If had an options, which one would you get and why?

 

i'd do headers
cuz its the biggest job ever
lol

 

headers... more power you can feel.

 

...because they look pretty.

 

nice pictures

 

crank pulley 100%
You will feel the increase in power in every gear and throughout the entire RPM range. It is cheaper, and MUCH easier to install.

headers barely made any difference in power or sound. a little mid to upper RPM gains, but nothing worth the trouble/$ of install.

Edit:
Also, when you realize N/A isn't all that it's cracked up to be, you won't have to take the crank pulley off when you install your turbo kit.

 

Headers all the way !

Pulleys have a bad reputation of sometimes have nasty vibration issues on some engines.

 

Crank pulley-its an easy 45 minute install. Save yourself hundreds. I have yet to see an independant dyno prove that headers add power to bolt-on Z's with STOCK cams. I believe stock headers flow very well, and many other people in the past have PM'd me saying "your right I gained nothing to very little on the dyno with my headers" Take it for what its worth

 

Please do a bit more research before you make statements like that. Tons of people run crank pulleys on Zs without issue.

FYI, the stock pulley does not have a harmonic dampner on it.

 

+1 I have had the UR CP for over 30K miles with the 7100rpm limit with no issues at all...

 

Good for you guys.

But it will take more than "I've hade it for XX miles with no problems" to satisfy someone who actually works in automotive design and has read real papers on the subject.

I don't want to highjack this thread, the subject has been discussed often enough. The OP asked our opinion, I gave mine.

 

Your arguement holds no water. If anything, reducing the rotating mass with the pulley takes stress off the motor. As long as the pulley is balanced, there is no issue. I know people that have built motors reported that the UR was very well balanced.

And again, the stock pulley does not have a harmonic dampner on it, so it is bascially just a heavy UR pulley. Besides, the VQ is internally balanced. If the crank pulley was such a potential issue, you could say the exact same thing about a lightened flywheel. It is basically the same thing as a crank pulley, just spinning off the other end of the motor.

Get you facts straight.

All that said, if you have fear of a crank pulley, I would do nether. headers just aren't worth the trouble of install.

 

What argument did I state? I didn't say anything!
Who said anything about lightned flywheels ? (these are actually less "bad" than UR pulleys)
And since when a rotating mass at the end of a shaft doesn't affect harmonic resonnance? Did physics change over the holydays?

A crank shaft twists back and forth all the time in an internal combustion engine. These oscilliations will resonnate along the shaft and combine with other oscilliation from the combustion in the other cylinders. Changing the natural frequency of the crank shaft assembly (with a lighter pulley or flywheel) will have different effect on the resonnances. Exactly what happens then, we don't know. Do aftermarket manufacturer test these engines with their own lightenent pulley? I don't think so. Did the engine manufacturer test it's engine's frenquencies? You bet they did!

The engine will certainly run a long time with no problem with a lighter pulley. Hopefully beyond the car's service life. If it does, great.

IMO, I think it's not the best way to improve an engine's perfomance.

The OP already has a header-back exhaust installed on his car. The headers would be most beneficial in his case.

 

HEADERS... WAY MORE POWER and sounds alot better!

 

Not sure about either headers or pulley.

All I know is that most pulley's that gain hp, actually are benifiting from not running the components they are driving the same RPM. Thus, less power is used to say run the alternator, not sure this is really a good thing to do? I know for sure if you have a turbo you can't do it.
They do make stock diameter pulley's that are lighter, yet I think you would gain more by getting a new flywheel that is lightwieght.

 

Your statement above is all speculation. The VQ is an internally balanced engine. Changing the crank pulley is essentially the same as changing a flywheel. If what you are saying about 'engine frequencies" was true, the VQ would be equiped with a harmonic dampner which it is not. Also, if what you are saying is true, any aftermarket part could potentially cauase the same issue as parts like plenums, headers, exhaust, etc and especially for people with built motors and cams definitely change the power delivery and frequencies at given RPMs.

In terms of gains. I ran them on my car with intake, test pipes, plenum and exhaust. headers made very minimal gains that couldn't be felt. In addition, they had litterely no impact on the exhaust note.

 

You're basically saying that building a VQ35 to output 350-400hp has no effect on reliability?

Any modifications to the performance of the engine will affect how long it will last. We're just eating up some of the security factor the engineers used to design the engine.

If the VQ35 doesn't have a funky crank pulley to act as a harmonic damper, it's because it doesn't need it under normal operation condition. So, yes you're right in that sense. It does not mean it doesn't need that 10-15 lb (I don't know how much the OEM pulley weights) pulley to function properly.

Anyways, I didn't want to engage in a lenghty discussion on the subject. I'm not a resonnance specialist, just a curious designer. I did my research and from my findings, UR pulley are not the best way to go. Improving the engines efficiency (intake, exhaust) and programing is more effective and reliable.

It's still only my opinion of course. Nobody has to share it. In fact, my Z doesn't have any engine mods and I don't plan to do any. I spend my money on track time.

 

the altima guys have been running aftermarket crank pullies with no problems for years with the VQ...there are Zs with 65,000 miles with aftermarket pullies with no signs of wear or problems.

 

Yea, I also want to find out what will give more gains...I just bought test pipes and exhaust so wouldn't it be easier to get headers and install it all at the same time?

 

I have yet to see any independent dyno that shows the crank pulley has any gains

The only dyno's I have seen are with no gain or loss of power.