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Discussion Starter #1 (Edited)
I need a new serpintine belt but local auto stores don't have my size i will be installing the MWR underdrive pulley set and was told to add 2 inches to the belt
The auto store told me that a A/C equipped spyder needs a 1695mm belt and the extra 2 inches makes that a
1745mm belt the auto store only has 1740mm or 1755mm belts can i use the 1755mm belt and just tighten the tensioner up a little more or do i have to find a 1745mm belt?
also the shop said i could use the bigger one and tighten up the tensioner up but i find that hard to believe
 

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Maybe I'm missing something but if they are underdrive pulleys I thought they would be smaller in diameter? Wouldn't it be two inches smaller belt? I'm probably wrong though.
 

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Discussion Starter #4
you would think so but underdrive pulleys are bigger overdrive pulleys are smaller, being bigger means they turn slower reducing the parasitic loss but at a cost of a slightly less affective part
 

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Yes you are one hundred percent correct. It is supposed to gain you a few hp, but I wonder how hard it will be to install the pulley.
 

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Discussion Starter #6
ive got a BGB and it does not look that hard pulling the alternator off looks tricky as there is not much room to work with and you have to drain the coolant to get the water pump pully on but thats about it,
im not interested in the extra few hp i get only a more responsive motor as that helps the SMT shift faster, but the extra few hp is welcome none the less
 

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Discussion Starter #8
you may be thinking of an underdrive crank pulley, i'm staying far away from those as they have no harmonic balancer and will cause problems with the crankshaft
i'm underdriving only the water pump and alternator im sure the battery can handle getting a little less of a charge (895 CA battery^_^) and i don't drive in peak hour traffic even going to work, the water pump is being relpaced with a 2zz unit which from my understanding is superior to a 1zz unit so underdriving that will not effect the cooling that much:huh:
 
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