Don't put words in my mouth. Aftermarket pulley's have not shown to be a catalyst of engine failure for our specific engine.

The stock pulley is not a harmonic dampener to remove potential damaging frequencies.

The stock pulley with the rubber dampening sandwiched between the cast iron pieces is for N/V/H and balancing of the pulley it's self. The pulley is also balanced afterward by tapping.

Torsional effects are mitigated by balancing the entire rotating assembly and adding counterweights to the crank. No external balancing was necessary.

Engineers that work on designing and manufacturing factory engines have advanced engineering to the point where in most cases, external balancing and/or harmonic dampeners aren't necessary.

I don't take your quotes out of context, please award me the same.

Just to add some more data into the debate, here is the US patent for a plastic hub torsional harmonic damper which has some good graphs that illustrate the effect on crankshaft twist in degrees vs engine RPM for various damper configurations including no damper.

Even if the engine is perfectly balanced there will always be torsional pulses which can and do form harmonic modes as a result of the discrete, not continuous combustion pulses (each cylinder firing in turn). Balancing the entire rotating assembly will not stop rotational twist of the shaft from the power pulse as each cylinder fires. It will stop out of axis oscillation.

The pulley being made out of cast iron is also on purpose, cast iron has one of the highest dampening capacities (google cast iron damping) of any metal.

If you don't want to read the whole document look at Figure 2 to see the effect on torrosional vibration via a typical damper (construction shown in Figure 1)

Love how everyone still skirts around the facts that these lightweight pullies to the crank...

Good info. It's the reason why I used the word mitigate. But was als curious about why iron is used and was thinking that in the back of my head.

Of course not. This isn't a 'grenade the engine in 15K miles' sort of issue. It will be extremely subtle and dependent on driving style. The resonance range is probably <500rpms.

source?

There's no question that the stock pulley gives the complete system a lower Q factor than any of the aftermarket pulleys available. Cast iron and rubber are unquestionably more efficient at translating vibration to thermal energy. Hysteresis loss is far higher in an iron/rubber assembly, vs an aluminum one.




The internal balance you describe is insufficient to completely mitigate the need for the damping we are discussion.

I'd love to see a source for the bolded part.


external balancing is not the same thing, and it is more or less impossible to completely eliminate the need for an external damper while still achieving the reliability levels expected from modern cars.


you keep saying this as a fact...I'd imagine it would be hard to determine this just by looking at it...:confused:

link? preferably with something other than a vendor backing the claim.

I'd be confused as to why a pulley needed a "harmonic dampener of sorts"

The rubber looks to be intact on all the high-mileage Z's I've seen. There's actually a lot of effort put into finding good materials to use in these applications.


Serious question--do you have any background that makes you qualified to discuss resonance? I'm curious what you are basing the bolded portion on. It would be quite impressive to be able to look at that component and visually determine that it did not serve any purpose in damping vibration.


The lack of directly linked catastrophic failures really doesn't show much. Most folks don't drive their Z's much, and the effects of mild, occasional impacts will manifest themselves slowly.


I absolutely agree with the first statement here. Data is in the numbers. Would be fantastic if a pulley vendor gave us a graph of the frequency response of the crankshaft with each pulley installed. THAT would tell you something.


Engines have evolved, but the physics behind resonance haven't.





Cool link. Pretty crazy to look at old patents and realize how much of the work was done through trial and error.

If you don't install them I may take them off your hands if the price is right, I just have the normal size stillen crankshaft pulley, I wouldn't mind having an under driven set :tup: something to think about.


Sent from my iPizzle using magic and new-fangled science stuff

I said I was gonna lowball him first!!! Lol

from what i read OP is that pulley mods will give you like 2-3whp in 1st gear, 1-2whp in 2nd, and 3rd all gains are negated from the underdrive pulley

honestly it isnt worth the money and the risk, if you want better throttle response, buy a light weight flywheel or have up rev change the throttle tables

the only situation i can see a pulley being worth the money is when you are building an N/A race car and you were given the car for free and given a budget to spend on building the car, then picking up 3whp here and there will add up and might give you the upper hand in the race

Again, this is arguably the most polarizing issue here on the forum, and we ain't getting anywhere quickly

Let's leave it to the car owners to install of not install these... If anyone bought a kit and feels it's unsafe, feel free to contact me and I'll lowball you for a quick sale, LOL :tup:

I'm not an engineer although I'd really like to think I am... If these REALLY caused premature failure in ANY WAY, SHAPE, OR FORM, there would be overwhelming evidence showing that... We unfortunately are all ASSuming what counterweight this, harmonic that, and pulling quotes from the Internet and other forums, which can be the LEAST reliable sources of information...
I DO believe and will state again that shítty install causes pulley issues...

I have a Stillen 20% under drive, would I ever take it off? No, will I continue to install one on every car I own? Yes
Hell, I already have a kit for the Maxima I am forcing my dad to buy, lol


Some of us (7AT) don't have a flywheel, and it's also about removing rotational mass, so the car feels peppier. I try to explain it as, "Have you ever driven a car with a lightweight flywheel? Well this is like 10% as much as that does"


If it makes díck difference, I'll ask my best friend's dad who IS an engine engineer (for Cummins diesel though) if he has any input

absolutely. I don't give a crap what you do to your car, but I do think it is important that others making this decision have the requisite information.

Most modifications are not done for reliability, and it is absolutely up to the owner to decide what is worth it for them.

This piece is something I don't agree with. First of, I'm not assuming anything, or basing my stance on what I read on some random internet site. I've got a pretty decent background in frequency response of systems (admittedly not in the mechanical domain, but the math is all the same), and a basic understanding of physics. Most of this stuff is pretty basic physics 101 (OK, maybe 201).

To poke holes in the claim that "if this caused failures, we'd have OVERWHELMING EVIDENCE proving it," let me present the following:

As someone who understands cars, your forehead would probably leave an imprint on your desk/keyboard if someone came on the forum and made such a claim. It's an absolutely ridiculous statement (though it does seem these cars will run for a surprising amount of time with no intake filters, who knew?)

Unfortunately, the general populace is poorly educated on things like frequency response of a system, compared to the intake operation of a combustion image.

To be clear, as I've said before, I'm not sure how dramatic of an effect removing this part will have. But again, neither does anyone else who hasn't modeled the part.

Removing it may shorten the life of the engine by 80%, or 3%. In all likelihood, you'll have the part on for 30-50K max, and no failures will ever be linked back directly to the pulley.

The point here is twofold:

1) Let's make sure we paint the whole story to those who might consider this part. Evidence of operation without failure is great to share, and helpful in establishing just how much the part matters (or doesn't). Pretending like the 3-4 guys that have more than 25K with a pulley unquestionably establish the reliability is silly

2)Don't be a lemming. There's no reason we shouldn't demand more information from pulley manufacturers to show that they've done their homework. It might be enlightening.


that could actually be enlightening. See if you can get him to sign up on the forum.

^rep added

I agree with most of what Red_Zed has said


Again, if it was a piece that really ruined the engine, we WOULD see at least ONE damn failure or engine blowing up, lol
I have seen a broken pulley due to shite installation...
Just saying that at least if the parts were made bad we'd have more than ONE failure... But I don't think we do... And a lot of us BEAT on our cars, people track with them too


And about the harmonics thing, (again, I'm not an engineer) but lets be real, cast iron isn't a precise science, under heat it can expand and stretch more UNEVENLY than billet aluminum, messing with those harmonics, yeah, 8k RPMs is fast, but I think the amount of play in the pulley will be there with out without that BS rubber band...

Ex: most people think glass is a solid... Watch Mythbusters where they break wine glasses with sound, that bítch bends and wobbles as much as any liquid I have seen (yeah for the record, glass is more a liquid btw) so what makes us think the unrefined MASS produced pulley doesn't wobble that much...


And I also think it's one of those scenarios where the manufacturer tries to make things NICE...
They TRY to make the intake boxes flush, they try (maybe not in our cars) to make them quiet (the exhaust is), they Make the engine mounts and trans mounts rubber... Things like that...
And I bet those intake boxes were "engineered" 15-100 times more than any Stillen, AEM, or Takeda intake, why? To make it quiet or nice looking...

Replace those bushings and intakes and exhausts, the car gets louder, it becomes sharper, you get more power... (they make the car for the 90%, not us forum ássholes 10%, lol)

:yum:



;)

^^ Just to correct an error so people don't get wrong info, Cast Iron has a CTE (Coefficient of thermal expansion) of 5.8 10e-6 in/in deg F, Aluminum 6061 or 7075 has a CTE of ~13.0 10e-6 in/in deg F, (not picking on you DE) the cast iron actually expands less than the billet aluminum by about half as much.

... Maybe with a nice quality piece of cast iron... That POS the crank pulley is made from... Mehhhhhh... I bet it expands more, or more importantly, unevenly vs aluminum

(That's more what I meant, the uneven expansion in shítty cast iron)

I'm going to sleep now at 6AM hopefully.

You guys have fun beating this dead áss horse, and when I wake up I'll jump in again too! YAY!!! Lol

Well, I'm sure we will see pulley-attributed failure, eventually, if the threads aren't out there already waiting to be found. Some will be installation issues, and some will be choosing the easy target when the real cause of engine failure hasn't been accurately determined and they want a scapegoat. Separating out the true pulley-induced failures over the internet would be difficult in itself.

My engine's at ~34K miles now, with over 2K of that as track miles. I've had Stillen's 20% underdrive pulley on for most of the engine's life, and not had any issues so far as I can tell. I think it's probably reasonable to assume, although certainly not proven, that altering the weight there could at least wear out some bearings faster, as mentioned above. Does it make a 5% difference or more? No idea. If anyone's done the engineering study to figure that out, you'd think it would be the pulley mfgs.

I also question why people never bitch about swapping in lightweight flywheels as much as they bitch about this mod. The flywheel would be at least as important in terms of balance (but maybe not so much damping), and is far more difficult (and critical) to balance correctly when manufactured.

If you're on the fence (not because the data's on the fence, but because nobody here really has conclusive information), my gut feeling is that even if you believe the worst, it's probably even safer on a 7AT car than a 6MT car, as the 7AT has the crankshaft coupled to the Torque Convertor, which probably acts as a huge fluid damper most of the time anyways.

The most-legitimate reason I've seen to fear this mod so far is what GTM documented and others have verified (and makes basic sense): these Al pulleys will often weld themselves to the crankshaft over time. Dissimilar metals and heat and a tight fit and constant rotational torque, etc. If you ever want to take that pulley off again (e.g. to do some engine-internals work... or I think it also has to come off to replace the oil pump) or plan to go FI (which probably ups the harmonics risks and makes it pointless to worry about little things like pulleys), you need to be aware that removing the Al pulley could be very very difficult and require some serious heat and torque.

A lightweight flywheel does not balance anything. Our cars use a dual mass flywheel to eliminate gear chatter and and make it easier, smoother to get going.

well im just giving OP my opinion on the mod, from what i have read on mustang forums, LS1tech, honda forums, other nissan forums, ect. that underdrive pulleys are generally not worth the money in the same sense that headers are not worth the money and i have read about pulley attributed damage(whether or not it was cause of bad installation is a whole other story) and honestly it doesnt seem like a risk I would be willing to take for just 2-3whp in first gear(again from what i have read whether its Z related or other car related)

if someone likes swapping pulleys on their vehicle, then more power to them, if OP decides to put an underdrive pulley on his car, then more power to them
i personally wouldnt swap pulleys on my car, but thats just my $0.02

Here is the issue regarding arguing my points. There isn't an aftermarket company on the planet that has the R&D of a car manufacturer. Due to the nature of the industry, Most Engineers that design cars are not going to expound in much detail, if at all on why they may have done things a certain way. There is plenty of research on resonance, torsion, N/V/H, and negative harmonics because it's already a known. Most of my findings are from manufacturers, but also reading about the issue at hand. I haven't read a single cited source that has said specifically, the way our pulley was designed, that it is a dampener of potentially destructive harmonics. Every description and engineering paper I read shows a rubber dampener that is encased with the rubber set vertical, or viscous. Ours is horizontal to the motor and only about 5mm thick. It looks like it's preventing all the accessories from vibrating or introducing more N/V/H to the crank as opposed to removing bad harmonics from the engine itself.

Every car company is going to say, leave your engine alone and it will be fine. Every aftermarket company that makes parts for said manufacturer is going to say, "Buy this and it will be even better" Who do you believe? Forums like this is feedback from everyone. I said it before, take everything you read in here with a grain of salt. Yes, even everything I say and argue about, which I admittedly do a lot sometimes. I'm not out to convince the World, but there are always two sides to the story. Obviously, it's difficult to go wrong with a stock crank pulley. I 100% agree. I also believe a well engineered aftermarket crank pulley can be safe to use. Some do not. People ask why, we say what we think, preferably have relevant source material to back our findings. Could I be wrong? Absolutely. Is the Bible indisputable fact? Do you believe every animal floated around Noah's ARK for months and the entire Earth flooded?

I used the word mitigate because regardless of internal or external balancing, spin a motor fast enough and even the best motors can grenade to harmonics. If Nissan plans on spinning the VQ to 9-10,000 rpm or higher, I'm pretty sure we would see a different crank pulley, maybe to a true dampener.

FYI, I never stated my finding's as absolute facts. I listed my arguments to the topic.

Regarding my statement about external balancing not being necessary, it is absolutely true for some smaller displacement motors. I think the VQ fits in this category, but there is room for argument there.

Lastly, and I'm repeating myself, DO YOUR OWN HOMEWORK AND COME UP WITH YOUR OWN CONCLUSION!!! I'm tired of people giving recommendations like it's fact and not letting them decide for themselves by only giving them one side of the argument.

Just a FYI, the DE motors use the same crank as ours, on an old Maxima DE of all engines, so it just adds to my skepticism

Link of the pic: 3rd gen VQ35DE Full ECU Swap Progress Thread - Maxima Forums

How do you determine that from looking at it?



wat?


We are not discussing balancing.



Got it. I guess I am misreading these posts then:

Dear lord please show me the engineers that have figured out how to remove the harmonics. For some reason they still haven't filed a patent, and I need to beat them to it.
"non-existent super dangerous vibrations"...Please explain this one.


:rolleyes:




Still not discussing balancing.


I guess you failed to read the post you replied to. Shocker.

Guys, I doubt either of us are actually ássholes, I bet this thread will get locked


Please lets take a step back, smoke a cigarette, pop a pill, whatever we need to do to relax, lol


AT THE END OF THE DAY, NONE OF US ARE ENGINEERS WHO WORKED ON THIS MOTOR

OP, AND TO ANYONE ELSE WHO WANTS TO INSTALL A LIGHTWEIGHT/UD PULLEY, ITSTALL IT AT YOUR OWN RISK!

We have provided enough data and opinions and such to last a lifetime, and to anyone thinking about it, use google, lol

even without being an engineer, i know what happens when u mate 2 different metals with 2 melting/annealing points. but hey, i'll go ahead and stop mentioning it

How long will it take for the metals to melt into each other?

How about this Red, you prove me wrong, I know how you love to try, so go ahead. I'm waiting.

Just to add some thought to those discussing AL melting points...

For the NST Pulley:

http://www.nonstoptuning.com/images/...13710KRG-2.jpg
From: http://www.the370z.com/engine-drivet...no-charts.html OP

There is a Steel sleeve around the internal part of the pulley. Won't that prevent some of the fusing you guys are projecting as a potential fail point?

Not trolling, this is what I was told that makes NST sets better than most.

I'm not saying you're wrong, I'm just saying you don't know enough to take the stance you are taking with any sort of authority.

Nobody here knows much about this, and the stance I've taken from the beginning is exactly that.

The steel sleeve is for just that reason companies that don't put that much thought into this issue will have an issue with the metals fusing as stated above. And no i dont have an exact time from on how long this takes to occur

with all the given controversy as it is, WHY even risk it to gain a neglegable amount of power?? why risk it?

I think the answer I saw earlier in the discussion was "because racecar"

If it seems like that, that's not the case. I'm no authority and I'm all for differing opinions. I don't like when it starts feeling like a personal attack because we hold opinions. But I'm happy to take a stance.

It doesn't help this is probably the most opinionated modification.

I think posts like the below leave potential for someone to believe you are speaking fact, rather than your opinion.

The way the bolded reads, there isn't room for another thought. The statement that it is not a harmonic damper is actually wrong--we just don't know whether it is an important harmonic damper

All I'm seeking to do is clarify the reality for anyone that is confused and considering the mod.

Honestly, like I said before, I didn't really do it for power.

I did it because I noticed a distinct improvement of engine response, and smoother revs. Power gain was minimal, but a bonus. Plus in terms of other mod/hp (intake/exhaust) it was fairly cheap.

And my experience has been the same with anything down to a recently searched thought on 7AT fluid changes, it all comes down to who does it. If installed properly, potential for failure is minimal. If installed improperly, potential for failure is exponential. Just my :twocents:

I agree 100%

I don't know why edub cares so much what the rest of us do with our cars
Turbocharging and supercharging will destroy the engine MUCH quicker than a pulley, probably much quicker than the metals fusing to each other



Guys, this thread has gone too far
We're still not getting anywhere

Lets cut our losses

:iagree:

Stillen has the ring too

Just because I've been really enjoying the discussion.

I think it's about time to toss this old classic into the mix:

JAY.mp4 video by GTMPOWER | Photobucket

Is it because there wasn't a steel sleeve?

Unorthodox Racing... Not Stillen/NST

No mention of Steel Sleeve in advertising, and no pictures of the backside of the pulley.

From: http://www.the370z.com/drivetrain-en...check-out.html
:ugh2:


Off the record though, classic as it may be that isn't a VQ37... So it's not representative of this specific platform. Why? Because impact wrench.

THANK YOU!

I had been looking for that vid since this thread started. and while its not a vq37, its still a good representation of what happens when mating to unlike materials

Just to address an issue brought up in several posts "The rubber annular ring is only about 5mm thick, it can't fix or do ___X____"

This ring sets up a torsional "lag" between the inner and outer cast iron pieces, the thickness along with the durometer of the rubber dictates the response of the torsional damper. This thickness would be calculated to dampen in the target frequency (RPM) range.

The ring itself is not doing to dampening directly, it is coupling the inner and outer masses which as an entire system does the damping it really is a case of the result is more than the sum of its parts, it's how they work together.