Underdrive pulleys [ merged 1/6/07]

[larryd]

Worth it or not? I'm thinking of going with the AEM tru-power pulley kit. Anyone used them?

 

[JBDdsmer610]

Yea i didn't thing so. IM just going to buy an OEM

 

[snowboarda10hal]

I was looking around for a crank pulley and i found one that said New Megan Racing Underdrive Pulley for your 4g63. This pulley will replace your harmonic balancer for added horsepower. So my question is, is the harmonic balancer the same as underdrive pulley?

 

[Defiant]

Minor semantic correction: the harmonic damper doesn't so much deal with vibration as crank windup. As one cylinder fires and another's trying to do compression, the crank twists. A harmonic "balancer" absorbs some of this twist, then gives it back as the crank tries to "untwist". How soon a crank will let go because this twisting isn't fought by an underdrive pulley is largely conjecture, and a matter of how lucky the owner is.
I don't know what engines are sent out the factory doors without dampers, but surely some are. DSMs weren't in that batch.

 

[buugiewuugie]

Hey guys, I am in the middle of a rebuild and I was wondering. Is it a bad idea to get a lightweight crank pulley? I will be doing the balance shaft removal mod and it seems that would be a lot of vibration to the motor to have that gone and a underdrive pulley w/out the dampener.

I read there are some problems with crankwalk with these pulleys but on 7 bolts. I have a 90 6 bolt so i curious if I will be ok?

I was thinking about going with one of the ebay ones cause its cheaper but I dont want to mess up my engine either if I have to go with the more expensive one I will.

Thanks

 

[oldman]

Stick with the stocker or spend $350 for an underdrive with dampener. With that said, it shouldn't be done for performance gains (little to speak of), it should be done to prevent the well known stocker failures.

 

[twicks69]

I would not reccomend removing the stock crank pulley unless your motor has been fully prep'd, spec'd, and balanced (rotating assembly and clutch assembly together).

Even then, I would not go with a cheap pulley.

Stick with stock; yes I know it costs more for a new one, but they are more reliable than the cheap pulleys from Ebay.

 

[GRNDSM]

I would not reccomend removing the stock crank pulley unless your motor has been fully prep'd, spec'd, and balanced (rotating assembly and clutch assembly together).

Even then, I would not go with a cheap pulley.

Stick with stock; yes I know it costs more for a new one, but they are more reliable than the cheap pulleys from Ebay.

Please do not use the balancing of the rotating assembly and an underdrive pulley (often mistakenly called a "harmonic balancer") in the same sentence... Those are completely unrelated types of "balancing" (one is balancing while the other one is damping and of two different things...).

But your overall advise is valid: if you care about your engine, ether use OEM pulley or $300+ dampers.

Unless, you do not care about your bottom end and are looking to make some kamikaze runs and you MUST have those extra 10hp .

 

[Andrew Dahms]

Do you really need the harmonic balancer that is built into the stock crank pulley if the bottom end is professionally balanced with a lighter pulley w/o the hb?

btw this is without balance shafts

 

[gsx951]

Do you really need the harmonic balancer that is built into the stock crank pulley if the bottom end is professionally balanced with a lighter pulley w/o the hb?

btw this is without balance shafts

Yes.

First, the term "balancer" is incorrect. The device on the end of the crank is a Harmonic Damper.

The function of the damper is to quell the oscillations within the crank that are created when each cylinder fires. The rod journals are offset from the main journals and when the cyliners fire, they place a torsional load on the crank. The crank winds up under this load and then springs back. If left unchecked or undamped this osccillation can and often does result in premature wear and failure in the crank shaft.
[Post #113]

It is unrelated to the balancing of your internal components.

Read This: http://www.atiperformanceproducts.com/products/dampers/101/index.htm

 

[realhp=turbo]

What would the advantages or dis-advantages be of having an underdrive pulley on an everyday driver?

 

[flyinghighlm]

Ad- I know it will allow you to free up horsepower due to parasitic drag created by everything moving around..Basically you can Rev faster, which is a good thing

Dis- Obvisiouly you will have a bit more motor vibration becuase you have pulled off the harmonic balancer/crank pulley

 

[VelocitàPaola]

Why is this in the 420A section? Does this question specifically pertain to a 2GNT?

Underdrive pulleys reduce parasitic power draw, as mentioned above, by altering the "gear" ratios between the crank pulley and the accessories. That means the accessories spin less quickly then they would stock, increasing power to the wheels.

In some cases the accessories (PS, A/C, alternator) can't cope with the loss of power, but most of the time, engineers make the stock crank pulley much too large. Thus, a reduction in size usually doesn't hurt your electrical system/AC/PS system.

On the 2GNTs, the stock pulley acts as a horrible dampener, so replacing it with a solid underdrive pulley doesn't really add much in terms of torsional crankshaft vibration.

In other words... there's really no reason not to get a UDP. Just buy it from a good company - you wouldn't want a cheap pulley shredding belts because it wasn't machined correctly.

 

[azdave]

Please read this from Unorthodox Racing website.
It explains the confusion about what the rubber ring on the stock 420A crank is there for.

Be sure to click on the link as there is much more there to read about UDPs.

http://www.unorthodoxracing.com/faq_pulleys.html

Cut and pasted from their site:
People are getting their crank pulleys confused with the harmonic dampers found on some V6 / V8 engines. "Harmonic Balancer" is a term used loosely in the automotive industry. Technically, this type of device does not exist. The "balancer" part comes from engines that are externally balanced and have a counterweight cast into the damper, hence the merging of the two terms. None of the applications we offer use a counterweight as part of the pulley, as these engines are all internally balanced.

The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that makes them look similar to a harmonic damper. The elastomer in the OEM pulley serves as an isolator, which is there to suppress natural vibration and noise from the engine itself, the A/C compressor, P/S pump, and alternator. This is what the manufacturers call NVH (Noise Vibration & Harshness) when referring to noticeable noise and vibration in the passenger compartment. It is important to note in these applications, the elastomer is inadequate in size and durability to act as an effective torsional damper. If you look at the pulleys on some imports there is no rubber to be found at all. We have samples of these, mostly from Acura/Honda, the Nissan Altima, 1.8L Eclipse, 2.3L Fords, Chrysler 2.2L's, and 1.8L VW's, to mention a few. This is not to say with our pulleys you will hear a ton of noise or feel more vibration from your engine compartment. Most owners who have installed our pulleys notice the engine actually feels smoother. This is result of replacing the heavy crank pulley with our crank pulley. NVH is variable and unique to every car. NVH will increase with the installation of an aftermarket intake and/or exhaust, for example. Think of OEM intake systems in newer cars, they use baffles and resonators in the intake to quiet all the intake noise. Aftermarket intakes eliminate these resonators and create dramatic increases in engine noise from the throttle opening and closing. So to most tuners, certain types of NVH can make the driving experience more enjoyable.

The purpose of a traditional harmonic damper is to protect against crank failure from torsional movement. This is not necessary in most modern engines because of the many advances in engine design and materials. Factors such as stroke length, displacement, inline, V configurations, piston dwell time, piston pin off-set, power output, etc., do determine when and how these harmonics and torsional movements occur.

 

[dr1665]

So yeah. What Dave said.

 

[realhp=turbo]

Thank you guys, you have essentially answered my question. And yes this does pertain to 420a nt / turbo conversion. The pulley was perchased and installed but the motor failed to start so far. Not due to the UDP obviously. I think the head gasket was installed improperly. Brand new motor and compression numbers are, 90, 20, 20, 20. Oops.

mike

 

[talonation777]

I was just wondering what people thought of the ebay underdrive pulley on there 2gnt. If anyone has/is use(d)(ing) this pulley, let me know what you think of it. A buddy of mine has it and doesn't want it some he's willing to give it to me cheap. He hasn't installed it on his car so I couldnt ask him. Let me know what you guys think and how it compares to higher end ones, such as unorthadox racing and AFX. Is it worth the money to go with the better one, or is the ebay one just as good? Please let me know, any information will be extremely helpful. Thanks!

 

[GSGoinFast]

I was just wondering what people thought of the ebay underdrive pulley on there 2gnt. If anyone has/is use(d)(ing) this pulley, let me know what you think of it. A buddy of mine has it and doesn't want it some he's willing to give it to me cheap. He hasn't installed it on his car so I couldnt ask him. Let me know what you guys think and how it compares to higher end ones, such as unorthadox racing and AFX. Is it worth the money to go with the better one, or is the ebay one just as good? Please let me know, any information will be extremely helpful. Thanks!

Well I personally wouldn't go with a knock off brand UDP, any imperfections could cause you trouble. The AFX isn't very expensive, I would just go with that. Thats just my opinion though.

 

[BigRand]

Well I personally wouldn't go with a knock off brand UDP, any imperfections could cause you trouble. The AFX isn't very expensive, I would just go with that. Thats just my opinion though.

+1, becareful with moving parts from ebay.

 

[bullettdsm]

I was just wondering what people thought of the ebay underdrive pulley on there 2gnt.

Verwy, Verwy dangerous! Out of balance pulley, makes out of balance rotational set-up, makes for rockin' and rollin' crank, makes for bad engine

IMO

MB

 

[Locke]

I hear this all the time, but I am personally curious if anybody has actually used one, or checked it's balance or centricity? It seems that everybody just assumes it may be bad, because it is a cheap no-name ebay brand, and is afraid to use it. Has anybody actually used one?

 

[VelocitàPaola]

One of my buddies used one on his Eclipse. I guess I can't really speak for its balance, but it didn't fit too well. Rather than wedging on the crank snout, it just rested there. As long as the crank bolt was removed, you could pull the thing off with your hands. It was responsible for multiple broken belts.

 

[Locke]

I can see that happening. Thank you, Paul.

 

[black97talon]

i have one i have had it on for about 5k miles been good havent had any problems with it yet

 

[Locke]

Is it an interference fit, like the OE pulley?
Thrown belts?
Who was the eBay vendor you purchased it from?

I am interested in first hand information.

 

[DBordersX]

i have one that i'm putting on today

the engine's out of the car and it's been a while since i drove the car (i blew the engine last year and i'm resurrecting her this week)

i'll have an update when i get it all put back together

sadly, i won't be able to vouch for any noticable difference since i haven't driven the car in so long but i'll be sure to note any problems or anything like that