pulley...
 

http://www.nonstoptuning.com/pKitNis350.htm

10% underdrive sounds tempting....

Pullies typically get panned here, but I was curious about these, so I did some reading.

Here's a long thread on the 370z forums. The 370z shares the same crank & alternator pullies as the HR 350z, so the NST parts are identical:

http://www.the*370z.com/engine-drive...no-charts.html

(remove the * in the url above....)

NST claims that the OEM belt can be used, but many people are claiming it is too loose. Some are even claiming the tensioner is putting zero tension on the belt, and they can slide it off w/o de-tensioning. Lots of people are going with a 786 Gates belt as a result: http://www.amazon.com/Gates-K070786-.../dp/B001C9C00G

While the pullies are the same between the 350/370, I am still unclear as to whether the belts are. Even if the belts ARE the same, it could be possible that it fits tighter/looser on the 350 vs the 370....anybody know for sure? My guess is the mounting point on the block is the same between the two, so the belts should fit identically as well....

Leaking front crank seal -- this seems to be more a result of improper installation than the part itself. It takes a ton of torque to get the OEM pulley off, and this is likely where the front seal is damaged....too much man-handling. Install with an impact wrench is recommended so as to not put undue stress on the front seal.

It's 10% vs Stillen's 20%, but NST is claiming that the difference in whp is probably at or less than 1hp, but that theirs will not suffer from dimmed lights, etc. They include a 10% overdrive alternator pulley with the kit, so that the alternator will maintain OEM speed/rotations.

The local nissan dealer has these hanging on the wall. asked the parts guru about this problem he said he didn't know about it but if there was any problem he would give me a belt. Gonna be picking up a set, I'll let you guys know what i find on my HR. Just gotta decide between red or black...

Just FYI, I have had the Stillen Underdrive Pulley on my HR for close to 8k miles without a single issue. No dimming of lights or anything. It was installed with an impact gun. I will add though that I had it dynoed by Zfever here in Tampa with my Osiris Tune and it netted a whopping .5 whp. I dont know if it was worth all the trouble. If you are looking for every little bit of whp, then go for it!!!

10% is not even worth mentioning to be perfectly honest - you'll never feel it, particularly on a car with near/at stock redline limit. Neither is 20%, at least on a VQ. The real differences are felt with significant under driving of the pulley, but none are available for the HR that I've seen

I know the gains will be .5-1 HP, but I'll be buying them anyway. Just trying to get ALL the bolt-ons and a tune just to see what it can do before i rip into the block.

skip the pulley, do the tune..your results will be the same

Only reason I ask is because on my 06(Revup) i had OR underdrive pulley and it never gave me a problem. Yes, the horsepower increase was not that great, but the overall feel of the revving of the motor was awesome! It revved a little faster, a litter crisper and it just wanted to fly to the top of the RPM range. I miss that, if I could have that feelingback I would totally get this or even Stillen.

Join Date: Jul 2005

After 6 years maybe you should get one.

^^
only reason I havnt is because I've heard some horror stories of it causing major issues. Not sure if those issues are solved yet.

I have a NIB stillen underdrive pulley for the HR with the correct belt. I'd like to get rid of it. I chickened out on using it.

We can work something out.

Zim

Would a tune on a bone stock Z yield anything worth mentioning? Say an uprev tune...?

Not worth the trouble and money IMO.

If it's going to be your only mod, what's the point?

Hey Adam. So pulleys may have been shown to have a negligible effect on whp. But there's still the other aspect -- less mass = faster revs. Same effect as a lightweight fly, really. What's your take on this? It's obviously harder to measure objectively. Would losing 3lbs of pulley mass have roughly the same effect as losing 3lbs of flywheel mass?

I've been biting my tongue for a while....but you're probably adding more useless posts to this forum than anybody.

A lot of the time, you're right...some threads get old. But on the other hand, the forum would have almost no activity otherwise. I for one don't mind reading about things I feel I already know about, because even things you think you know well you can occasionally learn something new about...technology does advance, you know.

In this case, it seems like you are going out of your way to call somebody out on something. I also love how you dig up threads created years ago that haven't been touched in ages, just to call out people who probably don't even own a 350z any more....

Not trying to get personal or anything. Some of your posts are quite beneficial. But it bothers me that when I click on ANY thread in this forum my first thought is "I wonder if davidv is talking **** already". Anyways, it's a free world and you can obviously continue on if you want. But I'm sure I'm not the only one that feels this way. /rant

I can't count the times I've thought the same thing.

Yes, a lightweight pulley can be used for better engine response. But it's all a balancing act. When my engine was stock, the lightweight pulley worked quite nicely, and I was able to feel the change. I never had a lightweight flywheel on that engine. Then I used a new lightweight pulley combined with lightweight flywheel when we installed my built engine. Engine response was great but the clutch was difficult to drive - moreso than I was expecting. We eventually switched to a heavier than stock pulley (ATI) but it also had the increased benefit (for me) of being more underdriven vs stock, and more than the UR underdrive pulley I had previously been using. This paid nice benefits down low because the increased mass helped ease the driveability of the clutch. The increased underdrive nature of the ATI helped the power up top not fall off quite as much. Increasing the underdrive only pays dividends with a substantially increased redline, so for a stock engine, or even one with a flashed ecu and slightly bumped redline, it's probably not going to be worth it.

We would need someone with more of an engineering background (I can ask Kwame, or maybe Resolute on the forum) to know if the net change would be the same if mass is removed on either end of the crank. At first glance, I'd guess it could also have to do with the diameter of the item you're removing the mass from. For example, 3 lbs from the pulley is ~50% of its total weight. 3 lbs from a stock flywheel is ~10%. I would guess this might make a difference, but I'm not sure

That's pretty much what I was expecting. Good catch on the diameter...I've read of pullies that are 50-80% lighter, but that mass is all coming from a relatively short radius from the crank. I'd guess that in that regard, removing 3lbs of weight from a pulley would have LESS of an impact than removing 3lbs from a lightweight fly.

But mass is still mass....the question is, is it enough to notice. I can certainly see how a lightweight pulley and flywheel would be too much. Some people hate the feel of a lightweight fly even by itself.

What is important is where you remove mass as distance from the axis of rotation. It changes with the square of that distance. So 1 lb from 5 inches from the cranck is 4 times less important than 1 lb 10 inches fAr

Right. But it's very difficult to get the specs on weight distribution in that regard. I was just speculating that since a flywheel's diameter is so much larger, any weight reduction to it has a very good chance of being further from the crank than a pulley.