The Facts on Underdrive pulleys....from the Horses mouth!!

[cory2081]

After seeing all of the arguments on here about the ASP and Unorthodox pulleys, I decided to e-mail ASP and find out exactly why they designed the pulley to be used without the factory harmonic dampener.......this was thier response...

"Several ideas about this exist. ASP uses the theory that alum dissipates heat faster that steel so the heat caused by harmonic freqs is not an issue. As for mass without it we get knock scensor problems so ASP pulleys are not an ultra light or super light pulley even though they are made from alum we have to have some rotating mass on the crank. Now for the underdrive. This is where you get the most of the power not from less mass or weight. The underdrive slows down all accessories thus reducing the drag placed on the motor. To this day ASP has never had a claim for bearing failure or crank problems. If we did I would not make this or any other non dampner product anymore. "

Well, there you go. I hope that this clears up everything for people who are a little hesitant about this mod. I guess I'll be ordering another one, since I didn't install the first one that I bought b/c of this issue....lol.

[180fan]

but it depends on what type of aluminum they're using. Aluminum fatigues and over time, parts fail because of long term fatigue. They don't just dump off most of the stress they've built up from being used in that session, they hold it unlike alot of other ferrous alloys. That was a common problem for earlier aircraft and fatigue is still a big factor for what alloys they use for construction of aircraft. Although I doubt the crank pulley's going to fail due to material fatigue if bought from a reputable company that over builds their aluminum products but yeah, just something to consider.

[silkk]

good info to know

[cory2081]

I'm just passing on the info that they gave me. Just trying to shed some light on this debate, ya know?? I know all about metalergy, been around the machining business all of my life b/c my family has been in that business for a long time. Honestly, I don't think that the dampener is nearly as crucial to a 4 cylinder as it is to a V8. Anyway, after hearing ASP come out and explain their design, I feel alot safer.

[DAEDALUS]

"Several ideas about this exist. ASP uses the theory that alum dissipates heat faster that steel so the heat caused by harmonic freqs is not an issue.

Uh, heat caused by harmonic freqs? Someone explain to me what the heck that means.

[gumby]

i feel safer too. of course i aint shelling out no $400 on pulleys a flywheel, or a driveshaft. screw it i like engine drag it feels good.I'm gonna go tear out all my interior panels, center console, carpet, passenger and back seats. forget the A/C spare and jack who needs that crap ive got AAA a cell phone and windows. Then i can drift it sideways into a pole with no worries.

[cory2081]

Well, Daedalus, it's kinda simple. Have you ever taken a piece of plastic and bent it back and forth repeatedly?? It heats up after awhile doesn't it?? Well, that's basically it, only harmonics are on a much smaller scale at a much faster frequency than you bending plastic back and forth. When one of the cylinders in an engine fires, the crankshaft "flexes" or has some "torsion" applied to it. Remeber, this happens many times a second, depending on your RPM. The dampener is designed to absorb or counteract all of this. Because the ASP pulley is much lighter than the stock one, the amount of torsion that the crank sees due to inertia is reduced and b/c the pulley is aluminium, it can absorb and dissipate certain frequencies better than the crank can. I guess that's about as simple as I can explain it.

Oh, and the ASP pulley is like $100. I think if you only buy the Unorthodox crank pulley (not the set) it's like $190 or something. If it makes anywhere the difference on the KA as it did my Mustang, it is definitly worth it!! You may even see a slight increase in gas mileage.

[Dattebayo]

maybe thats not the correct "horses mouth".

The prolem is that no matter what they say, they are trying to push their porduct and sell as many as they can.

The issue of removing the harmonic dampener is not heat, but rather how it affects the lower end stability in high RPM's. If the crank is unbalanced for a long time, you may not know for a while untill it throws a rod through the block wall and screws you.

I would use every other pulley in the set EXCEPT for the crank pulley, and you will get almost as many poines freed up as you would with the crank added in. You might have a hard time sourceing a belt though...

[180fan]

2BN_S13, I'd have to agree. The balancer's just there to keep the inertia at each point along the curve the same. Otherwise you get increased stress at the massier points and causes premature failure.

[DAEDALUS]

Well, Daedalus, it's kinda simple. Have you ever taken a piece of plastic and bent it back and forth repeatedly?? It heats up after awhile doesn't it?? Well, that's basically it, only harmonics are on a much smaller scale at a much faster frequency than you bending plastic back and forth. When one of the cylinders in an engine fires, the crankshaft "flexes" or has some "torsion" applied to it. Remeber, this happens many times a second, depending on your RPM. The dampener is designed to absorb or counteract all of this. Because the ASP pulley is much lighter than the stock one, the amount of torsion that the crank sees due to inertia is reduced and b/c the pulley is aluminium, it can absorb and dissipate certain frequencies better than the crank can. I guess that's about as simple as I can explain it.

I've burned myself on quite a few things under the hood after long drives, but never on the torsional damper (not dampener). Conservation of energy applies, but discussing thermal benefits on a damper designed for a street engine seems like fluffing.

I'm not sure what you mean by "the amount of torsion that the crank sees due to inertia is reduced", but an aluminum pulley lighter than stock will increase the stresses on a crank, decreasing its fatigue life. It is probably true that an aftermarket pulley can damp some frequencies better than OEM, but natural frequencies are the ones that need to be damped, and OEM designs target the natural frequencies to prevent coupling.

Aluminum conducts heat far better than steel, but dissipation is another story. I assume "dissipation" means either convection to the surrounding air or conduction to the crank (though I bet the crank is usually hotter than the pulley). I don't think aluminum shows much difference from steel in either mechanism.

I am certain you can improve any part on a car if you're willing to throw enough money into design and analysis (more than what the big car companies are willing to spend on it). Be careful to not sacrifice too much longevity for a small gain in power.

Believe me, it's not that simple.

[Twiztid_S13]

my freind had a underdrive pully on his Integra and on his civic hatch .. blew the crank on both .. and he never really drove the cars .. integra is a show car .. just drove it to shows .. he had to rebuild the engine on the integra and we swapped a b16 into the hatch .. the mechanic said it was more then likely caused by the pulley .. the car only had 50K miles on it and engine was well maintained .. dunno .. i dont think much of pulleys .. but he may have just had sh**y luck

[cory2081]

I know it is not a simple matter and that there are wayyyy more physics involved than I wish to type out. I just wanted to hear ASPs side of the story and I did. So, I shared it with my fellow club members. Make of it what you will. I've had UD pulleys on my GN and my Mustang GT, Never had a problem and the gains were well worth the money. The difference though is that those engines have a Harmonic Balancer which is actually a combo of the harmonic dampener and a crank balancer. Without it, those engines would shake you to death!! I've ridden in a Mustang that had one go bad. The rubber broke lose and the balancer was wabbling. trust me, not something that you'd want to drive at all!! The funny thing is that they could design the pulley so that the dampener could be bolted to it, a "piggy back" as they are called for the 4.6 Mustangs since the balancer is made onto the stock pulley. i dunno, I'd like to clear all of the grey areas so that this mod was indeed safe.

[ShadowKnight006]

The funny thing is that they could design the pulley so that the dampener could be bolted to it, a "piggy back" as they are called for the 4.6 Mustangs since the balancer is made onto the stock pulley. i dunno, I'd like to clear all of the grey areas so that this mod was indeed safe.

That would be great, I wonder if one could be made from their existing design.

[cory2081]

I'm sure that it could. I tried to do it with the pulley that I had purchased, but, the balancer would not fit inside the UD pulley. I read the FAQ page on Unorthodox's website and the explanation that they gave was much better. The claim that there is not a harmonic dampener on these engines, it's only to deaden the vibration of the accessories. I know that the pulley that has the rubber inside of it drives the water pump and the power steering.

[Dattebayo]

well like i said, they will say what they need to to sell thier product. You will not sacrifice much power in using every pulley in the set EXCEPT the Crank pulley.

Really the difference is minimal. Just look at the dyno numbers of some of our best members. I dont see a crank UD pulley, and i sure as heck dont hear of any blown crankshafts.

We are not trying to flame you or whatever, there is a little experience and common knowledge here at best. I dont want you to make a mistake you will regret and its well founded.

So at least consider the advise given and research (i mean not like ask some dudes at a meet) rather research from INFORMED independants about the risks involved. Dont ask the company for anything more than spec's cause they will only have accurate information about that.

[Nismo_Freak]

Whats the difference between a lightened flywheel and a balanced lightweight pulley? Both are on opposite ends of the crankshaft.

[cory2081]

I'm just trying to seperate fact from fiction here for the people who keep posting and asking about pulleys. I'm out for any extra power that I can get right now, but, not at the expense of my engine. so, I'm trying to figure out if there is any real danger or not. Right now, I'm just doing as many bolt ons as I can until I get around to porting and polishing this '91 head that I have here and installing Nitride coated undercut valves along with the 91 cams of course. I'm just getting as much power as I can N/a for right now, until I can put some boost to this thing. If ASP and Unorthodox say it is safe, I know that it doesn't mean that it is, but, at least they wrote back to me and said it was. so, IF I get a pulley and it damages my engine, who do you think will be the first to hear about it?? lol

[Twiztid_S13]

ur wallet .... jk isnt there like some uderdrive pulleys they make that are smaller but are liquid filled to help balance them ?? i thought i saw something like that in a mag i flipped threw .. *shrug*

[cory2081]

haha, yeah. I don't think that I have seen those, not for a 240. I know they make harmonic balancers like that for domestics. Fluidampyr or something like that. They're for high HP applications.

[Dattebayo]

Whats the difference between a lightened flywheel and a balanced lightweight pulley? Both are on opposite ends of the crankshaft.

Uhh, not quite. You forget that a lightened flywheel weighs about 11 lbs at best (maybe less) and a pulley weighs about 1 -- 3 lbs.But i dont wanna really argue so i guess you are saying that if the weight and load ratio between the flywheel and pulley are close to stock, that there wont be a problem? I'd love to know if i'm wrong please...

[Asleep Altima]

the difference, at least in this issue, between an acura/honda engine and a nissan engine is that acuras/hondas are externally balanced and NEED that harmonic damper. nissan engines are internally balanced. thats why you hear of our engines going a couple hundred thousand miles with a ud pulley and not the hondas. also, aside from the possible hp gains you might experience, its a good thing to slow down the water pump on a nissan engine (ka for example) that will see its share of high rpms. by slowing the water pump down, it reduces cavitation at high rpms. that in itself is essential to the life of the water pump and the engine as well.

[DAEDALUS]

http://www.fluidampr.com/

They are probably the best, but unfortunately they don't have a listing for Nissans.

[240sxGT]

Does the U crank P and the rest of the Unorthodox set also actual slow the water pump? I have the whole 4 piece set. Some of the accesory pulleys are actual bigger than stock.

[cory2081]

A bigger pulley on any of the accessories will slow that accessory down. So, yes, it does slow down the water pump.

[DAEDALUS]

They need to be if their purpose is to drive the accessory slower than normal. For example, if you had an alternator pulley that was the same size as the crank pulley, it would turn 1x for each crank revolution. If you wanted the alt pulley to turn 1/2 as fast as the crank, you would have to double its diameter. Then every single revolution of the crank would turn the alt pulley 180*--Half the work needed than what the stock pulley ratios deliver.

[cory2081]

exactly