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| Decoupler Pulleys - for the 2.8-3.4? (Page 2/2) |
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Will
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MAR 14, 10:41 AM
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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 tensioner 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 drop the dual disk clutch hard enough to bark the 285's :wink:
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.[This message has been edited by Will (edited 03-14-2022).]
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fieroguru
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MAR 14, 05:14 PM
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I would like an overrunning pulley for the alternator on the LS4 just for the WOT upshifts at 7K rpm. I probably don't want to see what it does... but I did snap a tensioner arm twice before I upgraded it. Not something I am actively pursuing, but if someone finds a good solution, I will definitely jump on board.
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lou_dias
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MAR 15, 08:54 AM
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Now that I have an EV for a daily...
If you don't mind hooking up your car to a battery charger nightly and running a 100AH LiFePO4 battery, you can just dump the alternator altogether and just drive all day with more power and fuel economy.
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Blacktree
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MAR 16, 04:52 PM
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| quote | | Originally posted by Will: I don't know about the Duramax alternator, but my OM642 and OM648 (Benz diesel) alternators both have overrunning pulleys. |
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Volkswagen TDI engines (turbo-diesels) also have them. And if the pulley seizes up (or some nimrod installs a solid pulley), the vibration will literally beat the belt tensioner to death. But that's a diesel 4-banger, which vibrates a lot more than a Fiero V6.
The Fiero V6 doesn't have a belt tensioner. And during ~25 years of Fiero ownership, I've never seen or heard of anyone having issues with belt drive harmonics on the 2.8 / 3.1 / 3.4 V6 engines. So I don't think an overrun pulley will yield any benefit. But if you wanna do it, just to say you did it, I don't think it'll hurt anything. Make sure the overrun pulley lines up with the rest of the pulleys, and you should be fine.
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Will
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MAR 17, 12:25 PM
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The original Fiero belt drive is hardly reliable. It should only be showcased as an example of what not to do.
I think the diesel low redline RPM and high drive ratios make using the belt drive to spin down the alternator more problematic than it is with gasoline engines with higher redlines and lower drive ratios.[This message has been edited by Will (edited 03-17-2022).]
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82-T/A [At Work]
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JUN 29, 11:39 AM
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