Under Drive Pulley
Can you answer a simple question?
Who's opinion posted above would you put more value on? Someone that has no experience, or someone that has 8 years using a product, along with others to back up the claim?
I believe him and every other person who said it...I'm not disputing that at all...Im just saying that I (meaning me) wouldn't run a 25% underdrive pulley...not only does it effect alternator, but the other accessories as well including water pump, power steering, ac pump...I don't have one (as u may have figured out) but I know from the laws of gearing that by under driving the crank you freeing hp, but at the same time your accessories will be turning slower than normal, and while it may not have killed your charging system because you changed the diameter if alternator to compensate, unless you changed all the other pulley diameters as well then they are turning slower than normal...which includes your water pump...which means if for example you are in stop and go traffic your cooling system is not be as efficient as it once was because the pump is pumping at a lower volumetric flow rate, which in turn directly effects mass flow rate of coolant through the radiator. With slow movement of stop and go traffic there is less air moving through the radiator which lowers the effectiveness as well as the efficiency of the heat exchanging system your car originally came with. That's one of the reasons I wouldn't underdrive my ls1.
It saves wear and tear on the accessories, no ill affects are to be had. Not trying to be a dick but everyone is ganging up on you for a reason. There is a new generation of LS owners and all the new uneducated people dont need to be spreading misinformation. It pisses me off to no end when I see ebay ads for FAST 90s and they list " dont buy the 102, its too much for a stock cube motor". Those of us that have been around spread good info.
Unless you have every other HARD part maxxed out (h,c,I,Bolton) the pulley isn't worth it...sure you might get 5rwhp, but for the money I don't think...also if a pulley was that big of a gain I'm sure the engineers would have run 25% under driven..I'm just saying it effects charging system no matter what pulley you put on it
5-9Rwhp for 150-230$... YES please!
I believe him and every other person who said it...I'm not disputing that at all...Im just saying that I (meaning me) wouldn't run a 25% underdrive pulley...not only does it effect alternator, but the other accessories as well including water pump, power steering, ac pump...I don't have one (as u may have figured out) but I know from the laws of gearing that by under driving the crank you freeing hp, but at the same time your accessories will be turning slower than normal, and while it may not have killed your charging system because you changed the diameter if alternator to compensate, unless you changed all the other pulley diameters as well then they are turning slower than normal...which includes your water pump...which means if for example you are in stop and go traffic your cooling system is not be as efficient as it once was because the pump is pumping at a lower volumetric flow rate, which in turn directly effects mass flow rate of coolant through the radiator. With slow movement of stop and go traffic there is less air moving through the radiator which lowers the effectiveness as well as the efficiency of the heat exchanging system your car originally came with. That's one of the reasons I wouldn't underdrive my ls1.
Hey man I agree with you...I have read some dumb stuff ppl have written...sometimes I just theorize based on my engineering background, not trying to put down others knowledge or experiences, just giving my 2 like everyone else......all the stuff on this forum is technically not scientifically true or false that's why we debate stuff...believe me I trust in you guys that have been around for a while
TECH Fanatic
Joined: Aug 2004
Posts: 1,373
Likes: 4
From: Auckland, Nth Is, New Zealand.
As for sitting in heavy traffic, I am using a twin fan system that draws 3000cfm when both fans are on....I can sit in traffic all day long with no problems at all.
As has been said, accessories like alternator, water pump, power steer are all being spun a bit slower which inturn is helping them, not hurting them.
They all work perfectly...I have not had to change any of the accessories since the conversion in 02
Edit, I fitted a GTO LS2 water pump when I installed the Fast 102 so It cleared the intake etc & original accessory belt tensioner last month as it had become weak.
As has been said, accessories like alternator, water pump, power steer are all being spun a bit slower which inturn is helping them, not hurting them.
They all work perfectly...I have not had to change any of the accessories since the conversion in 02
Edit, I fitted a GTO LS2 water pump when I installed the Fast 102 so It cleared the intake etc & original accessory belt tensioner last month as it had become weak.
Last edited by ls1 1990 VN; Jan 23, 2012 at 01:25 AM.
Ls1 1990...see I never would have known that I would have to run a better cooling fan with an underdrive in heavy traffic had it not been for this conversation...I'm not attacking your cars performance just posting my view on things...wow do my fingers hurt from all this typing lol...good debate guys...
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I got a used Corvette pulley on ebay for $120, I've seen fbody ones sell for less. Sold my stock one to get some of that back. It made a noticeable difference in the way the engine revs (especially how quick it revs before hitting the stall). Car went faster in the 1/8th too.
I have an auto and the pulley is a 25%, no charging issues even when the amp/sub are drawing.
Well worth it IMO.
I have an auto and the pulley is a 25%, no charging issues even when the amp/sub are drawing.
Well worth it IMO.
I have a LS2 406 Stroker with a ASP 25% UDP and if I idle for over 30 minutes the temp will slowly raise. Its not my cooling system since I'm running a dual pass 3" core rad. Don't really have surging issues from the alt.
Also only a few alt are changeable with the pulleys. I didn't really see any reason to put it on. Probly will be putting a stock pulley back on.
Also only a few alt are changeable with the pulleys. I didn't really see any reason to put it on. Probly will be putting a stock pulley back on.
hey thanks for the debate guys. It seems to me everyone except a select few like and do not have much of an issue with a UDP. It is definetly now on my list of things to do in the near future.
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
The only people that need the overdrive alt pulley are A. Non-cammed auto cars with stock idles (550 in-gear) or B. cars with big systems. Other then that they aren't needed.
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
Hey man I agree with you...I have read some dumb stuff ppl have written...sometimes I just theorize based on my engineering background, not trying to put down others knowledge or experiences, just giving my 2 like everyone else......all the stuff on this forum is technically not scientifically true or false that's why we debate stuff...believe me I trust in you guys that have been around for a while
I'm assuming this alt has a higher amp output at idle then our smaller cases do?
That's what I've been told. You guys haven't let me down yet.... No seriously:
Its the same alternator that powers my Escalade with the big *** entertainment package the my kids absolutely ABUSE. Can't even get out the drive way unless I've twisted around sideways to hit play on "Dora's Pirate Adventure"
My PS hose has pissed more fluid all over the alternator than than I'd care to discuss. I'm doing this swap when I get home. I want to hook her up to a multimeter and post my results, but I figure if it'll keep the Esky's **** going, should have NO issues with the Camaro.
Its the same alternator that powers my Escalade with the big *** entertainment package the my kids absolutely ABUSE. Can't even get out the drive way unless I've twisted around sideways to hit play on "Dora's Pirate Adventure"
My PS hose has pissed more fluid all over the alternator than than I'd care to discuss. I'm doing this swap when I get home. I want to hook her up to a multimeter and post my results, but I figure if it'll keep the Esky's **** going, should have NO issues with the Camaro.
I have ran a BBK underdrive pulley for my lt1 camaro when I had it. My alternator charged a little slower an the lights would dim when the cam surged at idle, but no cooling or steering problems were caused. I have been stalking this thread pretty heavily lol and would like to know if the ati is worth the money (to buy used) or if a asp or SLP would suffice.
From page 5 of https://ls1tech.com/forums/generatio...ailures-5.html
Posted by Crainholio- UPDATE: I got the alternator back from the shop, the new rectifier is definitely fitted with larger diameter diodes than the Chinese unit. I installed the alt and put ~50 miles on it last weekend, charging is the usual 14.6VDC immediately after cold startup and stabilizes at 13.5VDC at hot idle.
Loading it with high beam headlights and both fans at idle brings it to 13.3VDC, at 800rpm idle and running an ATI 10% underdrive pulley. Increasing the idle speed to 1000rpm had no effect on voltage.
Posted by Crainholio- UPDATE: I got the alternator back from the shop, the new rectifier is definitely fitted with larger diameter diodes than the Chinese unit. I installed the alt and put ~50 miles on it last weekend, charging is the usual 14.6VDC immediately after cold startup and stabilizes at 13.5VDC at hot idle.
Loading it with high beam headlights and both fans at idle brings it to 13.3VDC, at 800rpm idle and running an ATI 10% underdrive pulley. Increasing the idle speed to 1000rpm had no effect on voltage.