Hey guys... not sure if everyone here knows what this is... but does anyone know if there's such a thing as a decoupler pulley that's available for the GM alternators in our Fiero?
It's something that I installed on my Crown Victoria, and really helps the reliability of both the alternator, the belt, and the accessory system.
Here's a good video to explain how it works:
Long and short... the civilian Crown Victorias didn't come with these, but the Police versions did because of the way they're typically driven. I upgraded my Crown Victoria years ago with most of the performance parts from the police and Marauder variant. The shift from 1st to 2nd, even with 2.73:1 gears at max RPM is just insane. There's so much difference in the belt speed that the pulley squeals for a quick second, even with all brand new parts (tensioner, and everything in good shape). It's a problem Ford fixed by installing these decoupler pulleys.
Just curious if anyone knows if there's any way to retrofit one of these pulleys onto the Fiero's alternator shaft?
Thanks!!!
[This message has been edited by 82-T/A [At Work] (edited 03-09-2022).]
Here is a really good video that shows the difference between using a solid versus an OAP at high speeds...
Aside from the obvious craziness with the belt... the big take-away is that the alternator is not really creating the lag on the motor that it would otherwise be doing at full throttle... so if I understand correctly... you're actually not getting that parasitic loss at WOT over a certain RPM.
I'm fairly certain most late model GM alternators use a pulley like this, I also think the make one in the same form factor as the alternator in my swap, I may try one out. to answer your question, I think the best way to find out is to take a ton of measurements off of the alternator you want to install the pulley on, send them to a manufacturer, and see what they say.
------------------ "I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
These are Not to "Save Power" for Engines at WOT or at any lower RPM. If anything will Create some Lag for the Alt...
Because Is to protect the Belt from the Alt's Rotor Mass. When you Hear Belt Squealing then the belt is "dead." These pulleys prevent belt death way before you hear noise.
Alt Rotor is Heavy and Slams the belt when Engine RPM changes suddenly. Don't think so? Put an alt bolted down to a bench and try to spin to just 2000-3000 RPM then try to stop fast. Alt can spin a lot more then that. Many have "Red line" at 9000 to 10,000+ Alternator RPM.
Worse, Many newer cars and Police versions have "Heavy Duty" alts like CS144 and related w/ rotors that are heavier than CS130 or 12SI.
Pulley w/ 1 way clutch only stops slamming for high to low Engine RPM. Advance Pulley w/ extra load spring can stop slamming in high to low and low to high.
Can you install them to replace solid pulleys? Maybe. Some move the pulley out and won't fit w/ OE Alt brackets to keep belt alignment. Some are bigger front to back and may cause clearance problems w/ Fiero frame. If you use the "wrong" advance pulley, even if it fits the belt setup, the "load spring" can made the alt to slip way more or never slip and either can cause problems.
Think the "Load Spring" as a non-adjustable Torque Wrench w/ a clutch instead of "click" bar. If set light then will slip more and wear out fast and may cause low power too. If set tight then will rarely or never slip and doesn't protect the belt.
Advance Pulley setup is likely affect or changes for Idler pulley setup. IOW They work together for long belt life.
Before you claim AC does the same... No. ECM/PCM can turn off AC at WOT or over some % Throttle for Decades and can be programed to turn off for other reasons. Fiero ECM can do this too but many Throttle Pedal and Cables have problems and TB/TBI never reaches WOT. Many can't reach 80-90% Throttle when you "Floor the gas" because of this.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
These are Not to "Save Power" for Engines at WOT or at any lower RPM. If anything will Create some Lag for the Alt...
Because Is to protect the Belt from the Alt's Rotor Mass. When you Hear Belt Squealing then the belt is "dead." These pulleys prevent belt death way before you hear noise.
Alt Rotor is Heavy and Slams the belt when Engine RPM changes suddenly. Don't think so? Put an alt bolted down to a bench and try to spin to just 2000-3000 RPM then try to stop fast. Alt can spin a lot more then that. Many have "Red line" at 9000 to 10,000+ Alternator RPM.
Worse, Many newer cars and Police versions have "Heavy Duty" alts like CS144 and related w/ rotors that are heavier than CS130 or 12SI.
Pulley w/ 1 way clutch only stops slamming for high to low Engine RPM. Advance Pulley w/ extra load spring can stop slamming in high to low and low to high.
Can you install them to replace solid pulleys? Maybe. Some move the pulley out and won't fit w/ OE Alt brackets to keep belt alignment. Some are bigger front to back and may cause clearance problems w/ Fiero frame. If you use the "wrong" advance pulley, even if it fits the belt setup, the "load spring" can made the alt to slip way more or never slip and either can cause problems.
Think the "Load Spring" as a non-adjustable Torque Wrench w/ a clutch instead of "click" bar. If set light then will slip more and wear out fast and may cause low power too. If set tight then will rarely or never slip and doesn't protect the belt.
Advance Pulley setup is likely affect or changes for Idler pulley setup. IOW They work together for long belt life.
Before you claim AC does the same... No. ECM/PCM can turn off AC at WOT or over some % Throttle for Decades and can be programed to turn off for other reasons. Fiero ECM can do this too but many Throttle Pedal and Cables have problems and TB/TBI never reaches WOT. Many can't reach 80-90% Throttle when you "Floor the gas" because of this.
I'm primarily looking for the "override" pulley. I have to assume that the shaft on the alternator is not something so unique that an existing pulley wouldn't fit. I think spacing is a problem I could easily fix, and the number of splines on our serpentine belt is fairly common.
I just can't imagine why others have considered this, or implemented it. It's only a net-positive as it reduces load on pretty much every accessory, including the bearings and brackets. It reduces load to the engine on acceleration, and on deceleration.
Are there any instances of a modern-V6/60 (gen 3 maybe) with this being used? Anyone know?
Originally posted by pmbrunelle: During acceleration, the overrunning pulley locks and becomes solid... so how would that reduce loads on everything during acceleration?
Mostly Correct. the 1 way unit will "lock" in accel and cruise then "Free wheel" when decel, more so when engine RPM drops fast. The "advance" pulley will "lock" most of the time but "Free wheel" when engine RPM changes fast in either direction. Or May "Eat" any shock from the alt to engine and the opposite. This version can be tuned for a given vehicle.
If OEMs setup the idler tension less that normal then belt strain on Alt & other bearings helps them too. Otherwise bearing loads don't change very much.
Brackets and other hardware won't change because of other loads and vibration are same.
quote
Originally posted by 82-T/A [At Work]: I just can't imagine why others have considered this, or implemented it. It's only a net-positive as it reduces load on pretty much every accessory, including the bearings and brackets. It reduces load to the engine on acceleration, and on deceleration.
Again. Assume you find either type w/ same diam and spacing as the solid pulley... Is often not a direct replacement. Alt Shaft maybe different or have clearance problems stated above.
Even If that doesn't happen, need special tools to install/remove them. Example: https://www.youtube.com/watch?v=XYi_w3ieGUo Likely isn't cheap when buying a pulley either. not something to find in most junk yards and Gates etc. are tell to change them every time you change the belt.
Quite frankly I don't like them. Modifying adds another element that could go wrong. I don't see any advantage on a classic hobby car that gets used little.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
IIRC the 3800 has an overrun pulley on the alternator. I think some other GM engines do, as well. Maybe you can adapt one of them? But to be honest, I don't see the point.
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).]
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.
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.
Originally posted by Will: I don't know about the Duramax alternator, but my OM642 and OM648 (Benz diesel) alternators both have overrunning pulleys.
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.
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).]
