OBX Overdrive Pulleys. Yay or Nay?

[Out Lander]

Hey guys, i've been doing some searching around for light weight parts for my 7mge. Now i know the the OBX crank pulleys are a bad idea but what about their Overdrive Pulley set (which has power steering and Alternator pulleys)?

I'm mainly considering these to save weight and for cleaning up the engine so if there's an alternative then i'm all ears.

Thanks
Luke B

[gofastgeorge]

Now i know the the OBX crank pulleys are a bad idea but what about their Overdrive Pulley set (which has power steering and Alternator pulleys)?




Well, if they are round, fit correctly, and don't wobble,
like the custom water pump pulley I bought from a wana-be vendor on this site,
go for it.

[Mk3runner]

nay on the crank pulley for sure.

[Flateric]

I've been strongly against the crank pulley and also of the opinion that it's not so bad.

One arguement for lightweight ones is, if your pulley now is really old and beat looking a light one has no chance of seperating and doing damage all over.

One arguement for the damped and a good one is the lightones damage bearings. My question on this one is how quickly and does my engine fall within this period of wear? Are we talking it'll cause me issues in like 40-50thousand KM? If so, I really don't expect to get that kinda milage out my motor anyways. Are we talking 5000KM? Well that is a big prob then.

Arguement for light ones, they reduce parasitic loss, are much more affordable (depending on answer results from the above milage ?), and look snazzy!

Arguement for the damped, obviously some momentum is gonna be a good thing in some situations.

So I've gone from being against, to being for, to being unsure, etc.

[jdub]

Solid aluminum crankshaft pulleys are NOT something you want to run. Read this:
http://www.dinancars.com/bmw/technial-info/the-dangers-of-power-pulleys-and-understanding-the-harmonic-damper

shaeff edit: Here's a cached version of the link above, as it's currently dead: http://tinyurl.com/Harmonic-Damper

It's written for a BMW, but applies to any motor...the longer the crankshaft (like an I6), the more pronounced the effect of harmonic vibration. Depending on how well the crank is balanced will determine how long it takes for harmonics to adversely affect the bearings. An ATI damper weighs 5 lbs less than stock...a far better alternative that a solid aluminum crank pulley.

For the accessory pulleys, go for it. There will only be a miniscule weight savings though.

[tlo86]

i'll stick by stock or after market harmonic dampener. nothing else.

[radiod]

I looked in to this and decided against it as well. Too much (possible) risk for too little gain.

[KicknAsphlt]

First, why would you want to overdrive your accessories? Second, due to the size of the pullies, any parasitic loss reduction will be minimal at best. Personally, I think underdrive/overdrive pullies are a waste of money...any hp gains is minimalistic (practically none), and they generally cause more trouble than they're worth.

**Edit** If you think about it, overdriving your accessories is going to cause more parasitic drag, even if you're going with lighter pullies. The whole point of underdrive pullies is to reduce the parasitic drag by turning the accessories slower, therefore reducing the rotational resistance. Overdriving the crank pulley is supposed to compensate for this by speeding the system back up by turning the belts faster. In most street vehicles however, you end up having charging issues under 1000rpm and can kill your battery pretty quick (not drain it, kill it). When you're overdriving your accessories, you're putting a smaller pulley on them, making them spin faster. With the crank rotating at the same speed though, it causes more resistance in the system causing more parasitic drag. Not only that, it also puts a bigger strain on those accessories being overdriven.

[Keros]

"If it ain't broke, don't fix it" is the motto... not "If it ain't broke, fix it 'till it is"

Just leave it alone if it works and spend the money on hookers and blow.

[tlo86]

thats why people buy the pulleys.. when their stock one breaks and buy a cheap alternative

[Flateric]

Anyone one know any figures for what kinda milage it starts going bad, yes I understand right away, but longevity?

Don't get me wrong here, I'm back in the don't camp, have been for awhile, but I'm more curious about the issue more than anything.

And I've read the dinan writeup too, and Reg Reimers writeup also about the specific 7m/2jz issues, but no one ever seems to say if its a limits your engine life to 15,000KM or if it's limiting you to 90,000KM. If you can see what I'm trying to say.

I drag my motor, I honestly will be shocked if I get 30,000KM out of it regardless of what crank I run. Although I did get 30,000KM out of my 7M running just shy of 500RWHP with a stock damped pulley.

I'm running a 2jZ now but still curious.

[TLDriver]

I am running the OBX pulley set. I also read a lot on how much harm they do and so on.. My mechanic actually installed it for me when I did my light weight flywheel and we revved the motor through out the full RPM range and he claims there was very little to no change in vibrations. I don't know if in the long run it will just give up but... at the moment it was worth it.

[funky_monkey58]

I am running the OBX pulley set. I also read a lot on how much harm they do and so on.. My mechanic actually installed it for me when I did my light weight flywheel and we revved the motor through out the full RPM range and he claims there was very little to no change in vibrations. I don't know if in the long run it will just give up but... at the moment it was worth it.

Sounds logical to me. :sarcasm:

Jesus Christ you are a fucking idiot are you not?

[figgie]

Ooks at NASCAR, hmm wonder why they run damped crank pullies in those v8s'???

[tlo86]

Ooks at NASCAR, hmm wonder why they run damped crank pullies in those v8s'???

:gaybar:
they are clearly mad men.

http://www.atiracing.com/products/dampers/damper_dinan.htm

annd isnt it required for NHRA?

[87tomanymods]

ive heard of lots of horror stories with aluminum pulleys esp like mentioned earlyier on long crank engines , but w/ that in mind ive also read that the 7m is a fairly well ballanced ,because of the way the cylinders are staggered in 3 pairs. i personaly have been runing a UR underdrive for 5 yrs and havn't had any problems ...........also i pulled this off of wiki hpe it helps ............... in inline six engine is in perfect primary and secondary mechanical balance, which can be achieved without using a balance shaft. The engine is in primary balance because the front and rear trio of cylinders are mirror images, and the pistons move in pairs. That is, piston #1 balances #6, #2 balances #5, and #3 balances #4, largely eliminating the polar rocking motion that would otherwise result. Secondary imbalance is avoided because an inline six cylinder crankshaft has six crank throws arranged in three planes offset at 120 degrees. The result is that differences in piston speed at any given point in rotation are effectively canceled.

[jdub]

I am running the OBX pulley set. I also read a lot on how much harm they do and so on.. My mechanic actually installed it for me when I did my light weight flywheel and we revved the motor through out the full RPM range and he claims there was very little to no change in vibrations. I don't know if in the long run it will just give up but... at the moment it was worth it.

So, your mechanic has the equipment to measure harmonic vibration...must be a shit hot mechanic to have that kind of equipment ;)
(or have an extremely sensitive ass)



ive heard of lots of horror stories with aluminum pulleys esp like mentioned earlyier on long crank engines , but w/ that in mind ive also read that the 7m is a fairly well ballanced ,because of the way the cylinders are staggered in 3 pairs. i personaly have been runing a UR underdrive for 5 yrs and havn't had any problems ...........also i pulled this off of wiki hpe it helps ............... in inline six engine is in perfect primary and secondary mechanical balance, which can be achieved without using a balance shaft. The engine is in primary balance because the front and rear trio of cylinders are mirror images, and the pistons move in pairs. That is, piston #1 balances #6, #2 balances #5, and #3 balances #4, largely eliminating the polar rocking motion that would otherwise result. Secondary imbalance is avoided because an inline six cylinder crankshaft has six crank throws arranged in three planes offset at 120 degrees. The result is that differences in piston speed at any given point in rotation are effectively canceled.

So, please explain why Toyota would feel the need to install a damper (that is more expensive to make) on the 7M from the factory?

You guys really, really need to read up on harmonic vibration and it's cause. A lot of BS is being laid down here...gonna have to roll my pants up to wade through it.

[IJ.]

This is like watching an episode of the Muppets http://forum.muppetcentral.com/image.php?u=6273&dateline=1238245802

[shaeff]

Sigh.

Straps 'em on:
http://www.lractive.com/catalog/images/neoprene_hip_waders.jpg

[Suprapowaz!(2)]

I hate to lay down some more poo, and I'm not trying to go against the theory of harmonic vibrations but I too ran an Unorthodox Crank pulley for roughly four years. The car was my daily driver and I did about 17K miles per year at the time.
My engine did finally let go, but due to the ringlands on #1 cylinder shattering. I missed a gear and overevved in third while making a pass. Now if a lightend crank pulley would cause that then that is what it was.
When I tore down the engine the rod and main bearings looked normal except for the metal shavings that scored them when the piston broke. I do have pics to show, but I"m not at my computer right now.
I didn't know then the dangers of running that kind of crank pulley back then. Now that I do I'm not doing it again. I'm going back to a stocker.
So, there's my contribution to spewing BS.

[chefma70]

ive heard of lots of horror stories with aluminum pulleys esp like mentioned earlyier on long crank engines , but w/ that in mind ive also read that the 7m is a fairly well ballanced ,because of the way the cylinders are staggered in 3 pairs. i personaly have been runing a UR underdrive for 5 yrs and havn't had any problems ...........also i pulled this off of wiki hpe it helps ............... in inline six engine is in perfect primary and secondary mechanical balance, which can be achieved without using a balance shaft. The engine is in primary balance because the front and rear trio of cylinders are mirror images, and the pistons move in pairs. That is, piston #1 balances #6, #2 balances #5, and #3 balances #4, largely eliminating the polar rocking motion that would otherwise result. Secondary imbalance is avoided because an inline six cylinder crankshaft has six crank throws arranged in three planes offset at 120 degrees. The result is that differences in piston speed at any given point in rotation are effectively canceled.


wow..........please tell me that supra in your sig isint the one your torturing.....and my professor said anyone who uses wiki answers for thier research instantly gets a ZERO on thier report. Wiki can be change by anyone anytime and is the worlds most unreliable source of information. Anyone that says the words "my mechanic",i instantly dont listen to a word they have to say. Your suppostu be the mechanic and especially if you own a oldschool supra.this room smells like my cats litterbox

oem crank pully ftw!

[gofastgeorge]

Don't worry chefma70,
87tomanymods also has a thread started about making an electric turbocharger...........

http://www.supramania.com/forums/showthread.php?t=103443

[IJ.]

I hate to lay down some more poo, and I'm not trying to go against the theory of harmonic vibrations but I too ran an Unorthodox Crank pulley for roughly four years. The car was my daily driver and I did about 17K miles per year at the time.
My engine did finally let go, but due to the ringlands on #1 cylinder shattering. I missed a gear and overevved in third while making a pass. Now if a lightend crank pulley would cause that then that is what it was.
When I tore down the engine the rod and main bearings looked normal except for the metal shavings that scored them when the piston broke. I do have pics to show, but I"m not at my computer right now.
I didn't know then the dangers of running that kind of crank pulley back then. Now that I do I'm not doing it again. I'm going back to a stocker.
So, there's my contribution to spewing BS.

Care to explain how the above happened?

Been sitting here watching this TrainWreck in the making for a few days here...

It's NOT VIBRATION Harmonic or otherwise that the Damper is primarily trying to control.

You drive the car from the flywheel end of the crank, as each Cylinder fires it's trying to twist the crank and this deflection/windup/twist (steel is elastic) can be violent if left uncontrolled (no damper)

In high output engines the BANG is bigger therefore so is the deflection/twist, this is why ATI list their off the shelf Damper to xxxrwhp then spec a bigger diameter custom one for higher HP.

Think of the Damper as a Shocker for the Crank nothing more.