Has there been any updates on a full size lightened pulley for our max???

 

Why would you want one? A lighter pulley with OEM diameter would gain some power, but the underdrive pulleys don't underdrive too much. I see no point in spending the same amount for less hp.
-hype

 

I think what he means is an OEM sized Lightned pully. That way we shave weight, but retain the same amount of juice for the alternator.

 

Yep, that's what I meant

 

I think that's what chinaonnitrous1 was talking about

 

Did you mean me?

If you read what I said
I said lighter pulley with OEM diameter (hence lightened OEM pulley). The point is that the current UDP hardly underdrives. It's pretty conservative, so you shouldn't notice any problems from your alternator or any of the accessories unless you have a HUGE stereo.

Icm=mr^2 The rotational inertia is lowered proportionally by decreasing the radius squared or by decreasing the mass. Tell me which you would choose if you had to choose one
-hype

 

I looked into this samething a few months ago.
Since I have a SC that is very important to me.
85% of your gain comes from the wight loss. I have one already but promised where I got it from that I would get them I dyno before & after the pulley install, before I tell who and where to get the pulley.

It will be a month or 2 befoe I can do that....I'm having a small engine problem.

 

how huge of a stereo are we talking about? is 2 15's with 1200watts too big for a UDP?

 

I don't think so cuz BigDogJon has alot of audio and video stuff with a UDP and he has NO problems.

 

Gabriel?

 

I seriously doubt that figure. For serious people with SCs I can see the purpose of only lightening the pulley, but for anyone who is NA it probably just won't be justifiable for the price.
-hype

 

The 3.0L UR pulley is ~3lbs. lighter, so that's 2.7hp/lbx3lbs=8.1hp NA NOT including underdriving(ignoring eccentric shaft condition for simplicity). If we only get 85% of the 8.1hp with an OEM pulley of the same weight, that's 6.885hp(worst case). An UR UDP w/belt($30ish?) is ~$210, which is $25.9hp. So, for an OEM size of the same $180 cost, you gain 6.885hp, which is $26.1/hp.

Now, if you choose the RVM UDP pulley for around $80(I think) w/$30 for a shorter belt, that's ~$13.6/hp for the same 8.1hp gain. However, for an OEM size of the same $80 cost, that's $11.6/hp.

A Y-pipe is considered the best bang-for-your-buck mod and gives say 25hp for $350+gaskets($15?), which is ~$14.6/hp, so I'd consider an OEM size lightweight pulley for $11.6/hp "justifiable for the price".

 

right! SC people need a lightweight pulley with stock diameter. smaller diameter will not spin the SC fast enough.

 

Some of the gains are probably from moving the mass closer to the center of rotation with the UDP. A stock size lightened pully would not have this benefit.

 

Yes...the server wont let me in as LatinMax so I had to make a alter ego.

 

First off let me say you made some good support for your argument

I think your 8hp is optimistic as a peak gain (looks like a UR claimed number "5 to 12 HP"), but I'll use it anyway. I don't like "general" hp claim numbers because most just list a peak hp gain.

This is extrapolated data because I don't know the real diameter of the OEM pulley (if someone provides it I'll redo my calculations). I used the weights from CustomMaxima so that the pullies would be weighed on the same scale. http://www.custommaxima.com/UnorthodoxPulley.php

UDP Diameter 4.875 inches / 2 = 2.4375 in radius

OEM
Diameter 6.21in /2 = 3.105 in radius

Radius Difference .6675 in
Percent Difference from Stock 21.5%

Weight
OEM
4.8lbs

UDP
1.56lbs.

Net Difference
3.24
Percent Difference from Stock 67.5%

Icm = mr^2
OEM I = 4.8lb * 3.105in^2 = 46.28 lb in^2

Lightened OEM = 1.56lb * 3.105in^2 = 15.034 lb in^2
Percent Difference from Stock 68%

UDP = 1.56 * 2.4375in^2 = 9.269 lb in^2
Percent Difference from Stock 80%
Percent Difference from Lightened OEM 38%

HP gain from UDP based from percentage calculations
8.7hp UDP (per your figures)
5.394 hp from Lightened OEM (per your figures)

This isn't the whole story, but it gives you a good idea. The weight does make a difference, but the radius (especially with the weight) makes the UDP even more worthwhile. You would have to remove another .61 lbs (40% difference from the lightened OEM, 81% difference from stock) from the lightened UDP to get the same gain as you get with the current UDP. Your 85% gain from weight does look to be pretty close in this situation though.

Since we didn't start with too much radius or weight to begin with there isn't a huge amount of room for gains. Overall, I do have to say that the gains for the lightened OEM pulley are pretty good, but unless you're SC why not get the underdriven pulley? HP numbers are speculative especially when dealing with peak numbers. Even though the difference between the two pullies may look small, you're getting a higher gain across the entire rpm band with a UDP which equates to a lot of area under the curve.
-hype

 

OEM pulley is 6.21" as calculated using the circumference measurement.

 

5 1/8" counting the edge that keeps the belt in place. I would guess the area the belt rides on is a little under 5" (~4 7/8") but I do not have calipers to measure it.

OEM pulley measures a shade under 6 1/2 when measued the same way, so the are the belt ride on is probably just under 6 1/4, probably about 6.21" or so .

 

Figures updated Thanks for the diameters guys.
-hype

 

That's not my figure...that's using UR's withOUT considering underdriving, so I figure worst case. Of course that's ASSuming all the weight is located on the eccentric shaft, which as you've explained is different.

6-3/8" overall diameter, however the belt is ~1/8" lower, so just say 6-1/2" diameter.

Using the 6-1/2" that's only a 16% difference(2.625/3.125).

K?

Yes, but with the OEM size, there is more of the mass from the outer area which can be removed. More room for improvement than an UDP. Look at how lightweight flywheels decrease the inertia, but keep OEM size diameters. It's probably going to be a wash in the end. You either underdrive for 15% gain or you remove more of the mass from the outer area. Not that hard really.

I agree. Why not underdrive? I don't care to underdrive my electrical system or any other system that is underdriven. It's a bad solution IMO. Now if they made accessory pulleys that compensated to counter the underdriving, then I'd get the underdrive pulley's smaller brother. Agree, but the difference is minimal.

I'll take the 85% gain that a lightened pulley provides for $80 and have the best-bang-your-buck mod available. Still worthwhile IMB.

 

IceY2K1 - Perhaps you haven't seen the updated figures yet but...

Accordng to xHypexs calculations gains from a UDPs weight savings would be ~8.7 HP and gains from a lightened OEM size pulley would be about 5.4 HP. While 3.3 HP is not a huge amount there is no reason to give it up.

In addition the UDP gives a small additional gain due to Underdriving. And I would think a stock size lightened pully would be heavier than a UDP simply because it is larger, meaning the gains of the lightened stock size pulley would be even less than the 5.4 HP estimated. With this taken into account the gains from a lightened OEM pully would probably be only about 1/2 those of a UDP

Can someone calculate how much slower the UDP turns the accesories? For example 3000 RPM with UDP is the same as 2000 RPM with stock pulley or something like that.

EDIT - I would definatly stay away from the RVM UDP so an $80 pulley is probably not an option. However I think the Definitive pulley is about $110 and looks OK, and the UR still gives decent HP per $$ gains IMO.

 

Yes, but I didn't feel like rewriting all that.



Maybe, maybe not.

If it underdrives 15%, than 3000rpm with the UDP is the same as 2550 rpm with the stock pulley.

Thanks! I'm looking to "other" sources though.

 

If anyone is intrested in an stock size lightened pulley Definitive is considering making one if they can get ten people to put down a deposit.

http://forums.maxima.org/showthread....hreadid=210431