UR Pulley Set
 

UR has a 3 piece pulley set avalible for pre order ($315 direct from them). They have a dyno showing a peak gain of 10.6 whp. Also, they say the pulleys only weigh 3lbs. That seems a bit lite to me. Their crank pulley alone for my 240sx weighs 3 lbs.

Got a link? Ever since I bought a DSM with a lightened flywheel, I've been all about rotational weight reduction. I'd love to see what the ACT ProLite (under 10 lbs) would do in combination with a lightened pulley set. Holy fast revs! :D

I couldn't find a dyno chart in their site. Anyone have a link? 10.6 rwhp is rather generous especially for 3 pulleys.

thanks... I am wondering if racingbeat, rotarygod or canzoomer is following this thread. I am still a tad bit skeptical.

Undriving pulleys has been around a long time. Just like a lighter flywheel, there's a payoff and a cost. With a flywheel you give up idling and with underdriven pulleys you loose a bit in recharging from the altenator and your A/C won't be has effective.

I am sorry but it can't be 10HP under any normal load on the dyno.

I'll do the math again if anyone wants but I would guess it will work out to be about 1HP.

-Mr. Wigggles

10 might be possible. For every pound of rotational weight remove from a motor that motor should make around +2-3 whp.

10ish HP is a typical stated gain on the website. Higher for FI cars. Who would spend $300+ for 1hp?

I am going to buy a set just to take to the dyno.

Do the math and we will compare results. I am going to dyno compare my CZ1 that I got yesterday and Royal Purple. I will do another pull with the pulleys as well - when they get to me.

My car baselined at 181hp @ 1,000 miles back in July.

Yup - if you drive a forced induction Miata or BMW, the cost is a blown engine. UR's lightweight crank pulley for those lacks the required harmonic damper, and it's been pretty much proven that UR pulleys lead directly to oil pump failures and thus blown engines on Miatas. I think their engineering is very suspect, and a 10 hp claim certainly does nothing to dispel that impression! I wouldn't touch a UR product (or any pulley) set, even for free. Even if the only downside is that the AC is not as effective - who thinks that the RX-8 AC is so strong that it can afford to be weaker? :p

Regards,
Gordon

Good point about the AC, Gordon. I think it would be better to wait for a proven reliable mod or at least something that would be covered under warranty, if per say something was going to come from Mazda, like a supercharger!

I would rather have a set of lighter pulleys rather then underdrive pulley's... the engineers that designed the belt system usually have a pretty good reason for sizing things the way they did...

I have had S.R. Motorsports pulleys on my 8 for about a month and I have experienced no problems at all. Expectedly, the charging system requires a few hundred more r.p.m. before the voltage regulator kicks in, but that's not really much of an issue for me. As far as power gains go, I can't say much about that because I changed a number of things at the same time. One thing I can mention is that the pulleys are much quieter than the stock setup. With less mass there is also less harmonic ringing when the engine is running. You won't notice what I am talking about until you hear it for yourself. The engine is mecahnically much smoother sounding now.

Charles

Just wanted to clear a few things up for those who might want some more info on the pulley kit. This is my personal vehicle by the way, so I wasn't about to play games with a $30,000 car (wife would NOT approve!). We put it though a number of tests to make sure it all worked well. This is what we came up with:

5% underdrive on the alt
15% on the water pump
20% on the A/C

Also... rumors about piston engines and breaking oil pumps revolve around the removal of the factory crank pulley with the rubber or elastomer ring (there is an FAQ on our site that goes into more detail). I am not going to get into that here because we rotary owners don't have such a device on the rotary engine.

If anyone has questions about the kit let me know. I am on and off the forum every few days :-)

Thanks for the info. Do you notice a difference with the A/C? The RX-8 is known for having a weak A/C unit as it is.

The A/C units might be a little weak from the factory, but it did not seem to mind the 20% underdrive. I was wondering, and this should probably be posted somewhere else, has anyone noticed the A/C gets better the more and more you use it? I remember when I first got the new VW Passat... A/C was weak at first and got better with time.

So the pullies reduce rotational weight which can help in throttle response, and faster revs? If so, I'd love to see some before and after footage of a CZ 1, 10lb ACT flywheel, and UR pully setup in an 8!

I live in Houston, and would like to find someone who makes A/C overdrive pulleys for the upcoming summer. ;)

UR pulleys
 

Unorthodox,
Ur underdrive pulleys add 10.9 hp according to your site.
Can you tell me what your lightweight flywheel would liberate Hp wise and also how much it will weigh including counterweight?
Finally by adding both UR pulley set and UR flywheel I would imagine that rx8 would be much faster but would drivability and noise worsen?
Could you predict a) total Hp increase with both

b) Approx inprovement in Standing 1/4 mile

Regards
Rexi

UR Pulleys group buy
 

I have contacted moderators and have not heard back yet. I am willing to start up a group buy for 20 people and the price would be $285 shipped within the lower 48 states. Comes in polished only.

I had an underdrive pully on my Subaru Impreza, made a surprisingly big difference, especially when paired with intake and exhaust mods.

Will this kit work for Auto's? It should right? The group buy sounds like a plan, if it gets going, I am in!

I was at the garage here in SLC and we did a few dyno tests on the A/C pulley. Ran stock then ran a test with the AC pulley disengaged. We found only a 1 hp power gain. It was our feeling that a pulley for the A/C would only damage the AC in the long run with0 no realy gains.

Typically the AC compressor shuts off under full throttle so a dyno test would not show a gain.

Well the tests we ran were enough for this place to tell another compnay not to bother with the AC.

So if the compressor shuts off at full. Then the only thing that would matter in a race is wasted power turning that little pulley. In that case with the different AC pulley you'll only get a boost of 1hp from it. Maybe you'll get gains if you are actually running your A/C while racing.