Crank pulley help in hp?
10-30-2010, 08:19 PM
#1
Crank pulley help in hp?
Im a vq swapped sentra. I think sometime ago i heard that a light weight after market crank pulley doesnt help add hp on the vq? Is this tru? Do they make all pullies?
I am looking to buy one, i am boosted and looking for more ponies..
if it does help what brand should i go with ? And what kinda power should i see
I am looking to buy one, i am boosted and looking for more ponies..
if it does help what brand should i go with ? And what kinda power should i see
Last edited by NoMam; 10-30-2010 at 08:24 PM.
10-30-2010, 08:23 PM
#2
it may help free up some power, but it wont be a lot. some people are believers, some are not. my best advice is for you to decide for yourself because you will get half and half response from here. if you do go with one, unorthodox racing would be your best bet.
10-30-2010, 08:29 PM
#3
Last edited by NoMam; 10-30-2010 at 08:33 PM.
10-30-2010, 08:34 PM
#4
i have it, and didnt pay all that.
10-31-2010, 08:07 PM
#12
Join Date: Dec 2009
Posts: 15
My OBX pulley weighs in at 1.6 lbs... its the vq30 pulley with the timing ring still bolted on for a vq30, but it'll work for the vq35... at least that's what I figure and once I remove the ring it'll be a bit lighter. The Cosmo site sells it's pulley that way I believe. Anyway I got mine in red anodized off amazon.com for $90 including shipping. Pretty cheap and looks nice. The stock VQ35 pulley weighs 6.2 lbs on my scale. Cheers!
http://www.amazon.com/OBX-Underdrive...8580776&sr=1-5
http://www.amazon.com/OBX-Underdrive...8580776&sr=1-5
Last edited by 5er; 10-31-2010 at 08:18 PM.
11-01-2010, 12:48 PM
#15
Goodluck. Im not much of a pulley fan. My brother installed his a few weeks ago and he said the biggest difference was that the revs went up alot quicker. Dont think you'll get much if any HP from it. What other mods do you have?
11-01-2010, 01:48 PM
#16
UDP is said to free up the engine a little, lessening the load from accessories and allowing it to rev faster (mind you, less power is going to accessories). While this does not produce an increase in HP, because it takes less time to rev you get the power in LESS TIME, which _should_ translate to faster acceleration.
11-01-2010, 01:51 PM
#17
11-01-2010, 01:52 PM
#18
UDP is said to free up the engine a little, lessening the load from accessories and allowing it to rev faster (mind you, less power is going to accessories). While this does not produce an increase in HP, because it takes less time to rev you get the power in LESS TIME, which _should_ translate to faster acceleration.
11-01-2010, 02:18 PM
#19
putting an underdrive pulley on a turbocharged car is asinine. they're pretty close to useless on an NA car, but on a turbo car where you can just turn the boost up another 1/4 psi and make more power than you would from a $150-300 pulley - why the hell would anyone do that. not to mention the liability of a pulley that a) has no harmonic dampener, and b) is of unknown quality.
i wouldn't put a UDP on a turbocharged maxima in a million years.
i wouldn't put a UDP on a turbocharged maxima in a million years.
11-01-2010, 03:27 PM
#20
Just because I'm bored I decided to do some calculations about the "gains" from a lightweight pulley.
I made a couple of assumptions, but I think they will shed some light on why I (and others who know what they're talking about) claim UDPs are virtually useless.
Basically I did the moment of inertia calculations for a hypothetical lightweight pulley. I kept the diameter constant because I did not know the exact diameter of the stock pulley nor that of a representative UDP, but it won't affect the calculations that much. Maybe 10-15% or so. I assumed a 6" pulley diameter, I assumed 6lb weight of the stock pulley, and a 2lb weight of the lightened pulley (that's a pretty big weight difference from stock pulley to lightened pulley I'd say, probably more than the REAL difference.)
Basically the way it works is that a rotating mass such as an underdrive pulley or lightweight flywheel's benefits diminish in each higher gear. The benefits are most pronounced in the lowest gear, and least in the highest gear. I used our stock gear ratios and stock tire diameter and came up with these numbers.
Going from a 6lb, 6" diameter pulley to a 2lb, 6" diameter pulley is equivalent to lightening the car by:
100.2lbs in 1st gear
26.6lbs in 2nd gear
14.7lbs in 3rd gear
10.0lbs in 4th gear
8.2lbs in 5th gear
Pretty worthless in my opinion.
If anyone wants to check my calculations, I used UUCs lightweight flywheel calculations and obviously changed the gear ratios to maxima 5spd gear ratios, tire size to maxima tire size, and flywheel diameter to maxima pulley diameter (approximated at 6" as stated above) and mass difference to what I felt was a good guess at maxima stock pulley and lightweight pulley differences. If anyone has actual diameters of stock and UDP, and actual weights of stock and UDP, I can do precise calculations to give the actual numbers, but these numbers give you a good idea of how pointless UDPs are from a performance perspective, let alone the risks I stated above (no harmonic balancer and unknown machining quality/balancing which in my opinion greatly increases the likelihood of engine damage).
Edit again:
I found claimed weights on Unorthodox's website. This still leaves my diameter assumption of 6" diameter, but using the weights on unorthodox's website (1.55lbs for their pulley vs 7.18lbs for the stock pulley) that puts the figures at:
141lbs in 1st gear
37.5lbs in 2nd gear
20.7lbs in 3rd gear
14.1lbs in 4th gear
11.5lbs in 5th gear
I made a couple of assumptions, but I think they will shed some light on why I (and others who know what they're talking about) claim UDPs are virtually useless.
Basically I did the moment of inertia calculations for a hypothetical lightweight pulley. I kept the diameter constant because I did not know the exact diameter of the stock pulley nor that of a representative UDP, but it won't affect the calculations that much. Maybe 10-15% or so. I assumed a 6" pulley diameter, I assumed 6lb weight of the stock pulley, and a 2lb weight of the lightened pulley (that's a pretty big weight difference from stock pulley to lightened pulley I'd say, probably more than the REAL difference.)
Basically the way it works is that a rotating mass such as an underdrive pulley or lightweight flywheel's benefits diminish in each higher gear. The benefits are most pronounced in the lowest gear, and least in the highest gear. I used our stock gear ratios and stock tire diameter and came up with these numbers.
Going from a 6lb, 6" diameter pulley to a 2lb, 6" diameter pulley is equivalent to lightening the car by:
100.2lbs in 1st gear
26.6lbs in 2nd gear
14.7lbs in 3rd gear
10.0lbs in 4th gear
8.2lbs in 5th gear
Pretty worthless in my opinion.
If anyone wants to check my calculations, I used UUCs lightweight flywheel calculations and obviously changed the gear ratios to maxima 5spd gear ratios, tire size to maxima tire size, and flywheel diameter to maxima pulley diameter (approximated at 6" as stated above) and mass difference to what I felt was a good guess at maxima stock pulley and lightweight pulley differences. If anyone has actual diameters of stock and UDP, and actual weights of stock and UDP, I can do precise calculations to give the actual numbers, but these numbers give you a good idea of how pointless UDPs are from a performance perspective, let alone the risks I stated above (no harmonic balancer and unknown machining quality/balancing which in my opinion greatly increases the likelihood of engine damage).
Edit again:
I found claimed weights on Unorthodox's website. This still leaves my diameter assumption of 6" diameter, but using the weights on unorthodox's website (1.55lbs for their pulley vs 7.18lbs for the stock pulley) that puts the figures at:
141lbs in 1st gear
37.5lbs in 2nd gear
20.7lbs in 3rd gear
14.1lbs in 4th gear
11.5lbs in 5th gear
11-01-2010, 03:54 PM
#21
Back in the late 90's I owned a 92' Mustang Saleen(official Saleen), I invested over 10 grand into her, under the hood/suspension/frame/exhaust. Anyway, I installed underdrive pulleys cause that was the only thing left to do basically. A couple of years later, maybe like 3 years later I think, the crank pulley snapped off while shifting into 2nd and broke the crank shaft. I actually owned my "DREAM CAR", not many of us dreamer's ever turn our dreams into a reality but I was there and that night the crank broke my dream broke. As you can tell I don't encourage the use of under drive pulley's. There not worth the risk anyway, they add no power, just a little bit of throttle response. Your better off replacing the crank pulley with a brand new OEM from Nissan or just leave the factory 1 alone. I don't mess around with UDP's and you gotta make sure that everything in that area is perfect; the timing belt/chain, accessory belts, pulleys, pumps, alternators, AC' compressors, tensioners. Use your money on something else.
11-01-2010, 03:58 PM
#22
Back in the late 90's I owned a 92' Mustang Saleen(official Saleen), I invested over 10 grand into her, under the hood/suspension/frame/exhaust. Anyway, I installed underdrive pulleys cause that was the only thing left to do basically. A couple of years later, maybe like 3 years later I think, the crank pulley snapped off while shifting into 2nd and broke the crank shaft. I actually owned my "DREAM CAR", not many of us dreamer's ever turn our dreams into a reality but I was there and that night the crank broke my dream broke. As you can tell I don't encourage the use of under drive pulley's. There not worth the risk anyway, they add no power, just a little bit of throttle response. Your better off replacing the crank pulley with a brand new OEM from Nissan or just leave the factory 1 alone. I don't mess around with UDP's and you gotta make sure that everything in that area is perfect; the timing belt/chain, accessory belts, pulleys, pumps, alternators, AC' compressors, tensioners. Use your money on something else.
11-02-2010, 02:35 PM
#23
Source: http://store.nexternal.com/shared/St...t=products.asp
So...14 BHP is first gear, using your calculations?
Cool!
11-03-2010, 11:44 AM
#25
60-1, built boosted. mevi, reflash ecu. the usual. prolly gonna get a safc2 or a vafc2 havent decided..
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