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Underdrive pulleys, an SC rebuild
#1

So we all know I went boom testing my manhood and my SC. I still have my cohones but no engine to speak of <img src="/forum/images/smilies/968/sad.png" class="smilie" alt="" />

Rebuild is starting soon and while the engine is out it's easy to do some fine tuning. I wanted to add a set of pulleys but I need to know if I will impact any of the SC functionality. As far as I can see the only thing I have to do is get a new drive belt as the path length will change. No? I con only see clearances getting better. Maybe the AC belt adjuster won't go far enough now?

http://www.lindseyracing.com/LR/Parts/PULLEYS.html



Guide me oh great one.
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#2

i had a set of those. i removed them. there is absolutely no reason to run those. you won't gain any power to speak of. remember that the AC, power steering, and alternator are all essentially "pumps". the gains you get will only be until those "pumps" achieve maximum pressure, then things flatten out. that happens before 3k rpm. also, the alternator underdrive is a problem if you plan on using any of your electrical stuff. i was constantly running in deficit mode in traffic.



you will also have a VERY difficult time finding a double sided belt. there are not many lengths of double sided belts from which to choose. i went through that when i was designing the drive system for the SC.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#3

Dave,



What model of SC are you using? I have an underdrive pulley on my alternator (because I fitted a larger crank pulley) - but it does not seem to have done much - and like Flash, I am not so sure it is making enough charge at low rpm.



Having been through the drama of trying to make a 928 Motorsports kit work, I can add some scars to the story.
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#4

he's got a D1R kit



that's the other thing. you CANNOT change the crank pulley size. that would spin the supercharger at a different speed, and would cause all tuning to be wrong.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#5

Yea, that ideas in the crapper now, Bob straightened me out.
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#6

[quote name='DaveN' timestamp='1353351574' post='134958']

... Bob straightened me out.

[/quote]



Glad there is someone around that can do that! <img src="/forum/images/smilies/968/clap.gif" class="smilie" alt="" />
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