Please enlighten me

tonybui · 03-27-2011, 11:50 AM

So what does a crank pulley do and does it add Any hp gains?

Trips · 03-27-2011, 12:26 PM

Lighter pulleys help in the unsprung weight on the crank and therefore giving you a small hp gain. There are two types Just a Lighter pulley or A Lighter Undersized pulley with a matching Alternator pulley in which you would also need a smaller belt. NST? Sells this version as a set and also Stillen? Sells the Lighter and Undersized type. You need to decide if its worth the expense and what type would work for you? I've been using the NST lighter undersized type with no problems and I did notice a slight off idle difference.

NST (NonStopTuning) 370Z VQ37HR Pulley Kit Review w/ Dyno Charts
NST - The Leader In Nissan 370Z Pulley Development

Stillen Underdrive Pulley - Review/Pics/Dyno/Vid
STILLEN : STILLEN Performance Lightweight Pulleys

NonStopTuning · 04-07-2011, 05:07 PM

Quote:

Originally Posted by Triple's

Lighter pulleys help in the unsprung weight on the crank and therefore giving you a small hp gain. There are two types Just a Lighter pulley or A Lighter Undersized pulley with a matching Alternator pulley in which you would also need a smaller belt. NST? Sells this version as a set and also Stillen? Sells the Lighter and Undersized type. You need to decide if its worth the expense and what type would work for you? I've been using the NST lighter undersized type with no problems and I did notice a slight off idle difference.

NST (NonStopTuning) 370Z VQ37HR Pulley Kit Review w/ Dyno Charts
NST - The Leader In Nissan 370Z Pulley Development

Stillen Underdrive Pulley - Review/Pics/Dyno/Vid
STILLEN : STILLEN Performance Lightweight Pulleys

Thank you sir! NST Pulleys have consistently shown positive gains across all platforms and are very popular here with the 370Z community.

Much more info here... NST (NonStopTuning) 370Z VQ37HR Pulley Kit Review w/ Dyno Charts
NST - The Leader In Nissan 370Z Pulley Development

ChipsWithDips · 04-08-2011, 11:09 AM

Quote:

Originally Posted by Triple's

Lighter pulleys help in the unsprung weight on the crank and therefore giving you a small hp gain. There are two types Just a Lighter pulley or A Lighter Undersized pulley with a matching Alternator pulley in which you would also need a smaller belt. NST? Sells this version as a set and also Stillen? Sells the Lighter and Undersized type. You need to decide if its worth the expense and what type would work for you? I've been using the NST lighter undersized type with no problems and I did notice a slight off idle difference.
...

A lightweight crank pulley reduces the rotating mass, but that is not the same as unsprung weight. Much of the unsprung weight also happens to be a rotating mass (wheels/tires/brakes), but the difference is that unpsrung weight also affects handling by changing the inertia that your springs must overcome to keep your tires stuck to the pavement.

But yeah the other advantage of an underdriven crank pulley is that your belt driven accessories(Power steering, A/C, Alternator) sap less power from your engine, at the cost of slightly reduced performance of said accessories.

The NST kit includes an overdriven alternator pulley, so that the net effect of overdrive + underdrive = normally driven alternator, so only the power steering and A/C would be underdriven.

tonybui · 03-27-2011, 12:34 PM

Thanks Triple, on NST site, they say it gains about 7-10 HP ??

frost · 03-27-2011, 12:43 PM

Seems like the threads I've seen, people were getting less than 4 (iirc)

jnaut · 03-27-2011, 07:21 PM

4 is a more realistic number...not 7- 10

jnaut · 03-27-2011, 07:23 PM

you gain hp by spinning the accessories at a slower rate due to the undersized pulley.

christian370z · 03-27-2011, 09:06 PM

If anything, the biggest reason to install a light weight pulley is to increase engine response as it has less rotating mass to spin up which lets it rev up and down more quickly as well as respond more quickly to throttle input.

onzedge · 04-08-2011, 10:27 AM

Quote:

Originally Posted by christian370z

If anything, the biggest reason to install a light weight pulley is to increase engine response as it has less rotating mass to spin up which lets it rev up and down more quickly as well as respond more quickly to throttle input.

tiller · 03-27-2011, 09:39 PM

installed a lightwheight standard size stillen crank pulley last year,definitely revs up quicker,if you can install these pulleys yourself i recommend them

issforged · 04-11-2011, 02:22 PM

just a little point to throw in here is that we've had problems with our bmw customers and a decent amount of others that have broken bearings inside the motor as well lost their motors because they've used different crank pulleys

the rotating assembly is balanced from factory with the stock front pulley so by changing it you essentially "unbalance" the motor...not to sure how this effects the 370s motor because in some cars this doesnt cause any issues for the most part

but just something to keep in mind...

ChipsWithDips · 04-11-2011, 04:37 PM

Quote:

Originally Posted by 370Fitment

just a little point to throw in here is that we've had problems with our bmw customers and a decent amount of others that have broken bearings inside the motor as well lost their motors because they've used different crank pulleys

the rotating assembly is balanced from factory with the stock front pulley so by changing it you essentially "unbalance" the motor...not to sure how this effects the 370s motor because in some cars this doesnt cause any issues for the most part

but just something to keep in mind...

What sort of bmw engines? From what I've heard and read, harmonics play a more important role the longer the crank is. If they were I6 that's a big difference from V6.

I'm still curious what the harmonic frequencies of a given crank would be and how those are determined. The hope is that the frequency is high enough for our motors that it's only an issue at a rpm higher than we are using (10k or something)

NonStopTuning · 04-11-2011, 04:58 PM

Quote:

Originally Posted by ChipsWithDips

What sort of bmw engines? From what I've heard and read, harmonics play a more important role the longer the crank is. If they were I6 that's a big difference from V6.

I'm still curious what the harmonic frequencies of a given crank would be and how those are determined. The hope is that the frequency is high enough for our motors that it's only an issue at a rpm higher than we are using (10k or something)

This topic has been discussed in great detail in the COMPREHENSIVE NST thread, linked above.

As a very short review...

1. No one has ever reported engine problems with NST pulleys for the 180SX, 240SX, 350Z, 370Z, G35, or G37.

2. The 370Z engine is internally balanced and the crank pulley does NOT serve as a balancer. Some engines do, this one does not.

3. When it comes to the natural harmonics/vibrations, the RPM range where the second (dangerous) wave could/would occur in such an engine would be near/upwards of 10,000rpm. A range that this engine will not see.

This is not a BMW engine. There are certain engines that we do not choose to build pulleys for, due to the concerns of vibrations and the concerns that certain communities have... whether valid or largely based on theory. The Nissan community has been using NST pulleys for years without issues.

To remind everyone again, we use our own products on professionally built RACE CARS that live at redline on race tracks. We use our own solid pulleys on these very cars. In order to be competitive we need these engines to be powerful, rev happy, and most importantly, RELIABLE. We would not use our products on these cars if they were not safe.

Much more info in the COMPREHENSIVE NST thread...
NST (NonStopTuning) 370Z VQ37HR Pulley Kit Review w/ Dyno Charts

christian370z · 04-11-2011, 03:33 PM

^I've heard about that on some cars too, that's why I would probably go for a lighter flywheel which nets the same results and has no effect on the engine internals.

03-27-2011, 11:50 AM	#1 (permalink)
tonybui A True Z Fanatic Join Date: May 2009 Location: Maryland Posts: 1,397 Drives: 09 Sports 6 Speed Rep Power: 427	Please enlighten me So what does a crank pulley do and does it add Any hp gains?

03-27-2011, 12:26 PM	#2 (permalink)
Trips Administrator Join Date: May 2009 Location: Disneyland, Ca Posts: 8,733 Drives: 🔰 Rep Power: 10	Lighter pulleys help in the unsprung weight on the crank and therefore giving you a small hp gain. There are two types Just a Lighter pulley or A Lighter Undersized pulley with a matching Alternator pulley in which you would also need a smaller belt. NST? Sells this version as a set and also Stillen? Sells the Lighter and Undersized type. You need to decide if its worth the expense and what type would work for you? I've been using the NST lighter undersized type with no problems and I did notice a slight off idle difference. NST (NonStopTuning) 370Z VQ37HR Pulley Kit Review w/ Dyno Charts NST - The Leader In Nissan 370Z Pulley Development Stillen Underdrive Pulley - Review/Pics/Dyno/Vid STILLEN : STILLEN Performance Lightweight Pulleys __________________ Last edited by Trips; 03-27-2011 at 12:33 PM.

03-27-2011, 07:21 PM	#7 (permalink)
jnaut A True Z Fanatic Join Date: Dec 2009 Location: wpb, fl Posts: 1,146 Drives: 09 370z Rep Power: 18	4 is a more realistic number...not 7- 10 __________________ Best 1/4 mile 12.24 Best mph 114.5_______

03-27-2011, 07:23 PM	#8 (permalink)
jnaut A True Z Fanatic Join Date: Dec 2009 Location: wpb, fl Posts: 1,146 Drives: 09 370z Rep Power: 18	you gain hp by spinning the accessories at a slower rate due to the undersized pulley. __________________ Best 1/4 mile 12.24 Best mph 114.5_______

03-27-2011, 09:06 PM	#9 (permalink)
christian370z A True Z Fanatic Join Date: Jul 2010 Location: Newport Beach Posts: 3,900 Drives: 2010 370Z/Saab 900se Rep Power: 432	If anything, the biggest reason to install a light weight pulley is to increase engine response as it has less rotating mass to spin up which lets it rev up and down more quickly as well as respond more quickly to throttle input. __________________ -320whp / 259wftlbs- SP Rays -- RE-11s -- SpecialtyZ Tune -- Swift Springs -- Stillen 25R Oil Cooler -- Stillen G3 Intakes -- Berk HFCs -- F.I. 12" CBE -- Stillen Sway Bars -- Es14 Spring -- INGS+1 lip -- CF Spoiler -- GTR Start Button -- VLED Parking Lights -- PWJDM V2 shift knob

03-27-2011, 12:34 PM	#5 (permalink)
tonybui A True Z Fanatic Join Date: May 2009 Location: Maryland Posts: 1,397 Drives: 09 Sports 6 Speed Rep Power: 427	Thanks Triple, on NST site, they say it gains about 7-10 HP ??

03-27-2011, 12:43 PM	#6 (permalink)
frost Retired admin Join Date: Dec 2008 Location: Winterfell Posts: 106,613 Drives: Your Wife Crazy Rep Power: 0	Seems like the threads I've seen, people were getting less than 4 (iirc)

03-27-2011, 09:39 PM	#11 (permalink)
tiller Enthusiast Member Join Date: Feb 2011 Location: ontario Posts: 370 Drives: 09 370z touring Rep Power: 15	installed a lightwheight standard size stillen crank pulley last year,definitely revs up quicker,if you can install these pulleys yourself i recommend them

04-11-2011, 02:22 PM	#12 (permalink)
issforged Track Member Join Date: Jan 2011 Location: Houston Posts: 668 Drives: '10 Nismo Rep Power: 16	just a little point to throw in here is that we've had problems with our bmw customers and a decent amount of others that have broken bearings inside the motor as well lost their motors because they've used different crank pulleys the rotating assembly is balanced from factory with the stock front pulley so by changing it you essentially "unbalance" the motor...not to sure how this effects the 370s motor because in some cars this doesnt cause any issues for the most part but just something to keep in mind...

04-11-2011, 03:33 PM	#15 (permalink)
christian370z A True Z Fanatic Join Date: Jul 2010 Location: Newport Beach Posts: 3,900 Drives: 2010 370Z/Saab 900se Rep Power: 432	^I've heard about that on some cars too, that's why I would probably go for a lighter flywheel which nets the same results and has no effect on the engine internals. __________________ -320whp / 259wftlbs- SP Rays -- RE-11s -- SpecialtyZ Tune -- Swift Springs -- Stillen 25R Oil Cooler -- Stillen G3 Intakes -- Berk HFCs -- F.I. 12" CBE -- Stillen Sway Bars -- Es14 Spring -- INGS+1 lip -- CF Spoiler -- GTR Start Button -- VLED Parking Lights -- PWJDM V2 shift knob