gentlejax2

I saw some pulleys on EBay today shaped like a rotor. I used underdrive pulleys for my old car but dont know if they are good or bad for the S5's.

are they? anyone using them?

thanks

Mike

xtremeskier97

I think dDub has a rotor shaped pulley...I cant remember. I dont think they are bad for the car.

Oh..and BTW...the 7 that you are driving now...the silver one...was it on Airline Dr. last night about 5:00-5:15pm ? If so...I think I saw it. If not...there is another S5 runnin around town. Looked like a GXL/GTU..not sure. Had the stock 5 star rims, stock spoiler, grey/silver in color.

BklynRX7

I would like to know also. i have always been unclear as to the gains of these pulley kits. i personally have no a/c or airpump so all ti would really be underdriving is my alternator. Are there any reall gains produced by this? i recently read an article where they put some $300 pulley kit on an rx-8 and it gained 8-9 hp on the dyno. But they never explained what they did exactly. I might just get the rotor shaped on for my ALT simply because mine is rusted ugly. Well BUMP for some intelligent answers.

bigturbo

Well the problem with t2s is that you cant underdrive the water pump(for a streetable car its a really bad idea) and the rotor looking ones you usually see on ebay probably look like this right
http://www.fc3spro.com/CATALOG/PARTS/pulleys.jpg

If so they are not bad for you car but they dont make any improvment. its a dual alt pulley which allows you to get rid of the belt that drives the air compressor without having to worry about the drive belt slipping at high rpms. My car doesnt have ac/ps or an air pump so there was only one belt groing around the air pump, main pulley and water pump. This dual alt pulley allows you to run two belts side by side on the same path so you dont have to worry about slip. If it is a true underdrive pulley kit they you will be underdriving the alt and waterpump( I feel its a bad idea because our alt isnt great in the first place so slowing it down isnt good and slowing down your waterpump.....rotary/cooling need I say more).

bigturbo

also if you want a dual alt pully banzaitoyota sells them for 20 bucks but they arent rotor shaped. Pm him for more info.

gentlejax2

I dont think these were double pulleys, not for sure.
I am not taking off my air pump so I dont need double pulleys.

the pulley kits I saw on were not double

gentlejax2

my sliver one has not moved since Saturday after work when I started swapping parts from it to my red 90.

If you see the red car with the dent in the passenger side rear then it is me. it also has COBRA wheels on it not staock.

gentlejax2

last thing I DONT HAVE A TURBO> IT IS NA!

so can we get more answers please.


MIKE Z

bigturbo

Well we need a link to the item because the only rotor ones I think anyone on this site has seen were for a double pulley unless it was an FD3S(3rd gen 93+) pulley in which case it wont work with your car unless you get an FD pulley. So send a link or what company makes it and we can give you more info. i did a search and only came up with FD setups. And turbo or non turbo doesnt change the pulleys or drive belts so it would be the same.

bingoboy

you don't want to underdrive your water pump or your alternator. the alternator is already taxed as it is. a new aluminum pulley set would be good to lower rotating mass and weight, but underdriving is not something you want to do.

there are rotor shaped pulleys that are not underdriven, check around for those. they are purely cosmetic, except for maybe a few ounces of weight savings from being aluminum.

turbine

iTrader: (1)

k

ddub

I have a hiGGi rotor shaped dual alt pulley for FD alt in an FC. I also have a Racing Beat main underdrive pulley installed.

Pulley swaps aren't a big deal, but be warned that underdrive pulleys can cause charging issues or a rise in coolant temperatures so make sure your car is in good shape mechanically and electrically if you're considering underdriving accessories.

ddub

The rx8 pulley kit you're thinking of is the Unorthodox SS ultra pulley kit. This kit significantly reduces rotating mass AS WELL as underdriving things. Proven (by members on rx8club ever) 10hp difference at the wheels. This included a pulley for the alternator, water pump, and main. Note, most cars do not see gains like this from pulley kits, the rx8 is lucky I guess. This will also be one of the first modifications on my rx8 for that reason.

Underdriving things causes you to gain some of the lost power your engine is making by turning those components slower. Reducing weight also causes less rotational mass for the engine to turn.

gentlejax2

I went back and checked and it was actually for a FD, so the other pullies you guys refered to were probably double pullies.

My mistake for not looking more closely to description.

I was just curious anyhow. not needing any more problems at the moment. got enough....

thanks for the help
Mike

Jager

iTrader: (10)

Of the people here, how many have actually ran dual pullies instead of heresay? Since I've really never heard anything too bad about them other then what is said here and the words of caution by dDub.

scheistermeister

i dont run a dual pully and i dont have ps, a/c or airpump and my car is fine, runns cooler sometimes.

bigturbo

you can also choose to get one of these if you have no air pump.

http://www.1300cc.com/howto/how2/belt.htm

Mills

iTrader: (1)

I have an older Mazda Racing underdrive pulley kit on my n/a but didn't use the dual alternator one. I used the right belt and proper tension and don't have any problems with belt slippage at high rpm. I also don't have any problems with voltage drop or increased temperature at idle so it seems a street car in good health isn't going to be hurt by underdriving those two things a little bit.

The main pulley does the underdriving, not the water pump or alternator pulleys. Most pulleys for those are stock in size and are just replaced for dual belt usage or cosmetic reasons.

ddub

That's not true for all underdrive pulley kits. An example would be the racing beat one, here is the description for the double sheeve aluminum alternator underdrive pulley:

"The Aluminum Alternator Double Sheave Pulley reduces alternator RPM approximately 20% from stock RPM, and is intended for high performance and moderate race use. It is compatible with either the stock main pulley, or assuming you are not using the air pump, our Double Sheave Aluminum Main Drive Pulley."

88 GTU

theres got to be another alternator we can use im gonna try a 110 amp gm alternator and see if i can make it fit

ddub

FD alternator, see the sticky at the top of the section.