OEM pulley not good for big HP :( ... sad news

[upgradedsupra]

I'm still perplexed why the 7M's crank pulley is HP limited, and I'm not accepting ATI's marketing. The only load or resistance on the pulley are those from the accessories; water pump + fan, alt, power steering, etc.. That load isn't changing, nor does it increase with HP. Rather, it's constant, and the only increase experienced is overcoming the rotational inertia upon initial startup.
I'll accept that the stock rubber components may deteriorate due to age, and may become succeptible to failure, but this mode is dependent on age, service condition, and not HP. The pulley isn't spinning any faster either...
I'll await engineering data from ATI, before I accept that their pulley is "better" than the OEM's.

How abut I say this: The OEM pulley I have is a very low milage unit (almost new) and the dampener is screwed up.

Figgie is right as I also spoke with ATI today. It is more than double the price of the OEM replacement since it is a custom order. (Mine will be an 8" OD) with custom trigger wheels built with it.

I raced mine with this hp twice at the track and it started to wiggle so I took it off. Proof enough that it isn't good anymore?

Duane

 

[figgie]

Figgie- Yep, I was just going by what the spec sheet on the damper says and what I was told bt ATI when I ordered them. Was told and read that they are good for 600 and under. Maybe they should stress the under part of that statement. Always good to jaw with you, remember all our debates we used to have over on I-supra.com back in the late 90's and early 2000's?

you sure it was me? I logged in the other day and my sign up date was 2003 But I think I recall that Mark changed the software so I vaguely remember. That was when I did not know anything. Today, i still don't know anything.. lol

 

[figgie]

ill agree with almost all of that...except the simple fact that the ati pulley is a good amount lighter then the oem pulley is reason enough imo to use it.

but i dont think i buy the HP rating on a crank pulley myself either. on top of that what is considered "sustained" for their hp ratings? two seconds? 10 seconds? 5 minutes?

didn't i put it on here??

NASCAR is sustained 600 hp.

Blackdevil

you are focusing on load when that is not the dampners job What it has to do with though, is with torsional dampening. Toyota not even in thier wildest imagination designed the oem to dampen more than oem hosepower (measure the thickness of the rubber). As power goes up torsional vibration becomes that much worse. Especially on the #1 powerstroke where it is the most severe. The wobble experienced by Duane was caused by the OEM attempting to dampen 800 hp worth of harmonics and torsional resonance. The rubber gave the ghost up. On the surface it would seem like a load driven failure but the real cause of the failure is the aforemention harmonics and torsional resonance that accompanies high HP engines.

 

[Doward]

"Sustained" = a constant load. I would not label something as 'sustained' unless I meant it could handle that load 24/7.

 

[figgie]

"Sustained" = a constant load. I would not label something as 'sustained' unless I meant it could handle that load 24/7.

All relative to the frame of reference. Sustained to me is constant measured in consecutive hours. Nascar, I consider sustained, as they are always spinning those motors for hours at a time. Not seconds. If it was the 24 hours of lemans, that also would be sustained.

 

[suprarich]

didn't i put it on here??

NASCAR is sustained 600 hp.

Blackdevil

you are focusing on load when that is not the dampners job What it has to do with though, is with torsional dampening. Toyota not even in thier wildest imagination designed the oem to dampen more than oem hosepower (measure the thickness of the rubber). As power goes up torsional vibration becomes that much worse. Especially on the #1 powerstroke where it is the most severe. The wobble experienced by Duane was caused by the OEM attempting to dampen 800 hp worth of harmonics and torsional resonance. The rubber gave the ghost up. On the surface it would seem like a load driven failure but the real cause of the failure is the aforemention harmonics and torsional resonance that accompanies high HP engines.

This is 100% correct and should end all the "stronger than stock" debate as it has nothing to do with strenght. In lay terms, a large piece of toilet paper is no stronger than a small piece, but the larger one will absorb more crap than the smaller.

 

[Supra7MG]

This is 100% correct and should end all the "stronger than stock" debate as it has nothing to do with strenght. In lay terms, a large piece of toilet paper is no stronger than a small piece, but the larger one will absorb more crap than the smaller.

Great analogy!

 

[IJ.]

The higher the hp output the more the crank will twist and wiggle around in the motor so you need a damper capable of absorbing this deflection without it's outer ring traveling past the limits of it's bonded construction and shearing.

I-6's have a big long wet noodle for a crankshaft you'd be surprised just how much torsional twist there is and the bizarre wear patterns you'll see on a high HP crank/bearings that's been run at high rpm for extended periods.

 

[GrimJack]

Anytime, Duane. Glad there wasn't any damage to speak of - I think pulling it off right away let you dodge a big, nasty, bullet.

 

[upgradedsupra]

Anytime, Duane. Glad there wasn't any damage to speak of - I think pulling it off right away let you dodge a big, nasty, bullet.

Yes I agree with you there I have some of the stuff cleaned up..man that takes time.

Duane

 

[Poodles]

I-6's have a big long wet noodle for a crankshaft you'd be surprised just how much torsional twist there is and the bizarre wear patterns you'll see on a high HP crank/bearings that's been run at high rpm for extended periods.

we're lucky though in that I-6's are one of the most inharently stable engine designs as most of the harmonics are cancelled out...

our dampners are TINY compared to most V style engines...

 

[suprra_girl]

so the oem replacement dampener from ati would be the perfect pulley for mine then?
i'm a bit concerned now with the balancing issue as i didn't get any of that done. I will only be running 400whp and will balance everything if i have the more power bug happen heh

 

[upgradedsupra]

so the oem replacement dampener from ati would be the perfect pulley for mine then?
i'm a bit concerned now with the balancing issue as i didn't get any of that done. I will only be running 400whp and will balance everything if i have the more power bug happen heh

The stock ATI damper for your HP application would serve you fine.

Duane

 

[suprra_girl]

sweet! thanks Duane

 

[NashMan]

i remmber back way back ortha docks made a light weight none dammping lower pullie death in a box i must say

if i remmber back way back dunae had one and it fell off

 

[kwnate]

if i remmber back way back dunae had one and it fell off

Thanks Duane for breaking things so I don't have to waste money.