alternator pullies.

[ericjon262]

A thread on Old Europe brought up decoupling alternator pullies, I had seen them in the past, and never given them much thought, the OE's are using them, so no doubt they do something, but are they worth anything? I'm fairly certain that there's an OEM alternator that will fit my low mount alternator setup, and I have a feeling my alternator is getting close to the end of it's useful life.

anyone have any thoughts?

https://www.youtube.com/watch?v=-FBeTBcBMk0&t=194s

https://youtu.be/OR0WEK3JEO4

https://www.fiero.com/forum/Forum2/HTML/145914.html

[pmbrunelle]

Hmmm, I didn't know about these.

There seems to be an angle of "reducing CO2 emissions" associated with these pulleys. Everything sounds green and humanitarian when you say it that way

So, if these pullies reduce the tendency for the belt to vibrate, then maybe less belt tension is needed to keep the belt under control and to avoid slippage. If the car is able to run less belt tension, then there is less friction loss in the bearings of the accessories, hence less fuel burn, and less CO2 emissions.

It would be interesting to see if the tensioners on cars with these pullies pull less tightly than on cars with standard (solid) alternator pullies.

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I do find that there's an inordinate amount of focus on tailpipe emissions, while nobody cares about embodied emissions and the throwaway consumer culture.

A solid pulley can be kept forever by the thrifty car owner; blast, paint, and repeat when rust comes back.

The overrunning pulley will eventually need to be rebuilt, and one day will no longer be easily replaceable/rebuildable. Perhaps some reduction of fuel burn while in use, but I am not convinced that it is a "green" design choice in the big picture.

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Leaded solder became a problem with discarded electronics in landfills, and so RoHS mandated the phasing out of lead from solder. Lead-free solder isn't as good as leaded solder, so that kind of precipitates the cycle of short-lived electronics that must be thrown away and replaced with new.

I'd rather see everything put together with leaded solder, which would last longer in the first place, and is easier to repair when the time comes. Then the old electronics wouldn't need to end up in the landfill...

Rant over!

[ericjon262]

I totally agree with your arguments, part of the problem, is that the average person doesn't know how to fix anything anymore. I'm not after emissions, I am more about belt stability and lifetime, but if there's something to gain, from a more or less bolt in swap, I'm always interested.

FWIW, the alternator I'm running actually has a "speed limit", or at least, according to this guy it does:

https://www.youtube.com/watch?v=l92t8q7 ... l=turbo_v6

So I may need a different pulley anyways, if I can get a different alternator and not mess with swapping pullies, that's a plus to me.

[Honest Don]

What alternator are you currently using?

[ericjon262]

What alternator are you currently using?

I have an alternator off of a ~2003 chevy astro 4.3, but that alternator frame interchanges, or is very similar to a huge number of GM alternators

[Honest Don]

What alternator are you currently using?

I have an alternator off of a ~2003 chevy astro 4.3, but that alternator frame interchanges, or is very similar to a huge number of GM alternators

AD230

If you're changing out anyway, what about fitting a DR44? Do you have an extra PWM output on your MS3? Managing the charge schedule around throttle input and other parameters might be worth looking into?

[The Dark Side of Will]

I don't know about the Duramax alternator, but my OM642 and OM648 (Benz diesel) alternators both have overrunning pulleys.

I think the high drive ratio for the diesels exacerbates the problem. Since the engines redline at 4300-4500 RPM, the drive ratios are higher in order to get alternator RPM higher. If the engine is turning 4,000 RPM and the drive ratio is 4:1, the alternator might be turning >16,000 RPM. When the tranmission upshifts, the engine is pulled rapidly down to 3,000 RPM. This is fine with the engine's rotating mass and moment of inertia, since the entire transmission absorbs the extra energy. As the engine spins down from 4,000 to 3,000, the alternator has to spin down from 16,000 to 12,000. The only mechanism to absorb that energy that fast is the tensions and slack side of the belt drive... so that mechanism is actually loaded higher relative to its max capacity than the transmission is. The overrunning pulley lets the alternator spin down according to the needs of the electrical system and saves wear/tear on the belt drive.

I'm starting to wonder if an overrunning pulley is available for the CS130 I have on the Northstar. If I turn the engine to 8,000 RPM and the drive ratio is 3:1 (I really need to measure the alt pulley to have a better number), then the alternator will hit 24,000 RPM with the engine at redline. That's a LOT of energy for my Rube Goldberg belt drive to dissipate when I grab a gear and drop the dual disk clutch hard enough to bark the 285's

EDIT: I read an article about the Ford GT 2.0 that said that you know you got a powershift right if the supercharger belt chirped.

[ericjon262]

AD230

If you're changing out anyway, what about fitting a DR44? Do you have an extra PWM output on your MS3? Managing the charge schedule around throttle input and other parameters might be worth looking into?

I have a PWM output available, and that was actually something I was planning to do, I will have to look into making the charge light work, but I believe the MS3 has the ability to control that as well. I'd like to get the tune hammered down a little cleaner before I mess with things like alternator control though, unless I end up needing an alternator sooner than I thought/hope.

[jelly2m81]

I've never replaced a conventional alternator pulley for failure, and I turned wrenches on QUITE a few cars in my time. I have how ever replaced a number of the decoupler pulleys in the relatively short time frame they have found their way's into cars.

And then there's the hassle of now making sure you have the correct alternator that spins the right way because the pulleys are treaded onto the Stator shaft, so there's right hand tread ones and left hand tread ones depending on the application.

Too much money, potential reliability issue for me for no real life gains.

[ericjon262]

I've never replaced a conventional alternator pulley for failure, and I turned wrenches on QUITE a few cars in my time. I have how ever replaced a number of the decoupler pulleys in the relatively short time frame they have found their way's into cars.

And then there's the hassle of now making sure you have the correct alternator that spins the right way because the pulleys are treaded onto the Stator shaft, so there's right hand tread ones and left hand tread ones depending on the application.

Too much money, potential reliability issue for me for no real life gains.

I hadn't heard of failures yet, but I also hadn't looked, and part life is definitely a real consideration here, as I really don't want to deal with replacing a pulley every 6 months. especially because I'm starting to drive the car more and more.

[The Dark Side of Will]

My '05 Benz has 212,000 miles, and when it was in the dealership for warranty work on the Sensotronic Brake Controller (SBC), the dealership noted it also needed a new alternator pulley. I have one, but the access to R&R isn't fun. Alternator still works and I never noticed a problem driving it.

My '07 Jeep with Benz engine has 215,000 miles. I just replaced the regulator and put the alternator back without replacing the pulley, which still worked. No idea if it was the original pulley or not.

I don't think part longevity is a problem.

[pmbrunelle]

I've never replaced a conventional alternator pulley for failure, and I turned wrenches on QUITE a few cars in my time. I have how ever replaced a number of the decoupler pulleys in the relatively short time frame they have found their way's into cars.

And then there's the hassle of now making sure you have the correct alternator that spins the right way because the pulleys are treaded onto the Stator shaft, so there's right hand tread ones and left hand tread ones depending on the application.

Too much money, potential reliability issue for me for no real life gains.

Are you a mechanic?

If you're a professional wrench-turner, then there may be some observer bias in there... people bring broken cars to the mechanic.

[jelly2m81]

Are you a mechanic?

If you're a professional wrench-turner, then there may be some observer bias in there... people bring broken cars to the mechanic.

Yes and Yes.

My point was that in 30 plus years I have never seen a * failed* conventional solid alternator pulley. I have replaced a few de-coupler pullies that have failed in several manners, locked up, free spinning.

If I am biased, yes Those things make me money

[jelly2m81]

the dealership noted it also needed a new alternator pulley. I have one, but the access to R&R isn't fun. Alternator still works and I never noticed a problem driving it.

My point exactly. We will not find any gain from it.

[The Dark Side of Will]

the dealership noted it also needed a new alternator pulley. I have one, but the access to R&R isn't fun. Alternator still works and I never noticed a problem driving it.

My point exactly. We will not find any gain from it.

Now that it's been warm enough to drive around with the windows open, there's some belt chirping on chop throttle and deceleration that may be the result of the seized pulley. Not a huge impact, but probably reducing belt life. Book time for belt R&R on '05 Benz E320 diesel is 1.5-2.0 hours so getting more life out of the belt is advisable.

[The Dark Side of Will]

the dealership noted it also needed a new alternator pulley. I have one, but the access to R&R isn't fun. Alternator still works and I never noticed a problem driving it.

My point exactly. We will not find any gain from it.

Now that it's been warm enough to drive around with the windows open, there's some belt chirping on chop throttle and deceleration that may be the result of the seized pulley. Not a huge impact, but probably reducing belt life. Book time for belt R&R on '05 Benz E320 diesel is 1.5-2.0 hours so getting more life out of the belt is advisable.

I spoke too soon... the belt drive started intermittently to squeedle(*) last weekend while I was on my way to Norfolk for drill.
I have some good documentation on alternator R&R from BenzWorld.org so I'll do the deed this weekend. I've had the pulley & tool in the car for months since the dealership told me it needed replacement.

Access is not fun on the accessory drive of an inline six squeezed into an engine bay designed for a V8.

Apparently, engine torque and alternator torque fluctuate enough, but for different reasons, that the tensioner has to be brutally stiff in order to keep the belt from "micro-slipping" at low tension points in the cycle. The caddy Northstar tensioner is an example of this. The waterpump drive tensioner can be operated with a 1/4" drive ratchet while the A/C-Alt-PS pump drive tensioner requires a 1/2" drive breaker bar. The Jeep's tensioner was not that stiff. I'll see if the Benz tensioner is that stiff. If the decoupler pulley allows reduction of belt tension AND reduction of belt slip at the same time, then it could contribute significantly to belt life.

Also, as noted previously, I'll end up turning the Caddy alternator up to 20,000 RPM or more, so a decoupler pulley might help belt wear on my distinctly non-OE belt drive.

(*) Technical term, like "chuggle" for a transmission malfunction

[The Dark Side of Will]

Update: I replaced the pulley and the noise did not go away.
On further evaluation, the noise responds to engine LOAD, not engine acceleration like I initially thought. This means it may be a PCV valve or something weird that is affected by boost, but almost certainly nothing in the accessory drive.