SteveWs6

iTrader: (1)

I am thinking about getting a 25% underdrive pulley for my car.

I do drive it very often in the summer. Not always short trips but not always long trips either. I have heard that there are concerns about the system charging. I do have a pretty fresh red top optima in the car if that matters.

Are there any other downsides and is this upgrade if I buy a used one worth the money?

meeklay812

iTrader: (6)

Possible belt slippage, depending on the brand. Which one are you looking at? SLP/Powerbond is probably the best "middle of the road" 25% UDP.

SteveWs6

iTrader: (1)

I haven't really decided which one to get yet (kinda needed that advice too)

But I definitely had heard most of those 2 brands. By default I was probably going to look at SLP

96capricemgr

iTrader: (1)

If you have a stock cam I would skip it. If you have an aftermarket cam and accompanying raised idle then I might consider it.

Optimas have gone way way downhill in recent years I wouldn't use that as an argument for being OK at idle but rather against being OK at idle with a stock cam.

badazz81z28

iTrader: (6)

I have driven in my SLP pulley for a little over a year and no charging issues. That being said, I'm carmed and it idles a little higher at 900 rpms. Stock at 600rpms, possibly....You're in luck though as I'm selling mine. The f-body accesories are not cooperating with my Detroit speed frame, so I'm moving over to corvette accesories and requires a different pulley

It's in the swap meet section for $150 shipped, only a little over a year old.

SteveWs6

iTrader: (1)

Ok thanks guys. I do plan on camming it but all depends when I have the money and stuff. I'll think about it but yeah I don't really want to create problems when my car already runs perfect.

My car does idle higher than 600 it's more around 900 I really don't know why though. I will be sending it out to Frost to get a mail-order tune for now since it isn't a full-out race car... just a bolt-on street car with occasional strip use. Maybe that will fix the idle or maybe that's just where my car likes to be, who knows.

96capricemgr

iTrader: (1)

Is the idle verified or trusting a stock tach?

ragtopz28

iTrader: (57)

^^This..stock tach is not accurate. And I and my buddies all run 25% with no issues from stock to wild.

badazz81z28

iTrader: (6)

Cheap easy bolt on. Most folks have a UDP

Carguy8888

iTrader: (1)

Thank you.

SteveWs6

iTrader: (1)

Good point guys, trusting stock tach but it does sound like a high idle... probably cause of the small stock cam in the 02 tho?

wayland1985

Sounds like good results with factory charging needs. What if you add a stereo/amp?

And what about power steering/AC, water pump?

99Bluz28

iTrader: (35)

With a M6 transmission the factory idle is 800rpm. So there's no need to raise the engine idle rpm. With a A4 transmission the idle rpm is a lot lower (550-600 rpm) so I'd recommend raising the idle up at least 100rpm to keep the alternator turning at least close to the stock rpm when using a 25% UD crank pulley, if you have issues.

gMAG

iTrader: (1)

March 25% UD. No issues whatsoever/ 5 years. I did not use the accompanying small alternator pulley.
It has stock idle/800, and charges @ 13.5v.

2001AntiVenom

iTrader: (84)

I have a stock internal motor in my 2000 ws6. I have the slp under drive pulley. No problems at all.

SteveWs6

iTrader: (1)

And did you guys have a noticeable increase in performance by using it? Was it worth the money that you spent? Thanks in advance

wayland1985

Bumping out of curiosity...

high n dry

iTrader: (18)

Do not raise the idle with ud pulley!
Do a slp/powerbond never look back! Also pick up arp crank bolt...

redbird555

iTrader: (14)

I've always "heard" of issues but never actually seen any. My ati is awesome hands down the best UD they make. The 25% ud ones make the same power as the 10% ati but dont dampen well

AnotherWs6

iTrader: (17)

Aftermarket stereo and a pulley would make me nervous at idle. I have a powerbond 25% and it's fine, blower speed is a little lower at idle when I have the AC ranking during the summer. Volts just drop a little bit at idle and full fan.