Underdrive Pulley(s)
04-21-2011, 01:21 PM
#1
On The Tree
Thread Starter
iTrader: (4)
Join Date: Aug 2007
Location: Louisville, KY
Posts: 123
Likes: 0
Received 0 Likes
on
0 Posts
Underdrive Pulley(s) When changing the size of a Underdrive Crank Pulley and reducing by 25%, is it required to change your alternator pulley to an overdrive pulley to bring alternator speeds back to near stock levels, or can you also reduce with a underdrive on it as well and further free up Horsepower??
This is for a 99 Auto TA
This is for a 99 Auto TA
04-21-2011, 08:02 PM
#4
I had issues with the Alternator....
way to tell is if your voltage output starts high at startup and doesnt drop, then you have issues and will be soon replacing a battery and an alternator..
also if you start to see things flicker, then you have an issue that needs teh alternator overdrive pulley
personally, I needed it..and its all of $25...and easy to put on and doesnt hurt your performance any.. if anything it ensure you have good voltage which will help with stable performance.
way to tell is if your voltage output starts high at startup and doesnt drop, then you have issues and will be soon replacing a battery and an alternator..
also if you start to see things flicker, then you have an issue that needs teh alternator overdrive pulley
personally, I needed it..and its all of $25...and easy to put on and doesnt hurt your performance any.. if anything it ensure you have good voltage which will help with stable performance.
04-22-2011, 06:51 PM
#5
TECH Regular
iTrader: (3)
Join Date: Jun 2008
Location: Atlanta
Posts: 465
Likes: 0
Received 0 Likes
on
0 Posts
I'm kind of confused... when swapping crank pulleys, wouldn't you want an OVERdrive pulley so it will spin faster?? It seems like if you were to put an underdrive crank pulley on, you would be slowing down the crank by adding more rotation and therefore losing power. Or do I have all this backwards? Please explain
04-22-2011, 07:20 PM
#6
I'm kind of confused... when swapping crank pulleys, wouldn't you want an OVERdrive pulley so it will spin faster?? It seems like if you were to put an underdrive crank pulley on, you would be slowing down the crank by adding more rotation and therefore losing power. Or do I have all this backwards? Please explain
accessories create parasitic loss...
slower turning accessories = less parasitic loss = more horsepower to the rear wheels.
overdrive for the alternator makes it spin back at original speeds allowing proper charging...
Trending Topics
04-23-2011, 01:38 PM
#8
On The Tree
Thread Starter
iTrader: (4)
Join Date: Aug 2007
Location: Louisville, KY
Posts: 123
Likes: 0
Received 0 Likes
on
0 Posts
Okay. I was really worried about killing my battery/alternator. did you lose much/any of the HP gains from going from just the underdrive crank to adding the overrive alt. pulley?
My main thought is if I change both, will I be about the same as where I was with the stock pulleys?
My main thought is if I change both, will I be about the same as where I was with the stock pulleys?
04-23-2011, 04:44 PM
#9
TECH Apprentice
Join Date: Mar 2011
Location: osawatomie ks
Posts: 392
Likes: 0
Received 0 Likes
on
0 Posts
04-24-2011, 08:42 PM
#12
some people dont mind tho, ive just been so used to not having ac at my fingertips that I forget to even use it most times in the bird.
04-25-2011, 12:15 AM
#15
Okay. I was really worried about killing my battery/alternator. did you lose much/any of the HP gains from going from just the underdrive crank to adding the overrive alt. pulley?
My main thought is if I change both, will I be about the same as where I was with the stock pulleys?
My main thought is if I change both, will I be about the same as where I was with the stock pulleys?
you can take away 25% of the drag from all your accessories combined..
the overdrive pulley for your alternator is the smallest of the pulleys and wingdings that are spinning... you wont see any loss from the small amount of lag the alternator would cause...
where the underdrive pulley helps with gaining you power is the Water pump and the AC as they are both very parasitic.
you can gain almost as much from the underdrive pulley as you can get from switching to an electric water pump
04-25-2011, 07:10 PM
#17
On The Tree
Thread Starter
iTrader: (4)
Join Date: Aug 2007
Location: Louisville, KY
Posts: 123
Likes: 0
Received 0 Likes
on
0 Posts
think of it this way...
you can take away 25% of the drag from all your accessories combined..
the overdrive pulley for your alternator is the smallest of the pulleys and wingdings that are spinning... you wont see any loss from the small amount of lag the alternator would cause...
where the underdrive pulley helps with gaining you power is the Water pump and the AC as they are both very parasitic.
you can gain almost as much from the underdrive pulley as you can get from switching to an electric water pump
you can take away 25% of the drag from all your accessories combined..
the overdrive pulley for your alternator is the smallest of the pulleys and wingdings that are spinning... you wont see any loss from the small amount of lag the alternator would cause...
where the underdrive pulley helps with gaining you power is the Water pump and the AC as they are both very parasitic.
you can gain almost as much from the underdrive pulley as you can get from switching to an electric water pump
