Custom Light Weight Pulleys...
 

Well I have decided to have some custom light weight pulleys manufactured since I do not want to under drive and no one makes them. They include the crank, alternator and water pump pulleys as well as all new nuts and bolts made out of titanium for added weight reduction. Even the main support that holds the crank pulley will be made out of titanium. I already have the nuts and bolts and have them installed on my car for testing; the pulleys should be here in about two weeks. I have detailed pictures of the stock pulleys and all the fasteners including the titanium bits and will post tomorrow.

I did all the design and drawings myself in AutoCad 2000 and then had everything checked by a good friend of mine who is a PE and everything was reviewed by the manufacturer I have machining them...

Once I have the complete set I will grab a demo stock 6sp RX8 of the lot and dyno before and after... The goal is 8-10hp with no under driving, and they will be very good looking pieces... :)

Here is an AutoCad screen shot of the alternator pulley:

That drawing is pretty cool. I once did a drawing of a rotary-geared pump with AutoCAD2000. Good luck with pulley set :).

Another...
 

Here is another CAD drawing of the alternator pulley before I added the belt grooves...

This is SO PRO, cortc.... cannot wait to see the final result.

Gee I am excited

Very cool Cort... have you considered selling these?

I would be interested in a lightweight non-underdriven pulley set... if one were for sale. :)

Grooves...
 

Will post more details in the morning...

One thing to note, in case you haven't already, is that the four bolts which mount the pulley to the crank hub are not equidistant from the center line. One bolt is on a slightly smaller radius from center to prevent the improper re-installation of the crank trigger, which sits behind the crank pulley.

Charles

Charles: Yes, noticed that; I have a complete set of stock pulleys from Mazda including the crank hub... The timing trigger is mounted first than the two stock pulleys, as the AC pulley is a separate piece... The new pulley set will reuse the crank trigger ring and I made sure that the alignment and bolt pattern is absolutely precise...:)

Omicron: I am currently focusing on the design and prototype set for my car, I have not decided if I will be making them available as a product... For the moment it is just a cool project of mine; if I do decide to produce it I will contact you and setup something to make sure no forum rules are broken...

Sounds good, Cort. I think there is at least some market for these, and if you do all the design work, it only makes sense for you to reap the benefits. :D

Once again, I anxiously await the results of your next mod cortc.

Make sure you get the torque figures when you dyno too... I'd very much like to see them.

Some more pics...
 

These are all of the stock pulleys with a few titanium bits...

Oh jeez i hate cad key but you seem very good at it. Good luck :cool:

Alternator...
 

This is a picture of the stock alternator pulley with its nuts and washer... The nut at the bottom is the new titanium piece; less then half the weight of the original... The other nut is being machined, the stock washer will be reused as it is a pressure and lock washer...

Water...
 

This is a picture of the stock water pump pulley...

Water pulley bolts...
 

This is one of the original bolts next to one new titanium piece... There are three and the three titanium ones weigh a little less than on of the stock ones... All these bolts have forged heads and have a smaller head for even more weight reduction...

Crank pulley...
 

Here is a picture of the stock crank pulley pulled apart... This is a very heavy piece... :eek:

Crank close-up...
 

A close up of the stock crank hub, the new one will be titanium; very cool and very light... :cool:

Crank bolts...
 

Picture of the crank pulley stock bolt and the new titanium pieces; again these are forged with smaller heads 8mm vs. 10mm for the stock ones (10mm is overkill and just adds weight, most probably an attempt to keep fastener sizes to a minimum)... All four titanium pieces weigh in just a bit over one stock bolt... I have the weights at work but if I remember correctly the bolts and nuts alone shed almost 1/2 of a pound...:)

I will post some weights tomorrow along with some more details... As soon as I get the actual pulleys will post pictures of those and then some of them installed on the car. I am going to do several dyno runs, one stock, one with pulleys only, one with pulleys and bolts and one with pulleys, bolts and crank hub...

Alex: Yes, I will post HP as well as torque figures...

thats sweet.. looks like the project is coming along...

I bet yours will be completed before Unorth even ships...

Keep up the good work!!!!

magixpuma: Thanks, I spent three years during college and in my first job for an engineering firm doing 2D and 3D CAD & CAM; I have alot of practice...

Yeah well top this 2 months in my 9nth grade engineering class and i made a small little tube with a turnip shaped spike on the top of it. then we made it in a wood cnc lathe.

Oh yeah lol. You are good and if this actually works out for you maybee you can make a career out of it Maybee.....
nah i would like some pulleys later maybee so keep those programs saved

Move yourself up Solidworks or Solidedge, that's where the power is at. Especially now since there are integrated FEA and dynamic analysis packages for each modeler.

I think they have student versions, otherwise they are relatively expensive.

Cortc, have you thought about getting your car featured in mags like Sport Compact Car? I think you have one of the most modified 8 on the forum that isn't a vendor car.

Those are good programs but I have to keep this on some sort of a budget... I may submit something to get the car featured; the titanium lugs get here in a week and this project should be done by the 15th of August...

Hey Cortc.. Would you comment on the following post for me... I was thinking about waiting for Unorth to release their pullies but now I may just go for SR Motors...

Thankx.. Or wait for yours of course :)

https://www.rx8club.com/showpost.php...1&postcount=27

Under-driving does have some negatives to it, that is why I decided not to with my set... The under-driving only adds about 20% of the power gain, the rest comes from the weight reduction; so I have choosen to go as light as possible including the titanium nuts, bolts and hub... I will have the testing results soon (In a few weeks) and my goal is 8-12hp gain... The RX8 does not use a harmonic damper so it does not apply in this case...:)

Hey, does the RX-8 have the same issue as the RX-7 regarding the main pulley hub? For the 7, many of the aftermarket main pulleys just bolt on to the existing hub, however Unorthodox replaces the whole thing. This is a more complete solution of course, but you have to be extremely careful when you loosen the eccentric shaft bolt or stuff inside the front cover gets out of whack and can be damaged. For more details go here. Again, just curious if this applies to the 8.

jds

UR does not replace the hub on the RX8, just the pullies...

Should be interesting. Wont these pulley mods affect the car in a similiar way to that of adding a lightened flywheel? i.e. - Less initial mass to spin up from low RPM?
You'll have to let us know how the car feels before, and after... :)

Thanks.

Yes, it adds power the same way; here is a picture of the UR set...

No crank hub...

Nice... :D

Allow me to enter my .02 cents.
The reduction of weight will not, can not add hp.
It can free up some power during fast acceleration.
But, the amount of help depends on the mass reduction and the polar moment. IE the distance from the center. So you can see where a flywheel can get some results. Taking mass off the center bolt will get you nothing.
If the outer bolts are on a large enough base circle there would be something. But they are not. The best place is the outer rim of the pulley. I don't know how big these are but the factory units are always thick. On top of that they are usually not round or true. they wobble That alone takes power away.


But if that helps why are you forgetting the wheels and the lugnuts. The lugnuts are bigger and on a larger base circle. As is the wheel rim. These are conected to the engine just as the pulleys are.

Having said all that, you can sell the pulleys on looks alone. Even if there is no gain in power. Should you find a market call me, we just got a new CNC lathe that needs paying for.

Just out of curiosity....how much is all this costing you? You seem to be going to great lengths to reduce the weight of just about anything you can. I think it's a great idea; just wondering what all this costs.

A few pennies...

I believe cortc has already replaced the lugnuts....and the wheel studs with titanium ones.

Yes Richard it does not add it frees it up, and like rxeightr said I have titanium lugs and light weight lug nuts...

I am also looking into having some two piece lightweight brake rotors with aluminum hats made up... They will be crossdrilled and sloted... Then some new calipers...

How much further beyond what SR Motorsports/Unorthadox are you going and what do expect to be the outcome?

There are a few people out there who have purchased pullies from these companies so maybe if you could expand on what you hope to further gain by replacing these other components would be great..

Above and beyond just the pullies of course..

thankx

We have a very low torque car. Best way to free up as much of it as possible is to lighten every thing (Jenny Craig anyone?). Unsprung weight is more important than sprung weight. I think the rule of thumb is 1lb of unsprung weight is equal to 10lbs of sprung weight.

I very much applaud what cortc is doing.

Yep, but winding out 1st and 2nd is a lot more fun. Has anyone made an electric water pump conversion? On any car?

I saw a kit for a honda, I think Summit Racing. Surely having a constant speed water flow and minus the drag of the pump during high RPM operation would be a noticable difference. For short periods, the additional energy would come from the battery.

Unsprung vs. sprung refers to weight that moves up and down with the wheel vs. weight that does not. Reducing unsprung mass pays great dividends in grip over rough roads, but has no special meaning from linear accerlation standpoint.

We are talking about rotating vs. translational mass. Reducing rotating mass is more important than reducing translational mass in terms of increasing straight line acceleration, but it's not 10x. Not even close.

To (sort of) echo GeorgeH

The unsprung vs sprung would work if you were changing the wheels vs pulling your passenger seat out (changing to lighter wheels would be better due to the ratio mentioned). Since this is an engine component, the resistance on the engine it frees up will be more important than the amount of physical weight it removes from the vehicle.

gee, I thought I said that. :rolleyes:

to remove one pound of weight from the wheels (total) would be like removing 10 pounds from the interior (such as one car seat).

it's not exact, it's a rule of thumb :p .


And no it does not add horsepower. It "frees" horsepower. Technically an exhaust does not add HP, it "frees" it. There are few things that do add horsepower (Nitrous and FI).

Now when you get on a dyno that measures HP at the wheels you can see the "added" (freed) HP from removing unsprung weight or any other efficiency improvement (exhaust, pulleys, valves, pistons, rotors, flywheels etc.)

I'll repeat myself... Good Job Cortc, keep us informed as to the weight savings :D

Yeah... you said it, but the point was, comparing, say, getting SSR Comps to getting a light weight flywheel and saying that the SSR comps will free up more horsepower is false and doesn't follow the 1:10 rule concerning freeing up power (well presumably, anyway... I've not tested this or any other particular example) because you are taking the weight off something the engine has to spin (ignoring that the engine does actually spin the rear wheels for the sake of simplicity... for arguments sake, if you don't want to give me the previous omission, we could say only getting the SSRs on the front wheels). Now, if you removed 10 pounds of passenger seats THAT would be worth one pound of wheel shave (assuming your 1:10 ratio was exactly correct, though, as you stated, it is a common/general estimate).

I was trying to reiterate GeorgeH but using more layman's terms, thus making it less complicated, but that fell through now :P The more I think about it, the more hairy it gets, so I'm assuming that we would be driving the car and attempting to feel freed up power, not sitting in a chair doing math...

Apologies to cortc for hijacking the thread.

Can anybody tell me the origins of the 10:1 rule, and what measure of performance it is supposed to represent? I've seen several mathematical analyses of the effect of rotating weight, and done one myself, and while they tend to disagree somewhat, I have never seen anything above 4:1 (mine came out at 2:1). Clearly, pulling 10 lbs out of your wheels (or even your tires, which would have a bigger impact) would not have the same impact on, say, 1/4 mile times as 100 lbs out of the chassis. It just isn't true. Or at least, I haven't seen anything that would indicate as much. If I am wrong, I'd love to see a reference describing why.

Now, if you are looking at lap times around a race track, then perhaps I can see the 10:1 rule for unsprung weight (which could be wheels, tires, the brake caliper, wheel bearings, etc). But that would of course be highly dependent on the course - a smooth course would show a lower improvement than a rough course.

Now, bringing it back to lightweight pulleys, neither of the above scenarios is appropriate - the effect the pullyes will have on acceleration will vary with the gear you are in, as has already been stated in this thread. Yes, what cortc is doing is cool. Let's just keep it in perspective.

Some weights:

Stock Water Pump Bolts> .175oz x 3 = .525oz
TI Water Punp Bolts> .075oz x 3 = .225oz

Stock Hub Bolts> .325oz x 4 = 1.3oz
TI Hub Bolts> .125oz x 4 = .5oz

Stock Alt Nut> .9oz x 1 = .9oz
TI Alt Nut> .5oz x 1 = .5oz

Total All Stock Nuts & Bolts> 2.725oz

Total All TI Nuts & Bolts> 1.225oz