I got an S4 TII with underdrive pulleys and electric fan, my battery is being drain badly. the fan is running straight out of the battery with a switch (done by previous owner) no fune, no relay, nothing. I'm about to wire it properly sunday and i wonder if my problems are going to end or not, i'm reading 13.5v-13.2v at idle. ones i turn the fan on it drops to 11.5 to 12.05v or something like that. I hope when wired won't draw so much power but i dont know if that is going to be enough or i need to modify my alternator some how. is there a way to get more amps out of the stock alternator ? that is brand new by the way...

 

most upgrade their alternator for the stock electrical system is barely up to par. fd alt swap.. look it up

 

yeah i searched for that also but i'm not shure.... you need an spacer and some other wiring bs, not that hard but i just got that alt couple of weeks ago before i seen the swap i'm not shure if i can return it. my friend broad his to a place where they mess with it and got it pumping more power, i lost contact with him now reasearching for a way.

 

ditch the nder drive pulleys U dont need them and they dont help or give u any extra horses

 

yeah.... i know... but i don't have the stock ones, i bought the car with those on. i guess i'll have to look for them.

 

underdrive pulleys dont make a difference??
It's all physics bro, just think about how the gears work on a bicycle.
I can't speak for the TII, but there was a noticable difference in performance in my friends N/A FC (underdrive alt pulley and underdrive eccentric shaft pulley).
He is running an electric fan with the FD alternator but I would recommend just having your stock alternator rewound. It is inexpensive and you can bump up the amperage higher than the FD alt. Also, check how many amps your fan is drawing... you can pick up an e-fan, i.e. perma-cool, that only draws 10 amps.

Peaaace

 

I know less spinning mass more useable tq and hp HOWEVER do u realize how much less we are talking and not only that BUT if u are losing electic current to the engine and other parts of the car u are losing more in the end..

IMO the amount u may gain (1hp 1tw) is outweighed by the amount of money u have to spend to gain that (cost of bigger alt, cost of pulleys, cost of everything it takes to go this route)

trust me I have ran under drive pulleys on other cars and the cons out weigh the pros.. in the long run it is a waste of money to do this under drive pulleys are NOT a "mod" on a low hp engine

 

Definitely wire in the relay and temp switch to that e-fan.
And, bump your idle. An idle of 800-900 will solve many charging problems caused by loads(e-fan, stereo,....) and the underdrive pulley.

How much time do you spend at idle anyway?

 

I think is problem is more about the smaller pulleys not spinning fast enough to charge the battery thats the problem with under drive pulleys. With smaller pulleys, they dont sping fast enough orpull long enough to spin the alternator and most other accesories enough to make them run properly.

the stock pulleys are what u should use unless u have a drag car or somethign that is ONLY spinning like a water pump. if u have a water pump, alt and or AC or p/s u should NEVER use under drive pulleys. remember a larger alt is not always best for a charging system and it is not a cure for the enertia that the under drive pulleys lack

 

btw I have the stock power steering and stock air conditions pulley if u want them give me a shout

 

to underdrive the alternator the alternator pully wouldnt be smaller it would be larger

 

under drive pulleys are smaller then stock pulleys

 

see the pic the guy is holding onto the LARGER stock pulleys the under drive pulleys are mounted on the car..

under driving an accessory will happen with a smaller pulley

 

not necessarily. think about it, if the alternator pully was say, half the size of the timing pully the alternator would then spin 2 times as fast for every 1 revolution the timing pully spun... step down the alt pully even smaller 1/4 the size and it would then spin 4 times for every 1 revolution the timing pully spins

 

SpooledupRacing
LOL
You need to go to 7Stock and hang out with them "stock" boyz... and talk about stock parts...
Your alternator is going to reach its full output at over ~2500rpm regardless...

 

only in theroy if u have an under drive crank pulley then u will loose your spinning mass


and I dont go for stock if u are refering to me I just dont think under drive pulleys are the way to go

 

i dont know what your talking about but im talking about keeping the timing or "crank" pully stock and changing the alternator pully only, the alternator pully would have to be larger to be underdriven with a stock timing pully

 

underdrive pulley is bigger, my car idles low around 7 something it feels like its going to stop. I'm looking for aplace to get my stock alternator rewound... lets see whats up i'm getting tire of charging my battery overnight just to last 3 or 4 starts..

 

Underdriving the alt will reduce its output, especially at low rpms. You can upgrade to an s5 alt and all you have to do is put on an s5 alt connector. They are good for an extra 10 amps.

 

This is why you should always buy the matching set. I have an underdrive crank pulley and dual alternator pulley from rb and I never have voltage issues. The fd alt. is definately a good idea anyway. I ran one for 3yrs when I was in to the stereos. The extra 30amps definitely comes in handy.

 

What difference will a matching set make? If you underdrive the alternator you get less out of it, period. If you then upgrade to an FD alt you'll be getting about the same electrical capacity and putting about the same load on the engine as the stock alternator was before changing the pullies, making the whole exercise pointless.

Underdrivng the accessories is only beneficial to an engine that spends most of it's time at high rpm, i.e. a race car. Even then the actual gains are quite small, the real benefits are reducing water pump caviation and extending bearing life. Neither of these are issues on a street car. It's a waste of time and money.

 

When you order a matching set the alternator pulley that they send you is sized properly to compensate for the underdrive crank pulley. The idea is to remove rotating mass from the crank and yes, it's better for the water pump.

 

On a race car, not a street car.

 

i got a matching set. (i don't know what brand they say Mazda Racing on them) i'm going to rip that fan right off and get me a stock one for now and stock pulleys.... i liked my clean engine bay but is not worth all this bs.