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Old 09-06-2006, 02:05 PM   #1
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Default water pump underdrive pulley

not tryin to be a noob but what realy is the point... any power increase?? or does it just make your pump spin faster?? or............ just totaly not worth it?
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Old 09-06-2006, 02:08 PM   #2
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It spins the pump SLOWER, supposedly saving power. I run one, and it'* not fun sometimes. I believe a 10% underdrive is too much for a daily driver in almost any climate. I'd prefer a 5%.

It may cause you to have to change thermostats a couple times a year. And dyno'* are historically unrepeatable at the low HP figures this thing claims to save.
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Old 09-06-2006, 02:38 PM   #3
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Mr Bill, do i remember you saying that the stock WP does something at WOT??? Cavate or something like that??
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Old 09-06-2006, 03:11 PM   #4
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I dont know if i am a one case person, but i gain a solid .2 in the quarter after installing mine. From before i installed it (16.0) to now (15.7-15.8 ) and also picked up a solid 2MPH in the quarter. And that is with several times testing before and after (about 15 each atleast). Could be a freak thing but my car pulls alot better from say 60 on. And it made a huge difference on the way top end say from 95-shutoff. BUT... on the bonne'* you have to modify the motor mount and it does take a while to get it enough for the pulley to fit. Got to go for now but if you want any info pm me.
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Old 09-06-2006, 03:18 PM   #5
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TJ, the 3hp that pulley could have gained you would possibly equate to a .05 second improvement if that.

No underdrive pulley ever gained anyone a fraction of a tenth. Your skill at launching and driving the car is what changed.
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Old 09-06-2006, 04:25 PM   #6
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Do H body'd L27'* need to modify their motor mounts as well?

Ditto on the time taken off. May have a been a few things, it would take a full underdrive set to gain .1-.2 off.
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Old 09-06-2006, 06:51 PM   #7
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Will, i thought and thought about that after it happened. And compared all my slips and what not. All my launches were 2.3. So it wasnt in the launch. Also if i launch better then and my 60'* were lower then that would actually lower my trap? correct? The only other thing i thought was i have a 1995 and it shifts at 6000. So maybe the fact that it was shifting at that before it was actually hurting me. Then that extra 3 or so whp over the longation of say 600 rpms maybe that did it. I am not sure. But i know i had a solid 15-20 passes before the swap and they were all 16.0-16.1ish. Then after the swap i hit a lot of 15.8'* and a 15.7. Also i have talked to people on the grand prix club and everyone except for maybe 1-2 said they gained .1. They all seemed to gain a solid tenth with the WP underdrive. The alternator one nobody seemed to get a real noticable gain from. I dont dissagree with you about the 3whp not giving a seeable gain. But i would have to say mine did.
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Old 09-06-2006, 06:54 PM   #8
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GP'* have different gearing, weigh less, and have different PCM'*. And anyone'* claim can be cut in half nine times out of ten. There'* no way a simple WP underdrive pulley would give you a noticable gain.

Track conditions, barometric pressure, relative humidity, temperature, and heatsoak will affect you that much or more. You cannot possibly begin to characterize and prove such a small gain without 20 dyno pulls before and after on the same day, same conditions, etc. Normal variance from dyno pull to dyno pull is more than 3hp.
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Old 09-06-2006, 07:01 PM   #9
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Yea i agree with the weather and track conditions. I dont know. Maybe it is just a freak thing. Just as i thought abotu my times and they were over the duration of about 2 months. All different days and some night and soem day and everything. And to this day with the same 60'* i am still atleast trapping 3 mph more. All my runs before the pulley were 86 and one was 87.0 and now they are all 89.5 to 89.7. I dont know. I have to say that i have to agree with you that it wouldnt make a difference at the track but.... lol
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Old 09-06-2006, 07:04 PM   #10
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I would like to give that TB of yours a try at the track. One of these nights when you are sitting there thinking of what to do (doesnt happen often i bet) . Say to yourself TJ needs a nice improvement in throttle reponse and go out there and do up a TB. kinda a Quote from gone in 60 seconds..... Have yourself a good time and make a little money It has to be a TB from a 97 grand prix or i think 95/96 bonneville, it has to have the extra vacumm for the tranny.
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