~$50 Ebay underdrive pulleys OK?

[fowljesse]

All I could find on here is that one was wobbly. Are they okay, or should I get a more expensive one?

[mx3autozam]

What brand is it?

The Cosmo ones are basically exactly the same as UR. If you wnat you can get one from RR Racing for $100 if you are concerned about cheap ones. But a few people are using the cosmo with no problems. Alot of people will argue this and alot of people will claim they are bad on the main bearings and oil pump. Especially on probetalk.

I will wait for someone to say there bad on the engine and then I will tell you MY reason why they are not!

[Kirk95gs]

I dont know if this is any help or not but I think Solo_ryder had one for sale not to long ago..

[fowljesse]

Thanks, guys. I didn't have any particular ones in mind, so the info about the cosmo ones is helpful.
It seems the only thing that could be different between the $50, and costlier ones is the dampening, and the 2 pieces ability to stick together. I read that someone's seperated, and the fins flew off!
Mx3autozam, if no one says they're bad, would you tell my why they're not bad, anyway?
I have the 2.5 alternator, and no significant amp draw.

[solo_ryder]

I had one yea, and I sold it, but apparently it id not fit his 94 probe... w.e lol. It is just a chunk of aluminum that is machined, so getting a RR racing one should be no different as it is still a machined peice of aluminum. I just didnt like the idea of my accessories running 25% slower because I have a decent stereo etc.

[lowflyinmx3]

I hate to thread jack but i'm curious. Could we put smaller pullies on the accesories? Wouldn't that save even more weight and prevent strain on the accesories as well?

[solo_ryder]

I hate to thread jack but i'm curious. Could we put smaller pullies on the accesories? Wouldn't that save even more weight and prevent strain on the accesories as well?

Sure, but that would cost some coin as you would need to get them custom made. They arent nearly as heavy as the stock crank pulley either. I do not think the gain would be worth it unless you can cnc something yourself.

[lowflyinmx3]

What about oe pullies off of other mazdas. Maybe there are smaller ones on other engines, then we could grab those at a junk yard.

[hgallegos915]

Stay away from ebay OBX. mine made my car run like crap..

[Volones]

if you're trying to put a underdrive pulley on the accessories, you will need a larger pulley not a smaller one. This will allow the accessories to turn at a slower rate than with the OE pulley. A smaller pulley on the crankshaft turns the belt at a slower rate than the OE pulley.

I know it sounds all backwards, but if you think about it right, it makes sense.

Vol

[Aston Wards]

Yeah, think of bike gears


The good thing about u/d pulleys is that your car revs up quicker, the downside is that the accessories are driven slower, waterpump, alternator, a/c. This is generally okay cos Mazda allows a certain margin anyway, but with your big stereo or turbo, or just a hot/cold day you can push the limits

The other (potential) problem is that manufacturers build their crank pulleys with harmonic balancers/dampers, again, this is a safety-first type thing, and i dunno about the MX3 community, but i've yet to hear any problems in the 300ZX community, both my cars have them...., i love them! I only buy the UR pulleys, if i'm gonna gamble i want a name i can trust.

If your concerned about your alternator or waterpump, you can get slightly larger pulleys made for them..., kinda defeats the purpose though


so...., are the $50 ones okay? probably, but for piece of mind, i wouldn't.

[Steeb]

i had one for a while and it was fine but now im working on building my engine so i havent been driving the car for months...

i have a spare one new if anyone is interested

[fieromx3]

well i bought a cosmo udp off mx3autozam a lil bit ago and just nstalled it... i had problem where the fin back plate just tuched the tensioner pully but barly and it made a 'tick' noise and made the back plate come loose..

i didnt have thread lock so i just took the screws out and put jbweld on the threads and tightened it back up and i piut a washer behind the tensioner pully to shim it out for clearance.. i have a crank position sensor code and tried resetting the ecu but it doesnt clear and happened after the udp install

[nsklzemx3]

well i bought a cosmo udp off mx3autozam a lil bit ago and just nstalled it... i had problem where the fin back plate just tuched the tensioner pully but barly and it made a 'tick' noise and made the back plate come loose..

i didnt have thread lock so i just took the screws out and put jbweld on the threads and tightened it back up and i piut a washer behind the tensioner pully to shim it out for clearance.. i have a crank position sensor code and tried resetting the ecu but it doesnt clear and happened after the udp install

Did you put a washer behind the underdrive pulley??
The reason I ask is that I fould a similar pulley on eBay and they suggest you may have to emlarge the opening in the timing cover to allow the pulley to set back in far enough. I think those "fins" are what the crank sensor reads from and yours may not be aligned??

[mx3autozam]

Alright so the thing is with undedrive pulley's is that there is no harminic balancer built in. if you go on probetalk and post this. Everyone will go nuts saying it will be harnfull to the engine. Technically they are true. Because the pulley is solid and doesn't ahve a balancer. I reality yes its gunna be more strain on the main bearings. But you will still get many years out of the motor.

here is my theory about this. Our cars do not have a Harmonic Balancer. They have a vibration dampener that is the piece of rubber on the crank pulley. That runs the belts on all the accessories. It just stops vibrations and makes the engine run smooth and quiet. The Mazda k-series is internally balanced anyways. We have a vety well designed crank that is balanced specifically with the rods and piston. Like for example. The ZE crank is balanaced differently than DE because the ZE has flat top pistons instead of dished so the flat tops would be heavier. therefore the crank is balanced to match them.

The block is also a 2 piece design instead of traditional bearing caps. We also have thrust washers. The K series in internally balanced and so is the oil pump which is 2 rotary gears that work together. In my opinion the UDP won't gain you much but if you going all motor and want to get every bit of power out of it, why not get it, its a simple and cheap mod. I have seen dyno sheets on Probetalk from liek 1998 when Sport Compact Car tested one on a probe and gained 8whp. I don't see it myself but who knows.