Dude,
Wow what a question. I didnt know the answer logic would tell me that if it is balanced with the pulley on for a crank driven cooling fan, changing it to an eletric driven fan, well we would start this discussion all over again. I sent an email to a buddy with Infiniti in Atlanta. He has heard where people are putting electric fans on the cars, basically the same setup as the coupe and just eliminating the conventional fan all together.
To answer your question exactly, the engines are balanced with the pulley for a crank driven fan, and balanced with the electric fan pulley on it for the coupes. My advice, if this is what your asking. leave the OEM crank pulley on your sedan, take the fan off, just bolt the pulley to the water pump and run the regular belt. Get an electric fan set up with the water temp sensor and run it that way. i dont know if the sedans have the connectors for the sensor or not. Maybe........Did this answer any of your questions? After reading it myself I kinda got lost....

Infiniti Gearhead

 

Well, it's a little more complicated than that...

I summon....DaveO ! !

(stop your lurking Dave... I know you're there!)

-Ted




'03.5 Sedan 5a: BS/G, Prem, Aero/Body, Sport, Nav
Click for MODS or Vote at Online Showoff

 

OK Ted.

I find the adult comments and discussions contained in this thread to be very interesting. For now I remain in a "hide in the weeds and watch" mode on the underdrive pulley issue.

Regarding the fan conversion. While the AT Sedan's mechanical fan is driven off the crank pulley, it's actually mounted on what Infiniti refers to as the fan pulley. On the MT Sedan, Coupe and 350Zs this device is identified as an idler pulley.

IMO, the chance that Nissan/Infiniti balances an AT Sedan engine differently than the others is practically nonexistent. Therefore, the stock engine's harmonic dampener/crank pulley is designed to handle any additional rotational loads or harmonics the mechanical fan provides. (By the way the mechanical fan assembly is heavier than I thought it would be.) Changing it out for an electric fan has worked very well for me.

Back to lurking for now.


DaveO - 2003 G35 Sedan / DP / Willow / AT / Premium / Sport
350Z Engine Cover, T-Stat & Air Duct / Stillen CAI
GG 7-Wire H-G Kit / TS ECM / E-Fans
Street Edge TC / B&M Cooler / Stillen Exhaust

 

Hey Dave0,
You are right, I think I misunderstood his question all together. I thought he was asking something totally different....

Infiniti Gearhead

 

So wouldn't a supercharger added to the crank load make for the most severe balance and harmonic variance from stock. What happenes to cranks under the add'l load of SCing??

Under the thoery line's of PRO pulley people, the rationale sounds like - if you can supercharge it, you can certainly put a smaller pulley on it. I certainly need help understanding whether adding a pulley and belt is altogether different than changing the mass/size of the crank pully? Bueller....



2003.5 DP 5AT Sedan (E-thing but Nav)
14.2 @ 97.18
Injen CAI
10 Wire Hyper-Ground
Crawford Plenum (V4)
UR Crank Pulley
Polk ex-3500 Tweeter Upgrade/Shock Sensor/H-Liner Under Hood

 

DaveO, please jump in here and take some of the burden off of me. Please.

A quick futile attempt to "justify" a supercharger specifically for sixfive...

The supercharger runs off of the stock pulley. That pulley is harmonically damped. The harmonics from the supercharger "should" be compensated for by the stock pulley. The problem with the supercharger is that our cars are designed (for the most part) for 280bhp PLUS some amount of tolerance. That tolerance might be 10-25% (could be more or less for all I know) however the superchargers are adding over 30% more horsepower at the crank. This causes problems with many of the components because they are not designed to handle loads of this caliber.

Eagle1 has made an educated guess at 80% engine life reduction (which might be generous), but if the VQ is designed for 250,000 miles, that 80% leaves 200,000 miles of really fun driving.

I'm really going out on a limb here, because superchargers are so much more involved than simply replacing a heavy, harmonically damped pulley with a lighter, non damped underdrive pulley. Also, you don't pay me enough money for the real analysis/answer... [img]/w3timages/icons/tongue.gif[/img]

300bhp??? We'll see... 5-22-2004

 

Has anyone ever told you, you think too much

Infiniti Gearhead

 

Has anyone with a supercharger done an oil analysis. Zimbo, dollar, etc.? I'm sure that the supercharger would, by itself, cause more wear on the bearings but if they are within reason...

 

neffster,

I fundamentally agree with your statement... "The supercharger runs off of the stock pulley. That pulley is harmonically damped. The harmonics from the supercharger "should" be compensated for by the stock pulley."

I've just started Corky Bell's book "Supercharged". Chapter 14 - "Drive Mechanisms" is loaded with interesting information. He talks about drive pulley requirements but not dynamic loads or harmonic dampening. (Hopefully I didn't miss it.) Since he seemed so thorough when I read his first book, "Maximum Boost", he evidently didn't think it was a major issue.

Additionally, I believe you need to continue expressing your well thought out opinions backed by sound engineering principles. While I may not necessarily agree with you in all areas, I do feel good opinions and quality information helps make good decisions.

A final point. Your math doesn't work out for me. If an engine's expected life is 250k miles and a supercharger reduces it by 80%, aren't you left with 50k miles? Hopefully Ed and your estimates prove to be very conservative.


DaveO - 2003 G35 Sedan / DP / Willow / AT / Premium / Sport
350Z Engine Cover, T-Stat & Air Duct / Stillen CAI
GG 7-Wire H-G Kit / TS ECM / E-Fans
Street Edge TC / B&M Cooler / Stillen Exhaust

 

Clarification...

DaveO, my post should have read a 20% engine life reduction. I did the quick math in my head and took 250000 and multiplied by 0.8 to get 200000 miles. The 0.8 translated into 80% in my post. doh... [img]/w3timages/icons/tongue.gif[/img].

I think I'm done with my pulley debacle. Thanks to everyone who made this an interesting discussion.

300bhp??? We'll see... 5-22-2004

 

Ok....this is trully a great thread and I have learned alot by just spending the time reading all of the great posts!

I have a UR pulley sitting in a box and was scheduled to have it installed next week Wednesday (by a pro mechanic) until this thread came out. Such a dilemma.....do I take a risk?

So I called my guy from Stillen and asked a few questions about the harmonic dampening and balance and potential issues of the pulley causing wear on the bearings.

**I don't know how true this information is since the motivation of Stillen or any other retailer is to sell stuff but I want to see what others think about what he told me...**

He told me that Stillen is one of the largest distributors of UR pulleys and have sold "thousands" of UR underdrive crank pulleys. He says they have had NO, NOT ONE complaint or report about engine bearing wear from excessive vibration from the UR crank pulley in the "thousands" they have sold.

He did mention that there could be potential problems if the pulley WAS NOT from UR as he said there are cheaper imitation pulleys from specifically Taiwan that utilizes cheaper materials and may not be completely balanced like the UR is supposed to be.

I asked about the small rubber ring on the stock pulley and if not having the rubber dampener on the UR pulley would make a significant difference in excessive vibration and premature bearing wear.

He said (and I don't know is this is true or not but he sounded confident in his answer) that the stock pulley has the very small rubber ring b/c the stock pulley is heavier, is made up of a cheaper material (vs. the aluminum craftmanship of the UR pulley), and that the stock pulley IS NOT COMPLETELY 100% BALANCED??? (True?) Therefore, the stock pulley has the TINY rubber ring to compensate/dampen for the heavier, more cheaply material construction and balance issues.

BUT, since the UR pulley is COMPLETELY balanced and is constructed of high-quality milleted (sp?) aluminum, there is no reason for the TINY rubber ring IF INSTALLED CORRECTLY.

Now, this makes sense to me but I'm no educated or trained engineer or material science PhD. I am only a lowly medical physician and they don't teach this stuff in medical school, just blood and guts stuff.

He then informed me that if I had any further questions, to call UR directly. UR's number for everyone's sake is 631-586-9525.

Can I get some feedback from everyone on this latest info I received? I am keeping my UR pulley install appt. for next week for now until I decide on the validity of this info from a Stillen rep. He happily stated I could return it if I wanted or changed my mind.


Thanks,
docron1

 

Return it to Stillen at your expense and with a restocking
fee! HeHe. Stillen does nothing fro free.........LOL

2003 TwBlue 5AT Sedan, sunroof,
Graphite Leather, splashguards, HKS exhaust,
14 wire Grounding kit, 350Z duct, Stillen CAI
Underbody rear diffusers, Drilled alum pedals

 

I would agree with Cato here. If your real hungry for the five horsepower you gain, but will never feel, go for it. Just ask yourself one question: Is it worth it?

Infiniti Gearhead

 

"this makes sense to me but I'm no educated or trained engineer or material science PhD."

Neither is Stillen. He's an entrepeneur. You probably will never have a problem with it. But is 5 HP worth the risk that you might? And some have had problems I'm sure. Here's the scenario:

You buy a G35 and throw a pulley on her, drive her around for 4 years, then sell. But you want to sell the pulley on ebay, or use it for an ashtray, or whatever, so you take the pulley off because you don't want the buyer to think you rode your G hard and put her away wet, so the buyer drives her around for a few years and maybe totals it, or maybe has bearing problems and takes her into the shop where they find they need new bearings. Well, how does that soul know to call Stillen? You took the pulley off. The bearing wear doesn't happen in a day. And it probably won't happen in the time you own her, but God forbid you driver around for 4 years and fall in love with her and your oil analysis starts to show lots of lead.

Stillen, UR, and everyone else keeps saying "no one has had a problem yet" Bull. No one has called THEM yet. That doesn't mean no one has had a problem anymore than it means that holding a pencil over my head prevents tiger attack (Simpson's fans can laugh here).





2004.5 Coupe/5AT/Ivory/Everything but chin spoiler/Z Tube-Popcharger/Crawford V5 Plenum on the way

 

"Stillen, UR, and everyone else keeps saying "no one has had a problem yet" Bull. No one has called THEM yet."

I have to disagree with your point here. When someone has a problem with a part, they invariably post either to vent or seek help from the other forum members. Just in the recent past, I can recall complaints (here, FA, my350z) regarding:
1. the rogue and b&m shifters
2. kinetix plenum, cats
3. injen, nismo exhausts
4. rt cats
5. hawk brake pads
6. tein coilovers
... you get my drift.

Even though most of us would agree that vendors are in general, honest, there is an obvious conflict of interest in proclaiming their products to be defective. However, I don't think any of the forum members would be so reticent to come forward if they ever had a problem with a pulley.

Cat, if you had a problem with a pulley, would you not contact the seller/manufacturer and post here to warn your fellow enthusiasts? If you wouldn't, could you tell us why?