He said 20% reduction... so it will be smaller.

Reading your previous posts cort, I thought under driving is not a good thing to have when you change the pulleys. But now from robertdot's explanation and yours, it seems that it is even better. Can you please clarify that? Are there any implications/problems with underdriving?
Thanks

 

Thank you Robert. what are the negative effects of underdrivng?

 

Under driving is good and bad, good in that it frees up horsepower and reduces long term ware on the accessories and bad in that it reduces cooling capacity and charging capacity at idle...

I will be producing both, but will come out with lightened non-under driving pulleys for those of us that do not want to get to aggressive and also because that is what’s not available yet...

 

and i want the lightend set no under driving for me

 

So uh...when do we start signing up? heh

 

well, that's^^ what I was going to ask^^ you beat me to it:D

oh, and thanks for the answer cortc

 

Can someone please confirm, that the A/C uses a clutch mechanism which causes the A/C end pulley to freewheel when sufficient cooling is detected. If this is the case, then would it be possible to equip the A/C with an OVERdrive pulley (on the A/C end, if the crank pulley is shared)? My 8 has REALLY crappy A/C (the A/C controller TSB is installed, but didn't help) and I need to keep revs above 1.5k for any hope of cooling, especially in the recent high heat/humidity days in SoCal. I'm sure the problem is in the A/C controller cycling too early, but Mazda doesn't seem to want to fix it due to MPG concerns. thx

 

Count me in for a set of the lightened pulleys!

 

i'll take a set of lightened with the 20% reduction.

 

Don't all automotive AC systems have a clutch like this?

If your AC is that bad, I think you probably have other issues. I'm in South Florida, which is pretty hot and humid as well, and my AC is pretty good. I'm not sure overdriving it would even result in an improvement, to be honest...it may work even worse.

jds

 

Yes they all have clutches and almost all of them don't run the compressor during high load conditions such as acceleration...

 

how about getting yourself a patent on ur design.

 

hey cortc, how do you get the alt pulley off. the puley turns when i try to turn the nut off ,right hand treads right do you have to jam something then turn.
chuck

 

Well other than the application there is not much to patent, it is offered by many companies and for many different cars...

 

You should remove the alternator from the car, grab the pulley with a soft vice and torgue off the nut... Prying it against the alternator with something will damage the pulley and the alternator...

 

What worked for me when I removed the factory alternator pulley was to tighten the alternator belt up a bit, use the appropriate wrench on the nut, and tap the wrench with a dead-blow hammer. To re-install do the reverse but have someone grab the belt to keep the new pulley from slipping. Then, adjust the belt tension to the proper level.

Charles

 

Cortc,

I would be interested in a set of the pulleys as well. Lightened would be my first choice, but ill take the under driven too.

 

Ok, this is the final pricing on the pulleys if they go up for sale:

*** Mod edit*** Sorry, can't discuss prices here *** Mod edit***

Pulleys only (Choice of color; red, blue or silver)
Titanium Nut & Bolt Set:
Crank pulley with 10% under drive:

No titanium crank hub yet, will be available later and pricing will be XXXXXX (No hp numbers yet but should be good for 1-2hp in addition to the other numbers...

I have to make 10 sets otherwise the price goes up, will post official results later but so far testing of the pulleys with no under driving yielded 6.2hp/2.4lbs, pulleys and bolts 7.1hp/2.9lbs... Had one crank pulley made with 10% under drive that gave 8.9hp/3.9lbs... Testing was done on a stock RX8 demo with 3700 miles on the odometer...

These are real numbers...

I know some of the other manufactures have claimed 10-12hp and up to 6.9lbs-ft of torque but that was with a 20-25% reduction in under driving (And those numbers may be a little optimistic)… I may do a crank pulley with a 15% reduction I estimate should get me to about mid 9hp and mid 4lbs-ft of torque without the titanium crank hub as I don’t see a 20% reaching 10-12hp and 6+lbs-ft of torque…

Maybe with the titanium crank hub and a 25% reduction crank pulley with no a/c pulley we might see 12hp and 6lbs-ft…

All testing was done with the engine at full operating temp, we ran her stock for about 30 minutes driving around tested let her cool down installed the pulleys ran her for 30 minutes again driving around then tested again…

 

Cortc -

It seems to me these gains would be strongly dependent on the gear used for the pull (and the inertia of the rollers). Can you shed any light on this? Do you think these gains would be typical in, say, second gear (for example)?

 

GeorgeH: Will post details on the testing soon including gear used during dyno runs etc... But basically like a flywheel you will see the most benefit in the gears that wind up faster like 1st-2nd-3rd...

The results of light pulleys are very well documented, this really is not some rare mod, and much information is available on the net...

 

Cortc...I PM'd you for an order. is that the way you want orders. or would u rather have it on here, or e-mail, or phone? Thanks --Mark

 

Thanks Cortc. Wasn't implying that pullies are an unothodox mod - quite the contrary, as you say. Just wondering about the details.

 

GeorgeH: I understand... markris77: Will start a group buy when the time comes for the pulleys with forum approval...

 

Cortc,
is there a chance that you'll produce pulleys exactly the same color as stock, so that the dealers won't understand the change? they are giving us hard time with the warranty here

With the underdrive pulley, what are the effects on the car? handling, drivability?

 

I am in.