Underdrive pulley, yet again (searched, plenty)
 

Hey everyone, I read a lot on here about underdrive pulleys but didn't get a clear answer on the question i had. I'll be upgrading my alt anyway by getting it re-wrapped and was wanting to also get an underdrive main pulley, not one for the water pump or alt. I want the pulley for better throttle response and was wanting to know if it's worth the seventy or so dollars. My car is an 87 TII with an efan, and air pump, no ac, no ps. All the other threads i read were mostly about underdriven acc. pulleys and few about Just the main.

Hoping to get some responses from the same people i saw during my search since they had had pretty good info :)

I haven't seen an underdrive main pulley, however I also haven't looked specifically for it. I'd say search here, google, and ebay. But while I'm here, I'll make some comments.

I like the idea. I do wonder, however, if it would be a pain for part makers to make pulleys for our FC's. The main pulleys all have a special bolt hole pattern so that they only fit on one direction, this facilitates the timing marks being correct. Furthermore, I have proof through my rebuild that some front hubs; even from FC's of the same make, model, package, and year; differ from each other. It was a source of great trouble for me. Unless you send the hub you're going to use, a manufacturer wouldn't have a good way of knowing how your hub is built as it's the only way to provide accurate timing marks for you. You can do it yourself the hard way, and you really don't want to, I don't want to. I pulled the front hub for the third or fourth time (the priors were for other reasons) to avoid having to find TDC on my own, and I definitely came out better than finding TDC the hard way.

http://www.srmotorsports.com/sr86plly.html

thats the link for the main pulley, but they say with all three underdrive pulley's they free'd up 10 hp, that seems fishy to me.

I had one. It was trash. The car wouldn't charge at idle with the smaller main pulley. The worst part about it was i blew a motor because of it. Long story short, the main hub and the pulley have to be a matched set, meaning if you put a different pulley on a hub, the timing marks wont be accurate. There is no telling how far the timing marks will be out if you put one of the pulleys on.

Or you can purchase the underdrive pulley listed on Mazdatrix.com. Instead of it being a 2 part, they combined it to be just 1 piece and plus it is set to have your timing dead on or something of that sort. I was thinking of purchasing one, just so I know that my timing is absolutely correct and that my car will be running properly.

The pulleys i were looking at were the srmotorsports one and the rotorsports one. Like i said about the charging, I'll have an upgraded alt by the time i get the pulley and the only extra item i have that draws off of it is the efan.

I thought of something else yesterday. Since underdriving could possibly be bad for a couple reasons, does anyone know if they make regular sized pulleys, but just lightweight, maybe out of alum. ? If it's just lightweight, shouldn't that still cut down on rotational mass?

The pulleys don't weigh enough to gain much from changing material.

If you spend most of your time in traffic an underdrive pulley might not be the best thing. I've always used the Racing Beat e-shaft pulleys with great results. They slow all the accessories down including the water pump which can free up power to move the car. And yes, 10 HP is reasonable to figure on getting.

So if you have every power sucking item on your car and drive in the city all the time, probably not good for you. My cars only get track time and I even put a bigger pulley on the water pump and alt(if I have one on the car). My big alt pulley and small shaft pulley make it so the car does even make 12V until over 4000rpm.

Is that the only place to get them nowadays?:wallbash:

they are not worth the time and money. unless you keep that thing at redline all damn day, than its not worth it.

You need to research this some more. When you rewind an alternator to increase the amperage output, you always have issues with charging at idle. The rewinding increases the output yes, but at the cost of less output at idle. Many high output alternator vendors size a pulley that increases the alternator speed at idle to compensate for this effect, basically an 'overdrive pulley' This is just the opposite of the underdrive pulley. Get a rewind and an underdrive and you may not be a happy camper.

This is why I decided not to have my S5 rewound, instead custom fitting a 130 amp alternator to my Vert.

This "overdriving" of the alt doesn't have any ill effects at high RPM?

What did you get the 130 amp alt from? Thanks for the heads up

That's an excellent idea. They only cost about sixty bucks or so. Peace of mind is the name of the game.

Thats a distinct possibility, another reason not to go down that path.

Ford Taurus, 130 amp. 1996 3.0 ohv. $20 at salvage yard. Custom bracket, simple rewire.

It's a bad idea, and it does squat for any gain in performance.
I run an FD alternator, and a stock sized pulley can barely keep the voltage up at idle at night.


-Ted

Really? I have no problems keeping 14.5v at idle at night.

i would only consider the mazdatrix or racing beat but im pretty sure theyre both for high performance engines