ddub

hey those of you running alternator underdrive pulleys... where did you get yours? I know rx7.com carries them and they say it doesnt come with a belt for it and to contact them for sizing. Well ive tried contacting them and no ones gotten back to me. Where did you guys get your belts from? What size was it? How much was it? thanks for any info

ddub

bump

NZConvertible

Why would you want an underdrive alternator pulley on a street car? Do you really want to downgrade an electrical system with very little spare capacity just to gain ~0.5hp?

RETed

Racing Beat http://www.racingbeat.com/
I do sell hIGGItrix ones or get the direct from hIGGI at: 
http://rx7cz.net/shop/

Either will use two STOCK alternator/water pump belts - you can get them from the local auto parts stores.  I think hIGGI can sell you the belts also if you get the pulley from him.


-Ted

ddub

i have an FD alternator so im really not going to be downgrading.. underdriving the FD will still be as good or better than the stock.. plus im always running at higher than 15volts because of the FD alt which ive been told is too high for some of the stock electrical components, so an underdrive pulley will actually help in that sense

RETed

Funny, you seemed to have missed the thread where hIGGI was offering pulleys for FD alternator into FC.

If the alternator is running 15VDC, something is wrong - it has nothing to do with the pulley.



-Ted

ddub

I've heard of other people getting numbers this high as well, with no accessories/lights on it is about 15 or a little more.. but when the lights are on at night or heat or various accessories it drops into the 12-14 range

SDrotary-FC

i use the racing beat duel pulley set up and i get the 808 miser belts that work for it

1987RX7guy

iTrader: (3)

14.7 volts should be what you get from the laternator. Higher and something is wrong.

truespin88

I get almost 15v on my stock alt.
However.
it doesn't stay there because my stereo eats it up. at night I'm lucky to hold 12v...

ddub

people keep saying that something is "wrong" but what could it be? also, how accurate is the stock volt gauge? cuz its usually *around* 15

ddub

also, if when installing the alt i switched the two plug that go into it by accident, would that cause it to run too high? would the alt work at all if they're switched?

1987RX7guy

iTrader: (3)

Mine is around 15V also. Get a digital one and that should be really accurate.

Most components in a car or made for cars will run ok on 12 to 14.7 volts. The alternator on all three of my cars charges to 14.7. Sans load ofcoarse. turn on the heater and it all goes to **** with an FC alt. I wouldn't worry too much about it. Just take a DMM and take it to the engine bay and put the neg terminal on the battery's neg post and the pos terminal on the alternator post. This "should" read the voltage that is being put out by the alt. If its higher than 14.7 there may be a problem with the regulator.

RETed

Yeah, good point.
Use a DMM to verify - stock (gauges) suck.


-Ted

ddub

so aside from something might be wrong how do you think running an underdrive pulley with the FD alternator would work out?

1987RX7guy

iTrader: (3)

if your trying to get power out of your car. Go somewhere else. I don't think its worth it for "power" gains. But if your a road racer that see's constant track outings it would benefit your alternator. Less RPMs=less wear and tear on bearings and such so it would help marginally and increase the alt's lifespan.



Santiago

RETed

If I had a choice of running a normal sized pulley, I would.
In fact, I'm changing out my RB one for a hIGGItrix one very soon, cause I'm tired of the voltage drop at night.  I do run a dedicated VDO voltmeter to monitor the electricals.  Engine running during day (i.e. no headlights, no aux electricals) is almost 14.0VDC.  Voltage during night with headlights on and electric fan on is a little over 12.0VDC.

Stop lamps take up close to 10 amperes every time you step on the brake pedal!  That's a significant amount of current even at idle.  Even the upgrade alternator I know of, it only makes 15A at idle speeds...


-Ted

SnowmanSteiner

I definately would not go by the stock gauge. I would also not go with an aftermarket volt meter unless you are physically touching the two terminals. This is why, I have a Greddy Turbo Timer that also has the function of a Volt meter. The Greddy reads .3 volts higher than what the Haltech says.

- Steiner

NZConvertible

So you've upgraded the alternator and now you want to reduce its output back to stock? What is the point of that? Do you want an improvement or not?
Either the gauge reading is wrong or the internal voltage regulator is malfunctioning. Repairing the alternator is a far more logical way of solving that problem.

ddub

The point of the underdrive pulley was not to fix the problem, I dont even know if it is a problem yet until I check it with a more accurate meter. The point was to get the little gain from underdriving the alternator, and since I dont have a huge stereo or anything, but I do have the upgraded FD alternator, then I figured it'd be about stock or maybe a lil higher, I dunno, which is fine. I would never underdrive the stock S4 alt, that'd be way too low.

NZConvertible

What's the underdrive ratio on that pulley? If it's 30% (which I think most are) then you're right back at 70A where you started. Same electrical output, same power draw on the engine. No matter how you look at it, it's one step forward and one step backward.

Instead of paying for a pulley, why not just replace the old alternator for free?

ddub

nvm im done with this thread, thx ted and 1987 for ur help

NZConvertible

Funny how some people just don't like hearing the truth. Oh well...

ddub

Uh huh yep thats exactly it... thank you so much nz convertible for showing me the light, i understand now how i am so stupid and wrong all the time.. thank you for continually putting me down in my threads, i appreciate it

1987RX7guy

iTrader: (3)

Jason if I may try to intellegently attack your statements about alt UD pullies how exactly does slowing the alternator down hurt amperage? At cruising speeds it "should" still be able to spin as if it was going down the street without an UD pully. I would understand problems at idle and really low rpms. But I know that most alts have internal regulators that adjust according to RPM. I can see my FD alt's reg work at idle. It will be at ~13v then slowly rise back to 14-14.7


Please elaborate.