdrive supercharger pulley.....

 

[2012korn]

Your crank wasn't spinning faster first of all.....
And second on a new SHO, there isn't one available. And highly doubt it would be beneficial. We only have two accessories it spins anyway.

 

[StealBlueSho]

So I had one of these on my ****** gt back in the day... it helps reduce rotational weight was the big advantage if I remember...

It definitely made a difference! However, now with all the sensors and monitoring who knows if an UDP wouldn't cause a problem..


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[Sgtmeatsauce1]

The crank itself, no it is not spinning faster, but the crank pulley being a smaller diameter does spin faster, my G8 only had 2 belts on it and it made a big noticeable difference, but.....thank you for pointing out the Suttle difference.

 

[SilverSH0]

The crank itself, no it is not spinning faster, but the crank pulley being a smaller diameter does spin faster, my G8 only had 2 belts on it and it made a big noticeable difference, but.....thank you for pointing out the Suttle difference.

They would spin at the same RPM regardless of pulley size. The crank pulley is keyed into the crankshaft so 1 revolution of the crankshaft will always result in 1 revolution of the pulley regardless of pulley size.

We're talking about under drive pulleys so what you're noticing is that a smaller crank pulley results in the accessories spinning slower for the given crank speed. Slower spinning accessories means they provide less drag and result in less parasitic loss in the system which would be more power for the wheels.