UR Underdrive Crank Pulley/Crank Pulley Update

[gentledental4u]

Originally Posted by Danni3

too bad theres no lightweight stock diameter pulley for the i4 =[ I don't want to overdrive my alternator, I guess the p2r downpipe is next on my list

Originally Posted by PHOsho

just a quick off-topic question,
what does replacing stock downpipe with p2r downpipe do?
i saw it on throwdownperformance but it didnt really explain what it does :l

What are you two doing here? Please do not hijack.

If you want your question answered, you can either pm each other or pm throwdownperformance. Mark is a really nice guy and he takes care of his customers.

[denbry]

Originally Posted by MackDaddy

I"m no physics teacher, but I'll be the first to tell you (or anyone who asks) it makes a significant performance difference. Well worth the $200 I spent. No question.

OE is 88.46oz
UR is 18.28oz

That's 4.39Lbs of rotating mass weight reduction off the crank snout. Think about it.

Like you said: you're no physics teacher, and I have thought about it. I have an engineering background so I might be more qualified than you to assess what 4.39 lbs of rotating mass close to a shaft (we're not talking about a shaved 50 lb flywheel that is two feet in diameter) will or won't do.

Take into consideration that any difference of acceleration/torque you think you "feel" as a result of a reduction of 4.39 lbs. has to travel through the inertia and mass of the engine, driveline, and wheels against more inertia and resistance of a 3400 lb. car while accelerating.

If you take the belt off and rev your engine you might notice quicker revs but I doubt it with that small of a pulley. But wishful thinking is cool and if you believe it makes you faster, go for it. And it's good for the guy that makes the stuff too.

[Artema]

Originally Posted by denbry

Like you said: you're no physics teacher, and I have thought about it. I have an engineering background so I might be more qualified than you to assess what 4.39 lbs of rotating mass close to a shaft (we're not talking about a shaved 50 lb flywheel that is two feet in diameter) will or won't do.

Take into consideration that any difference of acceleration/torque you think you "feel" as a result of a reduction of 4.39 lbs. has to travel through the inertia and mass of the engine, driveline, and wheels against more inertia and resistance of a 3400 lb. car while accelerating.

If you take the belt off and rev your engine you might notice quicker revs but I doubt it with that small of a pulley. But wishful thinking is cool and if you believe it makes you faster, go for it. And it's good for the guy that makes the stuff too.

You made some analogies, but forgot to prove your point. It does make a difference, even the stock diameter version. How does pseudo-cleverly suggesting it is a waste of money add to the conversation?

[Danni3]

Originally Posted by gentledental4u

What are you two doing here? Please do not hijack.

If you want your question answered, you can either pm each other or pm throwdownperformance. Mark is a really nice guy and he takes care of his customers.

I'm stating my opinion that its a shame that theres only the v6 light weight with stock diameter ones... you made a thread about UR pulleys and though my reply is a tiny bit off topic it still pertains to the original post

heres the deal:

because you're changing the mass of the rotating object at the end of the shaft the stress model of the shaft that its attached to changes significantly and therefore the life of the shaft supporting it changes.
Imagine you have two bearings supporting a rotating rod with a pulley at the end, if the pulley is heavy than the bearing is rated at a higher load/life, but if you replace the pulley with a lighter one than the bearing is running a significantly less load and thus will last longer (bearing with only a radial load, only not sure about the shaft).

it could be that you're creating an axial load on the (I assume) fluid based bearing that will reduce the life of the bearing.

Obviously there is a power increase because of the lighter pulley, however there could be a lot of small negative consequences, I can't really tell what they are unless I run a full stress analysis (gears/pulleys/shafts/bearings). A ridiculous amount of calculations and engineering analysis goes into cars, the car's warranty is based on these calculations, if a lighter pulley would have been more beneficial to the car without breaking anything else the engineers would have already done it (theres no reason not to: less stress on engine, more hp, more torque, higher mpg).

If you don't plan on running this car into the ground and its only short term (aka until you get your next car) than its a good mod I guess, the possibility of under driving your alternator is something else though >.>

!@#$ mechanical engineering classes

[MackDaddy]

Originally Posted by denbry

Like you said: you're no physics teacher, and I have thought about it. I have an engineering background so I might be more qualified than you to assess what 4.39 lbs of rotating mass close to a shaft (we're not talking about a shaved 50 lb flywheel that is two feet in diameter) will or won't do.

Take into consideration that any difference of acceleration/torque you think you "feel" as a result of a reduction of 4.39 lbs. has to travel through the inertia and mass of the engine, driveline, and wheels against more inertia and resistance of a 3400 lb. car while accelerating.

If you take the belt off and rev your engine you might notice quicker revs but I doubt it with that small of a pulley. But wishful thinking is cool and if you believe it makes you faster, go for it. And it's good for the guy that makes the stuff too.

We'll agree to disagree on this right now. I'm certainly no expert, but have been modifying & tweaking cars & motorcycles a long, long time. I'll do further in depth research for my application from trusted ASE certified master mechanic/friends, on the J35 installation long term implications (of which I've done quite a bit already.) If the consensus is I'm better off in the long run with the OE steel damped pulley, so be it. Back on it goes.

Bottom line, the pulley I've installed makes ~ 9HP & 20Ft/Lb Tq at the wheels over and above a bone stock 8th gen 5AT V6. Dyno proven. Believe what you want, numbers don't lie.

Not trying to be a dick, just stating what I know. I will investigate the no bullsh!t opinion of others who are far smarter than I in this area.....

Enjoy,
Jim

[LUCKY#SLEVIN]

Originally Posted by Danni3

I'm stating my opinion that its a shame that theres only the v6 light weight with stock diameter ones... you made a thread about UR pulleys and though my reply is a tiny bit off topic it still pertains to the original post

heres the deal:

because you're changing the mass of the rotating object at the end of the shaft the stress model of the shaft that its attached to changes significantly and therefore the life of the shaft supporting it changes.
Imagine you have two bearings supporting a rotating rod with a pulley at the end, if the pulley is heavy than the bearing is rated at a higher load/life, but if you replace the pulley with a lighter one than the bearing is running a significantly less load and thus will last longer (bearing with only a radial load, only not sure about the shaft).

it could be that you're creating an axial load on the (I assume) fluid based bearing that will reduce the life of the bearing.

Obviously there is a power increase because of the lighter pulley, however there could be a lot of small negative consequences, I can't really tell what they are unless I run a full stress analysis (gears/pulleys/shafts/bearings). A ridiculous amount of calculations and engineering analysis goes into cars, the car's warranty is based on these calculations, if a lighter pulley would have been more beneficial to the car without breaking anything else the engineers would have already done it (theres no reason not to: less stress on engine, more hp, more torque, higher mpg).

If you don't plan on running this car into the ground and its only short term (aka until you get your next car) than its a good mod I guess, the possibility of under driving your alternator is something else though >.>

!@#$ mechanical engineering classes

i was all gung-ho about getting the stock diameter pulley done but the more i see posts like this it def. makes me think twice about not getting it...

[denniswolf]

I think there are a lot of people on the net who are armchair experts and engineers. It's always important to go with trusted sources that you can actually verify like MackDaddy said and go where the actual proof is, not just theoretical rhetoric. I have seen the dyno charts as well and that is a noticeable increase!

[MackDaddy]

Agreed DW. The bottom line UR has been in business making lightweight pulley's for many years. They know what they're doing. I wouldn't trust just anyone making this device, as it needs to be a meticulously crafted piece. I'm happy with the decision I made for now. But if I do in fact learn that this is not such a wise idea for extreme long term durability it will come off. Simple as that.

I bought this car to last for the next 10-15 years, and hope to get well over 200k miles out of it. No sense doing power-train mods that won't allow me to enjoy the car as intended....

YMMV

[t-rd]

So report back after 100k miles.

"I've been ok 20k miles with this pulley" doesn't mean s***. I put up 30k miles a year with sometimes a 150 mile commute a day. I have been stranded in the past with over-hyped but unproven mods. Until then, I'm staying off.

[denbry]

Originally Posted by MackDaddy

We'll agree to disagree on this right now. I'm certainly no expert, but have been modifying & tweaking cars & motorcycles a long, long time. I'll do further in depth research for my application from trusted ASE certified master mechanic/friends, on the J35 installation long term implications (of which I've done quite a bit already.) If the consensus is I'm better off in the long run with the OE steel damped pulley, so be it. Back on it goes.

Bottom line, the pulley I've installed makes ~ 9HP & 20Ft/Lb Tq at the wheels over and above a bone stock 8th gen 5AT V6. Dyno proven. Believe what you want, numbers don't lie.

Not trying to be a dick, just stating what I know. I will investigate the no bullsh!t opinion of others who are far smarter than I in this area.....

Enjoy,
Jim

Jim,
I'm not trying to be a dick either (and I too have been a motorhead most of my life) but some time ago I asked to see the before and after dyno results and all I got was the after and the rest was confusing. Additionally, to be fair, the tests should have been done by a third uninterested party, otherwise, in some cases, the incentive to sell might influence outcome.

[MackDaddy]

Originally Posted by t-rd

So report back after 100k miles.

"I've been ok 20k miles with this pulley" doesn't mean s***. I put up 30k miles a year with sometimes a 150 mile commute a day. I have been stranded in the past with over-hyped but unproven mods. Until then, I'm staying off.

We shall see. If it stays on the car, I'll be sure and keep you all informed.

Originally Posted by denbry

Jim,
I'm not trying to be a dick either (and I too have been a motorhead most of my life) but some time ago I asked to see the before and after dyno results and all I got was the after and the rest was confusing. Additionally, to be fair, the tests should have been done by a third uninterested party, otherwise, in some cases, the incentive to sell might influence outcome.

I'm going on BPearl's dyno results posted here on this website for power numbers. I'm still going to further check into the longer term durability issues with this installed. That's the main concern for me at least. It does free up power to the wheels, no question. In addition to everything else I've done to my car car thus far, she runs fantastic. Fun old mans car, that's for sure!

Take care,
Jim

[gentledental4u]

Good news! I'm selling my car soon, so won't be putting it on. Debate is over! yay! I'm going to sell the part, so anyone wants it, pm me

[DownShft4TheWin]

Originally Posted by gentledental4u

Good news! I'm selling my car soon, so won't be putting it on. Debate is over! yay! I'm going to sell the part, so anyone wants it, pm me

I'm all over this also...looks like I'm coming to your house with a bunch $ in hand