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Old 07-11-2015, 03:20 PM   #1
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Underdrive Pulley

Question on the benefits of the underdrive pulley. Just purchase a 98 boxster that I am slowly turning into a spec car but does see occasional street driving. Would it be better to place the underdrive pulley when it is solely a track car. what would be the effect on the alternator at around town rpms?
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Old 07-11-2015, 04:47 PM   #2
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I have an underdrive pulley on my 98. Street car only. No ill effects. The car seems to rev a little quicker, kinda like the difference between AC on and off.
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Old 07-11-2015, 05:02 PM   #3
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Tracked cars rev higher more often. I lost a steering pump from high revs the first year tracking. I changed the pump and pulley. Unfortunately last year lost another pump. Now I run an electric pump. I can tell you the pulley was much easier to change than the pump. On a Spec car the HP improvement should be noticeable with your weight reduction.

PS if you do, hold on to your old pulley for service / timing work.
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Old 07-11-2015, 08:44 PM   #4
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Answers are all here...

Underdrive Pulley Questions

Which Under Drive Pulley to Use
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Old 07-11-2015, 10:09 PM   #5
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From reading up on UD replacement I'm noting that a crank pulley lock down boss would be useless after grinding. I'm not quite ready for the IMS yet but thought of doing the UD so what are alternate methods to lock down UD pulley when doing IMS? Anyone?
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Old 07-12-2015, 09:34 AM   #6
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Quote:
Originally Posted by Lapister View Post
From reading up on UD replacement I'm noting that a crank pulley lock down boss would be useless after grinding. I'm not quite ready for the IMS yet but thought of doing the UD so what are alternate methods to lock down UD pulley when doing IMS? Anyone?
No you only take off what you need to get the pulley to fit. I believe I had to cut 5/16" or 8mm. There's a lot of hole left.

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