Underdrive pulleys?
Racer
Joined: May 2004
Posts: 305
Likes: 9
From: Martell NE
Science, well reduced parasitic horsepower loss. Since the accessories spin at a lower RPM with the underdrive pulleys it results in less friction. Less friction is more HP.
I put them on mine and the only thing I noticed was that the Alt at idle was barely charging if any at all. Not that big of a deal.
I put them on mine and the only thing I noticed was that the Alt at idle was barely charging if any at all. Not that big of a deal.
Race Director
Joined: Aug 2003
Posts: 11,043
Likes: 3
From: San Jose Pat Tillman - American Hero
Originally Posted by bowersock
Let's talk about underdrive pulleys? Is there any valid science to this mod?
Thanks
Roger
Thanks
Roger
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 32
From: The Top of Utah
And a slower turning water pump. There is no question that the power not used, is available to drive the car. I'd be curious how much that really is. I could see it for a racer, looking for a hundredth or two, in the 1/4, but I'm not sure I would care to compromise the daily driving reliability. Since the power consumption of an accessory increase with the speed of that item, the power savings (gain to the rear wheels) would be the greatest at high rpms. I doubt there would be anything noticeable below 3000 rpms, except to the cooling and charging systems.
RACE ON!!!
RACE ON!!!
Burning Brakes
Joined: Nov 2004
Posts: 1,057
Likes: 0
From: Warren Ohio
On LT1's, a 25% underdrive pulley is supposed to be worth 4hp, according to ASP. Not much bang for the $180 it would cost with shipping, etc. www.ws6.com has a dyno test showing 1hp and around 5ft/lbs torque, if I recall correctly.
Other engines which run the water pump off of the serpentine belt should see a greater gain.
Other engines which run the water pump off of the serpentine belt should see a greater gain.
Racer
Joined: Jan 2003
Posts: 360
Likes: 0
From: Sumter South Carolina
I did the crank and alt pulleys and noticed a quicker revving engine. As far as the idle speed went in regards to the alt, I did not notice any drop in idle voltage. IMHO, you will not lose drivability if you do both pulleys. Just my $0.02 worth.
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Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
Originally Posted by bowersock
Let's talk about underdrive pulleys? Is there any valid science to this mod?
Thanks
Roger
Thanks
Roger
I have gone to 10% under drive with ATI damper.....
No effect in terms of waterpump as I have electric waterpump...
I see no problem with alternater or A/C as 1) the car idles about 10% higher than stock and with 4.10 gears it is always reving at least 10% more than stock.....
Will extend the life of all these items by fewer turns, more mpg since turning slower, a little more hp since turning slower, a little more reliable since reduce their max rpm back to what GM intended...
Weight of the damper is reduced by ?????? around 10pounds...so couple more hp...
Power wise I don't expect more than 5hp, but there are other benefits....is it worth it......I don't know...probably not...but I did it..
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
The pulley set was the 2nd mod to my car when I bought her almost 10years ago. I will never forget what a mechanic at mineke said after he went for a test drive with me to check on the brakes.. "Man this thing revvs up faaast"
Other than that I did feel faster after having it installed, but didn't take it to the track back then yet.
Other than that I did feel faster after having it installed, but didn't take it to the track back then yet.
Burning Brakes
Joined: Nov 2003
Posts: 914
Likes: 1
From: Redding Ca
Earlier this week a post from Vic's89 claimed a solid .10 gain. This from a fairly stock car running mid-12's. Pretty impressive performance. I think it was under the heading, "first run of the seaon" by Vic. That may not be the right title but its close. 
